I have MTHFR — do I need methylfolate?

It's one of the most common questions I get asked, almost always after someone has seen MTHFR flagged on a genetic report or their blood test results.

And I understand why. The message online is often very simple:

"You have an MTHFR variant, so you need methylfolate."

But it's not that simple.

MTHFR is one gene in a much bigger system — and supplementing with folate is not where I start.

What does MTHFR actually do?

MTHFR is the gene that codes for an enzyme involved in the folate cycle, helping convert folate into its active form, methylfolate (5-MTHF). Methylfolate then works with B12 to recycle homocysteine back into methionine, which your body uses to make SAMe — its main methyl donor.

Methylation is a fundamental biochemical process involved in neurotransmitter production, gene expression, DNA repair, detoxification, hormone regulation and many other essential functions in the body.

There are two common MTHFR variants you'll often see on genetic reports: C677T and A1298C.

The C677T variant can significantly reduce enzyme activity. If you carry two copies — the TT genotype — enzyme activity can be reduced by around 70% [1]. Compound heterozygosity — one C677T and one A1298C — can also substantially reduce enzyme activity, with studies reporting activity around 50% of normal [2].

So an MTHFR result is important information.

But it isn't a prescription for methylfolate.

Why the whole pathway matters

When I see an MTHFR variant, I don't look at that gene in isolation. Other genes, nutritional status, functional markers and lifestyle factors can all influence how the methylation cycle is functioning. That includes:

• Other genes that influence methylation — including MTR and MTRR, which use B12 to recycle homocysteine; BHMT, which provides a backup route for recycling homocysteine; TCN2, which transports B12 into your cells; and COMT, which uses methyl groups to clear dopamine, adrenaline and oestrogens, and can influence how some people tolerate methyl donors.
• Nutritional foundations and cofactors — including B2, B6, magnesium and zinc, as well as adequate B12 status. Riboflavin (B2) is the cofactor MTHFR itself needs to function — inadequate B2 can further reduce enzyme activity regardless of genotype, and status has also been shown to modify how both MTHFR and MTRR variants affect homocysteine [3].
• Functional markers — particularly homocysteine, and methylmalonic acid (MMA), a useful marker of B12 status at a cellular level.
• Lifestyle and health factors — including diet, stress, sleep and other factors that may place additional demands on the methylation cycle.

This is why I don't believe in testing — or treating — an MTHFR SNP in isolation. Someone can have the same MTHFR variant as you and have a completely different biochemical and nutritional picture.

B12 is one I always check first. Methylfolate relies on it to do its job — without enough of it, methylfolate can become metabolically "trapped," unable to be used further along the pathway [4].

That's why B12 often needs to be on board before methylfolate.

So, what about the different forms of folate?

This is where things can get confusing, because folate isn't just one thing.

Folic acid — a synthetic form of folate used widely in fortified foods and supplements. It requires conversion to reduced folate forms before it can enter the folate cycle. It is not a form I recommend.

Folinic acid — a reduced, active form of folate that skips the slow conversion folic acid needs. It can be used for DNA synthesis and repair, or converted by MTHFR into methylfolate — and because it doesn't carry a methyl group, it can be a gentler option for people who are sensitive to methyl donors.

Methylfolate (5-MTHF) — the end product of the MTHFR pathway, ready for your body to use. It carries a methyl group, which is why some people who are sensitive to methyl donors don't tolerate it well.

Natural food folates — naturally occurring folates found in foods such as beef liver, leafy greens, lentils, asparagus and avocado.

Where do I start?

My approach is food first wherever possible. I look at the nutritional foundations of the pathway, the individual's genetic picture and functional markers, and lifestyle factors that may be placing additional demands on the methylation cycle before considering supplemental folate.

The point isn't that methylfolate is "bad" or that nobody with an MTHFR variant should use it. It's that the right form of folate — and whether you need supplemental folate at all — depends on the rest of the picture. Some people are particularly sensitive to methyl donors and may experience symptoms such as anxiety, irritability or sleep disturbance when introducing methylfolate — another reason I don't recommend choosing a folate supplement based on an MTHFR result alone.

Want to understand your MTHFR result?

If MTHFR has been flagged on your results, don't panic — and don't reach straight for methylfolate.

Find out which variant you have, what the rest of your methylation pathway looks like, and what your functional markers are telling you.

Because when it comes to methylation, one gene is never the whole story.

References

1. Frosst, P., Blom, H. J., Milos, R., Goyette, P., Sheppard, C. A., Matthews, R. G., Boers, G. J. H., den Heijer, M., Kluijtmans, L. A. J., van den Heuvel, L. P., & Rozen, R. (1995). A candidate genetic risk factor for vascular disease: A common mutation in methylenetetrahydrofolate reductase. Nature Genetics, 10(1), 111–113. https://doi.org/10.1038/ng0595-111
2. van der Put, N. M., Gabreëls, F., Stevens, E. M., Smeitink, J. A. M., Trijbels, F. J. M., Eskes, T. K. A. B., van den Heuvel, L. P., & Blom, H. J. (1998). A second common mutation in the methylenetetrahydrofolate reductase gene: An additional risk factor for neural-tube defects? American Journal of Human Genetics, 62(5), 1044–1051. https://doi.org/10.1086/301825
3. García-Minguillán, C. J., Fernandez-Ballart, J. D., Ceruelo, S., Ríos, L., Bueno, O., Berrocal-Zaragoza, M. I., Molloy, A. M., Ueland, P. M., Meyer, K., & Murphy, M. M. (2014). Riboflavin status modifies the effects of methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) polymorphisms on homocysteine. Genes & Nutrition, 9(6), 435. https://doi.org/10.1007/s12263-014-0435-1
4. Smulders, Y. M., Smith, D. E. C., Kok, R. M., Teerlink, T., Swinkels, D. W., Stehouwer, C. D. A., & Jakobs, C. (2006). Cellular folate vitamer distribution during and after correction of vitamin B12 deficiency: A case for the methylfolate trap. British Journal of Haematology, 132(5), 623–629. https://doi.org/10.1111/j.1365-2141.2005.05913.x

Clinical disclaimer: This information is for general education and is not a substitute for individual medical advice, diagnosis or treatment. It should always be interpreted in the context of your symptoms, health history and other clinical findings with your qualified healthcare practitioner.