Chitosan is a natural fiber product derived from chitin, a substance found in the exoskeletons of shellfish such as shrimp, crabs, and lobsters. Unlike plant cellulose, which is negatively charged, chitosan has positively charged amino groups that bind to negatively charged fats and bile acids. Research shows that, under optimal conditions, chitosan can bind 4 to 5 times its own weight in fat and bile salts. For nearly 30 years, chitosan has been used in water purification plants for its unique ability to bind to toxic substances. It has also been used in the pharmaceutical, agricultural, and cosmetic industries for a variety of purposes. In recent years, chitosan has become popular as a "fat blocker" dietary supplement for weight loss. As a rich source of fiber, chitosan may also be helpful for promoting bowel function.
Chitosan has an excellent safety record, with studies using up to 6 grams per day showing no significant side-effects. Chitosan has no known toxicity, but it can interfere with the absorption of some minerals, essential fatty acids, and fat-soluble vitamins. Vitamin, mineral, and fatty acid supplements may be advisable for long-term chitosan users.