Niacin is a water-soluble vitamin that helps your body produce energy from foods and participates in a variety of biochemical reactions in the body. Among the B vitamins, niacin is unique in that the body can synthesize niacin from the amino acid tryptophan. This is not to say that your body doesn’t utilize the niacin that you consume from foods. It just meets its niacin requirement from both.
Foods high in proteins, such as poultry, fish and beef, are rich sources of niacin. Peanut butter and fortified cereals are also good sources of niacin.
Pellagra, the classic niacin-deficiency disease, is characterized by depression, apathy, headache, fatigue, memory loss, increasing mental confusion, diarrhea and skin problems. However, niacin deficiency is not seen frequently in industrialized countries except for in those individuals with chronic alcoholism or conditions, such as Hartnup’s disease, that disrupt the conversion of tryptophan to niacin.
It’s not likely that you’ll get toxic levels of niacin from food sources; there has been no evidence that this occurs. However, supplementation in high doses may cause adverse effects, such as flushed skin, nausea and vomiting, or liver damage.
The following table lists the recommended intake for healthy people based on current scientific information. These values are given in niacin equivalents (NEs) except for infants ages 0-6 months, where the value is in preformed niacin (niacin from foods). NEs account for the conversion of the amino acid tryptophan into niacin (1 mg of niacin = 60 mg tryptophan).