Prevalent in the united states during the early 1900s, pellagra was first thought to be an infectious disease. today we know that it is caused by a deficiency of

A deficiency of niacin, also known as vitamin B3, causes pellagra. B3 deficiency can be caused by a dietary lack of niacin, seen in poor and malnourished farmers in the 1900s, or from poor absorption of niacin, observed with certain diseases or how the food is prepared.