There is a great article this month in Atlas Obscura detailing how fine, polished white rice helped destroy the Japanese navy and upset most of the residents of Tokyo.
Gleaming white rice was a status symbol—it was expensive and laborious to husk, hull, polish, and wash. In Japan, the poor ate brown rice, or other carbohydrates such as sweet potatoes or barley. The rich ate polished white rice, often to the exclusion of other foods.
In his book Beriberi in Modern Japan: The Making of a National Disease, Alexander R. Bay describes the efforts of Edo-era doctors to figure out the disease. A common suspect was dampness and damp ground. One doctor administered herbal medicines and a fasting regimen to a samurai, who died within months. Other doctors burned dried mugwort on patients’ bodies to stimulate qi and blood flow.