Vitamin B1 (Thiamine) for Fatigue
Vitamin B1 (thiamine) reliably relieves fatigue only when that fatigue stems from a genuine thiamine deficiency. For everyday tiredness in well-nourished people, the human evidence is weak and contradictory, and no major regulator or clinic endorses it for this use.
Why this grade7-layer evidence engine
This claim earns a Weak (Tier C) grade because the only direct human trials are small and pull in opposite directions. A double-blind RCT in quiescent inflammatory bowel disease (PMID 33210299, n=40) found high-dose oral thiamine meaningfully cut chronic fatigue, but a similarly designed double-blind crossover trial in primary biliary cholangitis (PMID 38551983, n=34) found no benefit over placebo (p=0.55). The remaining support is an uncontrolled three-patient case report in Hashimoto's thyroiditis (PMID 24351023), which is too weak to establish efficacy.
Regulators and major clinics back thiamine only within a deficiency framework, not as a general anti-fatigue supplement. EFSA recognizes thiamine's role in normal energy-yielding metabolism, but this is a biochemical-function statement, not a treatment claim, and EFSA notably never authorized a 'reduction of tiredness and fatigue' claim for B1 (unlike several other B vitamins). The NIH Office of Dietary Supplements and Cleveland Clinic note that fatigue is an early sign of B1 deficiency, while Mayo Clinic, Harvard, and the UK NHS do not endorse routine supplementation for healthy adults.
Taken together, thiamine clearly helps when fatigue is driven by a true deficiency, but for non-deficient people the contradictory trial results and absence of any large RCT or guideline support justify only a weak, inconclusive verdict. Anyone with persistent fatigue is better served by addressing sleep, diet, and underlying medical causes than by assuming a B1 shortfall.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.44
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 無高階證據可裁決
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status