MTHFR genetic variants affect up to half of the population and may reduce your ability to process folic acid and turn it into folate. If you can't convert enough folic acid into folate, you may have low folate levels. Low folate levels has been proven to contribute to birth defects and can cause high levels of homocysteine in your body which may lead to cardiovascular problems. If you're a woman of childbearing age, it is especially important to check for the variants and keep track of your folate levels.
Additionally, if your diet is rich in folic acid from supplements and fortified foods and you have the variants that make it difficult for you to metabolize it, folic acid may build up in your body and cause you harm. Some studies have found that too much folic acid contributes to breast, lung, and prostate cancer. Learn more about folic acid and folate in my post here.
The easiest way to find out if you are affected by a variant (no doctor required):
Step 1. Order a 23andme DNA kit to have your DNA sequenced. When the results come back sign into your 23andme account. 23andme does not include MTHFR variants in your summary report because they feel that the health implications are inconclusive at this time (1). To find out if you have the variants, you will need to dig into your raw genomic data on 23andme by looking up at positions rs1801131 and rs1801133 in your genetic code. Luckily there is an easy way to do this.
Step 2. Check your DNA for MTHFR A1298C variant
To do this, go here: https://www.23andme.com/you/explorer/snp/?snp_name=rs1801131 to look at SNP rs1801131. If you see T/T on the right where is says "Your Genotype", you do not have the variant and this is the best case scenario. If you see G/G you are homozygous for the MTHFR A1298C variant and this results in 40% loss of function in processing folic acid. If you see G/T (as shown below) you are heterozygous for MTHFR A1298C and this results in 20% loss of function in processing folic acid (2). For more information about this piece of DNA visit: https://snpedia.com/index.php/Rs1801131
Step 3. Check your DNA for the MTHFR C677T variants
Next click on this link: https://www.23andme.com/you/explorer/snp/?snp_name=rs1801133 to look at SNP rs1801133. If you see G/G on the right where is says "Your Genotype", you do not have the variant for MTHFR A1298C and this is the best case scenario. If you see A/A you are homozygous for the MTHFR A1298C variant and this results in 70% loss of function in processing folic acid. If you see A/G (as shown below) you are heterozygous for MTHFR C677T and it is unknown how much loss of function this causes (3). For more information about this piece of DNA visit: https://snpedia.com/index.php/Rs1801133
If you are heterozygous for both A1298C and C677T as shown in the example above, this is called "compound heterozygous" and results in a 50% loss of function in processing folic acid. This happens in about 20% of the population (4).
Step 4. If you have found a variant and have reduced ability to process folic acid, I suggest reading this post I wrote on what to do about it.
You can learn more about the MTHFR gene at the National Institute of Health: https://ghr.nlm.nih.gov/gene/MTHFR
About the author
Jessica Glago is the CoFounder of the Wholesome App. After having two different cancers in her childhood she developed the app with the help of her husband to get more healthfulness out of her diet. To date, Wholesome for iOS has had over 250,000 downloads and over 1.5 million whole foods tracked. The app has been featured on BuzzFeed, LikeHacker, CultofMac, and The Seattle Times.