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High-Quality Studies Indicate 'Minimal' Weight Effect

Aug. 25, 2005 -- Researchers are still scratching their heads as to how effective the weight loss supplement chitosan is. Their findings appear in a new report.

Chitosan is made from chitin, which comes from the shells of shrimp, lobsters, and crab.

Researchers led by Cliona Ni Mhurchu, PhD, reviewed 14 studies on chitosan and weight loss. Writing in The Cochrane Library, they note "some evidence" that chitosan was more effective than a fake supplement for short-term weight loss.

But many of the trials were of "poor quality" and results varied, write the researchers.

Their bottom line: "Results obtained from high-quality trials indicate that the effect of chitosan on body weight is minimal and unlikely to be of clinical significance," write Ni Mhurchu and colleagues.

Review's Details

The review covered 14 studies with a total of more than 1,100 participants. All participants were adults; they were about 44 years old, on average. Three studies only included women.

Six of the studies were done in Italy. Others were done in the U.K., U.S., Canada, Singapore, New Zealand, Finland, and Poland.

In all of the studies, participants were given chitosan or a fake supplement (placebo). In eight studies, participants were also told to diet.

Chitosan doses and the studies' design, size, length, and quality varied. Some studies didn't report the chitosan dose used.

Findings Shifted

Overall, the data showed that people taking chitosan lost about 3.7 extra pounds and improved their blood pressure and cholesterol, compared with those taking the placebo.

But some of those results changed when the researchers took a closer look at the studies.

For instance, in trials lasting more than four weeks, people taking chitosan lost about 1.7 pounds more than those taking a placebo. For trials lasting up to four weeks, there was "substantial" variation in weight loss, write the researchers.

Looking only at high-quality trials lasting four weeks to six months, people taking chitosan instead of the placebo lost an extra 1.28 pounds. The researchers call that difference "minimal and therefore unlikely to be of clinical significance."

Tough Critics?

Three of the researchers had worked on one of the studies they reviewed.

The review was mainly funded by the Health Research Council of New Zealand, but some funds came from a chitosan maker, the researchers note.

They recommend that future studies last at least 24 weeks and provide more information on methods and outcomes.

The U.S. government does not check the safety, quality, or effectiveness of dietary supplements. The National Institutes of Health's Office of Dietary Supplements recommends that patients consult their doctors before taking any dietary supplements. People seeking to lose weight may consult doctors for guidance.

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