Across 3 studies, 2 reported beneficial effects on reducing homocysteine levels, with effect sizes that were mixed (small to moderate). The available evidence includes a meta-analysis (moderate effect) and a systematic review (small effect), supporting a beneficial effect. The median study duration among the limited reporting studies was 84 days, but dose and form data were insufficient to identify a typical regimen.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. The neutral study involved children with sickle cell disease and used folic acid 1 mg/day; its null finding may reflect population differences. One of the beneficial studies used combined B-vitamin supplementation, so the specific contribution of B9 is unclear. Duration data are limited (only one study reported 84 days).
folate showed an excellent safety and tolerability profile with only one adverse event reported among 1367 individuals.
from: Folate Supplementation for Peripheral Neuropathy: A Systematic Review.Folate significantly decreased homocysteine
Combined B-vitamin supplementation significantly reduced serum Hcy levels [mean difference: -2.36; 95% CI: (-3.09 to -1.62); p < 0.01]
There were no significant differences observed in 1-carbon metabolite concentrations (total homocysteine...).