Vitamin B3 is one of a select group of vitamins—along with C, D, B12 and thiamine– that actually has a deficiency disease associated with it. In the case of niacin, the disease is pellagra, a disease whose symptoms are often called the “Four D’s”: dementia, diarrhea, dermatitis, and death!
We don’t see much pellagra anywhere in the Western world, but it’s pretty clear that you’d be in deep trouble if you didn’t get enough niacin. Luckily, getting enough niacin to prevent pellagra is pretty easy to do.
As with other vitamins, the amount needed to prevent a horrible deficiency is not necessarily the same as the optimal amount. Niacin helps convert the food you eat into energy. Niacin also helps your body make both sex hormones and stress hormones, and it’s also been shown to suppress inflammation. Population studies have shown that people who get more niacin in their diet have less risk of Alzheimer’s(1)
Various forms of niacin have been used as supplements in the treatment of various health conditions, but the supplemental use of niacin is beyond the scope of this book.