Vitamin B1 (Thiamine)
water-soluble
Key Takeaways
- Critical cofactor in energy production from glucose via the Krebs cycle
- Deficiency causes severe neurological conditions including beriberi and Wernicke encephalopathy
- FDA daily value is 1.2 mg; widely available in whole grains, legumes, and pork
- Plays a role in acetylcholine and neurotransmitter synthesis
- Mild deficiencies are common in the general population but clinical consequences remain unclear
Evidence Spectrum
14 studies reviewed →14
Studies Reviewed
1.2 mg
RDA (Adults (FDA Daily Value))
water-soluble
Solubility
Role in the Body
Vitamin B1 (thiamine) plays a key role in energy production from glucose. Since the main fuel of the nervous system is glucose, thiamine is essential for proper neurological function. The active form, thiamine pyrophosphate (TPP), serves as a cofactor for several critical enzymes including transketolase and enzymes in the Krebs cycle (pmid:24298824, pmid:19663002). Beyond energy metabolism, thiamine contributes to myelin synthesis, antioxidative and neuroprotective effects in both the peripheral and central nervous systems (pmid:31490017). Thiamine also modulates inflammation and nociceptive pathways (pmid:35156556). Research has explored connections between thiamine status and Alzheimer disease, but clinical trials have not demonstrated efficacy (pmid:26971083, pmid:11405995).
- Cofactor for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase in the Krebs cycle
- Cofactor for transketolase in the pentose phosphate pathway
- Required for ATP production from glucose
- Involved in acetylcholine and neurotransmitter synthesis
- Supports myelin synthesis and nerve function
Supplement Forms
Thiamine hydrochloride
RecommendedBioavailability: 0.05%
Most common oral supplement form
Benfotiamine
RecommendedBioavailability: 0.25%
Fat-soluble derivative with higher bioavailability
Food Sources
Whole grains and fortified cereals
Pork
Legumes
Nuts and seeds
Yeast
Deficiency
Prevalence: Severe deficiency uncommon in general population but occurs in chronic alcoholics, after bariatric surgery, and during protracted vomiting in pregnancy (pmid:24298824).
Symptoms:
- Beriberi (wet: cardiac; dry: neuropathy)
- Wernicke encephalopathy
- Korsakoff psychosis
- Fatigue and irritability
Risk Factors:
- Chronic alcoholism
- Bariatric surgery
- Protracted vomiting in pregnancy
- Severe malnutrition
Safety & Interactions
Possible Side Effects:
- • Generally well tolerated orally
- • Rare hypersensitivity with IV administration (pmid:41598206)
Drug Interactions:
- • Alcohol decreases absorption and utilization (pmid:34466144)
Contraindications:
- • Known hypersensitivity to thiamine (rare)
Frequently Asked Questions
What does Vitamin B1 do?
Thiamine is essential for converting glucose into energy via the Krebs cycle and is critical for nervous system function.
What are B1 deficiency symptoms?
Beriberi, Wernicke encephalopathy, Korsakoff psychosis, fatigue, muscle weakness.
How much B1 daily?
FDA daily value is 1.2 mg. No established upper limit.
Research Sources
14 peer-reviewed studies analyzed from PubMed. 10 directly cited in this review.