Although the RDA for niacin is only 20 mg., levels of up to 3000 mg per day are prescribed by many conventional physicians for control of cholesterol levels. This is documented in the medical literature. Even higher levels of niacin have been safely and effectively employed for almost fifty years in treatment of psychiatric illness. The first double blind studies ever conducted in the field of psychiatry, in the early 1950's, showed the efficacy and safety of niacin in doses of 3000 mg per day or more, for control of schizophrenia. I have personally, over the past 20 years treated hundreds of mentally ill patients with niacin up to 3000 mg per day without evidence of toxicity.
Many patients remain well and out of mental hospitals for years on nutrient therapy.
Some people, especially those with hepatitis C, are especially sensitive to even moderate doses of niacin. Niacin can cause over-acidity in some people's stomachs. I know of no fatalities attributable to nutritional supplements. The well publicized case of illness and deaths associated with L-tryptophan in the late 1980's was not related to the amino acid itself, but to a contaminant introduced by genetic engineering of the organism that produces it, by Japanese manufacturer Showa Denko. It is beyond the scope of the model at this time to address the possible therapeutic benefits of higher nutrient intakes that may offset the risk of adverse effects.