The following message is from the PaleoDiet list this Wednesday and is Ward
Nicholson responding to Tom Billings' questions on the digestibility of
cooked foods, cross-posted with permission:

Best, Peter
[log in to unmask]

============================================

Ward:
I don't know the answers to very many, if any, of Tom Billings' questions,
but I'll take a few speculative stabs here that might hopefully stimulate
comment from the rest of you about just how foolish my musings here are, if
nothing else. :-)

Tom:
>Are cooked foods close enough in composition to their raw counterpart that
>we can digest them anyway (as we are omnivores, able to digest a
>wide variety of foods and survive on radically different diets)?

Ward:
That sounds plausible enough. It would seem to me that while cooking
changes things about foods, and the changes may seem like significant
changes--from the point of view total-raw-food enthusiasts--in the overall
the changes may not always amount to all that much in terms of
digestibility. I.e., they may be enough to introduce some additional toxins
perhaps, or change the character of the starch in some foods to make them
more digestible, or whatever.

But it's not as if all of a sudden the foodstuff was changed into something
so completely foreign to the digestive tract--like polybicarbonate plastic
or something :-) --that all of a sudden it becomes totally indigestible, or
even largely indigestible. Wouldn't the supposition hold that if the
protein in the food is still protein, the starch and sugars and other carbs
still carbs, the fats still fats, the body is going to digest it?

To me the question is not so much digestibility, but more whether any
potential side-effects due to the cooking might create any problems of
undue toxicity significantly above the level of toxins and antinutrients
that may be in raw foods to begin with. Although in some cases, of course,
cooking makes the foods a lot *more* digestible and less toxic than they
would be raw (many root vegetables, grains, etc.)--which of course might
beg the question of whether we ought to be eating these foods to begin
with, even though many people do eat them raw. (And that's whether or not
they are digesting very much of them even if they *can* eat them raw, and
have them go through their digestive tract without experiencing noticeable
problems or distress.)

Actually, I would think these same considerations apply to raw foods just
as much as with cooked foods, as far as the ratio or equation of usable
nutriment vs. waste/ toxic matter goes (playing the part of
equal-opportunity muckraker here :-) ). Obviously cooking affects
digestibility and/or assimilation, or we wouldn't do it in the case of
grains and tubers, to mention two items; and obviously many people in
today's world exist most of their lives on mostly cooked food. So to me in
most cases it seems like more a question of degrees and gradations of
digestibility, not either/or.

Tom:
>As an example, can I digest cooked starch because my ancestors ate raw
>starch foods in pre-fire days, and the chemical composition is
>altered some, but not that much, by cooking?

Ward:
Well, this question of course presupposes there wasn't any cooking in
prehistoric times for a long enough time to have affected the human genome,
and there may have in fact been--these days I am not convinced by what
evidence is available one way or the other. However, supposing for the
moment that were the case (no adaptation to cooking yet), I would tend to
think so (that the starch is digestible to what degree it is cooked based
on prior adaptations to raw starch). However, the kicker here is that from
what I understand, the starch in many root veggies and probably all grains
is much MORE digestible when cooked.

So the sword can cut both ways here, and when it cuts this latter way, it
sort of begs the question of how certain cooked foods could be more
digestible than raw if we hadn't encountered those cooked foods in
evolution before. The two possible answers would seem to be that: (1) we
HAVE encountered those foods cooked before and made more successful use of
them cooked than raw, or (2) we HAVEN'T encountered those foods, and we
aren't that well-adapted to them raw, but for whatever reason cooking
renders them--by fortuitous circumstance--more digestible given our
previously evolved digestive mechanisms.

Tom:
>Is grain close enough in chemical composition to say, tubers, that we
>can digest it OK?

Ward:
Hmmm. To my mind, the question would be not how close grains are to tubers,
but rather how compatible each _on_its_own_ would be with the human
digestive system. Comparing their digestbility based just on the criterion
of starch content may be rather arbitrary on our part. Since tubers and
grains are in two different biological classes of plants, the fact they
both are high in starch is just a similarity we happen to notice between
them because, say, that might be one way we classify foods according to
some recipe for eating. But that seems like it might be something of an
arbitrary scheme to me. They may be enough dissimilar in other respects
that you can't use the digestibility of one as a gauge for the other. I
wouldn't know enough to say.

Tom:
>Is dairy close enough in chemical composition to other foods (that is,
>it is similar to an average of meat + fruit, hence within the "range" of
>digestible "original" foods), that many of us can digest it?

Ward:
Again, I wonder if it really makes sense to be comparing dairy against an
"average" of meat/ fruit--rather simply on its own merits. Or according to
some sort of *independent* standard, to the degree that one is possible,
for what types of things are digestible in the human tract, and why. (Such
as, perhaps, the above hypothetical postulated thinking about carb/ fat/
protein content, or should that not be the applicable standard, whatever
else actually does apply, etc.) To me the question would be not so much how
similar one food is to another by some subjective classification scheme,
but rather what specific molecular compounds and elements they contain and
in what array, and which are attackable by the enzymes and so forth that
the digestive system can bring to bear. That may or may not correspond to
our own subjective classification schemes.

Tom:
>From having subscribed to the Paleodiet list here, it seems that everything
>comes down to very specific biochemical pathways, in terms of either
>enzymes or other controlling factors determined by specific genes, or in
>terms of specific autoimmune response to food antigens, etc.
>(Re: the above two questions: I acknowledge the serious problems some people
>have with gluten and lactose. I'm not suggesting everyone can digest them.)

Ward:
Agreed. Interesting in this connection, though, is that it takes a specific
enzyme (lactase) to digest lactose which is coded for by a specific gene. I
forget the process by which some people can handle gluten without
generating an auto-immune response (Ron Hoggan, aren't you the expert on
that?), but again, it is something that comes down to certain specifics. In
general, I think these two examples may be a good illustration of how the
general type of reasoning used in alternative diet circles as to
digestibility partakes too much of woolly thinking and vagueness; when, if
you get right down to it, everything probably has to do with *specific*
enzymes and if the food contains the specific class of substrates
attackable by those enzymes without too much leftover waste matter or toxic
material that the digestive system doesn't have ways of buffering
sufficiently, or is capable of eliminating it within the safety parameters
of the body's design for elimination.

Tom:
>You are free to post this on the Paleo lists if you wish - if you do that,
>I would be interested in any significant replies to these questions.

Ward:
Me too.