Sundown Naturals Niacin 500 mg is a great way to get a high-potency source of this essential B Vitamin in a single caplet dose. As part of the B family of vitamins, Niacin works to support energy metabolism and nervous system health. Niacin also provides support for heart health, and healthy circulation. An easy dose of just one caplet a day is specially formulated to provide a gradual release of Niacin over a prolonged period of time.