Encyclopedia · supplement
Folate (vitamin B9)
A B vitamin that is sometimes low in people with hair loss, but not a hair-growth supplement if your levels are normal.
What it is
Folate is a B vitamin needed to make DNA, which fast-growing cells such as hair follicles depend on. Folic acid is the supplement form.
How it works
It acts as a cofactor in DNA synthesis and methylation. Severe deficiency can slow follicle cells; the effect of topping up normal levels is not shown.
What the studies show
- A meta-analysis of 18 studies and 2,538 people found lower serum folic acid in those with hair loss after weight-loss surgery (standardized mean difference -0.88, p<0.0001). Ferritin was also lower; B12 and iron were not associated. Zhang 2021
- Small case-control studies suggest vitamin D, zinc and folate tend to be lower in alopecia areata, but evidence is insufficient to test or treat routinely. Thompson 2017
- A review concluded deficiency may be a modifiable factor in hair loss, while trials are lacking. Almohanna 2019
Side effects and safety
The European Food Safety Authority sets an upper limit of 1,000 micrograms a day of supplemental folic acid for adults. High folic acid can mask B12 deficiency, so check B12 as well. Folate before and early in pregnancy is advised for neural tube protection, which is a separate medical reason.
Bottom line
Fix a diagnosed deficiency, and get checked after weight-loss surgery or on a very restricted diet. It is not a hair-growth supplement for the well-nourished. Whether correcting low folate reverses post-surgery shedding is untested. Discuss with a doctor.
Studies 3
Zhang W et al. Hair Loss After Metabolic and Bariatric Surgery: a Systematic Review and Meta-analysis. 2021
Result: Hair loss in 57%; lower folic acid (SMD -0.88), ferritin and borderline zinc associated with loss; B12 and iron were not.
Read the study ↗Thompson JM et al. The Role of Micronutrients in Alopecia Areata: A Review. 2017
Result: Vitamin D, zinc and folate tend to be lower in alopecia areata; evidence insufficient for routine testing or treatment.
Read the study ↗Almohanna HM et al. The Role of Vitamins and Minerals in Hair Loss: A Review. 2019
Result: Vitamin and mineral deficiency may be a modifiable factor in hair loss, but well-designed trials are lacking.
Read the study ↗Related
- Vitamin B12A real but uncommon cause of hair loss when deficient, with no evidence that extra B12 helps hair if your levels are normal.
- Iron and ferritinLow iron stores are common in people who shed hair, but no trial has shown that iron pills regrow hair, and nobody agrees on a hair-specific ferritin target.
- ZincTrue zinc deficiency causes hair loss that zinc fixes, but zinc has not been shown to regrow hair in people who are not deficient, and too much causes copper deficiency.
- Diet and hairCrash diets and rapid weight loss cause shedding, ordinary diets rarely do, and testing beats guessing before you buy supplements.