You’ll find both niacin and niacinamide as supplements, and both are forms of vitamin B-3. These can be used interchangeably for some purposes, but some therapies require different forms of the vitamin. Always consult a doctor before trying either of these supplements to ensure you are taking the correct form, to check for drug interactions and to evaluate the risks of any side effects.
Niacin, or nicotinic acid, and niacinamide, make up vitamin B-3, according to the National Institutes of Health. In this form, it is found in cereal grains, yeast, milk, meat, fish, eggs and green vegetables. An amide is a chemical compound that contains a carbonyl group, or C=O, that is linked to a nitrogen atom.
Your body can convert niacin into niacinamide. Your body also makes niacinamide from tryptophan, which is an amino acid that is found in animal foods. The niacinamide you make from tryptophan, however, only covers a small amount of your body’s needs, according to Shari Lieberman and Nancy Pauling Bruning, authors of “The Real Vitamin and Mineral Book.”
Niacin and niacinamide have identical function when used as vitamins, say Andrea J. Mattiussi and Diane Blais in the "Journal of the Canadian Medical Association." Both are water soluble. However, their pharmacologic properties differ. For example, high doses of niacin can cause skin flushing. Niacinamide, however, does not have the same vasodialating, or blood-vessel widening, effects, that niacin has, so it does not lead to skin flushing. That makes it a good alternative when a doctor is preventing, treating a niacin deficiency, or treating pellagra, which is a wasting disease you can suffer due to vitamin B-3 deficiency, Blais and Mattuissi note. Nicinamide, however, can cause hyperhidrosis, or excessive sweating.
Niacin can be used to treat high cholesterol levels thanks to its role in fat metabolism, but niacinamide does not work for this purpose, according to Lieberman and Bruning. When niacin takes on an amide group, its cholesterol-lowering effects are inhibited, says Dr. Paul Jaconello of Toronto, Ontario, in the "Journal of the Canadian Medical Association."
Niacinamide may be useful for treating osteoarthritis, according to the National Institutes of Health, but more study is needed before a recommendation for this use can be made.
Only niacin is recommended for circulatory problems, say Bruning and Lieberman.
Either niacin or niacinamide can be used to treat mental disorders such as depression and anxiety. This usually is done in conjunction with other medications, note Bruning and Lieberman. Either form also may be used to address physical or emotional stress, say the authors.