Niacin is a vitamin that your body needs to turn food into energy and keep your cells healthy. Also called vitamin B3, niacin helps your body break down the carbohydrates, fats, and proteins you eat and convert them into fuel your muscles and brain can use.

You get niacin from foods like meat, fish, nuts, and whole grains. Your body can even make a small amount of niacin from an amino acid called tryptophan, which is found in turkey and other proteins. Without enough niacin, people can develop a disease called pellagra, which causes skin problems, digestive issues, and extreme tiredness. Pellagra was once common in parts of the American South where people relied heavily on corn for food, because corn contains niacin in a form the body can't easily use.

In the early 1900s, doctors discovered that niacin could prevent and cure pellagra, saving thousands of lives. Today, many grain products are fortified with niacin, meaning it’s added during processing to help make sure people get enough.