-------------------------------------------------------------------------------- Requirements/Sources Chitosan can be extracted from the shells of shrimp, crab, or lobster. It is also found in yeast and some fungi. Another inexpensive source of chitin is "squid pens," a byproduct of squid processing; these are small, plastic-like, inedible pieces of squid that are removed prior to eating. -------------------------------------------------------------------------------- Therapeutic Dosages The standard dosage of chitosan is 3 to 6 g per day, to be taken with food. Chitosan can deplete the body of certain minerals (see Safety Issues below). For this reason, when using chitosan, it may be helpful to take supplemental calcium, vitamin D, selenium, magnesium, and other minerals. Also, according to a preliminary study in rats, taking vitamin C along with chitosan might provide additional benefit in lowering cholesterol.1 -------------------------------------------------------------------------------- Therapeutic Uses Chitosan may make it harder for the body to absorb fat.2,3 One study suggests that use of chitosan may aid in weight loss, although two shorter, smaller trials did not.4,5,37 The difference in outcome may lie in the type of chitosan product used. The evidence is also mixed on whether it can lower cholesterol levels.614,36,37 Chitosan may be helpful in kidney failure.15 In this case, it is thought to work by binding with toxins in the digestive tract and causing them to be excreted. Studies in dogs have found that topically applied chitosan can help heal wounds.16 This effect might be due to stimulation of new tissue growth; in addition, topical chitosan appears to kill bacteria such as Streptococcus and yeast such as Candida albicans, which may also contribute to wound healing.17 Highly preliminary evidence suggests that oral chitosan may inhibit the expected rise in blood pressure after a high-salt meal.18 It has also been suggested that chitosan can stimulate the immune system and help fight tumors,19 but there is no real evidence as yet that it works in these ways. Animal studies suggest that some forms of chitosan may help to prevent bone loss;20 however, because chitosan also interferes with mineral absorption, the net effect in humans might actually be to increase bone loss (see Safety Issues below). -------------------------------------------------------------------------------- What Is the Scientific Evidence for Chitosan? Weight Loss An 8-week double-blind, placebo-controlled trial of 59 overweight individuals evaluated the effects of chitosan taken at a dose of 1.5 g prior to each of the two biggest meals of the day.21 No special diets were assigned. The results showed that, on average, participants in the placebo group gained over 3 pounds over the course of the study, while those taking chitosan lost more than 2 pounds. In contrast, an 8-week double-blind, placebo-controlled trial of 51 women found that use of chitosan at a dose of 1,200 mg twice daily failed to cause any weight loss.37 Similarly, in a 28-day double-blind trial of 30 overweight individuals, chitosan taken at a dose of 1 g twice daily did not induce weight loss.22 High Cholesterol Preliminary human and animal studies found evidence that chitosan can reduce cholesterol levels.2330,36,37 For example, an 8-week double-blind, placebo-controlled trial of 51 women found that use of chitosan at a dose of 1,200 mg twice daily significantly reduced LDL ("bad") cholesterol as compared to placebo.37 However, a 4-month double-blind, placebo-controlled trial of 88 individuals found no benefit with 1,000 mg 3 times daily of a different chitosan product.31 Kidney Failure People with kidney failure experience numerous health problems, including anemia, fatigue, and loss of appetite. In one unblinded study, researchers tested chitosan supplements in 80 people with kidney failure receiving ongoing hemodialysis treatment. Half the participants were given 45-mg tablets for a total of about 1,500 mg of chitosan daily for 12 weeks; the other half were not given a supplement.32 Those in the treatment group showed a significant decrease in urea and creatinine levels. Further, they had a rise in hemoglobin levels and reported improved overall strength, appetite, and sleep as well. -------------------------------------------------------------------------------- Safety Issues There is significant evidence that long-term, high-dose chitosan supplementation can result in malabsorption of some crucial vitamins and minerals including calcium, magnesium, selenium, and vitamins A, D, E, and K.33,34 In turn, this appears to lead to a risk of osteoporosis in adults and growth retardation in children. For this reason, adults taking chitosan should also take supplemental vitamins and minerals, making especially sure to get enough vitamin D, calcium, and magnesium. Another possible risk of long-term ingestion of high doses of chitosan is that it could change the intestinal flora and allow the growth of unhealthful bacteria.35 Finally, there has been a case report of arsenic poisoning caused by long-term use of chitosan supplements.38 Shellfish, it appears, can concentrate arsenic in their shells as part of their normal development; this in turn may lead to arsenic-laced chitosan supplements. Pregnant or nursing women and young children should probably avoid chitosan altogether. -------------------------------------------------------------------------------- References 1. Kanauchi O, Deuchi K, Imasato Y, et al. Increasing effect of a chitosan and ascorbic acid mixture on fecal dietary fat excretion. Biosci Biotechnol Biochem. 1994;58:16171620. 2. 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 Biotechnol Biochem. 1994;58:16131616. 3. 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 Biotechnol Biochem. 1995;59:781785. 4. Schiller RN, Barrager E, Schauss AG, et al. A randomized, double-blind, placebo-controlled study examining the effects of a rapidly soluble chitosan dietary supplement on weight loss and body composition in overweight and mildly obese individuals. J Am Nutraceutical Assoc. 2001;4:4249. 5. Pittler MH, Abbot NC, Harkness EF, et al. Randomized, double-blind trial of chitosan for body weight reduction. Eur J Clin Nutr. 1999;53:379381. 6. Ho SC, Tai ES, Eng PH, et al. In the absence of dietary surveillance, chitosan does not reduce plasma lipids or obesity in hypercholesterolaemic obese Asian subjects. Singapore Med J. 2001;42:610. 7. Maezaki Y, Tsuji K, Nakagawa Y, et al. Hypocholesterolemic effect of chitosan in adult males. Biosci Biotechnol Biochem. 1993;57:14391444. 8. Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure. J Pharm Pharmacol. 1997;49:721723. 9. Ormrod D, Holmes CC, Miller TE. Dietary chitosan inhibits hypercholesterolaemia and atherogenesis in the apolipoprotein E-deficient mouse model of atherosclerosis. Atherosclerosis. 1998;138:329334. 10. 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 Biotechnol Biochem. 1994;58:16131616. 11. 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 Biotechnol Biochem. 1995;59:781785. 12. 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 Biotechnol Biochem. 1995;59:12111216. 13. Kanauchi O, Deuchi K, Imasato Y, et al. Increasing effect of a chitosan and ascorbic acid mixture on fecal dietary fat excretion. Biosci Biotechnol Biochem. 1994;58:16171620. 14. Kobayashi T, Otsuka S, Yugari Y. Effect of chitosan on serum and liver cholesterol levels in cholesterol-fed rats. Nutr Rep Int. 1979;19:327334. 15. Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure. J Pharm Pharmacol. 1997;49:721723. 16. Koide SS. Chitin-chitosan: properties, benefits and risks. Nutr Res. 1998;18:10911101. 17. Koide SS. Chitin-chitosan: properties, benefits and risks. Nutr Res. 1998;18:10911101. 18. Kato H, Taguchi T, Okuda H, et al. Antihypertensive effect of chitosan in rats and humans. J Tradit Med. 1994;11:198205. 19. Koide SS. Chitin-chitosan: properties, benefits and risks. Nutr Res. 1998;18:10911101. 20. Li H, Miyahara T, Tezuka Y, et al. The effect of low molecular weight chitosan on bone resorption in vitro and in vivo. Phytomedicine. 1999;6:305310. 21. Schiller RN, Barrager E, Schauss AG, et al. A randomized, double-blind, placebo-controlled study examining the effects of a rapidly soluble chitosan dietary supplement on weight loss and body composition in overweight and mildly obese individuals. J Am Nutraceutical Assoc. 2001;4:4249. 22. Pittler MH, Abbot NC, Harkness EF, et al. Randomized, double-blind trial of chitosan for body weight reduction. Eur J Clin Nutr. 1999;53:379381. 23. Maezaki Y, Tsuji K, Nakagawa Y, et al. Hypocholesterolemic effect of chitosan in adult males. Biosci Biotechnol Biochem. 1993;57:14391444. 24. Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure. J Pharm Pharmacol. 1997;49:721723. 25. Ormrod D, Holmes CC, Miller TE. Dietary chitosan inhibits hypercholesterolaemia and atherogenesis in the apolipoprotein E-deficient mouse model of atherosclerosis. Atherosclerosis. 1998;138:329334. 26. 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 Biotechnol Biochem. 1994;58:16131616. 27. 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 Biotechnol Biochem. 1995;59:781785. 28. 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 Biotechnol Biochem. 1995;59:12111216. 29. Kanauchi O, Deuchi K, Imasato Y, et al. Increasing effect of a chitosan and ascorbic acid mixture on fecal dietary fat excretion. Biosci Biotechnol Biochem. 1994;58:16171620. 30. Kobayashi T, Otsuka S, Yugari Y. Effect of chitosan on serum and liver cholesterol levels in cholesterol-fed rats. Nutr Rep Int. 1979;19:327334. 31. Ho SC, Tai ES, Eng PH, et al. In the absence of dietary surveillance, chitosan does not reduce plasma lipids or obesity in hypercholesterolaemic obese Asian subjects. Singapore Med J. 2001;42:610. 32. Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure. J Pharm Pharmacol. 1997;49:721723. 33. Koide SS. Chitin-chitosan: properties, benefits and risks. Nutr Res. 1998;18:10911101. 34. 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 Biotechnol Biochem. 1995;59:12111216. 35. Koide SS. Chitin-chitosan: properties, benefits and risks. Nutr Res. 1998;18:10911101. 36. Tai TS, Sheu WH, Lee WJ, et al. Effect of chitosan on plasma lipoprotein concentrations in type 2 diabetic subjects with hypercholesterolemia [letter]. Diabetes Care. 2000;23:17031704. 37. Wuolijoki E, Hirvela T, Ylitalo P. Decrease in serum LDL cholesterol with microcrystalline chitosan. Methods Find Exp Clin Pharmacol. 1999;21:357361. 38. Caraccio, TR. Chronic arsenic (As) toxicity from Chitosanฎ supplement [Abstract]. Clin Tox. 2002;644. |
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