Vitamin B1 (Thiamine)

Thiamine was the first vitamin to be isolated (1926) — its deficiency causes beriberi, the disease that first proved certain "accessory food factors" were essential. Thiamine pyrophosphate (TPP) is a coenzyme for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase — central to carbohydrate metabolism. Body stores are small (~30 mg); deficiency can develop within 2–3 weeks of poor intake.

Daily requirements

• Adult men: 1.2 mg/day.
• Adult women: 1.1 mg/day.
• Pregnancy / lactation: 1.4 mg/day.
• No Tolerable Upper Intake Level — oral thiamine has no known toxicity.

Who is at risk

• Chronic alcoholism — the #1 cause in high-income countries. Alcohol impairs GI absorption and hepatic storage.
• Loop diuretics (furosemide, torsemide, bumetanide) — increase urinary thiamine losses; heart-failure patients are commonly deficient.
• Bariatric surgery — especially with post-op vomiting.
• Refeeding syndrome — starving patients suddenly given carbohydrates deplete residual thiamine catastrophically.
• Hyperemesis gravidarum — prolonged pregnancy vomiting.
• Total parenteral nutrition without adequate supplementation.
• Milled-rice diets in low-income settings (thiamine is in the germ, removed by polishing).

Deficiency syndromes

• Wet beriberi — high-output cardiac failure, oedema, dyspnoea, tachycardia. Reversible with prompt thiamine repletion.
• Dry beriberi — symmetric peripheral neuropathy, muscle weakness, foot drop.
• Wernicke encephalopathy — acute triad of ophthalmoplegia (eye movement paralysis), ataxia, and confusion. Neurological emergency; give IV/IM thiamine, do NOT wait for tests.
• Korsakoff syndrome — chronic irreversible amnesia with confabulation, often follows untreated Wernicke's.
• Infantile beriberi — breastfed infants of thiamine-deficient mothers; historically fatal without prompt treatment.

The "banana bag" and glucose caution

Emergency departments routinely give thiamine before IV dextrose to malnourished or alcoholic patients — administering glucose to a thiamine-deficient patient accelerates metabolic demand and can precipitate acute Wernicke's. Standard dosing: 100–500 mg IV thiamine, often bundled with folate and magnesium (a "banana bag").

Food sources

• Fortified breakfast cereal (1 serving): 1.5 mg
• Pork chop (3 oz): 0.7 mg
• Enriched white rice (1 cup cooked): 0.3 mg
• Black beans (½ cup cooked): 0.2 mg
• Sunflower seeds (1 oz): 0.4 mg
• Pecans (1 oz): 0.2 mg
• Whole wheat bread (1 slice): 0.1 mg