There are two basic forms of vitamin B-3, nicotinic acid (niacin) and niacinamide. The body obtains niacin in two ways: it makes it from the amino acid tryptophan, and it gets pure nicotinic acid from foods. Nicotinic acid was discovered as a result of pellagra epidemics in the southern United States at the turn of the 20th century. The heavily corn-based diet of the South, at the time, prevented an adequate dietary ingestion of the vitamin. Since 1939, white flour has been enriched with nicotinic acid as a preventive measure.
Some good sources of vitamin B-3 are green vegetables, meat, poultry, fish, whole-grain, enriched bread and cereal. Egg and milk don't have much B-3, but they contain tryptophan, an amino acid which the body can convert into nicotinic acid.
Niacin is essential for growth, for healthy tissues, and for the conversion of carbohydrates into energy. It helps produce fats in the body and it assists in processing alcohol. Vitamin B-3 acts as a coenzyme in many cellular reactions, is involved in generating energy for normal cellular function, and may be involved in the processes by which skin pigments are made. Without niacin, thiamin (B-1) and riboflavin (B-2) cannot function properly.
Normal dietary habits usually allow for an adequate intake of this vitamin. Also, B-3 is often an ingredient in B-complex, or multi-vitamin formulas. Niacin taken in excess of 50 mg daily may cause flushing, stomachache, or headache. If taken in large amounts, niacin can cause liver and eye damage, diabetes, gastritis and gout; therefore, it is important that high intakes of niacin, as used for therapeutic purposes, be closely monitored by a doctor or nutritionist.