Vitamin B3 (Niacin) is used commonly to refer to two different compounds, nicotinic acid and niacinamide. B3 was first isolated during oxidation of nicotine from tobacco and was thus given the name nicotinic acid vitamin, shortened to niacin. It is not, however, the same as or even closely related to the molecule nicotine. Niacin, as nicotinic acid or niacinamide, is converted in the body to the active forms, nicotinamide adenine dinucleotide (NAD) and a phosphorylated form (NADP).

Niacin is one of the most stable of the B vitamins. It is resistant to the effects of heat, light, air, acid, and alkali. A white crystalline substance that is soluble in both water and alcohol, niacin and niacinamide are both readily absorbed from the small intestine. Small amounts may be stored in the liver, but most of the excess is excreted in the urine.

Niacin is involved in reactions that generate energy in tissues by the biochemical conversion of carbohydrates, fats, and proteins. The two coenzymes of niacin, NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate), are essential for utilizing the metabolic energy of foods. Niacin is essential for growth and is involved in the synthesis of hormones. Niacin is absorbed in the intestine and stored in the liver. Excessive niacin is excreted in the urine. Helps synthesize DNA.

Vitamin B3 is required for cell respiration, helps in the release of energy and metabolism of carbohydrates, fats, and proteins, proper circulation and healthy skin, functioning of the nervous system, and normal secretion of bile and stomach fluids. It is used in the synthesis of sex hormones, treating schizophrenia and other mental illnesses, and a memory-enhancer.

Nicotinic acid (but not nicotinamide) given in drug dosage improves the blood cholesterol profile, and has been used to clear the body of organic poisons, such as certain insecticides. People report more mental alertness when this vitamin is in sufficient supply.

A deficiency may cause pellagra, the classic niacin deficiency disease, and is characterized by bilateral dermatitis, diarrhea, and dementia. A shortage of niacin may be indicated with symptoms such as canker sores, depression, diarrhea, dizziness, fatigue, halitosis, headaches, indigestion, insomnia, limb pains, loss of appetite, low blood sugar, muscular weakness, skin eruptions, and inflammation.

Nicotinic acid, but not nicotinamide in doses larger than 200 mg causes flushing by dilating the blood vessels, which can also cause the blood pressure to drop. These flushes are normally harmless. Large dosages can also cause itching, elevated blood glucose, peptic ulcers and liver damage.

Consuming alcohol and not having enough protein in your diet may increase your need for niacin. People with diabetes, glaucoma, any liver disease or peptic ulcers should be careful of niacin supplementation.

Liver, lean meat, poultry, fish, rabbit, nuts, peanut yeast, meats including liver, cereals, legumes, asparagus, seeds, milk, green leafy vegetables, and fish. Your daily cup of coffee also provides about 3 milligrams of niacin.