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An overview of the nutritional importance of vegetables.
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NUTRITION; THEORY > THE
EVOLUTIONARILY APPROPRIATE DIET > VEGETABLES
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We are a vegetable
eating animal
Wild humans eat
lots of
vegetables
Who said thats a 'vegetable'?
Tubers,
bulbs,
and other storage organs
Wild
African
and Asian vegetables
Wild African and Asian
tubers,
roots, rhizomes, bulbs and corms in an aquatic environment
Wild
African and Asian tubers, roots, rhizomes, bulbs and corms in a
woodland
and riverine savannah environment
Wild
African and Asian tubers, roots, rhizomes, bulbs and corms in temperate
& subtropic shoreline and upland environments
Plant
toxins
- our evolutionary adaptation to them
Domesticated
versus wild veggies
Essential protectants in
vegetables
Antioxidants in vegetables
Folic acid
Vitamin C
Vitamin A and Beta-carotene
Fiber
Links and further reading
Summary: Humans evolved from ancestral apes, and our genes are
still
reflect a vegetation and small animal eating past. Evolving in Africa
and
then Asia, we ate a huge range of leaves, buds, flower buds, stems,
gums,
roots, tubers, and even pollen.
The number of plant families we used as food was very much greater
than the restricted range we eat today. Wild foods were carefully
selected
to avoid the plants or parts of plants with bitter and unpleasant
taste,
which likely contained toxic compounds. Today's plants are more
palatable,
and yet paradoxically, we eat very few plants as part of our daily diet.
The major contribution of plants to human health has always been
thought to be the large amounts of vitamin A, the folic acid vitamin,
and
the vitamin C they contained; as well as a good amount of some minerals.
It is becoming more and more obvious that there are many plant
chemicals
that act together to protect the human body from the onset of cancers
and
heart disease, and that vitamin supplements can be helpful, but are not
as useful as the whole plant.
Very little is known about the health benefits or toxicity of the
wide range of plants we ate in the course of our evolution. After
millions
of years, they are now eliminated from our diet.
The small number of plants we do eat are being increasingly well
studied, so we know a lot about their vitamin content and antioxidant
and
health protective effects.
The most powerfully protective domesticated vegetables that we are
likely to eat are spinach, garlic, broccoli, brussels sprouts, carrots,
sweet potato, red pepper, winter squash, and frozen peas - more or less
in that order. These are outstanding vegetables, but every vegetable is
an important contributor to well being.
While tubers and roots are an important slow burning energy food,
vegetables are responsible for more subtle feelings of daily
well-being,
and for protection from long term degenerative disease. It is certain
that
Western people in particular are paying a heavy price - in any terms -
for their cultural alienation from a primal and essential natural food.
NOTE: THIS WEB PAGE
PRINTS
OUT AS ABOUT 27 PRINTER PAGES
Why do we eat vegetables?
This is a question that would never be asked of fruit. Fruit is
sweet.
We love sweet things. We love to eat fruit. But vegetables can be
bitter,
and apart from carrots and sweet potatoes, they are generally not
sweet.
How is it, then, that we came to eat vegetables? Partly, it is
'hardwired'
into us. For good body efficiency reasons.
Basically, we are an evolutionary line from a group of mammals that,
from about 65 million years ago until around 50 million years ago were
small insectivores, but which evolved to fill tree top
vegetable-matter
(foliage, fruit, tree seeds, or mixed vegetation based diets) eating
niches,
while still eating insects whenever we could (chimpanzees ,
orang-utans,
gorillas, gibbons, and the siamang - all apes - eat insects).
Gorillas probably branched out earlier from the ape human ancestral
line and so their life way gives us fewer insights into our ancestry
(they
probably went their separate way around 8 million years ago). Mountain
gorillas, in particular, are primarily foliage eaters, consuming large
amounts of pithy stems, buds, leaves and shoots. These foods are low in
energy density, and gorillas have to eat a lot of plant material to
meet
their energy needs. They are now fairly specialized vegetation eaters.
Chimps, which have more recently diverged from our ancestral line
(generally
estimated at around 4.5 million years ago), are more likely to reflect
at least some of our ancestral food preferences. Chimps don't seem to
tolerate
grossly fibrous food as well as gorillas. They chew leaves into a
"wadge',
and press the wadge against their teeth to extract the juicy parts,
then
spit out the fibrous residue. Chimps prefer insects and meat where it
is
available in their environment, but in their (primarily) forest
environment
it is not commonly available. Succulent piths - carefully peeled of the
tough exterior - blossoms, fruit, shoots, and leaves are the mainstay
(around
95%) of their diet, with insects, eggs, and monkey meat
opportunistically
thrown in as and when available.
Even limited omnivory is a conservative adaptive trait, and even in
the great apes, which have put 'all their eggs in one evolutionary
basket',
so to speak, retain the ability and desire to eat insects (and eggs!).
We eat vegetables because, while we intensively exploit ground based
and shoreline animal protein and fats, we share massive amounts of our
genetic profile with our related plant food subsisting apes (some
scientists
assert the genetic similarities are so overwhelmingly great that
chimpanzees,
the ape genetically 'closest' to us, ought to be classified as a
species
of human), and we are therefore genetically 'programmed' to exploit
plant
food as part of the primate omnivorous capabilities.
Even by the Australopithecine stage in our evolutionary line, we
lacked
the kind of molar configuration to deal with very pithy vegetation. But
we did have the kind of jaw form that could do a lot of chewing on
moderately
firm and fibrous foods - such as lizards, locusts, baby birds, and
plant
'underground storage organs' - tubers, roots, corms, bulbs - soft
new stems, immature flower buds, fleshy leaf bases, tender new shoots,
tree seeds (once opened with rocks), fungi, and acacia gums. The
microscopic
wear marks on Australopithecus afarensis front teeth are very
similar
to those on baboon front teeth - suggestive of an intake of similar
highly
selected, nutrient dense shoots, bulbs, and leaves.
Our gut has become overall shorter, but with an increase in the
proportion
devoted to the small intestine (where high nutrient foods such as meat
are dealt to and absorbed) in order to be able to handle the higher
nutrient
density foods of seashore and hunt. The price of a shorter gut is less
efficient digestion of plant materials, as there is not enough room for
the necessary micro flora to help break it down (the female of our
species
is said to have a longer gut than men. It is an interesting speculation
whether this is an evolutionary adaptation to eating more vegetable
foods
than men, and whether this explains the difference in 'intestinal gas
production'
between men and women -women have more vegetable efficient guts).
Because we have taken omnivory far further than any other related
animal,
and can live quite well on an almost exclusive meat and fat diet if we
had to, does not mean that we can forever abandon eating plants. Plants
are 'powerhouses' of many and complex 'life enhancing compounds', and
we
almost instinctively 'know' that we need them. If our sense of taste
hasn't
been completely dulled and distorted by the cultural forces of our
urban
'fad' diet, we sometimes feel a craving for 'bitter herbs', and seek
them
out. There may be the distant echo of instinctive 'self medication', or
perhaps, 'self biochemical regulation' in this feeling.
Vegetables are an important - perhaps key - part of our 'generalist'
evolutionary niche, in that the reliable carbohydrate source of
bulbs
and roots (and certain seeds) acted as insurance against failure in the
high value but much more uncertain hunt. On top of this, humans need
far
more energy to fuel our brains than any other primate - around 300 kcal
when at rest, and it has to be in the form of glucose, because that is
the fuel the brain runs on. This energy requirement can be met
relatively
easily with some roots and tubers, depending on the carbohydrate
content
of the particular species. In some respects, we should perhaps consider
roots and tubers as a major food item, in a separate class to leafy
greens,
shoots, buds, and
flowers.
TOP
All hunter gatherers
eat veggies
"Their groups were small because the desert gives food
sparingly,
and often each family lived apart from other tribal members most of the
year. The women did much of the work of food gathering -- except
for meat...the Indians couldn't make a good living from the desert
alone.
They lived around the edges; they haunted the lakes for wildfowl, eggs,
tules, cattails, and yellow water lilies."
- commentary of an observer of the Paiute tribespeople of the North
American deserts, from earlier this century.
As an illustration of how wild humans use all the palatable
plant
foods in a given environment, here is a list*
of plants the Paiute, a desert edge tribe, were known to have eaten.
Some
of the plants are probably weeds introduced by European colonizers.
Weeds - dock, tarweek, mustard, lamb's quarter.
Water plants -- yellow pond lily, rushes, sedges, tules.
Trees -- sugar pine, Pinus lambertiana. Edible half
inch long seed, sweet but rather laxative gum exudes from injured
branches.
Food from Leaves and Young Shoots
Dock, ? Rumex hymenosepalus - The bitter
succulent
leaves were roasted on hot ash beds. (Young leaves of some
species
are more edible, and even used to be cultivated as a vegetable in
Europe.
A native African dock, 'Abyssinian spinach', R. abyssinicus has
been domesticated.)
Camas, Camassia sp. - a bulbous plant of damp places,
marshes and lake edges. Altho' they are edible raw, the bulbs were
usually
baked (on ashes, in an earth oven), or cooked and dried and the flour
extracted.
(Not to be confused with the very similar 'death camas', Zygadenus
venenosus.
No doubt the Indians people didn't confuse them, as they only gathered
them in the flowering season, when they could distinguish between the
two...urban
westerners need to be extremely cautious in areas outside their life
experience.
Don't eat what you don't 'know' is safe!). Murderous tribal wars were
fought
over this resource.
Sedge, ? Scirpus sp. - grows in damp and
marshy places by lakes. The young shoots are edible.
Cattail, Typha latifolia - water margin plant, the
young shoots ('Cossack asparagus') are edible from spring onward, as
are
the immature flower heads, and later, the pollen.
Reed, ? Phragmites communis, a plant of damp places
and lake shores
Mint, Mentha sp.
Wild parsnip, ?Phellopterus montanus
False dandelion, Pyrrhopappus catolianus. The roots
are also edible in Autumn.
Mushrooms - various species. Puffballs, in particular were
valued by many West coast tribes, and were dried for later use.
Pigweek, Amaranthus palmerii and A. retroflexus
- the young leaves are very mild.
Watercress, Nasturtium officinale - introduced from
Europe
Shepherd's purse, Capsella bursa-pastoris - A small,
common weed. The whole plant is edible.
Lamb's quarter, Chenopodium album - An introduced
annual, grows to seven feet. The leaves are quite mild.
Dandelion, Taraxacum officinale - the leaves are
bitter,
but edible, Young leaves are used raw.
Mustard, Brassica campestris - the lower leaves, or
very young plants, which are least hot, are eaten.
Fireweek, Erechthites (Senecio) hierarcifolia - a
thistle like plant.
Wild lettuce, Mimulus guttatus - a low growing plant
found on wet ground, the leaves are like a somewhat bitter watercress.
Peppergrass, Lepidium freemontii - A small land cress
with 'hot' tasting leaves
Mallow, ? pimple mallow, C. pedata of Western USA.
Wood sorrel, Usually, Oxalis sp. ? Oxalis tuberosa,
or O. enneaphylla. (Oxalis species leaves and bulbs were once
commonly
eaten wherever in the world they were found - Africa has around 130
indigenous
species - in spite of their oxalic acid content.)
Plantain, Plantago sp.
Solomon's seal, ?Polygonatum giganteum - the very
young shoots of the related European P. officinale were used
like
asparagus; perhaps the Paiute used P. gigantuem the same way.
(The
rhizomatous roots of P. giganteum are also starchy, and were
used
by the Ainu people of Northern Japan as a food source. P. giganteum
grows in both Asia and America)
Purslane, Probably Portulacca oleracea, a sour
tasting
introduced annual weed with succulent crisp textured leaves; possibly Portulacca
retusa, known to be used by tribes in the Southwest as a vegetable,
or Calandrinia sp. - adapted to dry western parts of USA. Or
maybe
even Lewisia rediviva, a purslane
more
commonly known as 'bitter root', altho' it is usually harvested for its
very nourishing flour (in spite of its common name!), rather than as a
vegetable.
Bracken fern, Pteridium aquilinum - the very young
shoots ('fiddle heads') are eaten raw or cooked, when they taste like
somewhat
bitter asparagus.
Bulrush, Typha latifolia. - see
below
Sow thistle, Sonchus sp. - very young leaves are
edible.
Chickweek, Stellaria media - a common small annual
plant with vaguely cabbage tasting leaves.
Pennycress, ?Thlapsii sp, a relative of 'shepherd's
purse', Capsella bursa-pastoris.
nettle, ?Urtica sp. - in other countries, fresh nettle tops
are regarded as a very nutritious spring 'spinach', usually used in
soup.
Wild violet. Viola sp., possibly V. palmata,
or V. papailionacea - While viola flowers, at least, have been
used
in food in Medieval time, the roots are poisonous - except the
mucilaginous
roots of V. palmata. The basal leaves of
V. papailionacea are still collected for greens today.
They are quite extraordinarily rich in vitamin A.
Food
from
Roots and Tubers
Wild onion, ?Allium validum - 'swamp onion'. - there
are many species of wild onion, most have small bulbs, and are found in
a variety of habitats, depending on the species.
Mariposa lily, Calochortus sp. - 'Indian potato'.-
a wide ranging genus with corms that can be eaten raw or cooked. They
can
also be dried and pounded into flour.
Camas, Camassia sp. - a bulbous plant of damp places,
marshes and lake edges. The bulbs were baked, or cooked and dried and
the
flour extracted.
Bitterroot, ?Lewisia rediviva, see above
Cous, Pastinacea cous - a close relative of the
parsnip,
P.
sativa
Ipo (squaw root) cattail -? Typha sp.
Brodiaea, a pretty flowering 'bulb', most species of which
are edible. They produce their edible corms in a wide range of
habitats,
according to the species.
Yellow bell, ? species
Primrose, ?Primula sp. In Europe the leaves and
flowers
of 'cowslip', P. veris, have a history of use as salad greens.
Which
species - if it is a Primula - that was used by the Paiute, I have no
idea.
Water parsley, Oenanthe sarmentosa - the black tubers
are said to have a 'cream-like taste'. The leaves and stems are also
edible,
tasting a bit like celery. Some similar looking species are poisonous.
Balsam root (Oregon Sunflower), ? possibly a species of
sunflower,
Helianthus.
Many sunflower species have edible roots.
Wocus (water lily) N. advena - the roots are starchy,
and can be baked, grilled, pounded for flour, or stored whole for
winter
use ("hundreds of bushels" were stored for winter time by west coast
tribespeople,
according to a note written by a European observer in 1855). The seeds
are also edible.
*
italicized
notes are mine
The list was compiled by a European. A tribespersons list would
certainly
have been more detailed than this. The identification of the botanical
names is mine, and is based on the common english name, which may be
misleading.
The notes in italics are also mine.
This is simply an illustration of the general principle that we ate
everything in the environment. There is always a hierarchy of
preference,
of course, but in general, there was probably not a great deal of
freedom
to choose. Some environments are very difficult to make a living from
-as
we have seen - maybe they are dry, or very cold, for example. The
richest
pickings are at the margin of two different ecosystems, such as forest
edge abutting a lake or shoreline. When times were hard, we turned to
our
least preferred vegetables-
"Although the lichens were not regarded as common foods, in emergencies
many types were eaten. They were scraped from rocks or trees and eaten
raw or boiled with fat. To remove the bitter taste, some tribes washed
them in water mixed with the ashes of a campfire."
M.A. Weiner, 'Earth Medicine-Earth Foods'.
It is worth noting - given the long period much of Europe was glaciated
- that native people in the North of North America made a kind of soup
of the contents - chiefly lichen in winter - of caribou stomach. The
permanently
frozen ground beneath the surface of soil was used to store
baskets
of spring greens and berries for winter use (meat and fish was also
stored
this way). The original packet of frozen spinach! There is no
reason
to suppose ancestral humans were ignorant of the preserving effects of
freezing in such an environment. Our more recent 'wild living'
ancestors
had as much raw 'intelligent' capacity as we have. We are them; they
are
us.
TOP
What are 'vegetables'?
1. buds, flower buds, leaves, shoots
A vegetable is basically any part of a plant that can be eaten.
Plants,
naturally, are not too keen on being eaten, and have devised various
methods
of dissuading us from eating them. This aspect is discussed further
on. Luckily, humans are smarter than plants, and we have discovered
many ways to get past plants chemical defenses.
As a result, we have been able to eat many different parts of
selected
plants - flowers, flower buds (globe artichoke), leaves (lettuce), leaf
buds (Brussels sprouts), shoots (asparagus), shoot buds (cabbage),
stems
(celtuce), flower stem (broccoli), pollen (bulrush), immature seed pods
(green beans), fruit (chayote) , immature seeds (broad bean). We have
also
eaten gums (from acacia trees), sea algae (seaweed), and lichen.
If it's a plant, palatable and non-poisonous (at least, not medium
term
nonpoisonous), it's been food for humans. Guaranteed.
The fact we eat such a small range of vegetables is a matter
of luck, culture, and inertia; not because "these plants are vegetables
because I can get them at the supermarket, therefore only plants I can
buy at the supermarket are vegetables".
2.
tubers,
bulbs, and other storage organs
Tubers are the major fall back carbohydrate source, and are 'not'
veggies
You can live without greens for a long term - although there are
long
term consequences for fitness - but we must have fuel to burn for daily
activity. No matter what fiber, vitamins and minerals may be in tubers,
particularly starchy tubers, their main importance is as a fuel for
daily
life. It is in this respect that they perhaps ought to be thought of
more
as seeds are thought of - as a mainstay of life. Seeds are more
nutritionally
dense than tubers, especially oily seeds, and protein rich legume
seeds.
Even so, combined with even relatively small amounts of protein from
lizards,
locusts, mollusks, and other relatively easily collected animal food,
they
are a viable primary food for long periods, and as a bridge between
preferred,
nutritionally dense tree seed, legume, meat, fat, marrow, and internal
organ foods.
For example, in Africa the residual Tanzanian hunter gathers (the
Hazda)
live in a "game-rich habitat", and yet average only one large game
animal
every thirty days devoted to the hunt. Plant food is the mainstay that
fills the gap (women, mothers and grandmothers in the main, do the work
of collecting sustenance for the whole family ...), especially in the
dry
season, when children can't find enough of their own food. (Only s
are strong enough to dig up deeply buried tubers. Perhaps this explains
kids fixation with 'buried treasure, aarr, aarr!')
"underground storage organs occur at higher biomass in drier
sites because they store food and/or water during periods of climatic
stress
(Andersen 1987). In Tanzanian savanna woodland, for example, Vincent
(1984)
found densities of edible tubers averaging 40,000 kg per km2, compared
with only 100 kg per km2 found by Hladik and Hladik (1990) in a rain
forest
of the Central African Republic. (Even at a density of 100 kg per km2,
Hladik and Hladik considered them sufficiently abundant to support a
human
population.)"
Richard Wrangham et al 'The
raw
and the stolen: Cooking and the ecology of human origins'
The tuber resource in the dry season meant being able to maintain body
fat and being able to have a pregnancy sooner, rather than later on
when
food in general was more abundant. Older females without young children
could feed themselves, the men, and small children when food was
scarce,
meaning the group survival as a whole was greater. And of course,
mothers
could help gather food for lactating daughters with children on the
hip.
The same principal of 'plant underground storage organ bridging'
('PUSOB')
no doubt applied to Eurasian areas; especially during our evolutionary
history when Europe and Asia went through markedly colder, drier and
more
climatically extreme periods. These were the conditions Homo
erectus
had
to contend with when it radiated out of Africa. And H. erectus'
teeth wear patterns are not unlike pigs - an underground root finder,
as
any pig owner will tell you.(And fungi - don't forget truffles).
The following brief notes are just a few of the plants we probably
ate
in the course of our evolution and radiation out of Africa and into
Asia
and Europe.
African
and Asian veggie sources in the wild over evolution
Vegetables
Today we eat an astonishingly narrow range of vegetables if we compare
the local produce department with what scientists and historical
observers
have recorded as being eaten by tribespeople in Africa. One writer
lists
83
plants known to be used as vegetables in Zimbabwe; another records forty
different leaves used as greens; in one small part of South Africa more
than 120 plants were used as vegetables. In more
extreme
marginal environments the options are much fewer; yet one
observer
lists 18 plants used by the San of the arid areas of Namibia and
Botswana.
Much of the knowledge of what 'can' and 'can't' be eaten was passed
from mother to daughter and child to child (children live in a
'knowledge'
subculture passed by word of mouth eternally); our keen sense of taste
also alerted us to potentially dangerous chemicals in the plant. Then
as
now, we selected the youngest, least bitter parts, and the youngest
plants.
Most of the detailed knowledge about the wild vegetables we evolved
with
in Africa has now been lost, because we are no longer gatherer hunters,
and we don't need these mental encyclopedias any more. One of the very
best records of what knowledge remains is 'Food from the Veldt', the
source
for much of the data in this essay, and required reading for anyone
interested
in nutrition and the human animal (details below).
"...the flowers heads of this plant, which thrives abundantly
near the seashore, furnish a kind of culinary vegetable which
somewhat
resembles asparagus and is known as Hottentots' cabbage. When
stewed
and properly prepared they make no contemptible dish'
-L. Pappe, in 'Silva Capensis', 1862, referring to Trachyandra
revoluta, a strap leafed perennial of the lily family in South
Africa.
The italics are mine.
What we can say is that any plant or part of plant that was able to be
eaten was eaten. Different indigenous people put different
values
on some of the plants in their environment, and that is a matter of
culture
and other circumstances, not a comment on their absolute edibility.
People
then, as now, have a hierarchy of preference, closely aligned to
palatability.
'mouth feel', and learned prejudice.
Some of the vegetable matter we almost certainly ate for countless
millennia
in the course of our evolution we now never eat. For example,
the
gum exuded from the injured bark of some species African acacia (the
common
leguminous tree of the Savannah and open woodlands), such as the very
common
and very widespread 'karroo thorn', Acacia karroo, was eaten in
late summer, particularly by children (it has a sweetish taste).
The gum is apparently very nutritious, and can sustain life for days in
the absence of other food (180 grams/6 and a half ounces, has enough
calories
to meet an s energy needs for a day). The young leaflets of some
acacia
species were also eaten by some tribespeople. Small amounts of 'gum
arabic',
acacia gum, are used as thickeners in some industrial foods, but that
is
as close as we get to eating this ancient ancestral legume product.
The young shoots of trees are very rarely eaten in the West, yet
some
are highly nutritious. An Ethiopian tree, Moringa stenopetala,
has
leaves that are very nutrituious, edible flowers, edible pods, edible
seeds,
and the bark can be used as a 'hot' condiment (it is a close relative
of
the the Indian drumstick tree, M. oleifera, with one of the
highest
calcium levels and highest vitamin C level of any tropical vegetable,
beside
being the source of a very stable edible oil- Ben oil - and with
antibiotic
properties in the seed). In South East Asia young shoots of a small
evergreen
tree, Gnetum gnemon are regularly eaten, as are the immature
flowers.
They are quite nutritious, with 100 grams providing 104 calories, and
being
about 7% protein, around 19% carbohydrate, 11% fiber, and providing
excellent
vitamins and minerals - 1,680 I.U.. vitamin A, 121 mg vitamin C, and 44
mg of calcium. There are several species of Gnetum in
tropical
West Africa. Once the human is out of its natural environment, the
options
close out. But new ones come in...
One of the more surprising group of plants that clearly have been
part
of our diet ever since we evolved in Africa are the members of the
family
Asclepiadaceae. Several plants of the genus Asclepias provide
food
for the caterpillar of the monarch butterfly. Birds don't eat the
caterpillar
because the caterpillars concentrate within their body bitter chemicals
from the milky sap of the Asclepias plants they browse on. Even
altho' there are poisonous Asclepiadaceous species, indigenous
people
have used various parts of various species within this genus - raw
leaves,
cooked leaves, raw root, cooked root, raw stem, raw fruit, cooked
fruit,
varying with the particular genus and species. The various species in
this
family are spread over a wide range of environments, and are often
quite
common. The West African tuber-bearing species can be eaten raw or
roasted,
and one, the 'fikongo', Brachystelma bingere, is still popular
in
parts of Nigeria. It is interesting that when humans relatively
recently
radiated into North America, they immediately used the native american
Asclepias
species the monarch caterpillars feed on as a food source! Yes, the
'swan
plant' A. tuberosa, was harvested for its edible tuberous
roots!
In Asia, we found other members of the Asclepiadaceae we could eat -
several
creepers of the genus Telosma provide, variously, edible
flowers,
leaves, immature fruit, and roots.
However, accepting the principle that we ate all edible
parts
of all plants, it would take several books worth to mention
all
the plants we ate or probably ate over our evolutionary history in
Africa
and Eurasia. We will take a brief look at a few of the tiny number of
domesticated
plants that now constitute ( an insufficient!) part of our present day
rather odd - compared to our natural evolutionary determined
-industrial
diet.
The original asparagus that our species evolved alongside is Asparagus
laricinis, a somewhat spiny bush of South and South West Africa.
The
young shoot is eaten, and is still considered by some to be superior in
flavor to the domesticated asparagus, A. officianalis. Many of
the
wild species of asparagus are eminently edible, from the 'white
asparagus',
A.
allus that grows on the high plateaus of North Africa, to a species
in Southern Europe, A. acutifolius. And of course we ate the
wild
seaside asparagus, A. officianalis maritima, native to Europe's
Atlantic and Mediterranean coastline, and the possible progenitor of
today's
supermarket asparagus.
It wasn't really until we left Southern and Eastern Africa and moved
around the Mediterranean shoreline that we came into contact with the
seaside
plant, Brassica oleracea subsp oleracea, which is the
ancestors
of the cabbage, cauliflower and broccoli. But that is still half a
million
years or more. A long time to be a cabbage head. There is some
linguistic
evidence which suggests it was the young stems that were eaten. Several
other Southern European and Mediterranean shoreline species were also
probably
harvested - B. insularis (also found in North Africa), B.
macrocarpa,
B.
rupestris, and several others.
Brassicas are hardy, cold and salt tolerant plants, and therefore
well
suited to eventual domestication. But what about the more tender leafed
lettuce, you ask?
Lettuce is derived from the wild Latuca serriola, widespread
in North African and throughout Eurasia. The wild form is a annual
plant
of open woodlands and clearings, and forms a narrow leafed ground
hugging
rosette over winter, expanding into a stalk taller than the average
person
in summer. The leaves contain a very bitter milky latex, and no doubt
the
only young leaves were collected, as a winter green. Another species, L.
indica, native to East Asia, is a perennial plant whose leaves are
eaten either cooked or raw. Young plants and young leaves of biennial
plants
were the target in temperate areas. After that long winter, we craved
for
our tender 'spring greens'. Now, of course, we have different
cravings...
Humans seem to like 'umbelliferous' biennial herbs ('Apiaceae' plant
family). These plants form a strong root one year, and send up a flower
head made up up one or many umbrella shaped flower heads. Typical
examples
are carrots, parsnips, fennel, cumin, and celery. They are just about
all
strong smelling plants, and some 'umbellifers', such as hemlock, are
not
just strong smelling, they are deadly.
However, we have had a long evolutionary association with this plant
family. In Southern Africa the leaves and young shoots of a very common
grassland plant of this family, Peucedanum magalismontanum, are
eaten in some quantity by the indigenous people, mainly in the spring
and
summer wet season. All the several species of the genus Alepidea
in Southern Africa provide good greens when the young leaves are
selected.
Only A. amatymbica is too bitterly aromatic to be used at all.
While we didn't encounter the parsnip, Pastinaca sativa,
until
we radiated out into Central and Southern Europe, a related species
with
a "turnip- or parsnip-like root" [1]
page 85 , Annesorrhiza capensis, has been eaten since
time
immemorial in the Southern tip of Africa.
Green beans are in the genus Phaseolus, and come from South
America.
Why did we take to them with such enthusiasm? Because we have a long
evolutionary
history of eating legume pods (particularly some African acacias, such
as A. luederitzii, and Bauhinia sp. pods in Asia), and
the
vegetative parts of legumes in general. The leaves of the cow pea, Vigna
unguiculata, widespread in Southern Africa, are eaten by
tribepeople,
and sometimes in what can only be described as heroic quantities, even
although they can be quite bitter. Further brief notes on legumes in
Africa
are on the seed
and bean page. 'Green bean-like' legumes are well spread beyond
Africa.
For example, the Lablab bean, Lablab purpureus subsp. uncinatus,
is native to the Indian subcontinent. This climbing short live
perennial
'bean' has a seed pod which is eaten when immature, leaves
(unusually
high in protein - up to 28% in some varieties) which are edible, edible
flowers, and seeds which are edible if they are ground first (or cooked
for a very long time).
No salad would be complete without tomato. But they are also a South
American fruit. Africa and Eurasia doesn't have an equivalent, even
although
numerous members of its family the Solanaceae, have provided edible
leaves
and berries in the African and Asian environment since the faint
beginnings
of the evolution of the human species. The leaves of 'Ethiopian
nightshade',
Solanum
aethiopicum, are eaten by indigenous people as a vegetable, and the
immature fruit are cooked and eaten as well.
S. macrocarpon is used the same way. Another native African
solanum, 'gilo', S. aethiopicum ssp. gilo, also has
immature
fruit that are cooked as a vegetable. When we migrated into Asia, we
would
have been comforted to find a Solanum, the yellow berried nightshade, S.
xanthocarpum, that we could use in the same way as our native
African
species.
Perhaps the nearest we ever came to having an African tomato is the
fruit of the 'olive tomato', S. aethiopicum 'Gilo' group,
(synonym
S.
olivare) native to tropical West Africa, and eaten by the peoples
of
the region.
Solanums protect their leaves with acrid and poisonous chemicals to
greater or lesser degree, depending on the species. But, as with all
plants,
just because we evolved alongside these plants over an unimaginably
long
period of time doesn't mean we have evolved an ability to survive the
more
toxic species, or that we can eat the plant at the stage when they are
potent with damaging or irritating chemicals. Evolution has given us
elegant
sensory discrimination, and culture to pass on what has been learned,
without
each generation having to experiment with the safety of each plant
anew.
TOP
Tubers, roots, rhizomes, bulbs and corms
"During several years of living in the bush of southern and central
Africa I ate very little food that was not cooked on an open fire,
outside
on the ground...corms and bulbs dug up in the veld with a sharpened
stick
or oryx horn were also simply thrown in the hot ashes to cook"
-John Seymour, describing his life in sub-saharan Africa prior to
World War 2.
Every environment in our native Africa, and later Asia, had it's own
particular
root plants. These plants may have played a key role in the success of
the human animal as we moved into a multitude of habitats. Tubers are
not
as likely to be eaten by other animals, as they are hidden underground.
Only a tool using animal, such as Homo erectus and later H.
sapiens,
was able to dig down -sometimes quite deep - to reach the succulent
underground
tubers (although, only if the soil is not too hard; chimps
apparently
have been recorded as digging as far down as their arms can reach in
search
of tubers). Tubers and other underground carbohydrate organs go a long
way to solving one of the problems of feeding a family - they are
always there. Maybe not the preferred food, but reliable. And not all
tubers
need to be cooked. Quite some few can be eaten raw. Tubers are usually
roasted on embers, and no hearth (ring of stones) is needed to aid in
cooking
them (and starch extracted from roots can be cooked as 'cakes' in an
small
earth oven). Evidence of use of fire by humans stretches back to around
250,000 years ago, in the form of discernible hearths. But it is likely
that fire was used well before that to cook tubers, at least.
Certainly,
the calorific value of many tubers is increased when they are cooked;
so
there was an evolutionary advantage to those who discovered the
technique
(only a very small amount - around 7-10% - of the starch in cooked potatoes,
a typical 'starchy' rather than 'sugary' tuber, resists digestion and
becomes
'intestinal micro flora fodder'). A few tubers, like the water
chestnut,
remain crunchy even when cooked...
1. In an aquatic
environment
Trapa natans, T. natans
var.
bispinosa
(Roxb.) 'Water chestnut'
This vigorous water plant lives in shallow waters throughout Africa,
Europe and Asia, right up into the Russian far East, although it is at
its most abundant only in the warmest parts. Small, two horned fruit
ripen
in the leaf axils, and fall to the bottom if not collected. The seed
inside
can be eaten raw, boiled, roasted, or dried and ground into flour. It
is
sometimes called the 'water chestnut'. It fits nicely into the round of
seasonal water food collection in Southern Africa; as the swamps and
small
lakes drop in level over winter it becomes easy to search out the
'nuts'
in the mud. Until recently, at least, this underwater fruit
(technically
a nut) was a winter time staple of some of the river tribes of Southern
Africa; as it keeps well, a particularly useful food item.
This is an enormously productive plant where conditions suit it. An
estimated annual harvest of between four and five million kilograms
(approximately
4,000-5,000 tons) is taken from Wular lake, Kashmir. The lakeside
population
of around 30,000 humans live almost entirely on this food for five
months
of the year.
Archaeological evidence shows water chestnuts were used by
prehistoric
lake dwellers in Switzerland. This familiar and rich resource was
doubtless
exploited heavily as ancestral humans migrated through river valleys,
across
deltas and along lake shorelines on our radiation out of Africa.
From time to time, as climate changed in the distant past, rainfall
patterns changed, lakes filled with sediment, and temperatures dropped.
Water chestnuts and water lilies declined and then disappeared, and
their
place was taken by sedges (Cyperaceae family) and bulrushes (Typha
sp.), which are well adapted to cooler temperatures.
Typha sp. 'Bulrush'
Bulrushes ('cattails') in general are plants of marshes, swamps,
shallow waters, and wet ground. They are about as tall as an , and
one form of the most common species, T. latifolia forma capensis,
is common in marshlands throughout south west Africa. The species
itself,
T.
latifolia, is widespread in North Africa, and the whole of Eurasia.
In many parts of Europe it is regarded as a weed. The bulrush is a very
valuable plant. The root (rhizome) that grows in the mud is full of
starch
(about 30%) by autumn. Native people everywhere collect the
approximately
30cm/12 inch long roots, dry them, and pound them to release the
starch,
which can then be formed into cakes, flat bread, porridge, or whatever
(the roots also contain a small amount-about 8% - of protein). The new
spring sprouts from the roots are eaten raw, baked or boiled. Young
green
flower stalks can also be eaten, raw or cooked, and are said to have a
flavor "suggestive of olives and artichokes" (Ferdinand et al, 1958).
The
bright yellow pollen itself is highly nutritious - it contains about
19%
protein, about 18% carbohydrates, mainly sugars such as glucose and
fructose.
The pollen has about 1% fats, and while I have not seen an analysis of
the pollens fatty acid constituents, the fat component of the
actual
seed
when it forms is predominantly linolenic acid, an 'omega-3 fatty
acid,
and glycerides. Which may perhaps be suggestive of a good
omega-3
content in the pollen. Tribespeople in Asia, America and the Maori
people
of New Zealand have been recorded as using the pollen to make pollen
cakes
or 'bread'. Pima tribespeople of Southwest USA used to make a 'mini
earth
oven' and bake a pollen and water paste (on leaves, over hot ash, more
hot ash on top, then earth sealed to steam/bake). The result was a kind
of sweet 'biscuit'.
The plant as a whole is "said to be rich in vitamin B1, B2, and C",
but I have seen no analysis.
Beyond being a valuable autumn/winter carbohydrate source, and a
good
protein source in Spring, bulrushes are, like the water chestnut (Trapa.),
both enormously productive (estimates of whole plant mass vary
from
6 to 20 metric tonnes per hectare/approx 3 to 10 tons per acre per
year)
and widespread throughout tropical to cool temperate environments. As
with
water chestnuts, we have probably eaten bulrushes throughout the
greater
part of our evolutionary history.
The river beds of coastal South Africa and Botswana's Okavango swamp
both support dense stands of a bulrush-like semi aquatic
plant, Prionum
serratum, whose masses of roots have good supplies of carbohydrate
that, like bulrush rhizomes, can be separated from the fiber by
pounding.
The fresh young rootlets - before they are too fibrous - are also a
good
vegetable in themselves.
Eleocharis tuberosa 'Chinese water chestnut'
When Homo erectus left Africa and radiated into Southern China
and South East Asia (probably at least a million years ago), it would
have
found, and no doubt enjoyed, this crunchy aquatic root. And when H.
sapiens dispersed out of Africa and displaced (no doubt with extreme
crunchy munchy prejudice) H. erectus, we too, will have put
Chinese
water Chestnuts on the dinner mat.
Eleocharis is a kind of rush with one and a half metre long
slender
stems. The edible part is the under-mud corm (a corm is a bulb-like
storage
root). As it's name suggests, the crisp white flesh is sweet and
vaguely
nutty tasting, with chestnut being the best, but not especially
accurate,
approximation for the flavor. It is good either raw or cooked. A
related
species, E. platiginea (sphacelata), was eaten by
Australian
'Ab-original' people.
Phragmites autralis (communis)
'ditch reed', 'water grass'
This grass is common in marshes and watery places in Africa and
Eurasia,
whether tropical or temperate. The roots are edible, as are the seeds
(although
the yield is presumably poor, given the sparse references to it's use
by
indigenous people).
Nymphaea caerulea 'blue water
lily'
This water lily occurs in lakes, pools, ponds and the slower reaches
of rivers throughout Southern Africa. The tubers were collected and
dried
for later use by !Kung bushmen; and some of the Zulu people of South
Africa
historically collected the tubers in the plants winter dormant season
when
water levels were lower. In fact, the water lily tubers were a
winter/spring
staple for these people, and they cooked and ate them as westerners do
potatoes (they don't have to be cooked - some tribespeople in Zimbabwe
eat them raw). The edible seeds provide a late summer bonus - in
crocodile
and hippo free areas...
Other water lilies
The young roots and shoots of the Asian 'prickly water lily', Euryale
ferox, are edible, although not very nice (the seeds are the most
valued
part, as they can be ground into an acceptable flour). But most
important
are the water lilies of the genus Nelumbo. The sacred lotus, N.
nucifera, grows throughout South and Southeast Asia, and,
originally,
in North Africa. The young leaves are used as vegetables, the seeds are
eaten both raw and cooked (the edible seeds are available in Chinese
grocery
stores in the West), and the very large starchy rhizome is eaten raw,
roasted,
boiled, or the starch extracted and used as a flour to make flat
breads,
'cakes', or as a thickener. The roots and seeds of both the white
Egyptian
lotus, N. lotus, and the blue Egyptian lotus, N. caerulea,
are still eaten by indigenous people.
As we expanded into Europe, we ate the seeds and roots of the 'yellow
water lily' (Nuphar luteum), the roots of Nymphaea alba,
the white' water lily', amongst other aquatic and semi-aquatic plants.
The warmer waters of Africa don't just grow starchy tubers and
seeds;
a water plant called 'Cape asparagus', Aponogeton
diastychum, has a flower stalk (as its name suggests) that tastes
somewhere
between asparagus and spinach. But Asian members of this genus do
have edible tubers, and particularly desirable tubers. The tubers of
the
Indian A. monostachyum "are said to be as good as potatoes"[2]
and the tubers of several other Asian species in this genus have been
described
as 'excellent'[2].
TOP
2.
In a woodland and riverine savannah environment
The number of roots and tubers that hunter gatherer and indigenous
tribespeople
have been recorded as eating is so large that only a relative few will
be mentioned here.
The principle is that, as gather hunters, we were able to use every
available food source in whatever environment we were in, or had moved
into. Any edible root or tuber was exploited. Roots and tubers that our
taste buds indicated were toxic either weren't eaten, or were
de-toxified
by grinding and steeping in water, or by heat, or both. Our African and
Eurasian ancestors ate a vast range of plant underground storage organs
that makes our Western food choice of potatoes, sweet potatoes,
carrots,
onions and parsnips look like some crazy minimalist 'fad' diet. Which
in
many ways, it demonstrably is.
One of the most useful starchy roots of dry woodland and some
coastal
areas of both west equatorial and South Africa is the 'native
potato', Plectranthus
esculentus. This tall perennial has long, narrow tubers that store
well, or are fairly readily available when needed. The taste seems to
vary
with local populations, sometimes being described as having a taste
"similar
to sweet potatoes", "similar to parsnips but are an acquired taste
being
rather bitter", "well liked by blacks and Europeans" and "said to be
also
eaten raw".[1]
pages 245, 246. Several other Southern African Plectranthus
species are also edible, with one at least regarded as a delicacy in
its
winter season.
In the extremely arid parts of Namibia, 5-10 tubers of Walleria
nutans, a small arid land plant, made a filling and
satisfying
meal for the indigenous Bushmen families. These golf ball sized tubers
would be lightly baked in the ashes of a fire, and are said to taste
like
boiled potatoes. They can be successfully stored for three months.
Quite a few of the corms, bulbs and tubers our evolving ancestors
ate
in Southern Africa are known to us only as ornamental garden plants.
The
genus Babiana is named from the Dutch 'babanier', which means
baboon,
because the corms of these pretty little flowering plants of Southern
Africa
are a regular food of foraging baboons. Babiana
hypogea is recorded as being eaten by indigenous tribespeople, and
a thick rhizomatous rooted Babiana, the 'baboon root', B.
plicata
was also eaten by human residents of the South African Cape. The
domesticated
'Gladiolus' flower was perhaps better known by our distant ancestors as
a feast for the stomach, not the eye. Roasted corms of the 'edible
sword
lily', Gladiolus edulis, are
said to taste like chestnuts, the 'spiky sword lily', G. spicatus,
was eaten in tropical Africa, and in East Africa the 'Zambezi sword
lily',
G.
zambesiaticus, was a food resource for some of the local tribes.
Pelargonium rapaveum is a
dry land pelagonium with a thick underground tuber, an adaptation to
it's
seasonally arid environment. A writer from earlier this century
reported
that it was roasted in ashes by the peoples of the Bokkesveld. Young
leaves
and buds of other pelargonium species are eaten raw as a vegetable.
In the more desert like arid climate areas plants survive the dry by
storing nutrients and moisture in storage roots -sometimes very large-
deep underground. These underground food and water stores were one of
the
keys to survival in these more unforgiving marginal habitats. It may be
that in the course of human evolution one of the periodic climate
changes
may have made for a much more extensive arid area, with a much lower
carrying
capacity for a human population.
The ability to dig for, and live on, tubers such as those of the
Morama
bean (Tylosema esculentum) may
have been one of the deciding factors in preventing the unwitnessed
extinction
of the human species. This legume produces a large to very large tuber,
which, when eaten young (at about 1kg in weight) is slightly sweet and
pleasant (luckily for it, it is unpalatable when older). The plant is
highly
adaptable to variable rainfall levels, and is present in Southern
Africa
from Botswana south, as well as in South West Africa. Its astonishingly
nutrient density has already been mentioned.
Ethiopia and the Red sea shoreline are both areas where evidence of
human evolution has been found. So it is almost certain that we have
evolved
eating the large succulent roots of Ethiopian asparagus, Asparagus
abyssinicus, which is endemic to both areas. It may be that Homo
erectus feasted on oysters (stone tools have been found embedded in
ancient fossil coral reefs in the region) and asparagus at some times
of
year....mmmm, oysters and asparagus
again...
TOP
3.
Seashore, natural meadow, woodland and foothill environment; temperate,
warm temperate and subtropical
The move out of Africa was a move into different climatic
conditions,
seasonality, and plant ecosystem. As always, we ate all roots that
weren't
too fibrous or small, and all leaves, buds and stems that weren't too
bitter.
While in Southern Africa bulbs evolved as a mechanism to survive the
dry
season, for the most part, in the more temperate areas bulbs evolved to
survive the cold winter. Fleshy roots were a mechanism for plants to
build
up a good store of of plant food in one year (often in the form of
sugars
rather than complex starches), and send up a large and robust flower
and
seed stem the next. A bit like accumulating rocket fuel in one season
for
next seasons supreme effort of launch off. Carrots, parsnips, and
various
other obscure roots which have never been domesticated (caraway roots,
Carum
carvi; earth nut, Bunium bulbocastanum; the North African
'talruda'
B. incrassatum, and many others) follow this pattern.
Wild carrots, Daucus carota, usually have white roots, but
some
wild carrots in Afghanistan have red or purple roots, due to
anthocyanins
and other phytochemicals (including lycopene, found also in tomatoes
and
other fruits). Carotene is a pigment naturally present at low levels in
wild carrots, and this slight presence was amplified thru' selection
for
orange color in the seventeenth century, and the then predominant
purple
(and yellow, derived from the purple) domestic varieties faded from
favor.
Some temperate plants, such as Europe's lesser celandine, Ranunculus
ficaria, were starchy, and provided a useful energy source, albeit
the bulbs are small. Lesser celandine also provides tender new leaves
for
spring salads. A relative, the 'Arctic crowfoot', R. pallasii,
fills
the same dietary spot for Eskimo peoples in the more extreme cold of
Alaska.
While we evolved alongside numerous edible bulbs of the Liliaceae
family
that are present in Africa, and some, especially bulbs of the genus Dipcadi,
are superficially 'onion-like', there don't appear to be any members of
the genus Allium, to which the domesticated onion (and garlic)
belongs,
in Africa. (Although the small bulbs of the fairly widespread 'wild
onion',
Ornithogalum tenuifolium both looks and tastes like the ordinary
onion).
But the story changes as we radiate out of Africa into Eurasia and
South
Asia. Here ran into numerous wild Allium species, tasting like
the
Ornithogalum
we left behind. And from some of these species, the domesticated
onion, garlic, and leek arose.
One of the more widespread onion relatives is giant garlic, Allium
scorodroprasum, a bulbous plant something between an onion and a
leek.
This plant has a wide distribution across Eurasia, and would have been
one of the first Alliums we encountered as we came out of Africa and
radiated
into the Mediterranean and into Central Asia.
Also in Asia are 'Chinese chives', A. tuberosum, valued
mainly
for their leaves and edible flowers, and A. chinense in the
mountains
of central China. Oriental, or elephant garlic, A. ampeloprasum,
is a large cloved, extremely mild form of garlic, if it can be
considered
garlic at all, and possibly the ancestor of leeks. It is a native of
East
Asia. Garlic itself, A. cepa, is unknown in the wild, but it is
thought it may have derived from a species (A. longicuspis)
found
in the foothills of Central Asia.
Although Allium bulbs are not a great energy source - unlike
some of the more starchy tubers and roots - there must be something
about
them that the human species likes, because we have been eating them for
half a million years or more...and they still give us gas! fut, fut....
Liliaceous bulbs may have been a good food source in Africa, but I
haven't
seen any reference to edible members of the actual genus Lilium
there. But once we move out of Africa into Eurasia, we find many edible
lilies. The most widespread is Lilium martagon, growing
throughout
Eurasia. The bulb can be roasted, or dried for future use. This species
grows as far as Siberia, and other edible species, such as L.
dauricum,
L.
spectabile, and L. tenuifolium, are well adapted to to
these
colder climates. They may have been an important factor in helping tide
humans over times of food shortage as we radiated into colder climate
areas.
In subtropical Southern China, Lilium brownii fed us, in
western
China L. davidii, and in Northern China L. leichtlinii
and
L. maculatum.
The number of plants that live in Eurasia that have edible roots,
rhizomes,
corms or bulbs is quite substantial. The range of edible roots in
only one particular climatic and ecological environment has already
been
illustrated above,
with the notes
on the food plants of the North American Paiute tribespeople. This
range
is not unique to that environment, or to the North American continent.
It is to greater or lesser degree typical of most parts of the world,
including
Eurasia.
TOP
Plants
have
compounds to discourage eating
Plants weren't 'put here' for our benefit. They are as likely to be
'harmful' (a humancentric view!) as 'useful' . Obviously, plants don't
'want' to be eaten, so various bitter, acrid, soapy, or toxic compounds
are sequestered in the leaves and stems to dissuade browsers. Primates
have learned over the course of evolution to become finely tuned to the
times in a plants life cycle when they are most palatable.
Baboons, for instance, are highly selective about what they
eat.
A study of their eating pattern found that the vegetation in the study
area was changing almost every two weeks, with different fruits
and pods ripening, new plants flowering, or sprouting. But invariably,
the researchers found that the baboons would highly selectively only
feed on the the most nutritious part of the most nutritious plants.
The human animal was no less tuned into the seasonal environment.
The
particular advantage we had - and still have - is that we are able to
use
'culture' as a tool to pass on techniques to exploit plant food
resources
that would otherwise be unavailable to us. We do this by removing some
of the unpleasant compounds in the plant.
A variety of techniques are used by indigenous people to reduce or
eliminate
the bitter or acrid components that are common in leaves and roots (our
first technique, of course, is to select only those plants naturally
low
in such unpleasant compounds).
The simplest technique is to choose only the youngest and fastest
growing
plants, and, if necessary, only the youngest leaves of the young plant,
which are least likely to have a build up of bitter and unpleasant
compounds.
The African 'sow thistle', Sonchus integrifolius has, like
other
members of the genus, a bitter latex or 'milk' in the stems and leaf
veins,
but young plants are palatable, if still somewhat bitter.
The Maori people of New Zealand eat the related 'Puha', S.
oleraceus,
an introduced weed native to North Africa and Eurasia. The very
youngest
and tenderest plants are cooked, but as the plant ages it is necessary
to bruise the leaves and stems, and then wash them to remove the latex
before cooking. The older the plant becomes, the more processing is
required.
Some plants can have the bitter or dangerous parts removed by
leaching
in running water. There are half a dozen or so edible 'yams', genus Dioscorea,
in Central and Southern Africa. They are found in a variety of
ecosystems
in Southern Africa, for example; from dry savvanah forests, scrublands,
and forest clearings, to moist forests. Other edible species are also
in
West and East Africa, and throughout Eurasia and South East Asia. There
are even two edible species in Southern China that grow in the
mountains
up to about the 7,000 foot mark.
A few are 'sweet', having effectively no toxic compounds, and are
quite
palatable to most people; most others have a variety of chemicals,
which,
if not leached out, can, at the least, make you nauseous, and at the
worst,
cause paralysis of the lower limbs and other nasty effects. But once
well
leached and cooked are usually fine. Others have to be soaked with
ashes
before they are leached. Unsurprisingly, these more dangerous species
of
Dioscorea
are well down the hierarchy of preferred foods.
Some vegetables are soaked, then boiled. If older leaves are a bit
tough
- for example Vigna leaves - ash (an alkaline substance) is added to
the
water to tenderize them. They are sometimes left in the sun to reduce
the
bitterness.
And fire itself is a useful tool for de-naturing some chemicals,
making
an otherwise unpleasant food palatable.
One of the reasons we eat so many different species of vegetable in
the wild is that we have to stop eating a given species of plant
when it becomes older and unpalatable. In other words, we were
forced
to eat widely. Extremely productive, non bitter plants that had
spring,
summer, and winter harvests and were enormously productive -
particularly
bulrushes, Typha sp.- were very much the exception, not the
rule.
What is surprising is that we eaten of so wide a range of plant
families
with bitter, unpleasantly 'sharp', and probably slightly toxic chemical
constituents throughout the course of our long evolution.
One of the more intriguing aspects of our relationship to plants is
the idea of some foods being 'medicine'. As one scientist observes-
"Several chemicals that have been shown to be carcinogens at
high
doses in rodents have also been shown to be
anticarcinogens in other animal models at
lower doses, e.g., limonene, caffeic acid, dioxin, indole carbinol.
Therefore, the dose and context of a
chemical
exposure may be critical." (my emphasis)
The old adage about there being 'a fine line between pharmacology
and
toxicology' applies. Wild living humans had an extensive knowledge of
the
'medicinal' qualities of plants. Some were minor foods, some were
'medicinal',
and sometimes the line may have been blurred. But no doubt there was an
acute awareness of the dangers of certain plants at certain stages of
growth,
when it was 'safe' to eat them, and which were never safe.
After
all, the penalty for being wrong ranges from acute abdominal distress
to
death.
The most heavily consumed tuber in modern times is the potato, Solanum
tuberosum. While we have encountered members of the solanum family
all through our evolutionary history, we can't say we have become
'immune'
to some of their damaging self protective chemicals, such as the toxic
'solanine' in potatoes. Very high doses, such as are found in green
potatoes
- and especially green potatoes with skin damage - can be fatal. But,
again,
we are 'tuned in' to soapy and bitter and acrid substances. They are
unpleasant.
By the time we have leached them in water, denatured them with heat,
then
the small amounts of toxins left can be dealt to by our liver. It is a
testament to our discriminatory powers that only 30 people are recorded
as having died from eating green potatoes in this century. No doubt
both
desperate circumstances and youthful carelessness played a part in many
of these deaths. Human, the learning animal, has also learnt, during
domestication,
to select and re-select plant with lesser amounts of toxin than occur
naturally.
We can do it. Other animals
can't.
TOP
Modern
selective breeding - are domesticated plants 'better', 'worse', or
essentially
no different?
In the wild, selective breeding tends to happen in reverse - at
least
from the human point of view. All animals tend to favor the most
pleasant
and palatable of plants (even grazing animals like cattle and sheep are
quite selective), and so these individuals in the plant population tend
to be eliminated from the breeding stock. The most unpalatable
individuals
tend to be left to pass on their 'unpleasant eating' genes. That, of
course,
is evolution at work.
With the evolution of culture, part of which is agri-culture, we
very
quickly learned to 'keep the best' for replanting. Suddenly, selective
pressure was thrown into reverse (from the plants 'point of view') and
only those plants with the least amount of nasty, bitter, or
toxic
chemicals survived to pass on their genes.
So while our liver, our organ of detoxification, had to be able to
some
degree deal with a very wide array of low doses of toxic plant
chemicals
in its evolutionary journey, it now finds itself on a permanent holiday
(or it would if not for alcohol and 'never in our evolution
encountered'
man made environmental chemicals). Modern selections of the few plants
we eat generally have much lower concentrations of unpleasant
plant
chemicals than the wild forms.
This is a tremendous advantage, because we can now eat far more
vegetative material than our ancestors and still not reach the level of
possibly toxic plant chemicals intake that our ancestors livers would
have
been daily challenged with. The great irony is that most Westerners
actually
now eat only a fraction of the amount of vegetable matter we
ate
as a wild living animal (not the number of kinds, altho' this is also
true,
but probably irrelevant).
However, lowering the amount of 'bitter principals' in the
plants
we have happened to domesticate can be taken too far. Part of the
chemical
composition of Brussels sprouts, for example, is a chemical called
'sinigrin',
whose breakdown product is 'allyl isothiocyanate', and causes the
rather
strong smell of sprouts. Which is bad. The allyl isothiocyanate has
been
shown to destroy pre-cancerous cells colon cells - scientists suspect
that
occasional meals of brussels sprouts exert a powerful anti colon cancer
effect. Which is good. Scientists are interested in breeding sprouts
with
lower
levels of sinigrin so they are not so bitter, and so more people
eat
them. But is that good or bad?
In some cases, protective chemicals can be enhanced without
enhancing
bitterness and unpalatability at the same time. For example, another
isothiocyanate
is 'sulphoraphane', which also has powerful anti-cancer effect (by
stimulating
the body's 'phase II enzymes' to block the cancer). Fortunately,
sulphoraphane
doesn't cause an unpleasant taste, so it is a candidate for 'ramping
up'
for its protective effect. Broccoli is an excellent source of
sulphoraphane,
but the amount present varies with the particular variety. The variety
'Trixie', for example, has 150 micromoles per gram of plant, whereas
'Emperor'
has about 70 micromoles per gram of plant. By going back to the wild
seaside
cabbages our distant ancestors ate, scientists hope to find and
introduce
genes for higher sulphoraphane content. (Broccoli is a derived form of
the wild sea cabbage.) Recently (year 2000), they have succeeded. A
wild
Sicilian Brassica species has been crossed with broccoli to
develop
breeding lines with up to 100 times the sulphoraphane content
of
existing broccoli varieties, and with unchanged palatabilty!
At days end, modern vegetables are more palatable, less woody, have
lower oxalic acid, and in general, are pleasanter to eat. On the other
side of the ledger, some vegetables, such as cabbage, are not as deep
green
as their wild precursors, may have reduced amounts of protective
chemicals,
and suffer loss of nutrients in storage - but that is a different
issue.
Only cauliflower can be fairly said to be inferior to its wild
progenitor.
The white 'curd' contains only a few micrograms of vitamin A - a big
difference
from the ancestral cabbage. But plant breeding can change this.
Recently
a cauliflower has been bred with orange heads, and good amounts of beta
- carotene. What humans have done, can be undone.
We may have a dramatically reduced inventory of species to eat, but
we have a dramatic increase in availability year round, and some of our
domesticates are absolutely outstanding in their nutritional and
protective
profile.
It is actually difficult to compare the nutritional profile of very
recent industrial, domesticated vegetation and the other, wild
vegetation
we evolved with and once ate. The reason is that very few analyses have
been done on our evolutionary diet, because we have abandoned it in
large
degree. And because we no longer (or very rarely) eat these
plants,
there is little point in studying them.
Certainly, when fresh samples (uncooked) of leaves of wild plants
are
analyzed for vitamin A and C, there are good results-
Vitamin A/100gms
Vitamin C/100 gms
Spinach, fresh leaves (uncooked) for
comparison
6,715
IU
28
Blue Violet, Viola papilionacea
15,000
IU
130
Goosefoot, Chenopodium album
14,000
IU
130
Ground Ivy, Glechoma hederacea
14,000
IU
44
Garlic mustard Sisymbrium alliaria
12,000
IU
190
Ox eye daisy, Chrysanthemum leucanthemum
12,000
IU
23
Moringa tree, Moringa oleifera*
11,500
IU
134
Plantain, Plantago major
10,000
IU
19
Shepherd's purse, Capsella bursa-pastoris
5,000
IU
91
Judas tree, Cercis canadensis
-
75
Overground plant, Portulaca oleracea
6,100
IU
26
Adapted from 'Ascorbic Acid and Vitamin A
Content
of Edible Wild Plants of Ohio and Kentucky'.
*From CRC Handbook of Tropical Food Crops by Franklin
W. Martin. 1984
But again, we have to look at palatability. Its easy enough to eat
100
grams of spinach, but not so easy to eat 100 grams of plantain. And a
lot
also depends on the stage of growth of the wild plant - younger equals
more palatable. And, younger plants often have a higher
concentration
of vitamins. For example, the basal leaves of the Blue Violet, Viola
papilionacea, have 15,000 IU of vitamin A and 130mg/100 grams
vitamin
C in a mature plant; but in early spring, when they are tender and more
palatable, they have 20,000 IU of vitamin A and double the
vitamin
C content!.
Domesticated plants are always presented at their maximum
palatability,
so they are likely to be at their most nutrient rich at the point of
sale;
albeit storage does reduce the levels somewhat. Fresh is definitely
best,
but canned and frozen is powerfully good as well. The trend to 'bump
up'
both the protective phytochemicals and the vitamin content of
vegetables
through breeding is a fairly small one, but it will probably continue.
Even without 'beefing up', it is crystal clear that eating vegetables
is
vital to long term well being and prevention of
disease.
TOP
Benefits of veggie eating
The more science studies even the very few vegetables that western
humans
do eat -let alone the huge array of vegetables that we actually
evolved with, of which most researchers are entirely ignorant - the
more
evidence we find that they are essential to preventing disease and
maintaining
a state of well being. The more researchers look, the more they find.
The
antioxidant levels in some edible but wild species may greatly exceed
our
domesticated stars-
"Although wild edible plants of the western Sahel and other parts
of sub-Saharan Africa are consumed to some extent at all times of the
year,
greater amounts are consumed when cereal harvests are insufficient to
support
the populations living in these areas. The purpose of this study was to
use a recently reported Trolox-based assay to measure the total
antioxidant
capacity of aqueous extracts of 17 plants that we gathered from
southern
Niger. The antioxidant contents of the aqueous extracts were compared
to
those of spinach and potato. Of the 17 plants, 11 had a greater
antioxidant
content than spinach and 14 had a greater antioxidant content than
potato. The leaves of Tapinanthus globiferus had the greatest
antioxidant
content, and the fruit of Parinari macrophylla had the lowest. In
general,
leaves contained more antioxidants than either fruits or seeds. The
total
antioxidant capacity of the aqueous was relatively high, indicating
that
the wild plants of the western Sahel may contain substantial amounts of
water-soluble flavonoid glycosides, which are potent antioxidants and
have
been shown to have anticancer properties."
-Cook J A, VanderJagt D J, Dasgupta A, Mounkaila G, Glew R S,
Blackwell
W and Glew R H .1998. 'Use of the Trolox assay to estimate the
antioxidant
content of seventeen edible wild plants of Niger'. Life Sciences,
63(2):
106-110
While we could just take pills with protective phytochemicals
in them, it is quite likely that the wide variety of chemicals in
plants
interact to produce a greater health benefit than adding up the health
benefit of each identifiable chemical would indicate.
The studies pile up one after the other, almost ad nauseum.
We
can't be surprised that a good part of the answer is to eat as
evolution
has fit us to eat - eating vegetation of all kinds, and not just
selecting
those we find most palatable. Hunger was ever present in our
evolutionary
past, and we had much less chance to 'pick and chose'. Especially women
and children, who were likely to be the last fed, or may well have had
to find a good portion of their own food, as well as extra for 'the
boys'.
Anyway, here is but a sampling of the often 'reductionist' studies
on
the health benefits of vegetables, and/or the risks we take by not
eating
them-
After reviewing 156 studies of fruit and vegetable intake and its
relationship
to cancer risk, a University of California scientist determined that
128
of these studies supported the protective effect of beta-carotene-rich
foods.[4]
"Many large-scale studies have shown that folic acid plays a
significant
role in prevention of neural tube defects, such as spina bifida, which
occur when a segment of the spinal nerve cord grows outside the
bony
spiny column."
In the last 20 years there have been more than 3000 research studies on
the health effects of garlic. Mercifully, I will only mention a few
here-
While previous studies have been designed in such a way that they have
unwittingly created the false perception that you would have to eat
many
kilograms of raw garlic to gain sufficient of the active phytochemical
'diallyl disulfide' to have an anti-cancer effect, a recent study shows
that eating as little as half a clove of raw garlic, or if it
is
cooked, about four and a half cloves, may gain you meaningful
protection
against bowel cancer. The diallyl disulfide in these modest intakes of
garlic were shown to induce the production of protective enzymes by
between
20% and 60%.
Australia's Center for Research in Vascular Biology has shown that
garlic
inhibits the build-up of heart disease causing 'plaque' on artery walls.
" Japanese scientists working with cultured cells suggest that at least
some of the carotenoids (such as the beta-carotene in carrots) fight
cancer
cells by effectively putting malignant cells to sleep and suppressing
the
expression of a gene that might otherwise promote tumor growth". -
Science
News.
"The antioxidant potential of Beta-carotene and lutein, carotenoids
with
or without pro vitamin A activity, respectively, was evaluated using
the
human liver cell line HepG2.[ and then exposed to a chemical oxidant] Carotenoid-loaded
cells were partially or completely protected against oxidant-induced
changes
in lipid peroxidation, LDH release and amino acid and
deoxyglucose
transport. These data demonstrate that Beta-carotene and lutein or
their metabolites protect HepG2 cells against oxidant-induced damage
and
that the protective effect is independent of pro vitamin A
activity."
Lutein, a carotenoid with antioxidant properties has been shown to
inhibit
the growth of mammary tumors in experimental mice.
A USDA study found a low carotene diet (few fruit and vegetables)
compromised
immune function in otherwise healthy female humans.
A University of Nebraska study showed that that the blood cholesterol
levels
of rabbits on a high cholesterol diet could be pushed down by giving
beta-carotene.
Japanese scientists have shown in animal studies that the carotenoid
lycopene
apparently normalizes the immune function in animals with
experimentally
induced tumors.
Rats fed a diet that included the rat-sized equivalent of a large
spinach
salad showed that as they approached rat old age, their memory for maze
solving was better than non-spinach eaters, and they had better
movement
control. This is thought to be the result of the spinach (and by
extension
other greens) "retarding age-related central nervous system and
cognitive
behavioral deficits", according to the researchers.
A high blood level of the amino acid homocysteine is believed to be a
strong
risk
factor for heart disease. "Extensive research has shown that heart
disease
and stroke patients often have levels that are 50 to 100 per cent
higher [than the normal10-12mmol/L)... Homocysteine levels increase
with
age and are usually higher in men. High homocysteine levels are
believed
to be caused by low levels of folic acid and vitamin B12 ...High
homocysteine levels can be normalized by supplementation with vitamins
B6, B12 and folic acid..." Geriatrics, April 1999
The study of 34 middle-aged women found that brief periods of stress
increased
blood levels of homocysteine, an amino acid byproduct of the breakdown
of animal protein that is normally broken down in the bloodstream by
folic
acid and the B vitamins . “People who have deficiencies in folic acid
and
the B vitamins have higher sustained levels of homocysteine and
are
at increased risk for cardiovascular disease” -Dr. C. Stoney,
Ohio
University.
Naturally occurring flavenoids in vegetables (and fruits) have been
shown
to 'spare' the bodies vitamin E. Flavenoids are suspected to act as
antioxidants
and consequently reduce the 'consumption' of vitamin E in protecting
cell
membranes.
The natural plant chemical 'lycopene' when present in the bloodstream
has
been shown to protect low density lipoproteins (LDL) from oxidation,
the
oxidised
('rancid') form of this lipoprotein being suspected as a major cause of
arterial artery disease.
In a randomized prospective clinical trial, 15 milligrams of Lycopene
as
a pure tomato extract was administered for 3 weeks prior to surgery to
remove the prostate gland due to localized cancer. After surgery, the
lycopene
group proved to have smaller tumors that showed signs of regression and
decreased malignancy.
Epidemiological studies have shown an association between the
consumption
of tomato products and decreased risk of prostate cancer. However, the
studies to date that have shown protective effects are said to have
been
flawed in that they did not control for total vegetable consumption.
Vegetables
in general are protective against prostate cancer, and 5 studies on the
protective effect of tomato lycopene have found no protective effect
against
prostate cancer.
Eating three servings of vegetables a day can cut a man's risk of
prostate
cancer nearly in half, the strongest effect being for cruciferous
vegetables (broccoli, cabbage, cauliflower, brussels sprouts, mustard).
Journal of the National Cancer
Institute Jan 5, 2000.
"The bottom line is that if you eat a lot of vegetables, you
can
cut your risk of prostate cancer by about 45
percent," says Alan Kristal, Dr.P.H., co-investigator of the
study. "And, if some of those vegetables are from the
cruciferous family, like broccoli and cabbage, you may reduce
your risk even further. At any given level of total vegetable
consumption,
as the percent of cruciferous vegetables increased, the prostate-cancer
risk decreased"
An analysis of 72 studies looking at the association between
consuming
tomatoes and tomato based products concluded that " high consumers of
tomatoes
and tomato products are at substantially decreased risk of numerous
cancers, although probably not all cancers." The data are most
convincing
for cancers of the prostate gland, lung and stomach, and weaker but
suggestive
of protective against pancreatic, colorectal, oesophageal, oral, breast
and cervical cancers.
Mouse studies have shown that lutein in the diet helps protect against
formation of lesions in the aorta.
A study by researchers at Cambridge University in 1996 found the
level of lutein and other carotenoids in the blood of people in
Toulouse,
France, was higher than that of people in in Belfast, Ireland. Toulouse
has a low rate of heart disease. Belfast has one of the highest rates
of
heart disease in the world.
A study from the University of Wisconsin-Madison on two 'isoprenoids',
from a group of around 22,000 naturally occurring plant chemicals
derived
from mevalonic acid, demonstrates they inhibit three types of human
cancer
cell lines - at least, in the laboratory. The importance is that they
do
this at concentrations obtainable by following a diet that includes
plenty
of vegetables and fruit. That is, a diet natural to the human animal.
One
of the compounds, beta-ionone, is related structurally to beta
carotene,
and is widely found in vegetables and fruit. Beta-ionone was shown to
suppress
the growth of laboratory cell lines for human leukemia, breast cancer,
and human colon cancer. "Our studies showed that cancer cells were more
sensitive to these compounds than normal cells and that the two
compounds
had a stronger effect when combined than we would have expected from
the
action of either alone. These compounds act as a group to inhibit
cancer
growth with some enhancing the effectiveness of others. Our findings
strengthen
the idea that a diet rich in plants is beneficial because of the large
array of plant compounds rather than the singular action of one
kind
of plant or one compound in plants." - Charles Elson, nutritional
scientist,
University of Wisconsin-Madison.
A test, known as 'oxygen radical absorbance capacity', or ORAC,
measures
the ability of a given food to 'scavenge' and neutralize damaging free
radicals free radicals in the body. A USDA study at Tufts University
tested
the effect of doubling the intake of fruit and vegetables normally
consumed
by a group of men and women, between ages 20 to 80. Although the
test subjects had already been eating five plus serving of fruit and
vegetables
a day, in line with 'government' recommendations, doubling the intake
to
ten servings resulted in the blood levels of antioxidant, as determined
by the ORAC test, also almost doubling.
Women given 280 grams/10 ounces of fresh, raw spinach pushed their ORAC
score higher than when they took a massive 1.250 grams (1,250 mgs) of
vitamin
C (a powerful antioxidant).
Vegetables held retain stronger bones. Vegetables and fruits have
been shown to decrease the amount of calcium excreted in the urine.
Vegetables
and fruit as as an 'alkaline buffer' neutralizing acids produced when
fish
and meat are digested. These acids would otherwise tend to increase the
amount of calcium lost in the urine -sufficient fruit and vegetables
consumption
neutralizes this effect. [Appel et al.
1997].
TOP
Antioxidants in vegetables
As you can see, vegetables contain compounds that are valuable
antioxidants
and protectants.
Chief among these are the carotenoids. There are over 600
carotenoids
in plants and in some animals (pink salmon is pink because of the the
carotenoid
'astaxanthin' it contains). Only some - mainly beta-carotene- are
precursors
to vitamin A production by the body. The carotenoids not destined to be
converted to vitamin A and unconverted beta-carotene are present in our
tissues in very small amounts. The main carotenoids in human tissues
eating
a western diet are beta-carotene, alpha-carotene, lycopene, lutein,
zeaxanthin,
and beta-cryptoxanthin.
Lycopene has the greatest antioxidant properties,
beta-carotene
and cryptoxanthin has the next greatest activity, then lutein and
zeaxanthin.
One very useful measure of the protective antioxidant
potential
of a vegetable or fruit is to measure its ability to absorb damaging
oxygen
radicals. These free radicals are implicated in aging, especially
memory
loss and loss of co-ordination, and degenerative diseases. This does
not
measure the activity of specific protective phytochemicals that may use
other
biochemical pathways to inhibit tumors or protect blood vessel walls,
for
example. It does give us a way to measure one element of the
relative
health 'usefulness' of a vegetable, without having to understand which
natural plant chemical, or combination of chemicals acting together,
are
responsible for the effect.
From the measurements of various vegetables so far, scientists
estimate
that a single serving of fresh or freshly cooked vegetables has, on
average,
300 to 400 'ORAC units'. But some specific vegetables-such as garlic
and
kale-have particularly high antioxidant levels. A single garlic clove,
which weighs around 5 grams, has around 100 ORAC units - a massive
contribution
in a small package (it is interesting to note the annual garlic
consumption
per person in the USA is 900 grams/2 pounds, where in Asia it is supposedly
more like 23kg/50 pound per person - about 12 cloves a day!). But even
a small - 30 gram (about 1 ounce) - serving of carrots, much lower on
the
ORAC scale, just about matches a clove of garlic for oxygen radical
absorbance
capacity.
Oxygen radical absorbance capacity of some vegetables, per 100
gram
in 'ORAC units' (approximately rounded to the nearest 50)
Garlic, Allium sativum (note:100 grams of garlic is about 20
cloves!!).....2,000
Kale, Brassica oleracea var. acephala..................................................1,800
Spinach, Spinachia oleracea..................................................................1,300
Brussels sprouts, B. oleracea var. gemmifera........................................1,000
Alfalfa sprouted seeds (sprouts), Medicago sativa.....................................950
Broccoli, B. oleracea var. italica...............................................................900
Beet, Beta vulgaris...................................................................................850
Red Pepper, Capsicum annuum...............................................................700
Onion, Allium cepa...................................................................................500
Sweetcorn, Zea mays................................................................................450
Eggplant, Solanum melongena..................................................................400
Frozen peas, Pisum sativum.....................................................................400
Potato, Solanum tuberosum.....................................................................300
Sweet potato, Ipoemea batatas................................................................300
Cabbage, B. oleracea var. capitata...........................................................300
Lettuce, leaf, Latuca sativa.......................................................................250
Carrot, Daucus carota..............................................................................200
Green bean, Phaseolus vulgaris................................................................200
Tomato, Lycopersicon lycopersicon..........................................................200
Yellow squash ?courgette type ?Cucurbita pepo.......................................150
Lettuce,
iceberg/crisphead.........................................................................100
Celery, Apium graveolens........................................................................100
Cucumber, Cucumis sativus.....................................................................100
Adapted from [6]
Beyond anti oxidant activity, it is suspected that some carotenoids,
such
as lutein (found in dark green leafy vegetables), can act as an
immuno-stimulant,
perhaps influencing immune cells at the gene level. Lutein, in
particular,
is believed to be able to increase the density of the macular pigment
in
the eye and maybe reduce the risk of 'age related macular
degeneration'.
A good reason for parents to eat their greens, too.
There are other phytochemicals with helpful effects. The cancer cell
destroying properties of allyl isothiocyanate in brussels sprouts has
already
been mentioned. As usual, the more we look, the more we find. But most
of us have heard that vegetables 'are good for you' because of the
vitamins
and minerals they
contain.
TOP
Vitamins & minerals
Vegetables are important to get enough vitamins for health. They are
particularly important as a source of vitamin A, vitamin C, and
folate
(folic acid, folacin). These three are the 'biggies', but most
vegetables
are a 'good' source of thiamine (B1), potatoes and green leafy
vegetables
are rated a 'good' source of riboflavin (B2), and potatoes, broccoli,
cauliflower
and tomatoes are a 'good' source of pantothenic acid (B5). Pyridoxine
(B6)
is important in brain function, immune system function, and as a
precursor
to several important hormones. All the brassicas are rated a 'good'
source,
as are potatoes, spinach, peas, carrots, watercress, and onions. Many
vegetables
contain small but useful amounts of vitamin E. Vegetables are generally
very good sources of most minerals (with the exception of iron). Tubers
and roots as an energy source aside, it is the protective
phytochemicals
and the vital vitamin C, vitamin A, and folic acid content that make
vegetables
essential to human well-being. Vegetables are genrally a good source of
calcium, and green beans, in particular are a good source. There are
differences
between green bean varieties - the variety 'Hystle' has nearly double
the
amount of calcium as the variety 'Labrador'. It is likely that
scientists
will work to breed enhanced mineral and vitamin content in the future.
Folic acid
The word 'folate' is derived from the latin 'folium', a leaf
- a pretty good clue to its high concentration in green leafy
vegetables.
Many nutritionists believe that folate deficiency is one of the most
common deficiencies in the West. Deficiencies in pregnant women have
been
linked to particular forms of birth defects. This is because folate is
involved in enabling normal cell multiplication for growth and
development.
Folate deficiency means red blood cell production is reduced, resulting
in fatigue; white blood cell production is slowed, making us more
susceptible
to infection; in fact many tissues are affected to greater or lesser
degree
when folate is lacking. Even highly conservative government nutritional
advisors have become concerned enough to allow folic acid 'enrichment'
of the isolated carbohydrate extracted from whole grass seeds ('white
flour').
Folate is water soluble, and reduces in amount in storage.
Folate is stored by the body, so you have to wonder why deficiency
could
arise at all.
The answer is partly that folate is water soluble, and can be thrown
out when vegetables are boiled-raw cabbage 90 micrograms per 100 grams,
boiled cabbage 35 micrograms per 100 grams.
Add to that the losses in storage, and the fact that folate is
damaged
to some degree by heat.
But the real answer can be gleaned from the following list
of
folate rich foods.
The richest sources [1]
are:
wheat germ...................330 micrograms/100 grams
raw endive ...................330 micrograms/100 grams
bran flakes ...................260 micrograms/100 grams
liver .............................240 micrograms/100 grams
watercress ...................200 micrograms/100 grams
Spinach .......................115
micrograms/100
grams
parsley ........................116 micrograms/100 grams
Broccoli ......................110 micrograms/100 grams
Swiss chard/Silverbeet....92 micrograms/100 grams
raw cabbage ..................90 micrograms/100 grams
brussels sprouts..............87 micrograms/100 grams
(cooked) frozen peas .....78 micrograms/100 grams
How many have you eaten recently? Most of us will have eaten none or
very little of the very richest folate sources (200 micrograms
upwards).
Most of us probably eat two or three of the relatively rich
foods,
such as broccoli or raw cabbage, most days. (Or do we? A nutritional
epidemiologist
at the University of California tells us that "today, fewer than 9
percent
of Americans eat the recommended five daily servings of fruits and
vegetables".
This figure would be typical for most Western countries outside
continental
Europe.)
If we list the vegetables that we are actually likely to eat
at least 100 grams of, then our 'rich list' is:
watercress...................200 micrograms/100 grams
spinach........................115 micrograms/100 grams
broccoli.......................110 micrograms/100 grams
Swiss chard/Silverbeet ..92 micrograms/100 grams
raw cabbage..................90 micrograms/100 grams
(cooked) frozen peas.....78 micrograms/100 grams
If we marry this data with the ORAC (oxygen radical absorbance
capacity)
data, we get, im my opinion, this 'stellar' list*:
spinach
broccoli
frozen peas (cooked)
* there is no ORAC data for watercress or Swiss chard, so this list
is not entirely accurate. Watercress is a cruciferous plant, and is
likely
to score high in an ORAC list. Swiss Chard is botanically beetroot,
which
scores high in ORAC and may also score high in an ORAC list (altho' the
red anthocyanins in beetroot root may be the determining factor).
The Recommended daily intake of about 200mcg for an older child and
will be met by half a cup of cooked fresh spinach
(130 mcg), an orange (37mcg), and half an avocado (33 mcg) eaten during
the course of a day.
Probably the commonest green, lettuce, has variable amounts of
folate.
According to the USDA reference data, half a cup of lettuce has about
15
mcg if it is the rather pallid but very crisp 'iceberg' type, 20 mcg if
it is the soft boston/bibb/butterhead type, and a surprisingly small 14
mcg for half a cup of shredded dark green leaf lettuce. (Iceberg
lettuce
has a very low ORAC score, where leaf lettuce has double the ORAC
score,
but is still low.) But given that lettuce is so frequently eaten, it
makes
a contribution greater than it's fairly modest folate content would
suggest.
Pregnant and lactating women are advised by nutritionists to make
sure
they take in twice this amount. It is hard to see how these women could
be achieve the minimum RDA without either eating heroic amounts of
spinach,
frozen peas, and broccoli; or eating about a cup of raw peanuts; or eat
200 grams/ 7 ounces of liver every day...or a combination of these
three
high folate
foods.
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Vitamin C
We lost the ability to synthesize our own vitamin C early in our
evolutionary
history. While there is almost no information on the vitamin C content
of the plant foods we ate in the course of our evolution, there is
some data for the domesticated versions of the small range of plants we
eat in the industrial west. We are able to store vitamin C in our
bodies
for around 3 months - just long enough to see us through the dry
season,
or the winter in temperate climates - with small top-ups from tubers
and
dried fruits, of course. In sub tropical and tropical areas, young
palatable
vegetation is pretty much always available, so storage is not such an
issue.
Figures are for half a cup, unless
stated
otherwise
Red ripe sweet pepper (one, medium size)......................226 mg
Broccoli,
cooked..............................................................58
mg.
Brussel
sprouts.................................................................48
mg
Sweet potato,
baked........................................................25
mg
Cabbage, shredded,
raw..................................................16
mg
Watercress,
chopped.......................................................15
mg
Potato, baked, one
medium..............................................12
mg
Green pea, frozen,
boiled....................................................8
mg
Spinach,
boiled...................................................................8
mg
Cowpea (Vigna unguiculata) chopped, boiled leaf tips......5
mg.
Lettuce, looseleaf,
shredded...............................................5
mg
Lettuce,
butterhead............................................................3
mg
Carrot, slices,
boiled..........................................................2
mg
Again, if we marry this data with the ORAC (oxygen radical absorbance
capacity)
data, we get this 'stellar' list
red ripe sweet pepper
broccoli
Brussels sprouts
sweet potato
The other major contribution that vegetables make is vitamin A; or
rather,
the building blocks from which your body can construct vitamin A.
Plants
are full of natural pigments called carotenoids, generically referred
to
as vitamin
A.
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Vitamin A
is a loosely used term for retinol and beta-carotene. Retinol
'is' vitamin A, and is obtained from fish liver oils, liver, eggs, and
butter and cheese. Very large amounts of retinol are potentially toxic.
Vitamin A is concentrated in the liver of all animals, and the very
highest
concentrations are in the livers of carnivorous animals. Eating polar
bear
liver is definitely not advised. Eating cows liver definitely is advised.
Carotenes in general, and beta-carotene the most common, are
obtained
from plant foods. Beta-carotene is a precursor of vitamin A
(its
sometimes called 'pro-vitamin A'). Beta-carotene is converted to
vitamin
A by the body. Because the rate at which beta-carotene is converted to
vitamin A in the body is known, most often vitamin A content of foods
is
quoted as 'actual' vitamin A (retinol) - generally the number of
micrograms
per 100 gram sample - and the micrograms of beta-carotene are
converted
into International Units of vitamin A (by multiplying mcg of
beta-carotene
by 1.6). Beta-carotene is non toxic under most circumstances. In
fact, the body has a mechanism whereby it can regulate the absorption
of
carotenes (although absorption is generally rather low anyway - maybe
around
the 15-35% range). For raw carrots, for example, only around 1% of the
carotene present in the carrot ends up being absorbed. This rises -
variably
- to maybe 19% when the carrot is cooked. In spite of the fairly low
rate
of conversion, carrots alone provide 30% of the vitamin A in
the
USA diet. This is a marker of both how few kinds of vegetables we
westerners
eat, and how influential cultural practices are - as either gateways,
or
barriers to health. Even how a food is prepared, or how
it
is cooked influences its vitamin A value.
Fats in a meal improve the conversion of | |
