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.

Note: We do not recommend the use of chitosan in children or pregnant women due to concerns about possible delayed growth (see Safety Issues below).

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.