Niacin is a water-soluble B vitamin that can be synthesized in humans by converting tryptophan to niacin.
There are two forms of vitamin B3, each with different activities. Niacin, which is also known as nicotinic acid and Niacinamide, which is also known as nicotinamide

Plays an essential role in:

§          Reduces LDL (“bad” cholesterol) and triglycerides, and increases HDL (“good” cholesterol).

§          Oxidation-reduction reactions in the Krebs cycle involving the production of energy from carbohydrates.

§          Necessary for oxidative phosphorylation, as well as glutathione reductase and glutamate dehydrogenase enzymes.

§          Metabolism of Carbohydrates, fatty acids, and amino acids.

Vitamin B3 deficiency

A niacin deficiency can result in cracked, pigmented, scaly dermatitis, especially on parts of the skin exposed to the sun.
Severe deficiency is known as pellagra, which means rough skin. Symptoms of pellagra characterized by the “3 Ds”: dermatitis, dementia, and diarrhea. Pellagra occurs in areas where nutrition is meager and corn is the dietary staple.

Click here for Vitamin B3 RDA  table

Vitamin B3 Forms
Niacin, also known as nicotinic acid; niacinamide, also known as nicotinamide; inositol hexaniacinate, also known as inositol hexanicotinate.