thiamine

Thiamine, also known as vitamin B1, is a water-soluble vitamin that humans must obtain from the diet. In the body, thiamine is converted to thiamine pyrophosphate (TPP), an essential coenzyme for enzymes involved in carbohydrate metabolism and energy production, including pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, branched-chain α-keto acid dehydrogenase, and transketolase in the pentose phosphate pathway.

Dietary sources of thiamine include pork, whole grains, legumes, seeds, and fortified foods. Thiamine is sensitive to storage and cooking; because the body stores only small amounts, adequate daily intake is important to prevent deficiency. Adult daily requirements are commonly listed around 1.1–1.2 mg, varying by guideline and population.

Deficiency can cause beriberi, which presents as dry beriberi (neurological symptoms such as peripheral neuropathy) or wet beriberi (cardiovascular symptoms such as edema and heart failure), and in high-risk groups, especially chronic alcohol users, Wernicke-Korsakoff syndrome with ocular abnormalities, ataxia, and confusion. The condition reflects impaired energy metabolism in nervous tissue and other organs.

Diagnosis is based on clinical suspicion supported by laboratory tests showing low thiamine or thiamine pyrophosphate levels and reduced erythrocyte transketolase activity. In suspected deficiency, treatment should not be delayed for laboratory confirmation.

Treatment involves thiamine replacement, typically given by injection or intravenous administration (for example, 100 mg daily for several days, followed by oral maintenance). In suspected Wernicke encephalopathy, thiamine is administered before glucose to prevent progression. Addressing underlying causes, such as alcohol use or malabsorption, is also important.