Selenium is a trace mineral built into proteins called selenoproteins, several of which protect cells from oxidative damage. In the testes, selenoproteins are part of the structure of developing sperm, which is why selenium features in so many male fertility supplements. Good food sources include Brazil nuts, fish, eggs and meat, though the amount in plant foods depends on the soil they were grown in.
Selenium carries authorised UK and EU health claims: selenium contributes to normal spermatogenesis, and selenium contributes to the protection of cells from oxidative stress.
The best-known trial comes from Glasgow, a region with low selenium intake. Sixty-nine subfertile men with reduced sperm motility took selenium, selenium with vitamins A, C and E, or a placebo for three months. Sperm motility improved with selenium compared with placebo, and the authors linked the result to the men's low selenium status.1
What have studies found on selenium and sperm?
In subfertile men with low selenium status, selenium supplements improved sperm motility in a placebo-controlled trial. Semen volume has not been a focus of selenium research.
In the Glasgow trial, blood selenium rose in both selenium groups, motility improved compared with placebo, and adding vitamins A, C and E made no extra difference. Five treated men (11%) fathered a pregnancy, compared with none on placebo, and 56% of treated men showed a positive response.1
Selenium is also included in combination antioxidant products. The US MOXI trial gave 174 men with male factor infertility a blend including selenium, zinc, vitamins C and E, L-carnitine, folic acid and lycopene, and did not find a difference in semen parameters or sperm DNA integrity compared with placebo.4 Research is ongoing into which men respond best.
Can too much selenium be harmful?
Yes. Two large trials found that extra selenium in people who were not deficient was linked to higher risks of type 2 diabetes and, in men with higher selenium levels, aggressive prostate cancer.
In one randomised trial, people given 200 micrograms of selenium daily for an average of 7.7 years developed type 2 diabetes more often than those on placebo, with the highest risk in those who started with the most selenium.3 In the large SELECT prostate cancer trial, selenium supplements increased the risk of high-grade prostate cancer by 91% among men with higher baseline selenium levels; the authors advised men to avoid doses above recommended dietary intakes.2
Talk to a doctor before taking selenium if you have diabetes, a history of prostate problems or already take a multivitamin.
- Stacking products: many multivitamins and fertility blends already contain selenium
- Food sources: Brazil nuts are especially rich, so supplements on top can overshoot
How can men trying to conceive get enough selenium?
Most men eating a varied diet get selenium from foods such as fish, eggs, meat and Brazil nuts. If you are considering a supplement, talk to a doctor about your current intake first, because high intakes carry risks.
If you and your partner are trying for a baby, a semen analysis and a proper assessment help show where to focus. See lifestyle factors that affect male fertility for other changes worth considering.
Most selenium studies have measured semen quality rather than pregnancies, so research on birth rates is ongoing.
Common questions
Does selenium help sperm?
Selenium contributes to normal spermatogenesis. In a trial of subfertile men with low selenium status, three months of supplements improved sperm motility compared with placebo.1
Are Brazil nuts a good source of selenium?
They are one of the richest food sources, and the amount varies a lot between nuts. That makes it easy to overshoot if you also take a supplement.
Read more on this
Supplement ingredients for men’s sexual health: what the research shows
Lifestyle factors that affect male fertility: a practical guide
Sources
- Scott R, et al. The effect of oral selenium supplementation on human sperm motility. Br J Urol. 1998;82(1):76-80. PubMed
- Kristal AR, et al. Baseline selenium status and effects of selenium and vitamin E supplementation on prostate cancer risk. J Natl Cancer Inst. 2014;106(3):djt456. PubMed
- Stranges S, et al. Effects of long-term selenium supplementation on the incidence of type 2 diabetes: a randomized trial. Ann Intern Med. 2007;147(4):217-23. PubMed
- Steiner AZ, et al. The effect of antioxidants on male factor infertility: the Males, Antioxidants, and Infertility (MOXI) randomized clinical trial. Fertil Steril. 2020;113(3):552-560.e3. PubMed
Not medical advice. Written by Eric Stephens from the research cited above; not reviewed by a doctor. If something worries you, see a GP.