Vitamin B1, also called thiamine or thiamin, is one of 8 B vitamins. All B vitamins help the body convert food (carbohydrates) into fuel (glucose), which the body uses to produce energy. Vitamin B1 helps the body metabolize fats and protein and are also needed for  a healthy liver, skin, hair, and eyes. They also help the nervous system function properly and are needed for good brain function. All B vitamins are water soluble, meaning that the body does not store them. Like other B-complex vitamins, thiamine is sometimes called an "anti-stress" vitamin because it may strengthen the immune system and improve the body's ability to withstand stressful conditions. It is named B1 because it was the first B vitamin discovered. Thiamine is found in both plants and animals and plays a crucial role in certain metabolic reactions. Your body needs it to form adenosine triphosphate (ATP), which every cell of the body uses for energy. It is rare to be deficient in thiamine, although alcoholics, people with Crohn disease, anorexia, and those undergoing kidney dialysis may be deficient. Symptoms of thiamine deficiency are:
Headache Nausea Fatigue Irritability Depression Abdominal discomfort  People with thiamine deficiency also have trouble digesting carbohydrates. This allows a substance called pyruvic acid to build up in the bloodstream, causing a loss of mental alertness, difficulty breathing, and heart damage, a disease known as beriberi.