In a message dated 2/5/2002 7:19:35 AM Eastern Standard Time,
[log in to unmask] writes:

> It's far from clear, however, that complex carbs cause [IBS and IBD].

No one really knows the cause of IBD, although recently researchers have
isolated a gene that they think causes it (or so my gastroenterologist told
me).  IBD is an autoimmune disease--an overreaction of the body to
incompletely digested carbohydrates and the "bad" bacteria that feeds on it.
Usually these undigested carbs in the bowel are polysaccharides.
Disaccharides cause problems for some people, but not as reliably as
polysaccharides.

Sometimes undigested carbohydrates remain in the bowel because of small bowel
impairment--the microvilli that carry the enzymes are flattened from
inflammation and don't come in contact with the carbohydrate.  Or sometimes
the bowel is simply overwhelmed by the AMOUNT of carbohydrate, and part of it
passes into the large bowel undigested.  There are other possible mechanisms
as well.

When, for whatever reason, undigested carbohydrate remains in the bowel, two
very bad things can happen: (1) unfriendly bacteria and yeast start to
multiply and damage the bowel wall, and (2) the body identifies the
carbohydrates as "alien" and initiates a t-cell response (in which case you
have full blown IBD).

> [The idea that polysaccharides are no paleo] is simply not believable. We
secrete alpha-amylase in our saliva, the sole purpose of which is to initiate
the digestion of
starch.

Most modern humans also produce lactase, but that doesn't mean that cow's
milk is paleo.  Apparently evolution is fast enough that humans can start
producing enzymes for new foods over a period of 8000 years.  I've also read
that not eating certain foods for a period of time will cause the body to
stop producing the enzymes to digest it.  This happens with many fruitarians
(I read this on beyondveg.com).

> You would be hard pressed to find any modern
hunter-gatherers who do not make substantial use of root
vegetables, rhizomes, or tubers.

I think that root vegetables and rhizomes differ from starchy tubers in the
amount and type of  carbohydrate the contain.  I can't be sure about every
vegetable out there, but I know that beets for one contain sucrose--a
disaccharide.  That's easier to digest than starch (amylose or amylopectin).
Also, roots tend to be much lower in carbohydrates than starchy tubers.

> It's true that [Cordain says in his paleo diet book to avoid starchy tubers
and eat only honey as a sweetener], but unfortunately he offers no plausible
paleo-based justification for the restriction.

It's true that Cordain offers no paleo-based justification for this, or for
many of his other pronouncements.  This is what bothered me most about his
book.  But I think there is some evidence that our ancestors didn't eat a lot
of starch.

Our bodies don't well tolerate a very high carbohydrate diet. All kinds of
problems follow from this--rampant bowel disease (this is a very widespread
problem), insulin resistance, etc., etc.  This tends to suggest that we
evolved on a diet that was moderate in carbohydrates (that is to say, much
lower than the standard American diet), and this is the opinion of most paleo
nutritionists.

Starchy tubers and grains are the main source of polysaccharides in the
modern diet, and they are also almost pure carbohydrate.  If these foods were
as widely available in paleo times as they are today, then the paleo diet
would have been much higher in carbohydrates than it apparently was.  There
is fairly broad agreement that paleo people didn't eat grain.  Just the fact
that we are not designed to eat a very high carb diet tends to suggest that
starchy tubers also played a small role.  Many starchy tubers also need
cooking to be edible, which is another point against them.