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Evidence-Based Supplement Research
Evidence-Based Supplement Research
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Vitamin B9 and Improved Cognitive Function

Research synthesisLow evidenceMixed effect size3 studies · 2 beneficial · 1 neutral · 0 harmful

Across 3 studies, 2 reported beneficial effects (one moderate, one small) and 1 reported no effect (small, non-significant). Effects were mixed in magnitude. The median study duration was 176 days, and the evidence primarily comes from clinical populations with cognitive impairment or low folate levels.

  • Studied populations: clinical populations with cognitive impairment (e.g., cerebral small vessel disease) or low folate levels (e.g., schizophrenia patients)

Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. One study in schizophrenia patients with low folate found no effect with a high dose (5 mg/day), while a study in CSVD patients found benefit with 0.8 mg/day, suggesting dose and population may influence outcomes. The systematic review included multiple vitamins, so its effect size for B9 alone is not isolated.

Generated Jul 12, 2026
Doses used in studies
  • mg/day: 0.8–5 (median 2.9, IQR 1.85–3.95) — 2 studies
Time to effect
Median: 5.9 months · IQR 5.7 months–6 months · Range 5.6 months–6.1 months — Reported in 2 of 3 studies
3 of 3 papers
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