Chitosan is a form of fiber chemically processed from crustacean shells. Like other forms of fiber, such as oat bran, chitosan is not well digested by the human body. As it passes through the digestive tract, it seems to have an ability to bond with ingested fat and carry it out in the stool. For this reason, it has been tried as an agent for lowering cholesterol and reducing weight. However, the results in studies have been more negative than positive.
In addition, chitosan has been tried as a treatment for kidney failure and as an aid in wound healing.
We do not recommend the use of chitosan in children or pregnant women due to concerns about possible delayed growth (see
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.
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
below). For this reason, when using chitosan, it may be helpful to take supplemental
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
On the basis of chitosan's supposed ability to bind fat in the intestines, it has been tried as a treatment for
high cholesterol. However, the evidence regarding whether it really works is generally more negative than positive.31, 36,37,39,40, 42,43,45,48,49
At best, chitosan appears to offer no more than minimal benefit for high cholesterol.
Chitosan has also been proposed as a
weight loss treatment on the same principle.2,3
However, despite some mildly positive results, the current balance of evidence suggests chitosan does
not in fact significantly aid weight loss.4,5,37,41,44,46,49,50
Weak evidence hints that chitosan may be helpful in kidney failure.15
When used for this purpose, 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
This effect might be due to stimulation of new tissue growth; in addition, topical chitosan appears to kill bacteria such as
Streptococcus, which may also contribute to wound healing.16
Chitosan may also have activity against
Candida albicans, a form of yeast that causes
Highly preliminary evidence suggests that oral chitosan may inhibit the expected rise in
blood pressure after a high-salt meal.18
Other weak evidence hints that chitosan chewing gum might help prevent
It has been suggested that chitosan can
stimulate the immune system
but there is no reliable evidence as yet that it offers these benefits.
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
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 slightly reduced LDL ("bad") cholesterol as compared to placebo, but did not affect total or HDL ("good") cholesterol levels.37 Another 8-week trial, this one enrolling 84 people, also found modest benefits.39
However, a 4-month, double-blind, placebo-controlled trial of 88 individuals found no improvement in cholesterol with 1,000 mg 3 times daily of a different chitosan product.31 A 7-month study of 84 men given placebo or 1,200 mg of chitosan daily also failed to find benefit.43 Furthermore, in a 10-month, double-blind, placebo-controlled study of 130 men and women, use of a special microcrystalline form of chitosan at a dose of 1,200 mg twice daily again failed to improve cholesterol profile.40
These contradictory results suggest that if chitosan actually improves cholesterol profile at all, it does so to only a minimal extent.
Chitosan has been widely advocated as a
supplement, on the basis of its supposed ability to bind fat in the digestive tract. However, despite some positive results
21,46 the largest and best designed trial failed to find benefit.41
In this 6-month, double-blind, placebo-controlled study of 250 overweight people, use of chitosan at a dose of 3 g daily failed to enhance weight loss to any meaningful extent as compared to placebo.
Other studies have also failed to find significant benefit.22, 37,44,49,50
People with kidney failure experience numerous health problems, including anemia, fatigue, and loss of appetite. In one
open 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. However, these results must be taken with grain of salt, for only double-blind, placebo-controlled studies can prove a treatment effective. (For information on why this is so, see
Why Does This Database Rely on Double-blind Studies?)
There is significant evidence that long-term, high-dose chitosan supplementation can result in malabsorption of some crucial vitamins and minerals including
In turn, this appears to lead to a risk of
in adults and delayed growth 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.16
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.
Kanauchi O, Deuchi K, Imasato Y, et al. Increasing effect of a chitosan and ascorbic acid mixture on fecal dietary fat excretion
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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.
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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.
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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.
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Pittler MH, Abbot NC, Harkness EF, et al. Randomized, double-blind trial of chitosan for body weight reduction.
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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.
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Maezaki Y, Tsuji K, Nakagawa Y, et al. Hypocholesterolemic effect of chitosan in adult males.
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Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure.
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Ormrod D, Holmes CC, Miller TE. Dietary chitosan inhibits hypercholesterolaemia and atherogenesis in the apolipoprotein E-deficient mouse model of atherosclerosis.
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.
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Kato H, Taguchi T, Okuda H, et al. Antihypertensive effect of chitosan in rats and humans.
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Li H, Miyahara T, Tezuka Y, et al. The effect of low molecular weight chitosan on bone resorption
Tai TS, Sheu WH, Lee WJ, et al. Effect of chitosan on plasma lipoprotein concentrations in type 2 diabetic subjects with hypercholesterolemia [letter].
Wuolijoki E, Hirvela T, Ylitalo P. Decrease in serum LDL cholesterol with microcrystalline chitosan.
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Caraccio, TR. Chronic arsenic (As) toxicity from Chitosan® supplement [Abstract].
Bokura H, Kobayashi S. Chitosan decreases total cholesterol in women: a randomized, double-blind, placebo-controlled trial.
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Metso S, Ylitalo R, Nikkila M, et al. The effect of long-term microcrystalline chitosan therapy on plasma lipids and glucose concentrations in subjects with increased plasma total cholesterol: a randomised placebo-controlled double-blind crossover trial in healthy men and women.
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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.
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Guha S, Pal SK, Chatterjee N, et al. Effect of chitosan on lipid levels when administered concurrently with atorvastatin--a placebo controlled study.
J Indian Med Assoc. 2005;103:418,420.
Lehtimaki T, Metso S, Ylitalo R, et al. Microcrystalline chitosan is ineffective to decrease plasma lipids in both Apolipoprotein E epsilon4 carriers and non-carriers: a long-term placebo-controlled trial in hypercholesterolaemic volunteers.
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Mhurchu CN, Dunshea-Mooij C, Bennett D, et al. Effect of chitosan on weight loss in overweight and obese individuals: a systematic review of randomized controlled trials.
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Guha S, Pal SK, Chatterjee N, et al. Effect of chitosan on lipid levels when administered concurrently with atorvastatin--a placebo controlled study
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Kaats GR, Michalek JE, Preuss HG. Evaluating efficacy of a chitosan product using a double-blinded, placebo-controlled protocol.
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Hayashi Y, Ohara N, Ganno T, et al. Chewing chitosan-containing gum effectively inhibits the growth of cariogenic bacteria.
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Tapola NS, Lyyra ML, Kolehmainen RM, et al. Safety aspects and cholesterol-lowering efficacy of chitosan tablets.
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Last reviewed September 2014 by EBSCO CAM Review Board
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