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.

The role of niacin in the treatment of autism is not well studied, however, children with ASD often have diets that are relatively deficient in many nutrients.

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.