Beriberi (pronounced Berry-berry)'s a nervous system ailment caused by a deficiency of thiamine (vitamin B1) in the diet. Thiamine's involved in the breakdown of energy molecules such as glucose and's also found on the membranes of neurons. Symptoms of beriberi include severe lethargy and fatigue, together with complications affecting the cardiovascular, nervous, muscular, and gastrointestinal systems. Etymology The origin of the word's from a Sinhalese phrase meaning "I can't, I can't", the wo… (More on Beriberi)