B-Complex Vitamins (B1, B2, B3/Niacin, B5, B6, B7/Biotin, B9/Folate, B12) for Neuropathy
B vitamins reliably help neuropathy only when it is caused by a confirmed B12 deficiency; for general or diabetic nerve pain the evidence is weak and inconsistent, and chronic high-dose B6 can actually cause the very nerve damage these supplements claim to treat.
Why this grade7-layer evidence engine
The grade is held to weak (Tier C) because the benefit splits sharply by cause. In documented B12 (cobalamin) deficiency, replacement is established standard care and patients improve (PMID 12975298). But for general peripheral neuropathy the Cochrane review found insufficient evidence of efficacy (PMID 18646107), and supportive trials are thin: a systematic review of methylcobalamin in diabetic neuropathy rested on small, low-quality studies (PMID 16008162), while the one positive benfotiamine RCT ran just six weeks, was industry-funded, and moved a single symptom score (PMID 18473286).
Crucially, the same supplements carry a real harm signal. High-dose vitamin B6 (pyridoxine) is the one B vitamin proven to cause sensory neuropathy at supplemental doses: a landmark case series documented severe nerve damage from megadosing (PMID 6308447), and a safety review confirmed dose-dependent toxicity, setting an upper limit near 100 mg/day (PMID 2192616). The cheap inactive form may even suppress active B6 function (PMID 28716455).
Regulators and clinics echo this caution. The UK NHS warns that 200 mg or more of B6 daily can cause peripheral neuropathy and caps supplements at 10 mg/day; Cleveland Clinic and Mayo Clinic note B6 is toxic to nerves at high levels; and the American Academy of Neurology rates the B-vitamin product Metanx as possibly no better than placebo for diabetic nerve pain. Test for deficiency first rather than self-dosing high-potency B-complex.
Bottom line: useful and uncontroversial only as targeted replacement for a confirmed deficiency, weak and unproven as a general nerve remedy, and potentially harmful if high-B6 products are taken long-term.
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 = 0.405
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (2 篇 > 0 negative)
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 1 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status