Zinc and Selenium for Sperm Health: Do They Work?

Supplements marketed for male fertility commonly contain zinc, and many add selenium.¹⁶ That makes them a fair test case for the whole category: do supplements marketed for sperm actually change the results? Two large US trials have now tested exactly that.

Why zinc and selenium?

Zinc and selenium are essential minerals, and the case for supplementing them rests on limited early evidence, according to the FAZST investigators.¹ A 2023 review of 34 over-the-counter antioxidant supplements for male fertility found they contained 48 different active substances, cost an average of $53.10 per 30 days, and in 79% of cases contained at least one ingredient above the recommended dietary allowance.⁶ All of them made fertility or sperm-quality claims, yet only two had been tested in a good-quality clinical trial.⁶

Supplements are not FDA-approved: by law, the FDA does not approve dietary supplements or their labels before sale.⁷

Zinc and selenium: the evidence at a glance

The FAZST trial: zinc and folic acid

The Folic Acid and Zinc Supplementation Trial is the largest test of a male fertility supplement. Between 2013 and 2017, it enrolled 2,370 couples planning infertility treatment at four US centers.¹ Men took either 5 mg of folic acid with 30 mg of elemental zinc, or placebo, every day for six months.¹

The results were clear:

• Live birth was 34% with the supplement and 35% with placebo (risk difference −0.9%).¹
• Semen quality (concentration, motility, morphology, volume and total motile count) did not differ at six months.¹
• DNA fragmentation was slightly higher with the supplement (29.7% vs 27.2%).¹
• Side effects were more common with the supplement: abdominal pain or discomfort 6% vs 3%, nausea 4% vs 2%, vomiting 3% vs 1%.¹

The trial enrolled a general population of couples seeking fertility treatment, not only men with abnormal semen, and the authors concluded the findings do not support folic acid and zinc for male partners in infertility treatment.¹

The MOXI trial: a full antioxidant formula

The Males, Antioxidants, and Infertility (MOXI) trial tested a typical multi-ingredient formula in 174 men with low count, low motility, abnormal morphology or high DNA fragmentation.² The daily formula included 0.20 mg (200 mcg) of selenium, 20 mg of zinc, vitamins C and E, L-carnitine, folic acid and lycopene, taken for three to six months.²

After three months, there were no significant differences between groups in morphology, motility or DNA fragmentation, and sperm concentration fell slightly with the antioxidant (median −4.0 million/mL) while it rose slightly with placebo (+2.4 million/mL).² Cumulative live birth at six months was 15% with antioxidants and 24% with placebo; the authors note the trial was limited by its size.² The authors concluded antioxidants do not improve semen parameters or DNA integrity in men with male factor infertility.²

What about selenium on its own?

The best-known selenium trial is older and small. In 1998, 69 Scottish men with reduced sperm motility took placebo, selenium, or selenium with vitamins A, C and E for three months.⁵ Combining the two selenium groups, selenium significantly increased motility but not sperm density, and five treated men (11%) fathered a pregnancy, compared with none on placebo.⁵ Only 56% responded, and the study population had low selenium status, which the authors linked to the Scottish diet.⁵ The result may not apply to men with adequate selenium.

What Cochrane concludes

Cochrane’s reviews pool every randomized trial of antioxidants, including zinc and selenium, for subfertile men. The 2019 review of 61 studies with 6,264 men found low-quality evidence that antioxidants may increase live births (OR 1.79), but the effect disappeared when trials at high risk of bias were removed.³ The 2022 update, with 90 studies and 10,303 men, reached the same conclusion with very low-certainty evidence and called the overall evidence inconclusive.⁴

So should you take zinc and selenium?

If your diet is reasonable, there is no good evidence that extra zinc or selenium will improve your sperm or your chances. The two largest, best-designed trials found no benefit. Supplements may help men with a genuine deficiency, which is something a doctor can assess.

If you still want a supplement, choose one with doses near the recommended allowance and third-party testing. Lifestyle changes with better evidence are in how to increase sperm count, and our 90-day sperm health plan puts them on a calendar. If you have not had a semen analysis, start there; semen analysis results explains the numbers. More in the Partners hub.