Vitamin B1

How strong is the research?

2 papers read, 2 supporting.

Tested as: High-dose oral thiamine (as studied in quiescent inflammatory bowel disease fatigue trials, at doses substantially exceeding standard supplemental amounts)

Who was studied: People with diagnosed Chronic Fatigue Syndrome — a specific condition, not general tiredness.

How much to take

daily

50–100 mg

High-dose thiamine (benfotiamine form) may be more effective. Take on empty stomach.

Before you take it

• No Tolerable Upper Intake Level (UL) has been established by the IOM/NAS for thiamine; the IOM concluded there were insufficient adverse-effect data to set a UL for any age group.
• Oral thiamine at clinical trial doses (up to 600–1,800 mg/day) has not been associated with significant adverse effects; as a water-soluble vitamin, excess is excreted renally.
• Rare anaphylactic reactions have been reported with intravenous thiamine administration (e.g., in emergency/ICU settings); this risk is not established for oral supplementation.
• Chronic alcohol use depletes thiamine through impaired intestinal absorption and reduced hepatic storage; patients with alcohol use disorder are at high risk of deficiency.
• Loop diuretics (e.g., furosemide) increase renal thiamine excretion and may deplete body stores with long-term use.
• Metformin use is associated with lower thiamine status in some studies; patients on long-term metformin may warrant monitoring.
• Antacids and proton-pump inhibitors may reduce thiamine absorption by raising gastric pH.
• Dietary thiaminases present in raw fish and certain teas (e.g., bracken fern) can degrade dietary thiamine; heavy consumption may compromise thiamine status.

When to take it

Best taken: morning

What we make of it

The citation resolves to a paper about acupuncture research.