Common Names

  • Kitosan
  • Chitin
  • Polyglucosamine

For Patients & Caregivers

How It Works

Chitosan has been promoted for weight loss and for cholesterol reduction. However, there is not enough evidence to support such uses.

The main ingredient in chitosan (KY-to-san) is chitin, an extract from the shells of sea creatures such as shrimp, lobster, and clams. It can also come from the cell walls of  Reishi mushrooms. Marketers promote chitosan as a weight-loss product, claiming that it binds to fat and cholesterol in the intestine, preventing them from being absorbed. However, studies in people have found that chitosan did not increase levels of fat excreted in their feces. Chitosan is used as an ingredient for some medical applications such as bandanges, to improve wound healing. Scientists think it may enhance the process of new tissue formation.

Purported Uses
  • For weight loss
    There is not enough evidence to support the use of chitosan alone without dietary changes or exercise for weight loss.
  • To lower cholesterol
    Some clinical trials support this use, but long-term effectiveness is unknown.
  • Topically, for improved wound healing
    Laboratory evidence and a clinical trial support this use.
Do Not Take If
  • You are allergic to shellfish or mushrooms: Chitosan comes from either of these sources.
  • You are taking warfarin (Coumadin): Chitosan may increase the blood-thinning effect of this drug and increase the risk of bruising or bleeding.
Side Effects
  • Constipation
  • Flatulence, gas
  • Bloating, abdominal cramping
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For Healthcare Professionals

Scientific Name
Deacetylated chitin bipolymer
Clinical Summary

Chitosan (KY-to-san) is a derivative of chitin, extracted from the exoskeleton of crustaceans, including shrimp, lobster, and clams, and from the cell wall of Reishi mushrooms (13). Chitosan is used as an excipient in pharmaceutical formulations and in biomedical applications including wound dressings. It is also made into an edible film to protect food from spoilage (1). Chitosan is marketed as an all-natural marine fiber for weight loss management and to manage cholesterol.

Animal models suggest antiobesity properties with chitosan (14) (15) (16) (17) and derivative products (18) (19). In one animal study, a combination of capsaicin and chitosan increased this activity (20).

Findings from human studies are conflicting. Although marketers of weight loss supplements claim that chitosan can bind with fat in the intestine, some clinical trials did not find any increase in fecal excretion of fat or weight loss compared with placebo (2) (3) (4) (21). Other studies have had more positive results in combination with additional products or interventions. In a double-blind randomized controlled trial (RCT), polyglucosamine, a low molecular weight chitosan, along with a low-calorie diet and increased exercise for at least 6 months yielded additional weight loss compared with placebo and the same diet/lifestyle changes (22). Chitosan in combination with L-ascorbic acid produced some effects on bodyweight in overweight women, but there were no significant differences in fat mass, percentage body fat, body circumference, or skinfold thickness compared with placebo control (23). One single-blind RCT of fungal chitosan found significant bodyweight reductions and improved hemoglobin A1c, body composition, and anthropometric parameters in overweight/obese adults without diet restriction compared with placebo after 3 months (24). Howevever, due to heterogeneity of studies and mixed results, more trials are needed before definitive conclusions can be drawn.

In diabetic patients, chitosan reduced low-density lipoprotein (LDL) cholesterol (6), and decreased weight, body mass index (BMI), waist circumference, and triglycerides (7). A systematic review also concluded that chitosan reduces total cholesterol, but larger RCTs are necessary to determine its effect on other lipoproteins (8).

Chitosan may increase total plasma antioxidant activity and lower the indices of oxidative stress in humans (9). Limited clinical data are available regarding efficacy for anemia or chronic renal failure, although chitosan did show benefit in a small randomized study (10).

Reported adverse events include constipation and gastrointestinal distress (2). Patients allergic to shellfish or mushrooms should use related supplements with caution.

Purported Uses
  • High cholesterol
  • Weight loss
  • Wound healing
Mechanism of Action

Chitosan is a natural polysaccharide that consists of glucosamine and N-acetylglucosamine copolymers (14). It has been described as biodegradable, nontoxic, non-immunogenic, and biocompatible (25), with properties similar to cellulose (2).

In an in vitro study, chitosan demonstrated antioxidant effects by reducing albumin carobonyls and hydroperoxides in a time-dependent manner (9).

In animal models, antiobesity effects may occur through serum leptin and C-reactive protein modulation (14) or 5’ adenosine monophosphate-activated protein kinase (AMPK) activation and lipogenesis-associated gene inhibition (15). In porcine models, chitosan altered genes influencing appetite and feeding behavior in the small intestine (NPY), adipose tissue (Leptin), and the brain (HCRT, INSR, NMB, GHR, PPARG, NPY5R(17). It also downregulated FABP2 gene expression, increased serum leptin, and significantly altered gut microbial populations (16). In high-fat diet-induced obese rodents, chitosan oligosaccharides improved dyslipidemia and prevented body weight gain by inhibiting adipocyte differentiation (19). As an insoluble fiber, low molecular weight chitosan polyglucosamines can bind to fat in the intestinal lumen, forming a complex that is partially utilized by colon bacteria and partially eliminated (22) (26) (27), but appropriate concentrations are needed. In one of these animal studies, it was suggested that the more likely mechanisms for weight loss could include bacterial energy wasting, as increased acetate and glucose excretion were also present, suggesting that larger amounts of lipids and glucose were available as fuel for bacteria in the colon (26).

Hypocholesterolemic effects from chitosan in murine models were not due to reduced cholesterol absorption efficiency or increases in fecal sterol output, so that a major bile acid-binding capacity was ruled out (28). The more likely scenario is that the fiber’s influence on satiation and satiety reduces food intake suppression and therefore cholesterol (29).

Human studies suggest that it is unlikely that chitosan binds fat in intestines, and could therefore not support this purported mechanism of action (21) (30).

Topical application enhances wound healing by stimulation of granulation tissue. Possible mechanisms include formation of a gel-like fibronectin matrix that facilitates inward epithelial cell migration and the formation of heparin-chitosan complexes that activate growth factors that bind to stabilized heparin (12).


As chitosan products are derived from shellfish or mushrooms, patients who are allergic to these substances should use chitosan with caution.

Adverse Reactions

Constipation, flatulence, and GI distress symptoms (4) (8) (21) (22)

Herb-Drug Interactions

Warfarin (Coumadin): Chitosan may increase the anticoagulant effect of this drug (31).

Dosage (OneMSK Only)
  1. Cagri A, Ustunol Z, Ryser ET. Antimicrobial edible films and coatings. J Food Prot. 2004 Apr;67(4):833-48.

  2. Pittler MH, et al. Randomized, double-blind trial of chitosan for body weight reduction. Eur J Clin Nutr 1999;53:379-81.

  3. Pittler MH, Ernst E. Dietary supplements for body-weight reduction: a systematic review. Am J Clin Nutr. 2004 Apr;79(4):529-36.

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

  5. Hernández-González SO, González-Ortiz M, Martínez-Abundis E, et al. Chitosan improves insulin sensitivity as determined by the euglycemic-hyperinsulinemic clamp technique in obese subjects. Nutr Res. 2010 Jun;30(6):392-5.

  6. 8. Baker WL, Tercius A, Anglade M, et al. A meta-analysis evaluating the impact of chitosan on serum lipids in hypercholesterolemic patients. Ann Nutr Metab. 2009; 55(4):368-74.

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

  8. Koide SS. Chitin - chitosan: properties, benefits, and risks. Nutrition Research 1998;18:1091-101.

  9. Stone CA, et al. Healing at skin graft donor sites dressed with chitosan. Br J Plast Surg 2000;53:601-6.

  10. Mesa Ospina N, Ospina Alvarez SP, Escobar Sierra DM, et al. Isolation of chitosan from Ganoderma lucidum mushroom for biomedical applications. J Mater Sci Mater Med. Mar 2015;26(3):135.

  11. Walsh AM, Sweeney T, Bahar B, et al. Multi-functional roles of chitosan as a potential protective agent against obesity. PLoS One. 2013;8(1):e53828.

  12. Huang L, Chen J, Cao P, et al. Anti-obese effect of glucosamine and chitosan oligosaccharide in high-fat diet-induced obese rats. Mar Drugs. May 2015;13(5):2732-2756.

  13. Tan S, Gao B, Tao Y, et al. Antiobese effects of capsaicin-chitosan microsphere (CCMS) in obese rats induced by high fat diet. J Agric Food Chem. Feb 26 2014;62(8):1866-1874.

  14. Mhurchu CN, Poppitt SD, McGill AT, et al. The effect of the dietary supplement, Chitosan, on body weight: a randomised controlled trial in 250 overweight and obese adults. Int J Obes Relat Metab Disord. Sep 2004;28(9):1149-1156.

  15. Jung EY, Jun SC, Chang UJ, et al. L-ascorbic acid addition to chitosan reduces body weight in overweight women. Int J Vitam Nutr Res. 2014;84(1-2):5-11.

  16. Rios-Hoyo A, Gutierrez-Salmean G. New Dietary Supplements for Obesity: What We Currently Know. Curr Obes Rep. Apr 6 2016.

  17. Bondiolotti G, Cornelli U, Strabbioli RS, et al. Effect of a polyglucosamine on the body weight of male rats: Mechanisms of action. Food Chemistry. 2/1/ 2011;124(3):978-982.

  18. Bondiolotti G, Bareggi SR, Frega NG, et al. Activity of two different polyglucosamines, L112 and FF45, on body weight in male rats. Eur J Pharmacol. Jul 12 2007;567(1-2):155-158.

  19. Burton-Freeman B. Dietary fiber and energy regulation. J Nutr. Feb 2000;130(2S Suppl):272s-275s.

  20. Gades MD, Stern JS. Chitosan supplementation and fecal fat excretion in men. Obes Res. May 2003;11(5):683-688.

  21. Huang SS, Sung SH, Chiang CE. Chitosan potentiation of warfarin effect. Ann Pharmacother. Nov 2007;41(11):1912-1914.

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