C677T methylenetetrahydrofolate reductase polymorphism interferes with the effects of folic acid and zinc sulfate on sperm concentration

OBJECTIVE: To determine the frequency of C677T methylenetetrahydrofolate reductase (MTHFR) polymorphism in fertile and subfertile males, and the MTHFR-dependent response of sperm concentration after folic acid and/or zinc sulfate intervention. DESIGN: Double-blind, placebo-controlled intervention study.Two outpatient fertility clinics and nine midwifery practices in The Netherlands. PATIENT(S): One hundred thirteen fertile and 77 subfertile males.Daily capsules of folic acid (5 mg) and/or zinc sulfate (66 mg), or placebo for 26 weeks. MAIN OUTCOME MEASURE(S): Prevalence of C677T MTHFR polymorphism and the response of sperm concentration related to MTHFR carriership after intervention treatment. RESULT(S): The C677T methylenetetrahydrofolate reductase genotypes were comparable in fertile and subfertile males. Independent of fertility state, sperm concentration significantly increased in wild-types after folic acid and zinc sulfate treatment only. Heterozygotes and homozygotes did not significantly benefit from either treatment. CONCLUSION(S):C677T methylenetetrahydrofolate reductase polymorphism is not a risk factor for male factor subfertility. In contrast to heterozygotes and homozygotes for C677T MTHFR polymorphism, sperm concentration in wild-types significantly improved after folic acid and zinc sulfate intervention. A stronger role of other folate genes on spermatogenesis is suggested.