Deficiency of ______ causes a disease known as beri-beri.

• Beri-beri is a nutritional disorder caused by a deficiency of thiamine (vitamin $B_1$).
• It is caused by poor diet and excess drinking of alcohol.
• There are two main types: wet beriberi and dry beriberi. Wet beriberi affects the heart and circulatory system while dry beriberi damages the nerves and can lead to reduced muscle strength.