Thiamine also known as Vitamin B1, is classified as a B-complex vitamin. Thiamine is naturally present in some foods, added to some food products and available as a dietary supplement. This vitamin plays a critical role in energy metabolism and, therefore, in the growth, development, and function of cells. Vitamin B1 is among the nutrients most prone to destruction by our modern food production system. At each step along the way, from storage through refining up through cooking, we lose a big portion of the vitamin B1 content of foods. Vitamin B1 acts as the gatekeeper between the less efficient step of early carbohydrate breakdown and the very energy-rich Krebs cycle.