Vitamin B3, also called niacin, is one of eight B vitamins. As with all B vitamins, niacin helps in the process of enzymes converting food into energy. Niacin supports the function of over 200 enzymes around the body. As a supplement it is used in an attempt to improve cholesterol, cognitive function (nootropic), prevent type 1 diabetes, improve your skin, and many more. However, some doses can also cause serious side effects and not all types of niacin are equal.