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From: [log in to unmask] (Jay Mann)
Newsgroups: sci.bio.food-science
Subject: Re: Food Additives
Date: 13 Jun 1995 01:36:51 GMT

[snipped...]

There are two broad classes of "dietary fiber": soluble and insoluble.  The
insoluble fiber, typically coming from wheat bran, helps to soften stools
(motions), forming something like papier mache in the gut.  Insoluble fiber
is, primarily, cellulose.  Then there are soluble fibers (pectin, pentosan,
and glucans), which come from such materials as fruits, barley, oats, etc.
(I'm only listing foods with notably high levels of these materials.) The
nomenclature "fiber" is IMHO an abomination that is too strongly entrenched
to change.  "Soluble fiber" tends to form gels in the gut, helping to delay
the absorption of other food components, which is good for overweight people
but bad for growing broiler chickens. There is evidence that soluble fiber
reduces cholesterol levels, perhaps by carrying bile salts (made in the body
from cholesterol, and functioning as detergents) out of the gut.  Some
people believe there are specific chemical bonds with the soluble fibers,
but I think it's primarily a viscosity affair.

When soluble fiber reaches the large intestine (colon), the bacteria there
usually can break it down, sometimes with production of gas.

The usual recommendation is 2/3 insoluble fiber, 1/3 soluble fiber for human
nutrition.  But food labels don't distinguish between soluble and insoluble,
unfortunately.  Just remember, oat bran is better than wheat bran, in terms
of soluble fiber.   Also note that viscosity (thickness) of glucan and
pentosan solutions is exponentially related to concentration: half the
concentration can mean only 5% as much viscosity.  So if viscosity is the
key, don't crib on your fiber intake.

Jay D Mann  <[log in to unmask]>
Christchurch, New Zealand