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Vitamin B9

What does the research say about Vitamin B9?

2 health outcomes synthesised

Vitamin B9 (folate) has been studied in research for two health outcomes: reducing homocysteine levels and increasing folate levels. The strongest evidence, based on 7 studies, supports a beneficial effect on homocysteine reduction, with a typical dose of 1 mg/day across populations including healthy adults, patients with coronary heart disease, and those with type 2 diabetes.

Strongest evidence: The most robust finding is for reduced homocysteine levels, with high evidence strength from 7 studies (6 beneficial, 1 neutral). Effects were small to moderate, observed at doses around 1 mg/day over 8–12 weeks. For increased folate levels, evidence is moderate (3 studies, 2 beneficial with large effect size, 1 neutral), also at 1 mg/day.

Mixed or weaker evidence: No outcomes with low or very low evidence strength were identified in this synthesis. The folate increase finding is based on only 3 studies, so conclusions are preliminary.

Effective dose patterns: Both outcomes converge on a dose of 1 mg/day. The median study duration for both outcomes was 84 days, suggesting that at least 12 weeks of supplementation is typical for observing effects.

Population insights: Beneficial effects on homocysteine were seen in healthy adults, patients with coronary heart disease, type 2 diabetes, and older adults (50–65 years). For folate levels, studies included healthy adults and individuals with phenylketonuria. One study in children with sickle cell disease showed no benefit, indicating that results may not generalize to pediatric populations or those with certain comorbidities.

Notable caveats: The homocysteine literature is subject to publication bias (null results are less likely to be published). Most trials were short (4–12 weeks), so longer-term effects are less documented. For folate increase, one study used rice fortification with multiple micronutrients, not direct supplementation, and another used l-5-methyltetrahydrofolate, which may not represent all forms of vitamin B9.

Frequently asked

  • What is Vitamin B9 good for according to research?
    Research shows that vitamin B9 (folate) supplementation is beneficial for reducing homocysteine levels (6 of 7 studies, high evidence) and increasing folate levels (2 of 3 studies, moderate evidence). The effects are typically seen at doses of 1 mg/day over 8–12 weeks.
  • What dose of Vitamin B9 is typically used in studies?
    The most commonly studied dose is 1 mg/day. This dose was associated with beneficial effects on both homocysteine reduction and folate increase across the reviewed studies. The median study duration was 84 days.
  • Who benefits most from Vitamin B9?
    Beneficial effects on homocysteine reduction have been observed in healthy adults, patients with coronary heart disease, type 2 diabetes, and older adults (50–65 years). For increasing folate levels, studies included healthy adults and individuals with phenylketonuria. However, one neutral study in children with sickle cell disease suggests that the effect may not generalize to pediatric populations or those with certain comorbidities.
  • Are there caveats or limitations in the research on Vitamin B9?
    Yes. The homocysteine literature is subject to publication bias, as null results are less likely to be published. Most trials were short (4–12 weeks), leaving longer-term effects unclear. For folate increase, the evidence base is small (only 3 studies), and one study used rice fortification with multiple nutrients, not direct supplementation.
  • Does Vitamin B9 help reduce homocysteine levels?
    Yes, evidence is strong: 6 of 7 studies reported beneficial effects of vitamin B9 supplementation on reducing homocysteine levels, with small to moderate effect sizes. Doses of 1 mg/day were typical, and effects were observed at 8–12 weeks.
  • Does Vitamin B9 help increase folate levels?
    Moderate evidence from 3 studies suggests that vitamin B9 supplementation can increase folate levels, with 2 studies showing a large beneficial effect. The most-studied dose was 1 mg/day, and effects were typically seen at 12 weeks. One study on rice fortification showed a small neutral effect.

Most-studied combinations with Vitamin B9

most supplement research is combination research
Also studied with:L-Methylfolate (3), Blood Orange (2), Zinc (2), Magnesium (2), Iron (3), Vitamin B2 (2), Vitamin B6 (3), Vitamin B12 (7), Vitamin D (4), Vitamin E (2), Vitamin D3 (2)
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