July 16, 2000
Raw vs Cooked
Raw food enthusiasts have always been a part of the vegetarian/vegan
scene. Their core idea is that enzymes are still active in raw food
whereas they're denatured, hence inactive, in cooked food. No contest.
Next question: So what? The theory is that all food should be eaten
raw to avoid the destruction of the enzymes in the food itself which
are held to be essential to proper digestion. One afficionado has
stated that "enzymes present in raw foods take priority over secreted
Now Ganong's Physiology (1) lists 25 human gastrointestinal
digestive enzymes from salivary glands, lingual glands, stomach,
exocrine pancreas, intestinal mucosa, and the cytoplasm of mucosal
cells. There are at least 11 polypeptide gastrointestinal hormones
regulating the secretion of these digestive enzymes. If food, in
fact, could digest itself for us, why would a parsimonious evolution
(or an efficient God) have bothered installing these enzymes, hormones,
and the segments of the GI tract that are set up specifically to
process them and their respective food components?
Neither Ganong nor thousands of scientific writers on the subject
of digestion make mention of any value of intrinsic food enzymes
in human digestion. There is one exception:
Prochaska LJ; Piekutowski On the synergistic effects of enzymes
in food with enzymes in the human body. A literature survey and
analytical report. Med Hypotheses (ENGLAND) Jun 1994. In this
article the authors mostly repeat the well understood effects of
heat in breaking down vitamins, amino acids, and producing undesirable
cross-linkages in proteins, particularly in meat. They do not produce
a surfeit of evidence in support of the "enzyme theory", although
they do point out that cooking beans increases their digestibility
by destroying the trypsin inhibitors therein and they cite this
as evidence that these enzymes can survive the digestive enzymes
at least long enough to cause negative effects. They also
present tentative evidence that there is some degree of synergy
between some food enzymes and human digestive enzymes, a concept
that would at least seem plausible. However they admit: "In the
absence of active enzymes in food, the foodstuffs are still able
to be digested and the nutrient release from food still occurs,
but not at maximum efficiency." This is a far cry from "the enzymes
present in raw foods take priority over secreted enzymes."
A search of Medline and the American Journal of Clinical Nutrition,
however, failed to turn up a single additional article in support
of this thesis and four physiology, biochemistry, and nutrition
textbooks, while elaborating on human digestive processes to the
point of tedium, also did not mention any useful predigestion of
food by the food's own enzymes.
A teleological mind-set is reflected in the idea that a benevolent
nature designed foods to predigest themselves for the benefit of
man. Amylase, protease, and lipase are used to mobilize stored carbohydrate,
protein, and fat for the benefit of the food organism itself, be
it plant or animal. Animals have additionally evolved large organs
to synthesize and secrete other enzymes for digestion of food in
whatever form it comes. This evolved machinery would not have been
necessary if foods could adequately predigest themselves.
Cooking is a form of predigestion in which heat is used to hydrolyze
nutrients which would otherwise be hydrolyzed at body temperature
by digestive enzymes. The end result is the same, but one raw food
author seems to obliquely suggest that another reason for leaving
food enzymes intact is so they can be absorbed intact into the blood
stream to continue their digestive work there. Such a process would
be catastrophic as the absorbed enzymes would be peptide fragments
and would be more likely to generate allergic and autoimmune reactions
than robust good health..
Some of the pros and cons of the raw diet:
Pro: Humans are the only species on the planet who cook their food,
so cooking is unnatural..
Con: We're also the only species that build computers and write
treatises. That's unnatural, too.
Pro: We've only been cooking for a half million years so we're
not well adapted to cooked food.
Con: On the other hand, one recent author suggested that the learned
ability to cook raw tubers over a million years ago resulted in
such an increase in dietary Calories that it reduced sexual dimorphism
in the pre-humans who employed it, and that in turn led to the psychosexual
bonding that gave rise to human families and civilization (2).
Pro: A raw vegan diet rather reliably leads to weight loss and
that would be great for the 30% of Americans who are either overweight
Con: What happens to the people who are already raw fooders but
continue to lose weight from reduced Calorie intake?
Further food limitations on a raw diet:
A raw diet places even further restrictions on the vegan diet.
Among the first dietary restrictions would be grains. Human population
growth since the agricultural revolution 12,000 years ago has been
tied to grain cultivation and a 1994 Scientific American article
underscored this, ascribing wide spread spinal defects in ancient
female skeletal remains to the all-fours posture required to kneed
grains to the point where they could be cooked and consumed (3 ).
People have been pounding grains to insensibility as long as they've
been around, to get rid of the nutritious but poorly digestible
outer shell. American grocery shelves are not by accident stuffed
with white breads as far as the eye can see; many people do not
like or even tolerate whole grain bread. As example and according
to a mid-30s apologist for white bread, the Germans, after over-running
Belgium in WWI, decreed a 98% extraction rate for Belgian bread
in a well-intentioned attempt to improve Belgian nutrition. However,
Belgian tummies responded to the resulting German black bread with
epidemic malabsorption problems and the incidence of tuberculosis
went up. Whole grain bread may be good for most people but for a
subset of new vegans the gluten content may unmask a previously
unrecognized celiac syndrome.
Raw fooders respond to this by saying that grains should not be
milled but sprouted and this usually does improve nutrient values
and digestibility. On the other hand sprouted alfalfa contains a
non-protein amino acid L-canavanine
which is thought to trigger systemic lupus erythematosis (SLE),
an auto-immune disease. Various other seed sprouts may harbor Salmonella
and E. coli bacteria, although this probably reflects contamination
during production and distribution, rather than intrinsic fault
in the seeds.
On a raw diet, potatoes, a generally well tolerated staple, also
go out. To counter that, it can be said that potatoes with green
skin contain solanine, a toxic alkaloid that has been popularly,
though not scientifically, incriminated in some arthritic conditions.
But we could probably get along without potatoes, too.
Other casualties would be soy and many other beans. Raw soy contains
trypsin inhibitors, goitrogens, and a laundry list of other allegedly
adverse factors. If you have any doubt about the ability of raw
beans in general to cause gastrointestinal disturbance, try eating
some yourself. Even when cooked, fava beans, a Mediterranean species,
win a place for themselves in medical textbooks under the heading
The raw food literature is rife with "life force", a metaphysical
concept that dates back to ancient medical theory with more recent
abuse at the hands of George Bernard Shaw (Man and Superman-1903),
William Faulkner (Light in August-1932), and the red stripes
in the present Uzbekistan national flag. However, the German chemist
Friedrich Wohler by 1828 had carried out the first synthesis of
an organic compound, urea, an achievement that began the decline
of the vitalistic theory that had dominated organic chemistry and
that had required the existence of a "life force" for organic synthesis.
Modern biochemists synthesize vastly more complex molecules than
urea without any recourse to "life force." Perhaps, as it has been
suggested, metaphysics is for people too lazy to study physics,
a field in which there are still enough unexplained mysteries in
the fine structure to accommodate all the mysteries of life. It's
not necessary to sweep all those mysteries under a metaphysical
rug dubbed "life force."
Things that are alive exhibit metabolism, the combining of food,
water, and oxygen through enzyme-catalyzed chemical reactions in
order to obtain energy for functioning. They also exhibit such properties
as growth, reproduction, movement, and response to stimuli. But
pitching raw food on the basis that it is "alive" creates a semantic
minefield for vegetarians.
Sure, the greens are alive until they have been cooked and the
enzymes have been denatured, but then so is a piece of fresh beefsteak.
The cells from both could be kept alive in tissue culture. Does
that mean we should eat raw beef because it's "live food?" Does
it mean the cow that the live steak was taken from is still alive?
Does it mean that the dim consciousness that inhabited that primitive
skull and presided over all the fear reactions that we also experience
when faced with death is still there? Of course not; the cow had
something the greens don't have, a nervous system, it's consciousness
is gone forever, and that's what the whole ethical vegetarian case
is about. "Live food" arguments really muddy the waters when you're
trying to explain the ethics of vegetarianism to a meat eater.
All the foregoing sounds like a frontal assault on the raw fooders,
but it's not. I agree with them that raw foods should be a major
if not sole part of the diet but not for their reasons. Raw foods
are not healthiest because they're "live food" or because of "life
force", "living enzymes", "nerve energy", or "chi", but because
the foods that can be eaten raw (mostly vegetables, fruits, nuts
and seeds) coincidentally have enormously higher nutrient values
than the foods that either have to be, or usually are, cooked. Here
is a six-bar stacked and rotated graph assembled from Nutritionist
IV data and Quattro Pro showing the amounts of six important nutrients
in various foods with the RDA for the six nutrients at the bottom.
It should be self-explanatory, but the foods that are usually cooked
are shown in the upper part of the graph and the ones that can be
eaten raw in the lower part. The nutrient values, expressed as "Percent
of (Recommended Dietary Allowance [RDA] per Calorie)" are highest
for the raw foods. Note that potato, brown rice, winter wheat, pasta,
and 16 averaged breads don't even make it to the RDA (vertical light
blue arrow). 96 averaged vegetables are beginning to look pretty
good, however not all of the ones included can be eaten raw and
included among the 96 were a few raw seeds and nuts which dragged
down the nutrient indices considerably. Raw they may be but they
are also high in fat.
There are at least forty essential nutrients in the human diet
but Quattro can only show six at a time and RDAs have not been set
for many of the others.
(V4 juice is just a tomato, a bunch of parsley,
a carrot, and a stalk of celery run through a juicer.)
Summary: The Raw Fooders are probably right
but maybe not for their stated reasons.
1. Ganong WF. Review of Medical Physiology. Appleton &
Lange. Norwalk 1991. ISBN 08385-8418-7. p 438 p449.
2. Wrangham R, Jones JH, Laden G, Pilbeam D, and Conklin-Brittain,
The Raw and the Stolen: Cooking and the Ecology of Human Origins.
CURRENT ANTHROPOLOGY Volume 40, Number 5, December 1999
3. Molleson, T. The Eloquent Bones of Abu Hureyra: The
daily grind in an early Near Eastern agricultural community left
revealing marks on the skeletons of the inhabitants. Scientific
American August 1994.