Chitosan, a deacetylated chitin, is a popular over-the-counter dietary supplement marketed to decrease body weight via limiting fat absorption in the body and is known as a “fat binder”. Although evaluated in a number of trials its efficacy remains unclear.  Chitosan is a sugar (cationic polysaccharide) obtained from outer skeleton of shellfish .
Chitosan and weight loss
We decided to write about chitosan as we stumbled upon an advertisement that stated something like: “Chitosan is ideal for those who like to have a cheat meal every now and then without the risk of getting fat.” That really got us in the mood for some research and it didn’t took long to realise science literature is not as impressive as marketing claims.
Ni Mhurchu C.  and colleagues wanted to assess the effects of chitosan as a treatment for overweight and obesity. For that reason, they reviewed electronic databases, specialised web sites, bibliographies of relevant journal articles, and contacted relevant authors and manufacturers (up to March 2004). They evaluated fourteen trials with a total of 1131 participants. After reviewing all the relevant data authors concluded that chitosan is more effective than placebo in the short-term treatment of overweight and obesity. However, high quality trials indicate minimal effect of chitosan on body weight and is unlikely to be of clinical significance.
Richard B. Kreider and co-workers  more recently assembled a summary of categorization of dietary supplements based on available literature and categorised chitosan as apparently not effective.
Matthew D. Gades and assistants have shown that the effect of chitosan on fat absorption is insignificant and is the equivalent of approximately 9.9 kcal/day . In a follow-up research by the same authors it was concluded that fat trapped from supplementation would take more than 7 months for a male to lose a pound of weight, and that the effect was completely ineffective in women .
Chitosan side effects and risks
Because chitosan is taken from the outer skeleton of shellfish, there is a concern that people with allergies to shellfish might also be allergic to chitosan. However, experts believe that chitosan shouldn’t be a problem for people with shellfish allergy because people are allergic to the meat, not the shell.
Adverse effects most frequently include gastrointestinal symptoms such as constipation and flatulence .
Jull, Andrew B., et al. “Chitosan for overweight or obesity.” Cochrane Database Syst Rev 16.3 (2008).
- Find a Vitamin or Supplement – Chitosan Retrieved from WebMD.com at 1. May 2013
- Kreider, Richard B., et al. “ISSN exercise & sport nutrition review: research & recommendations.” J Int Soc Sports Nutr 7.7 (2010).
Gades, Matthew D., and Judith S. Stern. “Chitosan supplementation and fecal fat excretion in men.” Obesity 11.5 (2003): 683-688.
Gades, Matthew D., and Judith S. Stern. “Chitosan supplementation and fat absorption in men and women.” Journal of the American Dietetic Association 105.1 (2005): 72-77.
Pittler, Max H., and Edzard Ernst. “Dietary supplements for body-weight reduction: a systematic review.” The American journal of clinical nutrition 79.4 (2004): 529-536.