Niacin (also known as vitamin B3, one form of which is niacinamide)

Niacin, also known as vitamin B3, is one of the eight B-complex vitamins. Niacin cannot be manufactured by humans and is thus a true vitamin, obtained exclusively from the diet.

Niacin is a precursor of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are required for a very large number of enzymes in essentially all metabolic pathways, including central roles in energy metabolism.

Deficiency is rare, and generally found in individuals with highly-restricted diets and/or substantial gastrointestinal disease. Symptoms can include nausea, skin and mouth lesions, anemia, diarrhea, headaches, mental confusion, and tiredness.

Niacin is important for maintaining a healthy cardiovascular system and metabolism, especially balancing blood cholesterol levels. In addition, niacin helps with brain function, healthy skin formation, and the maintenance of normal blood sugar.

Niacin is water-soluble vitamin and thus considered to be generally non-toxic. Niacin in the form of nicotinic acid is well known for causing flushing, but it is harmless. The niacinamide (also known as nicotinamide) form of niacin does not cause a flush, but also is not effective in lowering cholesterol levels. Side effects are rare at usual doses of niacinamide used in supplementation.

Laboratory testing can reveal the presence of a deficiency of this nutrient, but is generally not likely to have clinically utility.