Chitosan: A Safe and Effective Weight-Loss Aid?
Joseph H. Muldoon
Chitosan is a naturally occurring marine fiber derived from a common byproduct of shellfish processing. It is formed by partially deacetylating chitin, the repeating amino polysaccharide (N-acetyl glucosamine) units of the crustacean exoskeleton.  The net positive charge of the polar amino polymer groups of chitosan provide for the unusual functional properties and subsequent diverse applications of this unique fiber source. Chitosan derivatives have been used in water treatment facilities to decontaminate reservoirs of PCBs and to condition sludge beds. In industry chitosan has also served to bond with and facilitate the clearing of petrochemical spills.  Recently, ingenious medical applications have been developed which use chitosan as a pharmaceutical drug carrier effectively encapsulating various anti-inflammatory and chemotherapeutic agents allowing it to function as a moiety for safe sustained release.  As a natural, completely indigestible fiber source with the ability to electrostatically att ract and bond with negatively charged dietary lipids thus prohibiting their absorption, chitosan has been touted as a natural cure for the fat indulgence endemic in the Western diet.
Claims regarding chitosan’s fat binding ability vary greatly, with up to 12 times its weight or 17-50% of fat consumed said to be inhibited from absorption. Additional claims for the usual “bigger and better” forms and patent-pending “fast-acting” products that are “300% more potent” with “50-150% more chitosan in the same capsule size” (and of course considerable price tags to reflect the “value” added to the product!) are readily found. Related claims regarding all the benefits of increased fiber consumption and chitosan’s effectiveness as an antihyperlipidemic agent are central to the promotional literature on chitosan as well.
A review of available research is generally very supportive of chitosan’s functional properties and its potential clinical applications. Its binding capacity’s dependence on variables such as bolus viscosity, pH, and ionic strength, and its potentiation by ascorbate are well demonstrated. [4,5] Chitosan’s mechanism of action — binding negatively charged fatty acids and bile acids in the GI tract and absorbing and entrapping them in unabsorbable fatty floccule in its insoluble mass, thereby decreasing bile acid resorption and increasing fecal lipid excretion — is well described and experimentally supported.  Inhibition of aortic atherosclerotic plaque formation in apolipoprotein E deficient mice via the hypocholesterolemic effects of chitosan was demonstrated in one well-controlled study.  These studies intriguingly support claims of chitosan’ s potential as an antihyperlipidemic and fat absorption deterrent; however, questions regarding the extent of its usefulness and potential for detrimental effect s are arguable.
Most of the studies reveal significant increase in fecal fat excretion, and total cholesterol reduction with modest HDL increases reported.  However, most of the study groups were small and the improvements noted, while statistically significant, were not surprisingly less than the remarkable potential touted in the claims. As an additional point of claims contention, the Helsinki report, which is widely quoted in claims literature to demonstrate the weight reducing efficacy of chitosan, utilized a restricted caloric intake in addition to chitosan. The diet itself was carefully formulated to simulate the fat enhanced intake of the typical Western diet, but it was still restricted calorically — a fact that chitosan promoters don’t emphasize when they report the average 8% loss in body weight in 4 weeks by study participants. In fact, a more recent randomized double-blind, placebo-controlled trial on overweight subjects instructed to maintain their normal diet concluded, “Chitosan in the administered dosage without dietary alterations does not reduce body weight.” 
This obviously leads to concern with the lay interpretation of claims literature and chitosan utilization. If any fat-blocking substance is, for example, 20% effective, that 80% that is still absorbable becomes as much or even more of a problem to the lay person who is lulled into the assumption that they are able to consume more fat because they are supplementing, or that healthy weight reduction can occur without additional dietary and lifestyle modifications.
Additionally, concerns regarding potential development of fat soluble vitamin and essential fatty acid deficiency states with overutilization of fat-blocking substances are rational. Studies which examine this line of concern with chitosan did report significant detrimental changes in vitamin E status in controlled animal experiments.  An additional study found increased urinary calcium excretion and decreased mineral absorption and bone mineral content with continuous massive intake of chitosan.  The potential for overutilization/abuse by the general public is more than conceivable considering the pervasiveness of the fat-free fervor in the public’s consciousness. To the credit of claims literature reviewed, cautionary statements and instructions regarding appropriate fat soluble nutrient and medication ingestion while supplementing with chitosan were provided. These precautions advised taking any fat soluble nutrient and minerals or medications four hours pre- or post-chitosan consumption.
In spite of the aforementioned concerns, chitosan may prove to be useful as a relatively safe and beneficial component of a well-structured weight reduction program. In most of the studies reviewed, no serious adverse effects were reported. All claims for lipid absorption aside, just increasing one’s fiber intake will confer significant benefit (increase bowel motility, decrease transit time and gut mucosal carcinogen exposure, etc.) Chitosan is particularly appealing in light of the pharmaceutical industry’s endeavors to produce a “magic bullet” in the form of pancreatic lipase inhibitors like orlistat (Xenical), which is associated with a myriad of adverse gastrointestinal effects (not the least of which is fecal incontinence) due to the passing of large quantities of undigested, unbound fatty acids into the colon (Olestra revisited!).  When compared to such undesirable adverse effects, chitosan’s risk to potential benefit ratio is considerably more appealing.
Recommended dosage range is 2-4 capsules (500-1,000 mg) with eight ounces of water one half hour preprandially twice a day. If the claims hold true, this could potentially inhibit absorption of up to 6-12 g of fat per meal or approximately 108-216 kcal of fat per day — a small but potentially helpful edge.
Provided a patient is properly monitored, in good general health, not pregnant or lactating, has no demonstrable fat soluble vitamin or essential fatty acid deficiency and no history of acute atopic reaction to shellfish, chitosan may be implemented to augment a weight reduction program founded on appropriate and concurrently implemented dietary and lifestyle modifications.
About the Author
Dr. Muldoon is a graduate of Northwestern College of Chiropractic (NWCC). He has attained diplomate status from both the American Board of Chiropractic Internists and the American Chiropractic Board of Nutrition. He is a charter member of the Midwest Chiropractic Internist’s Association. In addition, he serves as an Adjunct Clinical Faculty member in NWCC’s Community Based Internship program, mentoring upper trimester level students prior to their graduation and lectures regularly for local community education programs. Dr. Muldoon enjoys private practice in rural southwestern Minnesota. He serves on the boards of his local Developmental Achievement Center and Hospice organizations and maintains Allied Health Professional Staff privileges in the local community hospital.
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