Thiamine is a essential nutrient required for carbohydrate metabolism; also involved in nerve function. Biosynthesized by microorganisms and plants. Dietary sources include whole grains, meat products, vegetables, milk, legumes and fruit. Also present in rice husks and yeast. Converted in vivo to Thiamine diphosphate, a coenzyme in the decarboxylation of α-keto acids. Chronic deficiency may lead to neurological impairment, bariberi, Wernicke-Korsakoff syndrome.