What is the MTHFR mutation?

What is the MTHFR mutation?

What is the MTHFR mutation?


In France, almost all women wishing to become pregnant are systematically supplemented with folic acid: synthetic vitamin B9, a speciality reimbursed by the social security system, indicated at least three months before conception (if there is a desire to become pregnant), as well as during the first trimester of pregnancy. Vitamin B9, in its active form (5-methyl-tetrahydrofolate or 5-MTHF), plays an essential role in cell multiplication and contributes to the proper development of the embryo's nervous system l, in particular the closure of the neural tube.  

Most dietary supplements and medicines contain folic acid, which is not an active form of vitamin B9. It is a synthetic form. 

In order to make it active, our bodies are equipped with an enzyme: 5-MTHFR, encoded by the MTHF methylation gene. As it happens, there is a mutation in this gene in the population, which means that 16% of the female population does not produce an enzyme that functions at 100%. This mutation - which can be heterozygous (1 single allele of the gene mutated) or homozygous (2 alleles mutated with a loss of activity of 75%, which is very significant) - prevents you from correctly transforming this synthetic folic acid into its active methylated form: 5-MTHF (5 methyl-tetrahydrofolate), which has beneficial and indispensable effects on our body.

In Europe, according to recent estimates (2019), the polymorphism of this enzyme means that 40 to 51% of women are heterozygous (CT), and 10 to 18% homozygous (TT). In homozygous women, the enzyme's activity would be greatly reduced (by around 75%) and MTHFR synthesis would be insufficient, compromising assimilation of the synthetic form of folic acid. In the event of a mutation, synthetic folic acid will therefore accumulate in non-metabolized form and may have negative impacts on your body, notably by altering the functioning of the famous 5-MTHF enzyme.


But what is homocysteine?


lhomocysteine is a derivative of the amino acid methionine, which, if present in blood in excessive quantities, can have harmful effects on health.  

  • cardiovascular risk (it is 40 times more predictive than cholesterol) as it promotes latherosclerosis (it thickens the blood),  

  • Neuropsychiatric risk: its elevation correlates with the development of Alzheimer's disease Hu Q, Teng W, Li J, Hao F, Wang N. Homocysteine and Alzheimer's Disease: Evidence for a Causal Link from Mendelian Randomization. J Alzheimers Dis. 2016 Mar 22;52(2):747-56. doi: 10.3233/JAD-150977. PMID: 27031476. Xie Y, Feng H, Peng S, Xiao J, Zhang J. Association of plasma homocysteine, vitamin B12 and folate levels with cognitive function in Parkinson's disease: A meta-analysis. Neurosci Lett. 2017 Jan 1;636:190-195. doi: 10.1016/j.neulet.2016.11.007. Epub 2016 Nov 10. PMID: 27840145, or to the risk of onset of dementia Wald DS, Kasturiratne A, Simmonds M. Serum homocysteine and dementia: meta-analysis of eight cohort studies including 8669 participants. Alzheimers Dement. 2011 Jul;7(4):412-7. doi: 10.1016/j.jalz.2010.08.234. PMID: 21784352. 

  • Its impact on fertility in both men and women, as well as on the proper development of pregnancy (which is what matters to us here). In men, too high a level is correlated with poor sperm quality: azoospermia, asthenospermia (less mobility and more atypical shape) - or in women (essential for metabolism and hormonal balance), too high a level is linked to certain pregnancy complications (premature infants, childbirth complications, low birth weight, miscarriages). Timmermans S, Jaddoe VW, Hofman A, Steegers-Theunissen RP, Steegers EA. Periconception folic acid supplementation, fetal growth and the risks of low birth weight and preterm birth: the Generation R Study. Br J Nutr. 2009 Sep;102(5):777-85. doi: 10.1017/S0007114509288994. Epub 2009 Mar 30. PMID: 19327193. 

Homocysteine can be recycled into either methionine or cysteine to produce glutathione, the body's main antioxidant! You can see how important it is to recycle it. In fact, a lack of vitamin B6 (essential for transformation into cysteine), methyl-B9 and methyl-B12 (B vitamins in their active form) is directly correlated with a rise in homocysteine, since without them homocysteine recycling cannot take place. Since vitamins B9, B12 and B6 work synergistically together, it makes much more sense to take all 3 when supplementing than to take them on their own.

So we're not all equal when it comes to our ability to transform vitamin B9 (folates, folic acid) into methylated vitamin B9 due to this famous genetic mutation. 

Si vous vous interrogez sur votre génotype, vous pouvez bien sûr effectuer un test génétique ou, dans un premier temps, un dosage de l’homocystéine qui est un bon reflet de votre capacité de methylation. Le taux optimal est de 7 et pas simplement < 10 (valeur plus ciblée que celles de nombreux labos). Comme dans toutes réactions du corps humain, il y a un juste équilibre trop de methylation n’est pas bon non plus.

In any case, whether you have this mutation or not, it is possible to compensate for the potential loss of enzymatic activity by not taking synthetic folic acid, but rather B vitamins in active methylated form, directly assimilated and ideally taken in combination.

Léa's advice:


My advice if you want to get pregnant but are having difficulty getting pregnant and are subject to hormonal disorders(PCOS, endometriosis, PMS...) is to discuss these studies with your gynecologist and your possible prescription of synthetic folic acid at 0.4 mg. It is entirely possible to replace this with a methylated form which will be directly active and, what's more, more natural. The same applies to men, whose hyperhomocysteinemia is known to have a negative impact on sperm quality.

Finally, here's a list of tips for adapting your diet to promote the natural intake of folates. We recommend that you reduce your consumption of alcohol and tobacco, and include in your diet all foods naturally rich in folates, such as dark green vegetables, leaves and cruciferous vegetables (spinach, arugula, broccoli), raw or lightly cooked, legumes (peas, beans, broccoli, lentils), beef liver, organic chicken, flax and chia seeds, and aromatic herbs and spices such as turmeric and rosemary.


For all the most delicate moments in your life, Elia accompanies you with its range of menstrual pants.

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The information contained in the articles on www-elia-lingerie.com is general information only. Although reviewed by health professionals, this information is not error-free, does not constitute health advice or consultation, and is not intended to provide a diagnosis or suggest a course of treatment. Under no circumstances may this information be used as a substitute for medical advice or consultation with a healthcare professional. If you have any questions, please consult your doctor.