A member of the vitamin B complex. It is essential for human nutrition, the normal daily requirement for an adult being about 15–20 mg. A deficiency of nicotinic acid is one of the factors in the aetiology of PELLAGRA, and either nicotine acid or NICOTINAMIDE is used in the treatment of this condition. Nicotinic acid also reduces the concentration of blood lipids (see HYPERLIPIDAEMIA).