The MTHFR gene provides instructions for making an enzyme called methylenetetrahydrofolate reductase. This enzyme plays a role in processing homocysteine. Elevated plasma homocysteine is an independent risk factor for stroke and other cardiovascular events.3 It has also been associated with hypertension, preeclampsia, glaucoma, psychiatric disorders, and certain types of cancer.
In some studies[1, 2, 3], MTHFR variants and smoking behavior were associated with homocysteine plasma levels. Such an association may be a relevant confounder between MTHFR variants, homocysteine plasma levels and vascular diseases. Smoking is known to be associated with higher homocysteine plasma levels[3, 4].