Vitamin B-1 (thiamin) is essential for the metabolism of carbohydrates, some amino acids, and alcohol. It is also necessary for the production of the neurotransmitter acetylcholine, and for the detoxification of both alcohol and lactic acid (a by-product of strenuous exercise). Thiamin has important roles in the production of energy and ATP derived from reactions in the Krebs cycle. A high carbohydrate diet, strenuous physical exercise, or chronic alcohol consumption may increase the physiological need for vitamin B-1.