
Some websites and products have made bold claims that common genetic variants in MTHFR can cause a wide array of health conditions, ranging from blood clots and cancer to autism and migraines.
So we decided to dig deeper into the published scientific literature to evaluate the evidence.
Our conclusion?
Despite lots of research – and lots of buzz – the existing scientific data doesn’t support the vast majority of claims that common MTHFR variants impact human health.
The biology
The MTHFR gene contains instructions for making an enzyme that’s important for metabolizing folate (also called folic acid or vitamin B9). MTHFR also helps our cells recycle homocysteine, a chemical in the blood, into methionine, a building block for proteins.[1]
We also know that there are two common naturally occurring variants in the MTHFR gene, called C677T and A1298C.
When the MTHFR gene has either of these two variants, the resulting MTHFR enzyme is slightly less active, and this can lead to decreased levels of folate and increased levels of homocysteine in the blood.[1]
The hype
Another claim about MTHFR is that people who carry an MTHFR variant should avoid foods that are fortified with folic acid. However, there’s no evidence that individuals with an MTHFR variant should reduce their folic acid intake.
The scientific evidence
Over the past two decades, scientists have examined associations between the MTHFR C677T and A1298C variants and more than 600 medical conditions.[2] Despite thousands of scientific publications, the evidence linking MTHFR to most of these health conditions is inconclusive or conflicting.
For example, some studies report an increased risk of heart disease for individuals with two copies of the C677T variant,[3] while other studies report no association with heart disease.[4]
The same is true for cancer,[5][6] blood clots,[7][8] and many other well studied health conditions.[1][9][10]
[11][12] However, according to the National Institute of Child Health and Human Development, as well as other countries’ nationwide health programs, folic acid supplementation reduces the risk of neural tube defects in all pregnant women, including women with an MTHFR variant.[13]
The takeaway
In order for a connection between a genetic variant and a health condition to be considered real and clinically meaningful, well-run scientific studies need to show convincing and consistent evidence for that association. As statements from multiple scientific and medical organizations indicate,[14] [15] that is currently not the case for the common MTHFR variants. Our team will continue to monitor research in this area – as we do for a wide variety of genetic research – and evaluate new information as it becomes available.
[16] These variants are different from the common variants described here and discussed throughout the 23andMe community and online.
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References:
Sources for Information
Websites and blogs are filled with misinformation about MTHFR. When you’re looking for information about science and health, make sure you find trustworthy sources.
Here are a few of our favorite sites for information about genetics, health, and disease:
• Genetics Home Reference https://ghr.nlm.nih.gov/
• GeneReviews https://www.ncbi.nlm.nih.gov/books/NBK1116/)
•
Mayo Clinic (http://www.mayoclinic.org/patient-care-and-health-information)
• US National Library of Medicine (https://www.nlm.nih.gov/medlineplus/)
• Disease-specific sites National Cancer Institute (http://www.cancer.gov/), the American Heart Association (http://www.americanheart.org/), and the American Diabetes Association (http://www.diabetes.org/)
• Understanding Health Research (http://www.understandinghealthresearch.org/), a tool to help evaluate the quality of health studies.