Folic acid is the synthetic form of folate (vitamin B9) used in most UK supplements and food fortification. Approximately 40% of the UK population carries a common MTHFR gene variant that reduces the body's ability to convert folic acid to its active form (5-methyltetrahydrofolate, or 5-MTHF). For this group, methylfolate supplementation is more effective than folic acid. For everyone else, folic acid works adequately at standard doses. Here is how to know which applies to you.
What Is Folate and What Does It Do?
Folate (vitamin B9) is essential for three core biological processes:
- DNA synthesis and repair — folate (as 5,10-methylenetetrahydrofolate) is required for the synthesis of thymidylate, a DNA building block. Without it, cells cannot divide properly — which is why rapidly dividing tissues (gut lining, red blood cells) are first affected by deficiency.
- Methylation (homocysteine metabolism) — folate (as 5-methyltetrahydrofolate) donates a methyl group to convert homocysteine to methionine. Elevated homocysteine is a cardiovascular risk factor and is associated with cognitive decline.
- Neural tube development during pregnancy — the critical role for which folate is most known. Adequate folate in the 4 weeks before and 12 weeks after conception significantly reduces the risk of neural tube defects (spina bifida, anencephaly). The UK NHS recommends 400mcg folic acid daily for all women who may become pregnant.
What Is the Difference Between Folic Acid and Folate?
Folate is the naturally occurring form of vitamin B9, found in green leafy vegetables, legumes, liver and eggs. It exists in several forms, all of which must be converted to the active 5-MTHF to function metabolically.
Folic acid is the fully oxidised synthetic form used in supplements and food fortification. It is more stable than natural folate but requires two enzymatic conversion steps — dihydrofolate reductase (DHFR) and then MTHFR — to reach the active 5-MTHF form.
Methylfolate (5-MTHF) is the active, end-form of folate — the form that cells actually use. It requires no conversion. It is the form produced by fermentation or chemical synthesis that is increasingly used in premium supplements.
What Is MTHFR and Why Does It Matter?
MTHFR (methylenetetrahydrofolate reductase) is the enzyme responsible for converting 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate (the active 5-MTHF form used in methylation). Two common variants of the MTHFR gene — C677T and A1298C — reduce this enzyme’s activity:
- C677T heterozygous (one copy): ~30–40% reduction in MTHFR activity. Approximately 40% of the general population.
- C677T homozygous (two copies): ~70% reduction in MTHFR activity. Approximately 10–15% of populations of European descent.
People with reduced MTHFR activity convert folic acid less efficiently. At standard supplemental doses (400mcg folic acid), most people with heterozygous variants still convert enough — though methylfolate is more efficient. For homozygous variants, methylfolate is clearly the better choice.
How Do You Know If You Have an MTHFR Variant?
MTHFR genetic testing is available through GP referral in specific circumstances (recurrent miscarriage, thrombophilia workup) or via direct-to-consumer DNA tests (23andMe includes MTHFR status). Elevated homocysteine on a blood test is a functional indicator of impaired methylation — it does not confirm MTHFR genotype but suggests methylation may be suboptimal.
Without testing, the practical approach is to choose a supplement containing methylfolate (5-MTHF) rather than folic acid — this is appropriate and beneficial for everyone regardless of MTHFR status, since methylfolate bypasses the conversion entirely.
Folic Acid vs Methylfolate: A Comparison
| Factor | Folic Acid | Methylfolate (5-MTHF) |
|---|---|---|
| Conversion required | Yes — 2 enzymatic steps (DHFR + MTHFR) | No — already in active form |
| Affected by MTHFR variant | Yes — reduced conversion in 40% of population | No — bypasses MTHFR entirely |
| Neural tube defect prevention | Strong evidence (standard recommendation) | Equivalent evidence; increasingly preferred |
| Homocysteine reduction | Good in most people | More reliable across MTHFR variants |
| Unmetabolised folic acid concern | High doses may leave unmetabolised folic acid in blood — unknown long-term effects | No unmetabolised folic acid |
| Cost | Lower | Higher |
Pregnancy: Does the Form Actually Matter for Neural Tube Prevention?
The original neural tube defect prevention evidence was established with folic acid, not methylfolate. Both forms raise blood folate levels and reduce neural tube defect risk. Current evidence does not show methylfolate is superior to folic acid for neural tube prevention at the recommended 400mcg dose. However, for women with known MTHFR variants or elevated homocysteine, methylfolate is a reasonable and increasingly recommended choice. The NHS currently recommends 400mcg folic acid for pregnancy; women with MTHFR variants should discuss with their GP.
Daily Multi Complex by BioBodyBoost includes folate as part of comprehensive B-vitamin coverage. ZenBlend includes a full B-vitamin complex including folate, B12 and B6 — the three B vitamins central to homocysteine metabolism. Both halal certified, vegan, UK GMP manufactured. Browse the full range.
