Chitosan is a type of fiber derived from chitin, a substance that develops in the hard outer shells of crustaceans such as crab, crayfish, shrimp and squid. Like other forms of fiber, chitosan is indigestible and it moves through the gastrointestinal system without being absorbed. Chitosan is available as a dietary supplement purported to help people lose weight and lower cholesterol levels. Consult with a qualified health care provider before taking chitosan supplements.
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Chitosan has an additional potential benefit than most other types of fiber, explains Health Services at Columbia. When traveling through the intestines, chitosan binds to a small amount of dietary fat and takes it along out of the body, preventing this fat from being absorbed. This action accounts for the theoretical effects of chitosan on cholesterol levels and weight, but chitosan may not bind with enough fat to cause substantial effects.
Mixed Research Results
A review of studies published in a 2008 issue of the "Cochrane Database of Systematic Reviews" evaluated the effectiveness of chitosan for health benefits in overweight and obese people. The 15 studies included 1,219 participants. On average, chitosan intake led to significant weight loss, reduced total cholesterol and decreased blood pressure as compared with placebo. The authors cautioned that when they narrowed the studies to those of higher quality with larger numbers of participants and longer duration, the improvements were much smaller.
Research appearing in the June 1999 issue of "Methods and Findings in Experimental and Clinical Pharmacology" found that otherwise healthy obese women taking chitosan supplements did not experience significant decreases in cholesterol or triglyceride levels when compared to women taking a placebo. In fact, the group taking chitosan experienced slightly increased triglycerides. Neither group lost weight. The women taking chitosan consumed three 400mg capsules twice per day for eight weeks.
In contrast, a study published in the Winter 2003 issue of the "Journal of Medicinal Food" found benefits of chitosan supplements for people with type 2 diabetes and abnormal amounts of blood lipid levels. Participants ate either a specific daily amount of bread containing 2 percent chitosan or they ate regular bread. Participants eating the chitosan bread experienced lower levels of low-density lipoprotein, or LDL, cholesterol, the so-called bad cholesterol, and significant increases in high-density lipoprotein, or HDL, cholesterol, the good cholesterol. No significant weight reduction or changes in triglyceride levels occurred.
The fat-absorption activity of chitosan also prevents some absorption of the fat-soluble vitamins A, D, E and K, as well as phytochemicals that help to prevent disease, cautions Health Services at Columbia. In addition, some medications such as birth control pills are fat-soluble, and chitosan could affect their absorption.