Hello, I can understand regarding safety of folic acid supplement while suffering from MTHFR gene polymorphism. It is safe to take folic acid supplement while having heterozygous state. The methylenetetrahydrofolate reductase (MTHFR) enzyme converts synthetic folic acid and dietary folate into its active form, L-methyl folate which plays a critical role in neurotransmitter synthesis. Individuals who carry this MTHFR gene polymorphism will have a reduced capacity to create L-methyl folate. Heterozygotes will have 35% reduction in enzyme activity as compared to 70% reduction in activity by the homozygotes. Both L-methyl folate and folic acid are possible treatment options for individuals with reduced MTHFR activity. In addition, you may also take high-folate foods like green leafy vegetables, beans, lentils, broccoli, avocado, bright-colored fruits, such as oranges and mangoes. Along with the folic acid supplements you also need to take Vitamins B6 and B12. These are easily obtained from quality protein foods such as organ meats, nuts, beans, nutritional yeast and raw/fermented dairy products. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Mohammed Taher Ali