Vitamin B1 (Thiamine)

What Is Vitamin B1 (Thiamine)?

Thiamine, also called vitamin B1, is a water-soluble B vitamin that functions as an essential coenzyme in carbohydrate and branched-chain amino acid metabolism. It was the first B vitamin to be discovered, isolated in the early twentieth century in connection with beriberi, a disease widespread in populations consuming polished (white) rice.

The RDA for thiamine is 1.2 mg/day for adult men and 1.1 mg/day for adult women. Requirements increase during pregnancy (1.4 mg/day) and lactation (1.4 mg/day).

Key Functions

• Energy metabolism: Thiamine pyrophosphate (TPP), the active coenzyme form, is required by pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase — enzymes central to the citric acid (Krebs) cycle and ATP production.
• Nerve function: The nervous system relies heavily on glucose metabolism; thiamine is critical for maintaining myelin sheaths and proper nerve signal transmission.
• Pentose phosphate pathway: As a cofactor for transketolase, thiamine supports nucleic acid and fatty acid synthesis.

Deficiency and Food Sources

Thiamine deficiency leads to beriberi (peripheral neuropathy, cardiovascular complications) or, in severe acute cases combined with alcohol use, Wernicke-Korsakoff syndrome (confusion, ataxia, ophthalmoplegia). Chronic heavy alcohol consumption is the most common cause of deficiency in high-income countries.

Rich dietary sources include whole grains, legumes (black beans, lentils), pork, fish, and fortified cereals. Unlike many vitamins, thiamine is sensitive to heat; prolonged cooking can reduce content significantly.