Vitamin B1 (Thiamine)

Direct Answer

Vitamin B1 is a water-soluble pyrimidine/thiazole vitamin acting as the Thiamine Pyrophosphate (TPP) coenzyme in pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase. Adult RDA is 1.2 mg (men) / 1.1 mg (women) (no Upper Limit established).

Source: NIH ODS / EFSA · Last reviewed Aug 28, 2026

Specs

Nutrient Type	Water-Soluble Thiazole Vitamin
Adult RDA / RDI	1.2 mg / day (Men) / 1.1 mg / day (Women) (+0.3mg during pregnancy)
Tolerable Upper Limit (UL)	None Established (Rapid renal clearance of excess)
Chemical Forms	Thiamine Monophosphate, Thiamine Pyrophosphate (TPP / TDP, active coenzyme), Benfotiamine (Lipid-soluble synthetic)
Primary Biological Function	Pyruvate dehydrogenase complex (Links glycolysis to Krebs cycle), Transketolase (Pentose Phosphate Pathway), Myelin neurotransmission
Deficiency Condition	Beriberi (Wet beriberi: high-output heart failure; Dry beriberi: peripheral neuropathy), Wernicke-Korsakoff syndrome
Top Whole Food Sources	Pork Tenderloin, Sunflower Seeds, Nutritional Yeast, Enriched Grains, Black Beans, Flaxseeds
Thermolability & Alcohol Interaction	Degraded by alkaline pH and high heat cooking; alcohol blocks intestinal active ThTr-1 transport

The Pyruvate Dehydrogenase Bottleneck

Without TPP, pyruvate cannot be converted into acetyl-CoA to enter the mitochondrial citric acid cycle, forcing pyruvate into lactate and leading to severe lactic acidosis and neuronal ATP depletion.