A new review published in the Cochrane Library assessed the results of 14 randomized controlled trials on chitosan supplements and found that people taking the supplement had an average weight loss of almost 4 pounds more than those on placebo in the short term.
It also concludes that the supplement-takers saw their cholesterol and blood pressure levels decrease more than those in the placebo group.
But the authors write that although "this review has indicated that chitosan may be an effective aid to weight loss… many of the included trials have been limited by poor methodology and reporting".
Lead author Cliona Ni Mhurchu from the University of Auckland in New Zealand was also the author of a trial on the supplement published earlier this year.
Writing in issue 3 of The Cochrane Database of Systematic Reviews, she notes that not all of the studies included both men and women and some of the chitosan doses were as little as a quarter of a gram a day. The supplement was assessed for only four weeks in some cases, which cannot show long-term weight loss.
Bjarte Langhelle, marketing director of Primex, which sells the LipoSan brand chitosan, agreed that there are a lot of "not so good trials out there" but he added that the review does not pick up on the material used in each study.
"They generalize the chitosan too much. If you actually looked at what type of chitosan was being used and disregarded the poor quality products, the results would be different," he told NutraIngredients.com.
Langhelle believes that numerous chitosans on the market are totally insoluble, making them ineffective.
"Chitosan needs to solubilise in the stomach. Otherwise it cannot precipitate to form a gel in the intestine that binds to the fat," he explained.
Primex is currently working on research to demonstrate the mechanism by which Liposan helps weight loss.
The company estimates that about 2,000 metric tons of chitosan supplements are sold annually, the majority for weight loss applications.