Chitosan is obtained from the exoskeletons of marine organisms such as crabs, shrimp and lobsters. As a dietary supplement, it is promoted for weight management and cholesterol-lowering effects. Some believe that chitosan binds to dietary fats and bile acids in the digestive tract, reducing their absorption and resulting in lower caloric intake and possibly weight reduction. It is thought that binding to bile acids and increasing their fecal excretion may reduce cholesterol levels because cholesterol is used to re-synthesize bile acids. Unfortunately, however, according to the Memorial Sloan-Kettering Cancer Center, chitosan studies offer only weak evidence of these claims. On the other hand, the website DiagnoseMe.com indicates chitosan has proven useful for renal failure patients receiving hemodialysis.
Side Effects
Studies involving chitosan have lasted from four weeks to six months. Reported side effects are generally limited to gastrointestinal issues since chitosan is not digested or absorbed to any significant extent. As with other dietary fibers, side effects include nausea, flatulence, increased stool volume and constipation. If chitosan were able to prevent enough absorption of dietary fats, loose and oily stools could be a possible side effect.
Health Condition Interactions
Chitosan is derived from shellfish. Therefore, those with shellfish allergies should avoid using it. The safety of chitosan in pregnant and lactating populations is unknown and should be avoided. Anyone considering chitosan as a dietary supplement should first discuss the risks and benefits with a qualified doctor or nutrition professional.
Drug and Nutrient Interactions
Because chitosan might interfere with the absorption of fatty substances from the diet, there is a concern that the fat-soluble vitamins A, D, E and K may not be absorbed properly. Drugs.com, however, states that vitamins A, D and E were shown to be unaffected by chitosan in a clinical trial. In theory and based on a single case report by Shao-Sung Huang, M.D., and colleagues and published in "The Annals of Pharmacotherapy," chitosan could block vitamin K absorption enough to increase the actions of blood-thinning drugs. As with other dietary fibers, chitosan should be taken separately from all drugs and dietary supplements to prevent slowed or reduced absorption.
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