Vitamin B3, also called niacin, is one of eight water-soluble B vitamins. All B vitamins help the body to convert carbohydrates into glucose (sugar), which is burned to produce energy. These B vitamins, often referred to as B complex vitamins, are essential in the breakdown of fats and protein. B complex vitamins also play an important role in maintaining muscle tone along the digestive tract and promoting the health of the nervous system, skin, hair, eyes, mouth, and liver.

Niacin plays an important role in ridding the body of toxic and harmful chemicals. It also helps the body make various sex and stress-related hormones in the adrenal glands and other parts of the body. Niacin is effective in improving circulation and reducing cholesterol levels in the blood. Niacin needs can be partially met by eating foods containing protein because the human body is able to convert tryptophan, an amino acid, into niacin.

Dietary deficiency of niacin tends to only occur in areas of the world where people eat corn as a staple and don't use lime in fertilization. Corn is the only grain that is low in niacin. Lime releases tryptophan which, again, can be converted to niacin in the body. Symptoms of mild deficiency include indigestion, fatigue, canker sores, vomiting, and depression. Severe deficiency of both niacin and tryptophan can cause a condition known as pellagra. Pellagra is characterized by cracked, scaly skin, dementia, and diarrhea. It is generally treated with a nutritionally balanced diet and niacin supplements. Niacin deficiency also results in burning in the mouth and a swollen, bright red tongue In the United States alcoholism is the prime cause of Vitamin B3 deficiency.
Uses

Extremely high doses of niacin (available by prescription) have been shown to prevent and/or improve symptoms of the following conditions. Because of risk of toxicity people should always consult a knowledgeable health care provider before starting high doses of niacin.