Vitamin B3 (Niacin)

The amount of vitamin B-3 found in food does not cause side effects. However, taking high doses of vitamin B-3 as a supplement can result in adverse effects.

These include:

- flushed or itchy skin
- nausea
- vomiting
- constipation
- headache
- rash
- dizziness

Excess vitamin B-3 can also:

- reduce glucose tolerance and insulin resistance
- trigger an attack in people with gout
- result in eye problems
- lead to gastrointestinal problems
- increase the risk of liver damage
- lower blood pressure, leading to a loss of balance and risk of falls

A person who lacks vitamin B-3 may experience:

- a pigmented rash on skin that is exposed to the sun
- rough appearance to the skin
- bright red tongue
- fatigue or apathy
- vomiting, constipation, and diarrhea
- circulatory problems
- depression
- headache
- memory loss
- in severe cases, hallucinations

Niacin deficiency can result from inadequate dietary intake of niacin and/or the amino acid tryptophan. Tryptophan, obtained from the breakdown of dietary protein, can be converted to nicotinamide by liver enzymes that require vitamin B6, riboflavin, and iron. Deficiencies of these constituents can contribute to the development of niacin deficiency. Hartnup's disease, a hereditary disorder that reduces tryptophan absorption, can lead to niacin deficiency. Carcinoid syndrome diverts tryptophan to the increased production of serotonin and can reduce the production of nicotinamide. Prolonged treatment with isoniazid has also been associated with niacin deficiency.

Niacin deficiency can affect the skin, digestive system, and the nervous system. Severe niacin deficiency, referred to as pellagra, has been associated with the "four Ds": dermatitis, diarrhea, dementia, and ultimately death. Pellagra dermatitis is characterized by a thick, scaly, darkly pigmented rash that develops symmetrically in areas exposed to sunlight. Digestive system symptoms include vomiting, constipation or diarrhea, and a bright red tongue. Pellagra can also cause neurologic symptoms, including apathy, fatigue, depression, headache, disorientation, and memory loss.

Other names: Niacin / Nicotinamide / Nicotinic Acid

Niacin (nicotinic acid) is a water-soluble vitamin that is also referred to as vitamin B3.

Nicotinamide (nicotinic acid amide) is the derivative of niacin that is incorporated into the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP).