The dietary supplement chitosan lowers serum phosphorus in a hemodialysis patient not tolerating prescription medications.

Chitosan is a widely available, nontoxic, biodegradable biopolymer that binds negatively charged molecules. Its use as a dietary supplement for weight loss derives from its purported ability to bind negatively charged lipids and bile acids and prevent their gastrointestinal absorption. Here, we report the case of a dialysis patient who did not tolerate prescription phosphorus binders and who has been able to control her serum phosphorus levels for a year by taking 3.5 g of chitosan a day with meals. A quantitative analysis shows that chitosan may bind between 16 and 41 mg of phosphorus per gram, comparable to prescription binders. Chitosan may provide an over-the-counter alternative as non-calcium phosphorus binder for patients not tolerating prescription phosphorus binders because of side effects, cost, or efforts to limit their medication burden.