Niacin is basically one of the essential B vitamins. It's main function is to promote a healthy cardiovascular system as well as help boost your immune system. I haven't personally taken niacin but have read up on it after watching a weight loss special on tv. It is supposed to convert food into energy almost identically to that of L-carnitine(a non-essential amino acid). Niacin also helps digestive enzymes break down fats, carbohydrates and protein. Niacin is also supposed to help in breaking down triglycerides in the bloodstream and tissues. You can pretty much find niacin in most daily vitamin/mineral supplements.