When and where did pellagra start?

Pellagra was first identified in the early 18th century in Italy, particularly in the regions of Lombardy and Emilia-Romagna. The condition became more widespread in the southern United States in the early 20th century, particularly in the 1900s to 1930s, often linked to diets heavily reliant on corn. It is caused by a deficiency of niacin (vitamin B3) and is associated with symptoms such as dermatitis, diarrhea, and dementia.