Chitosan is derived from chitin, a substance found in the hard outer shells of marine crustaceans such as crab, crayfish, lobster and squid. This indigestible fiber passes through the digestive tract without being absorbed. People take chitosan supplements to lose weight and lower cholesterol because of claims that chitosan binds to dietary fat and carries it out of the body, thus preventing absorption of a certain level of fat and calories. The Memorial Sloan-Kettering Cancer Center explains that research does not support this theory. Negative effects from chitosan are rare and typically minor.
Gastrointestinal Distress
Gastrointestinal distress may occur in patients taking chitosan, according to the Memorial Sloan-Kettering Cancer Center. Symptoms include constipation or diarrhea, gas and abdominal discomfort.
Prevent Nutrient Absorption
Because some vitamins are fat-soluble, chitosan can prevent absorption of these vitamins if it works as claimed. This would affect vitamins A, D, E and K. The Memorial Sloan-Kettering Cancer Center cautions pregnant women not to take chitosan because of a possible reduction not only in vitamin D absorption but also in calcium absorption. Drugs.com also cautions that research is lacking on whether it is safe to take chitosan during pregnancy and breastfeeding.
Allergic Reaction
People with a shellfish allergy should not take chitosan, as noted by the Memorial Sloan-Kettering Cancer Center. Signs of an allergic reaction may include difficulty breathing, tightness in the chest or throat, chest pain, itchy or swollen skin, and a rash or hives. An allergic reaction to chitosan should be considered a medical emergency. Also, the Physicians' Desktop Reference notes that reports have been made of swollen wrists and heels occurring when taking chitosan.
Combination Product Effects
Some weight loss and fiber supplements include chitosan along with other substances, and it is not always possible to determine which ingredient is responsible for negative effects. A study published in the June 2004 issue of "The American Journal of the Medical Sciences," for instance, reported a case of rhabdomyolysis that developed after a woman took an herbal weight-loss supplement containing chitosan as well as ma huang, guarana, Garcinia cambogia and other ingredients. Rhabdomyolysis involves muscle breakdown, which releases proteins into the bloodstream that can cause kidney damage. Additionally, supplements that list chitosan as the primary ingredient may include fiber powders such as glucomannan and psyllium. These substances can be dangerous if people consume them without adequate fluid, because any left in the throat or esophagus may swell and cause choking.
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