Dietary supplements do not improve fertility in men

Taking folic acid and zinc supplements does not improve men’s sperm quality or increase the likelihood of their partners getting pregnant, according to a large study of couples seeking infertility treatment published in JAMA (doi:10.1001/jama.2019.18714).

In the study, the men in 2370 couples attending infertility centres in the USA were randomised to receive either 5mg of folic acid and 30 mg of zinc or placebo daily for six months.

Live births were not significantly different between treatment groups, 404 (34%) in the folic acid and zinc group and 416 (35%) in the placebo group (risk difference, -0.9% [95% CI, -4.7% to 2.8%]). Semen quality (sperm concentration, motility, morphology, volume, and total motile sperm count) were also not significantly different between treatment groups at six months after randomisation.

Gastrointestinal side-effects were more common with folic acid and zinc supplementation compared with placebo (abdominal discomfort or pain: 66 versus 40; nausea: 50 versus 24; and vomiting: 32 versus 17).

Dietary supplements are widely marketed to improve male fertility based on limited trial evidence of improvements in semen quality. Until now no large scale study has tested this.

According to the authors their study does not support the use of folic acid and zinc supplementation by male partners in the treatment of infertility.

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