Evidence check: MTHFR in the context of Sport

Evidence for MTHFR variants (especially C677T) in sports is weak to moderate. Mechanistically, MTHFR affects folate metabolism and homocysteine levels, which could theoretically influence recovery, inflammation, and cardiovascular endurance. However, robust human studies showing direct performance benefits from genotype-specific interventions are lacking. Many direct-to-consumer companies overstate clinical relevance. Most carriers are asymptomatic; elevated homocysteine can be normalized by adequate folate intake (e.g., leafy greens) without needing methylfolate supplements. For athletes with recurrent injuries or unexplained fatigue, a homocysteine test may be reasonable, but routine genetic screening is not supported. The German Society for Sports Medicine does not recommend genetic testing for performance assessment. Conclusion: MTHFR testing in sports is low-evidence unless there is medical suspicion of hyperhomocysteinemia. Consult a physician before supplementing.