Chitosan fails to reduce the weight
Taking a daily chitosan supplement had little effect on weight
loss in a new study on obese volunteers.
Chitosan supplements, derived from the chitin naturally present
in large quantities in shellfish, are marketed as a weight loss
product as the fibre has been shown to bind fat in the intestine,
blocking its absorption. Not all trials have proven its efficacy
in weight loss management.
The new study, published in the September 2004 issue of the International
Journal of Obesity, is one of the largest to date.
The researchers assigned 250 adults to receive either 3 grams of
chitosan daily or a placebo for 24 weeks. All participants received
standardised dietary and lifestyle advice for weight loss.
The researchers from the Clinical Trials Research Unit in the University
of Auckland report that the chitosan group lost more body weight
than the placebo group, but the effects were small. The chitosan
group lost an average of 0.9 pounds compared to a 0.4 pound gain
in the placebo group.
Similar small changes were seen in the total and LDL cholesterol
levels and there were no significant differences between groups
for any of the other measured outcomes such as body mass index,
waist circumference, body fat percentage, blood pressure or quality
of life.
"We do not know of any limiting factors in our study that
would have prevented a greater effect on weight loss. Our trial
was designed and analysed according to international clinical trial
standards and is the largest trial of chitosan to date with the
most outcome measures," says Dr Cliona Ni Mhurchu, senior research
fellow at the Clinical Trials Research Unit.
"It is unlikely that a longer follow-up period would change
the outcome since it is common in weight loss studies to lose more
weight in the earlier than in the later stages," she adds.
"Our dose is similar to that used in other studies and is greater
than that advised by the manufacturer."
The product tested was a beta-chitosan supplement derived from
New Zealand squid pens. It was 76% deacetylated and had a molecular
weight of 130,000.
But James France, general manager of Wilkie Resources which markets
the LipoSan Ultra brand chitosan in the US, notes that there are
significant issues with bioavailability of chitosan, which could
prevent some supplements from having a significant effect.
"Chitosan is a very large fibre that is difficult to get into
a solution. Regular chitosan is so tightly bound that it does not
dissolve enough in the stomach to allow it to interact with the
fat."
The LipoSan Ultra chitosan has been modified using succinic acid
which holds the fibre apart enough to allow it to dissolve, forming
a gel with fat modules and binding them so that they move out of
the gastrointestinal tract before being broken down by lipase.
The former manufacturer of LipoSan, Vanson Halosource, carried
out a randomized, double-blind, placebo controlled clinical trial
of chitosan for weight loss on 59 mildly obese women. After 8 weeks
a statistically significant reduction in weight was seen in the
chitosan group.
"I don’t refute their results [the New Zealand trial]
but you need to look at how this particular product behaves,"
says France.
Natrol
Natrol, Inc., and its president Elliott Balbert have agree to pay
$250,000 to settle charges that they made false and misleading advertising
claims for their chitosan-based weight loss products, some of which
contained more lead than allowed by state law.
Starting in 1998, they marketed Absorbitol Fat Binder, making claims
that the chitosan ingredient in the product would cause the user
to lose weight by absorbing fat and that it could bind "178% more
fat than other brands" and 10.8 ml of fat "per gram of active ingredient."
In 2001, it began marketing Chitosan 500 mg, Ultra Chitosan Fat
Intercept, and Ultra Chitosan Fat Intercept Plus with similar claims.
An investigation found that there is no valid scientific evidence
to support claims that the ingestion of chitosan causes fat to be
"trapped" or "bound" in the human G.I. tract, or that the use of
chitosan-based dietary supplements causes any significant or noticeable
weight loss results.
The investigation also revealed that Chitosan 500 mg, Ultra Chitosan
Fat Intercept and Ultra Chitosan Fat Intercept Plus contained lead
in amounts that exceeded the 0.5 microgram daily limit allowed by
Proposition 65.
References
Mhurchu CN, Poppitt SD, McGill AT, Leahy FE, Bennett DA, Lin
RB, Ormrod D, Ward L, Strik C, Rodgers A. The effect of the dietary
supplement, Chitosan, on body weight: a randomised controlled trial
in 250 overweight and obese adults. Int
J Obes Relat Metab Disord. 2004 Sep;28(9):1149-56
http://www.ftc.gov/opa/2004/08/pvt.htm
http://www.sonoma-county.org/Da/press_091404.htm
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