Vitamin B1
Thiamine (Vitamin B1)
Thiamine (Vitamin B1) is a water-soluble essential vitamin that plays a critical role in carbohydrate metabolism and neurological function. It is primarily used to prevent and treat thiamine deficiency states including beriberi and Wernicke-Korsakoff syndrome, and is commonly supplemented to support energy metabolism, cognitive function, and peripheral nerve health. High-dose thiamine (benfotiamine or TTFD forms) is also used therapeutically in diabetic neuropathy and fatigue syndromes.
Mechanism of Action
Thiamine is phosphorylated intracellularly to thiamine pyrophosphate (TPP), which serves as an essential cofactor for key enzymes in energy metabolism including pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase in the pentose phosphate pathway. These enzymes are critical for ATP production, acetylcholine synthesis, and the maintenance of myelin sheaths around peripheral and central nerves. Without adequate thiamine, cells—particularly neurons and cardiac myocytes—cannot generate sufficient energy, leading to oxidative stress and functional impairment.
Evidence by Health Goal(17 goals)
Dosing Protocols
With or without food; fat-soluble forms (benfotiamine) taken with meals for best absorption
Standard dietary supplement doses range from 1-100mg; high-dose protocols (100-600mg) are used for neuropathy or fatigue. Benfotiamine (fat-soluble prodrug) offers superior bioavailability for neurological applications at 150-300mg/day.
Administered intravenously or intramuscularly in clinical settings
Parenteral administration is reserved for severe deficiency states (e.g., Wernicke's encephalopathy), alcoholism-related deficiency, or malabsorption. IV administration should be performed slowly under medical supervision due to rare anaphylaxis risk.
Safety & Side Effects
Thiamine has an excellent safety profile as a water-soluble vitamin; excess is readily excreted in urine, making toxicity from oral supplementation extremely rare with no established tolerable upper intake level. Parenteral administration in clinical settings carries a small risk of allergic reaction and should be performed with monitoring, particularly for the first dose.
Possible Side Effects
- !Generally well-tolerated at standard doses with minimal adverse effects
- !Gastrointestinal discomfort (nausea, upset stomach) at high oral doses above 500mg
- !Mild skin flushing or warmth, particularly with injectable forms
- !Rare hypersensitivity or allergic reactions with parenteral administration
- !Anaphylaxis (very rare, primarily associated with IV injection)
- !Mild headache reported at high supplemental doses in sensitive individuals
- !Urine discoloration (yellow-orange) due to excess excretion of water-soluble forms
Interactions
- -Loop diuretics (furosemide) increase urinary thiamine excretion and can deplete thiamine stores with chronic use
- -Alcohol significantly impairs thiamine absorption and increases metabolic demand, markedly raising deficiency risk
- -Raw fish and certain shellfish contain thiaminase enzymes that degrade thiamine; avoid large quantities when supplementing
- -Antacids and proton pump inhibitors may reduce thiamine absorption by altering gastrointestinal pH
- -Metformin has been associated with reduced thiamine status; concurrent supplementation may be beneficial in long-term users
Cost & Where to Buy
Standard thiamine HCl supplements are inexpensive at $5-10/month; fat-soluble benfotiamine or TTFD forms cost $15-30/month due to enhanced bioavailability and production complexity. Price varies by dose, brand, and form.
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