The murky, multi-billion dollar supplement industry is buoyed by untested claims of treatments and cure-alls — and fertility is no exception.
But two supplements that have caught scientists’ attention are folic acid and zinc. There’s some evidence to suggest that taking folic acid — a supplement more readily associated with pregnancy — and zinc daily could boost sperm counts in men.
But a large clinical trial conducted in thousands of men concludes that taking the pair of supplements daily does not improve fertility in men.
The results contradict previous, smaller studies that did find the supplement combination to increase semen quality, specifically by raising sperm concentration. The researchers on this new trial say these previous findings may reflect the homogeneity of the study participants, although other factors may account for the discrepancy.
The findings were published Tuesday in the Journal of the American Medical Association.
Testing supplements for fertility
Male partners from couples planning to undergo treatment for infertility participated in the study. Researchers split the group of 2,300 men in half: 1,150 took 5 milligrams of folic acid and 30 milligrams of elemental zinc daily for six months. The remaining participants took a placebo every day instead.
The researchers looked at two outcomes: improved semen quality and rate of live birth — the latter, naturally, an important outcome for parents-to-be. In the group that took the supplements, 35 percent ultimately had a successful live birth, but that rate didn’t differ significantly from the placebo group.
If anything, some participants taking the supplements saw an unexpected result: mild gastrointestinal problems.
The study does have some limitations. It’s possible that some couples conceived before they started taking the supplements, which may have skewed the results. Also, most participants were white, non-Hispanic, and had a high socioeconomic status, so the results may not apply to people from other socioeconomic or ethnic backgrounds.
The new report speaks to the need for large-scale clinical trials to examine effects of supplements like zinc and folic acid on semen quality and other aspects of men’s health.
IMPORTANCE: Dietary supplements marketed for male fertility commonly contain folic acid and zinc based on limited prior evidence for improving semen quality. However, no large-scale trial has examined the efficacy of this therapy for improving semen quality or live birth.
OBJECTIVE: To determine the effect of daily folic acid and zinc supplementation on semen quality and live birth
RESULTS: Among 2370 men who were randomized (mean age, 33 years), 1773 (75%) attended the final 6-month study visit. Live birth outcomes were available for all couples, and 1629 men (69%) had semen available for analysis at 6 months after randomization. Live birth was 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%]).
Most of the semen quality parameters (sperm concentration, motility, morphology, volume, and total motile sperm count) were not significantly different between treatment groups at 6 months after randomization. A statistically significant increase in DNA fragmentation was observed with folic acid and zinc supplementation (mean of 29.7% for percentage of DNA fragmentation in the folic acid and zinc group and 27.2% in the placebo group; mean difference, 2.4% [95% CI, 0.5% to 4.4%]). Gastrointestinal symptoms were more common with folic acid and zinc supplementation compared with placebo (abdominal discomfort or pain: 66 [6%] vs 40 [3%], respectively; nausea: 50 [4%] vs 24 [2%]; and vomiting: 32 [3%] vs 17 [1%]).