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, 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's a synthetic form.
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 mutated gene) or homozygous (2 mutated alleles 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 unmetabolized form and may have negative impacts on your body, notably by altering the functioning of the famous 5-MTHF enzyme.
But what is homocysteine?
Homocysteine is a derivative of the amino acid methionine, which, if present in blood in excessive quantities, can have harmful effects on health.
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cardiovascular risk (it is 40 times more predictive than cholesterol), as it promotes atherosclerosis (it thickens the blood),
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Neuropsychiatric risk: its elevation is correlated 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 at risk of developing 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.
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Its impact on fertility in both men and women, as well as on healthy pregnancy development (which is what we're concerned with here). In men, too high a level is correlated with the quality of spermatozoa: 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 babies, 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! The importance of recycling is obvious. 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.
We are therefore not all equal in our ability to transform vitamin B9 (folates, folic acid) into methylated vitamin B9 due to this famous genetic mutation.
If you're wondering about your genotype, you can of course carry out a genetic test or, as a first step, a homocysteine assay, which is a good reflection of your methylation capacity. The optimum level is 7 and not simply xtagstartz 10 (a more targeted value than many labs). As with all reactions in the human body, there's a fine balance: too much methylation isn't good either.
