Niacin synthesis is deficient in carcinoid syndrome because of metabolic diversion of its precursor, tryptophan, to form serotonin. In some untreated individuals this can even lead to pellagra. Hence the recommendation for niacin supplementation. Niacin supplementation (in the nicotinic acid form) of up to 10 times the RDA (recommended dietary allowances which range from 15-20 mg/day to prevent pellagra), i.e., up to 200 mg per day, does usually not cause flushing or other side effects. Megadoses of nicotinic acid (100 mg – 3 g), which are sometimes given to people with hypercholesterolemia, on the other hand, have well-documented side effects of flushing, hyperuricemia, abnormalities in liver function, and occasionally hyperglycemia. Not a very good idea for carcinoids. The purpose for supplementation in carcinoids is to prevent pellagra not hypercholesterolemia, therefore lower levels of niacin intake is prudent (in either the acid or amide form). Megadoses of nicotineamide (as well as other water-soluble vitamins) may also have equally detrimental effects. Since very little documentation exists about the toxicity of large doses of this form (except in mice), it is recommended to stay within close proximity of the RDAs. The statements regarding various treatment options on our web page are very general, on purpose, since they are not meant to be used as self-treatment unsupervised by a physician or, in the case of nutrition, by a trained professional, but rather informational as to most available treatment today. Therefore, an amendment to this statement cannot be made.
