Pellagra, a disease caused by Niacin deficiency, was epidemic in the American South during the 19th century. At the time, the diet of the rural poor was based heavily on corn and did not include enough protein-rich foods like meat, milk, eggs, or legumes.

In Meiji-era Japan, many people suffered from Beriberi, a disease caused by thiamine deficiency. This was especially prevalent in the Japanese navy. The cause for this deficiency was a switch from unpolished brown rice to polished white rice (the rice husks removed by polishing contained a lot of protein). The Japanese navy eventually added barley to its rice rations to combat this disease.