Chitosan

What does it do?

Chitosan is a polysaccharide found in the shells of crustaceans.

Like dietary fiber, chitosan is not digestible but may have beneficial effects on the gastrointestinal tract. Chitosan appears to reduce the absorption of bile acids or cholesterol; either of these effects may cause a lowering of blood cholesterol.1 This effect has been repeatedly demonstrated in animals, and a preliminary human study showed that 3-6 grams per day of chitosan taken for 2 weeks resulted in a 6% drop in cholesterol and a 10% increase in HDL ("good") cholesterol.2 Another preliminary trial showed a 43% lowering of total cholesterol in people being treated for kidney failure with dialysis who took 4 grams per day of chitosan for 12 weeks. These people also appeared to have improved kidney function and less severe anemia after chitosan treatment.3

Chitosan in large amounts, given with vitamin C, has been shown to reduce the absorption of dietary fat in animals fed a high-fat diet.4 5 6 However, the absorption of minerals and fat-soluble vitamins was also reduced by feeding animals large amounts of chitosan.7 No studies have been done on the effects of chitosan on dietary fat absorption in humans.

Chitosan may also have an effect on the type of bacteria living in the intestines or on the action of these bacteria. A small human study found that taking 3-6 grams per day of chitosan for two weeks reduced indicators of putrefaction in the intestines,8 a change that might help prevent diseases such as colon cancer.9

Where is it found?

Chitosan is extracted from the shells of crustaceans, such as shrimp and crab.

Chitosan has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating Health Concerns
1Star

High cholesterol

Kidney failure
3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Who is likely to be deficient?

Chitosan is not an essential nutrient, so deficiencies do not occur.

How much is usually taken?

Most human research has used 3–6 grams per day with meals.

Are there any side effects or interactions?

While no long-term studies of the effects of chitosan on human health have been done, animal studies suggest that this compound could inhibit the absorption of minerals and fat-soluble vitamins. Adverse effects on the growth of children and on the outcome of pregnancy are also possible.10 In addition, although chitosan-included alterations in intestinal flora are believed to be beneficial, the possibility that these changes may have negative long-term consequences has not been ruled out. People with intestinal malabsorption syndromes should not use chitosan.

At the time of writing, there were no well-known drug interactions with chitosan.

References

1. Koide SS. Chitin-chitosan: properties, benefits and risks. Nutr Res 1998;18:1091-101 [review].

2. Maezaki Y, Tsuji K, Nakagawa Y, et al. Hypocholesterolemic effect of chitosan in adult males. Biosci Biotech Biochem 1993;57:1439-44.

3. Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure. J Pharm Pharmacol 1997;49:721-3.

4. Deuchi K, Kanauchi O, Imasato Y, et al. Effect of the viscosity or deacetylation degree of chitosan on fecal fat excreted from rats fed on a high-fat diet. Biosci Biotech Biochem 1995;59:781-5.

5. Deuchi K, Kanauchi O, Imasato Y, et al. Decreasing effect of chitosan on the apparent fat digestibility by rats fed on a high-fat diet. Biosci Biotech Biochem 1994;58:1613-6.

6. Kanauchi O, Deuchi K, Imasato Y, et al. Increasing effect of a chitosan and ascorbic acid mixture on fecal dietary fat excretion. Biosci Biotech Biochem 1994;58:1617-20.

7. Deuchi K, Kanauchi O, Shizukuishi M, et al. Continuous and massive intake of chitosan affects mineral and fat-soluble vitamin status in rats fed on a high-fat diet. Biosci Biotech Biochem 1995;59:1211-6.

8. Terada A, Hara H, Sato D, et al. Effect of dietary chitosan on faecal microbiota and faecal metabolites of humans. Microb Ecol Health Dis 1995;8:15-21.

9. Bone E, Tamm A, Hill M. The production of urinary phenols by gut bacteria and their possible role in the causation of large bowel cancer. Am J Clin Nutr 1976;29:1448-54.

10. Koide SS. Chitin-chitosan: properties, benefits and risks. Nutr Res 1998;18:1091–101 [review].