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.
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
For Healthcare Professionals
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.
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).
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).