What does a MTHFR genotype mean for lifestyle?

The MTHFR C677T variant is a well-studied SNP that reduces methylenetetrahydrofolate reductase enzyme activity by about 30–40% (heterozygous) to 60–70% (homozygous). This affects folate and homocysteine metabolism. For lifestyle, the main implication is ensuring adequate folate intake from leafy greens, legumes, and fortified foods. Some individuals with C677T may benefit from active methylfolate (5-MTHF) instead of folic acid, as conversion may be impaired. However, evidence is mixed: randomized trials show only small or no benefits for the general population. The variant is not a clinical diagnosis – effect sizes are small, and diet, lifestyle, and other genetic factors dominate. A single DNA test does not warrant drastic changes. If homocysteine is elevated or specific risks exist (e.g., pregnancy), medical advice is reasonable. Beware of overpriced 'MTHFR diets' lacking solid evidence. Evidence: human-moderate.