Chitosan
Chester J. Zelasko, Ph.D. |
December 4, 2001
It seems you can't
pick up a magazine or turn on the television without seeing an ad for a fat
blocker. "Take these pills and you'll lose weight because they block fat!"
Sounds too good to be true, doesn't it? You get to eat anything you want and
all you have to do is take a few pills. What is this stuff? Does it work?
Almost every product available contains a form of chitosan. This is a type
of fiber that's extracted from shellfish--people with shellfish allergies
can't take it. Chitosan (pronounced KITE-o-san) can't be absorbed by the
body--most types of fiber can't. Chitosan's claim to fame is that it will
bind to fat molecules and prevent them from being absorbed, too. But it will
also block the absorption of fat-soluble vitamins and beneficial omega-3
fatty acids. The chitosan-fat complex then passes through the body and is
eliminated in the stool. The question is does chitosan work?
Most of the evidence is anecdotal--testimonials from people who have used
the product. A Medline search found only a single study testing the efficacy
of chitosan (1). The results were not encouraging--after 28 days, there were
no differences in body weight between the placebo group and the group using
chitosan. A single study doesn't mean that the product doesn't work.
However, after being available for many years, it seems there should be
several studies providing at least some support.
Why would someone lose weight taking chitosan? There may be a couple of
explanations. First, at least one form of chitosan recommends that the
product be taken 3-5 hours before bedtime with no food after that. Because
most overweight people eat at least one-half their caloric intake after 5
p.m., the reduction in calories would explain most of the weight loss.
Another chitosan product recommends that a person take the product 20
minutes before eating along with a full glass of water. That may also cause
a person to eat less because the fiber and water would promote a feeling of
satiety.
Does fiber block fat absorption? Yes, all types of fiber do to a limited
degree. Eating five servings of fruits and vegetables every day will prevent
the absorption of 75-150 calories from fat--and you'll be getting a whole
lot more nutrition. It may not be as exciting, but it's tried and true.
If you really want to block the absorption of fat, do it the old-fashioned
way: don't eat it.
Reference:
- Pittler M, et. al. Randomized, double-blind trial of chitosan for
body weight reduction Eur J Clin Nutr 53(5):379-81. 1999.
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