Vitamin B12 for Depression
Verdict: Insufficient Evidence
Across 6 PubMed studies, the evidence for Vitamin B12 in Depression grades Tier D — counter-evidence. Research is still too limited to draw a firm conclusion.
D 🔴 D Counter-Evidence Insufficient Evidence
Why this grade7-layer evidence engine
⚖️
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditableRaw score 0.32
D
C
B
A
S
← counter-evidence / ineffectiveeffective / strong evidence →
Final grade
D · Insufficient Evidence
Confidence
86%
Highly consistent evidence
Evidence level
E2
Multiple high-quality MAs (≥2 independent, consistent)
▸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 = 0.323
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 negative 主導 (2 negative > 0 positive)，下層 RCT 不能推翻
- 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
PubMed studies (6)L2 · primary research & systematic reviews
Effects of Vitamin B12 Supplementation on Cognitive Function, Depressive Symptoms, and Fatigue: A Systematic Review, Meta-Analysis, and Meta-Regression
Finding: Across 6 of the 16 RCTs reporting depression, B12 (alone or in B-complex) had no effect on depressive symptoms (pooled SMD = -0.049, 95% CI -0.146 to 0.047, p = 0.50).
View on PubMed Assessment of Vitamin B12 Efficacy on Cognitive Memory Function and Depressive Symptoms: A Systematic Review and Meta-Analysis
Finding: The most recent meta-analysis found B12 supplementation had an insignificant effect on depressive symptoms (SMD = -0.01, 95% CI -0.077 to 0.053, p = 0.708).
View on PubMed Systematic review and meta-analysis of randomized placebo-controlled trials of folate and vitamin B12 for depression
Finding: Folate+B12 did not reduce depressive symptom severity short-term (SMD = -0.12, 95% CI -0.45 to 0.22), but prolonged use lowered relapse (OR = 0.33, 95% CI 0.12-0.94) and onset of symptoms in at-risk groups (RR = 0.65, 95% CI 0.43-0.98).
View on PubMed Effects of Two-Year Vitamin B12 and Folic Acid Supplementation on Depressive Symptoms and Quality of Life in Older Adults with Elevated Homocysteine Concentrations: Additional Results from the B-PROOF Study, an RCT
Finding: Despite greater homocysteine lowering, daily 500 ug B12 + 400 ug folic acid for 2 years produced no between-group difference in GDS-15 depressive symptoms (only a small positive effect on one quality-of-life measure).
View on PubMed Mental health literacy, folic acid and vitamin B12, and physical activity for the prevention of depression in older adults: randomised controlled trial
Finding: Daily 400 ug folic acid + 100 ug B12 for 24 months did not reduce depressive symptoms versus placebo (F(3,856) = 0.83, p = 0.476).
View on PubMed Vitamin B12 supplementation in treating major depressive disorder: a randomized controlled trial
Finding: In B12-low-normal MDD patients given injectable B12 plus an antidepressant, 100% achieved >=20% HAM-D reduction vs 69% on antidepressant alone (p < 0.001; remained significant after baseline adjustment, p = 0.001).
View on PubMed Regulatory & authoritative positionsL4/L5 · FDA / EMA / NIH ODS / Cochrane / Mayo …
L4a US FDA
Supportive
NUTRIENT SUPPLEMENT source↗
L4b EU EFSA
Supportive
a cause and effect relationship has been established source↗
L4c UK NHS
Supportive
Adults aged 19 to 64 need about 1.5 micrograms a day of vitamin B12. source↗
L4d TW TFDA / 衛福部
Supportive
維生素B12之足夠攝取量(AI)成人為每日2.4微克 source↗
L4e WHO
Supportive
Vitamin B12 or folate supplementation during pregnancy is not recommended as an intervention to improve maternal and infant health outcomes source↗
L5a NIH Office of Dietary Supplements
Supportive
Vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit. source↗
L5b Mayo Clinic
Cautious
Vitamin B-12 and other B vitamins play a role in making brain chemicals that affect mood and other brain functions. Low levels of vitamin B-12 and other B vitamins may be linked to depression, but more research is needed. Study results have been mixed on whether vitamin B-12 supplements can help lower the risk of depression or ease symptoms. Because B-12 and other vitamin supplements can intera… source↗
L5c Cleveland Clinic
Cautious
Getting vitamin B12 injections to raise your B12 level to where it should be often improves [symptoms including depression]. If your B12 level is normal, there is little evidence to support that they actually work for these purposes. source↗
L5d Harvard Health
Cautious
a severe vitamin B12 deficiency can lead to deep depression, paranoia and delusions, memory loss, incontinence, loss of taste and smell, and more. source↗
L5e Specialty Society (condition-mapped)
Cautious
The FDA has not approved any natural products for treating depression. Although research is ongoing and findings are inconsistent, some people report that natural products, including vitamin D and the herbal dietary supplement St. John's wort, helped their depression symptoms. Do not use vitamin D, St. John's wort, or other dietary supplements or natural products without first talking to a heal… source↗