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.