Niacin is a member of the B vitamin complex. Structure of nicotinamide Principal sources in nature Nicotinamide and nicotinic acid occur widely in nature.
Nicotinic acid is more prevalent in plants, whereas in animals nicotinamide predominates.
Yeast, liver, poultry, lean meats, nuts and legumes contribute most of niacin in food. Milk and green leafy vegetables contribute lesser amounts. Specific food processing, such as the treatment of corn with lye or lime water increases the bioavailability of nicotinic acid in these products. Important food sources of tryptophan are meat, milk and eggs. Body stores Both acid and amide forms of the vitamin are readily absorbed from the small intestine.