What Is Vitamin B3 (Niacin)?

N iacin is an essential water-soluble B vitamin that is required by all cells of the body.

During digestion of food containing it, niacin (the form in food) is changed in the small intestines to the active form niacinamide (niacin plus an amide group), which is then absorbed into the bloodstream. 

Niacinamide is converted by the body into co-enzymes which are present in all cells. These are niacinimide adenine dinucleotide (NAD) and NADP. NADP is formed when the body adds a phosphate to NAD.

Q: How do these enzymes work?

A: These enzymes function in oxidation-reduction reactions essential for release of energy from carbohydrates, fats, and proteins and are needed as components for more than 200 enzymes involved in metabolism.

In addition to producing energy, niacinamide is essential for healthy skin and the mucosal lining of the digestive tract, normal functioning of the brain and nervous system, and production of steroid hormones in adrenal glands and hormones in sex glands.  Functions are more fully described below.

Urinary excretion of niacin cannot be detected when vitamin intake is below the required levels. On the other hand, when intake exceeds saturation in the body, the vitamin and/or its metabolites are actively excreted into urine to prevent excessive toxicity of the vitamins.¹

What Is Niacin Deficiency In Celiac Disease and/or Gluten Sensitivity?

1. Shibata K, Hirose J, Fukuwatari T. Relationship Between Urinary Concentrations of Nine Water-soluble Vitamins and their Vitamin Intakes in Japanese Adult Males. Nutr Metab Insights. 2014 Aug 5;7:61-75. doi: 10.4137/NMI.S17245. eCollection 2014. [↩]