Niacin is a vitamin. Your body needs a little of it for healthy skin and nerves, and for turning food into energy. It is also called vitamin B3. You get it from meat, fish, peanuts and some grains. Though actually, the name is a careful invention: in 1942 scientists built it from nicotinic + acid + vitamin, because “nicotinic acid” sounds as if it belongs with nicotine, the drug in cigarettes. They did not want people to think vitamins were tobacco, or that smoking gave you vitamins. Eating a niacin-rich meal is nothing like smoking. Too little niacin over a long time can cause a serious illness called pellagra; that is rare now where diets are mixed. Doctors sometimes use much larger amounts as a medicine for blood fats — that is not the same as the small amount in food, and it can have side effects. On a label you may also see nicotinic acid or nicotinamide; those are the vitamin B3 family, not nicotine.