Why Folic Acid Plays a Critical Role in Hair Biology
Folic acid (vitamin B9), along with its active form folate, is needed for one of the most fundamental processes in biology: cell division. Hair follicles contain some of the most rapidly dividing cells in the human body—the matrix cells in the hair bulb divide every 23-72 hours during the anagen (growth) phase. This rapid cell division depends on folate for DNA synthesis, amino acid metabolism, and the methylation reactions that regulate gene expression. When folate is deficient, rapidly dividing tissues are the first to suffer—and hair follicles are among the most immediately affected.
A study by Patel et al. (2017) in the Journal of Clinical and Aesthetic Dermatology identified folate deficiency as a contributing factor in some cases of telogen effluvium, though the authors noted that isolated folate deficiency causing hair loss is uncommon in developed countries due to food fortification programs.
Folate vs. Folic Acid: Understanding the Difference
Folate: The naturally occurring form of vitamin B9 found in food. A complex of various reduced forms of the vitamin (tetrahydrofolate, 5-methyltetrahydrofolate, etc.) that are directly usable by the body. Found in leafy green vegetables, legumes, liver, and citrus fruits.
Folic Acid: The synthetic, oxidized form of vitamin B9 used in supplements and food fortification. Must be converted by the enzyme dihydrofolate reductase (DHFR) to the active form (5-methyltetrahydrofolate, or 5-MTHF) before the body can use it. This conversion is slow and inefficient in some individuals.
Methylfolate (5-MTHF): The active, bioavailable form of folate that bypasses the DHFR conversion step. Approximately 30-40% of the population has a genetic variant (MTHFR C677T polymorphism) that reduces their ability to convert folic acid to 5-MTHF by up to 70%. For these individuals, methylfolate supplementation is more effective than folic acid. A study by Mayo et al. (2020) in the Nutrients journal confirmed that methylfolate supplementation was more effective than folic acid at raising red blood cell folate levels in individuals with the MTHFR C677T variant.
The RDA and Upper Limit
The RDA for folate is 400 mcg DFE (dietary folate equivalents) per day for adults. The Upper Limit (UL) is 1,000 mcg per day from fortified foods and supplements—this limit does not apply to naturally occurring folate in food. The UL exists because excessive folic acid intake can mask vitamin B12 deficiency (by correcting the anemia without addressing the neurological damage), and some studies suggest possible associations between very high folic acid intake and cancer risk, though the evidence is inconclusive.
For hair health, the RDA of 400 mcg DFE is likely sufficient for most individuals with normal MTHFR function. Those with the MTHFR variant may benefit from 400-800 mcg of methylfolate instead of folic acid.
Top Folate Supplements for Hair
Thorne Methyl-Guard Plus (Methylfolate + B12 + B6): $35 for 90 capsules. Contains 400 mcg of 5-MTHF (methylfolate) plus methylcobalamin (active B12) and pyridoxal 5′-phosphate (active B6). This is the optimal formulation for those with MTHFR variants, as all three B vitamins are provided in their active, coenzymated forms. Third-party tested. Cost: approximately $0.39/capsule.
Solgar Folate 400 mcg (as Metafolin): $11.49 for 100 tablets. Contains 400 mcg of 5-MTHF (as Metafolin, a patented form of methylfolate) rather than synthetic folic acid. USP-verified. A straightforward, affordable option that uses the active form. Cost: approximately $0.11/tablet—excellent value.
Now Foods Methyl Folate 1,000 mcg: $9.99 for 90 tablets. Contains 1,000 mcg of 5-MTHF per tablet—above the UL for folic acid but this limit does not apply to methylfolate, which is the naturally occurring form. Suitable for those who need higher doses to correct deficiency. Cost: approximately $0.11/tablet.
Garden of Life Vitamin Code Raw B-Complex: $24.99 for 60 capsules. Contains 400 mcg of folate from whole-food sources plus all other B vitamins. Includes live probiotics and enzymes. The whole-food folate is naturally in the 5-MTHF form. Cost: approximately $0.42/capsule.
Nature Made Folic Acid 400 mcg: $5.99 for 250 tablets. Contains synthetic folic acid rather than methylfolate. Suitable for individuals without MTHFR variants who want the most affordable option. USP-verified. Cost: approximately $0.02/tablet—cheapest option.
Dietary Sources of Folate
The best dietary sources of natural folate include: spinach (263 mcg per cup cooked), lentils (358 mcg per cup cooked), black beans (256 mcg per cup cooked), asparagus (262 mcg per cup), avocado (122 mcg per cup), and liver (215 mcg per 3oz serving). A diet rich in these foods can provide the RDA without supplementation. Since 1998, the US has mandated folic acid fortification of enriched grain products (bread, cereal, pasta, rice), which has significantly reduced the prevalence of folate deficiency.
Folate and B12: The Critical Pairing
Folate and vitamin B12 work together in the methionine cycle, which produces S-adenosylmethionine (SAMe)—the body’s primary methyl donor involved in over 100 methylation reactions, including those that regulate gene expression in hair follicles. Supplementing with folate without adequate B12 can mask the hematological signs of B12 deficiency (anemia) while allowing neurological damage to progress. Always ensure adequate B12 intake when supplementing with folate. Thorne Methyl-Guard Plus ($35) includes both active folate and active B12 in one formulation.
Frequently Asked Questions
Q: Should I take folic acid or methylfolate?
A: If you know you have an MTHFR variant (testable through 23andMe or a healthcare provider), choose methylfolate. If you do not know your MTHFR status, methylfolate is still the safer choice because it is effective for everyone, while folic acid may be suboptimal for the 30-40% with MTHFR variants. The price difference is minimal (Solgar Methylfolate at $0.11/tablet vs. Nature Made Folic Acid at $0.02/tablet).
Q: Can folate supplementation regrow hair?
A: Only if your hair loss is caused or worsened by folate deficiency. In developed countries with food fortification, folate deficiency is uncommon. If your levels are normal, additional supplementation is unlikely to improve hair growth and may carry risks at doses above the UL.
Q: Can I take folate with other B vitamins?
A: Yes—B vitamins work synergistically and are best taken together. A B-complex supplement provides balanced amounts of all B vitamins. Just be mindful of the total folate/folic acid content across all your supplements (including multivitamins) to stay within the 1,000 mcg UL for folic acid.
MTHFR Testing: Should You Get Tested?
Given that 30-40% of the population carries at least one MTHFR C677T variant, testing for this genetic polymorphism is a reasonable consideration for anyone experiencing unexplained hair shedding. The MTHFR enzyme converts folic acid to its active form (5-MTHF), and reduced enzyme activity can lead to functional folate deficiency even with adequate dietary intake. The test is available through most major genetic testing services (23andMe includes it in their health reports, and standalone MTHFR tests are available for $50-150).
If you discover you have an MTHFR variant, the practical implication is straightforward: switch from folic acid to methylfolate supplementation. There is no medical downside to taking methylfolate instead of folic acid—methylfolate works for everyone, while folic acid may be suboptimal for those with MTHFR variants. Given that methylfolate supplements cost only marginally more than folic acid (Solgar Methylfolate at $0.11/tablet vs. Nature Made Folic Acid at $0.02/tablet), some practitioners recommend simply choosing methylfolate by default, eliminating the need for testing. This pragmatic approach—use the active form that works for everyone—is increasingly recommended by integrative medicine practitioners.
Folate-Rich Foods: Meeting Your Needs Through Diet
Before considering supplementation, evaluate whether your diet provides adequate folate. The adult RDA for folate is 400 mcg DFE (dietary folate equivalents) per day. Rich dietary sources include: lentils (358 mcg per cup cooked), spinach (263 mcg per cup cooked), black beans (256 mcg per cup), asparagus (262 mcg per 6 spears), avocado (122 mcg per half), broccoli (104 mcg per cup cooked), and fortified cereals and grains (400 mcg per serving—mandatory fortification in the US since 1998). A diet rich in these foods can easily meet or exceed the RDA without supplementation.
However, several factors can reduce folate absorption from food. Cooking destroys 30-50% of folate in vegetables—raw spinach has 50% more folate than cooked. Alcohol consumption interferes with folate absorption and increases folate excretion. Certain medications (methotrexate, anticonvulsants, sulfasalazine) are folate antagonists that increase requirements. If you have any of these risk factors, supplementation is advisable even with a folate-rich diet. Choose methylfolate (Solgar Methylfolate 400mcg, $11.99/100 tablets) over folic acid for optimal absorption, particularly if you have an MTHFR gene variant.
what matters most
Folate is needed for the rapid cell division that occurs in hair follicles during the anagen phase. For most people, the RDA (400 mcg DFE) can be met through diet, and supplementation is only necessary if you have a deficiency or increased needs (pregnancy, certain medications). If you do supplement, choose methylfolate (5-MTHF) over folic acid—Solgar Folate 400 mcg as Metafolin ($11.49/100 tablets) is the best value in the active form. Pair folate with adequate B12 (Thorne Methyl-Guard Plus includes both). Test your folate levels if you are experiencing unexplained hair shedding—a simple blood test can identify whether deficiency is a contributing factor.