Across 6 studies, 5 reported beneficial effects on reducing homocysteine levels, with effect sizes ranging from small to large (mixed). The median study duration was 84 days (12 weeks), indicating effects typically observed at that timeframe. Most studies used doses of 400 μg to 1 mg per day in diverse adult populations, including healthy adults, patients with coronary heart disease, and those with type 2 diabetes.
Caveats: Some studies used combined B-vitamin supplementation, making it difficult to isolate the effect of vitamin B9 alone. One trial in children with sickle cell disease found no significant effect, suggesting the benefit may not generalize to all populations. Both folic acid and l-5-MTHF forms were effective, but differences between forms remain underexplored.
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
The folic acid and l-5-MTHF groups had 17% and 15%, respectively, lower (P < 0.001) plasma total homocysteine concentrations than did the placebo group at 12 wk; there were no differences between the folic acid and l-5-MTHF groups.
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...).
Folic acid supplementation significantly revealed a large effect size on homocysteine levels compared to placebo, SMD = -1.53, 95%CI (-2.14,-0.93), p < 0.05.
In both groups, a significant decrease in the mean Hcy level after intervention period was observed.