脚気 (きゃっけ, kyakke) is a condition caused by a deficiency of vitamin B1 (thiamine). It primarily affects the nervous system and can lead to symptoms such as weakness, numbness, and pain in the limbs. In severe cases, it can result in heart problems and difficulty walking. Historically,脚気 was common among populations with a diet high in polished rice, which lacks essential nutrients. The condition was notably studied by Kawasaki Shōzō, a Japanese physician, who linked it to dietary habits in the early 20th century, leading to increased awareness and prevention efforts.