The disease beriberi is caused by a deficiency of which vitamin?

Beriberi refers to a cluster of symptoms caused primarily by a nutritional deficit in vitamin B1 (thiamine). Beriberi has conventionally been divided into three separate entities, relating to the body system mainly involved (peripheral nervous system or cardiovascular) or age of person (eg. infantile). Beriberi is one of several thiamine-deficiency related conditions which may occur concurrently, including Wernicke's encephalopathy (mainly affecting the central nervous system), Korsakoff's syndrome (amnesia with additional psychiatric manifestations), and Wernicke-Korsakoff syndrome (with both neurologic and psychiatric symptoms).

Historically, beriberi has been common in regions where what is variously referred to as polished or white rice forms a major part of the diet. This type of rice has its husk removed to extend its shelf life and palatability, but this has the side effect of removing the primary source of thiamine. It was not known until the end of the 19th century that polishing rice was associated with beriberi.