Selenium and Male Fertility: Finding the Sweet Spot

Selenium is one of the most commonly included ingredients in male fertility supplements. It’s often marketed as an important nutrient for sperm production, antioxidant defence, and male reproductive health. Many fertility supplements contain selenium alongside nutrients such as zinc, CoQ10, omega-3, vitamin C, vitamin E, carnitine and folate.

Selenium didn't become popular in fertility circles by accident. It is involved in several biological processes that are important for sperm development and function.

Selenium is an essential trace mineral that forms part of several important proteins involved in antioxidant defence, thyroid hormone metabolism, and reproductive function (NHMRC, 2006). Within the male reproductive system, selenium-containing proteins appear to play important roles in sperm development and maturation, particularly through their involvement in protecting developing sperm from oxidative damage (Patel et al., 2026).

At first glance, the case for selenium seems straightforward. Selenium deficiency can impair reproductive function in animal models. Observational studies have reported lower selenium concentrations in blood, serum, and seminal plasma among men with infertility compared with fertile controls. Selenium is also involved in the activity of glutathione peroxidase enzymes, which help protect sperm from oxidative stress during development (Patel et al., 2026). Given these findings, it would seem logical that increasing selenium intake should improve fertility.

Yet when researchers have attempted to test this theory in clinical studies, the results have been far less consistent. While some clinical trials have reported improvements in sperm concentration, motility, and morphology following selenium supplementation, other studies have found little or no benefit. More recent evidence reviews have also highlighted a lack of convincing evidence that selenium supplementation improves pregnancy or live birth rates (Michaelsen et al., 2025). Adding further complexity, selenium is one of the few nutrients where both too little and too much may be problematic. Unlike nutrients with a wide margin of safety, selenium appears to have a relatively narrow therapeutic window. The Recommended Dietary Intake for adult Australian men is 70 micrograms per day, while the Upper Level of Intake is 400 micrograms per day (NHMRC, 2006). This raises an important question: Is selenium supplementation correcting a deficiency, optimising an existing intake, or potentially pushing intake beyond what is beneficial?

In this article, we'll examine what selenium actually does, why it has attracted attention in male fertility research, what the clinical evidence shows, and why the answer may be less about taking more selenium and more about finding the right amount.

Selenium is just one of many factors that can influence sperm health. If you're looking for a broader overview of the nutrition and lifestyle factors that may help improve sperm quality, you can read our guide on How to Improve Sperm Quality Naturally.

Why Selenium Matters for Sperm Health

Selenium is classified as an essential trace mineral, meaning the body requires it in small amounts but cannot produce it itself. Instead, it must be obtained through food. Its importance comes from its role in a group of proteins known as selenoproteins. These proteins are involved in several critical functions throughout the body, including antioxidant defence, thyroid hormone metabolism, immune function, and cellular signalling (NHMRC, 2006; Patel et al., 2026).

Within the male reproductive system, selenium appears to play several important roles. One of the most well-studied selenium-containing proteins is glutathione peroxidase 4 (GPx4). This enzyme helps protect developing sperm cells from oxidative damage by neutralising reactive oxygen species and lipid peroxides that can damage cell membranes and DNA (Patel et al., 2026). This is particularly relevant because sperm are highly vulnerable to oxidative stress. Unlike most cells in the body, sperm contain large amounts of polyunsaturated fatty acids within their cell membranes. While these fatty acids are important for sperm function, they are also highly susceptible to oxidative damage. Excessive oxidative stress can impair sperm motility, damage DNA, and reduce the ability of sperm to successfully fertilise an egg. If you'd like a deeper explanation of oxidative stress and why antioxidant supplements often produce inconsistent results in fertility research, you can read our article on Antioxidants and Male Fertility. Selenium also appears to contribute to the structural development and maturation of sperm. GPx4 is not only involved in antioxidant defence but also becomes incorporated into the developing sperm midpiece, where it helps stabilise structures that are important for sperm movement and function (Patel et al., 2026).

Animal studies have consistently shown that severe selenium deficiency can impair spermatogenesis and reduce fertility. Observational studies in humans have similarly reported lower selenium concentrations in blood, serum, and seminal plasma among men with infertility compared with fertile controls (Unar et al., 2025). Taken together, these findings provide a strong biological rationale for why selenium has attracted attention in male fertility research. The important question, however, is whether correcting or increasing selenium intake actually translates into better fertility outcomes in clinical practice.

What Does the Research on Selenium Supplementation Show?

Given selenium's biological role in sperm development and antioxidant defence, researchers have spent decades investigating whether supplementation can improve male fertility.

Early findings were encouraging. One of the most frequently cited studies was published by Scott and colleagues in 1998. In this trial, men with reduced sperm motility received 100 micrograms of selenium per day for three months. The researchers reported improvements in sperm motility and observed higher conception rates among couples in the selenium group compared with placebo (Scott et al., 1998).

As additional studies were published, researchers began pooling the available evidence to determine whether these findings were consistent across different populations and study designs. The results appeared broadly supportive. A systematic review and meta-analysis by Salas-Huetos and colleagues identified improvements in sperm concentration, total motility, and normal morphology among men receiving selenium supplementation, leading to growing interest in selenium as a potential fertility intervention (Salas-Huetos et al., 2018).

At first glance, these findings seem to support the idea that selenium supplementation may improve sperm quality. However, there are several important caveats. The number of selenium-specific trials remains surprisingly small. Many studies involve relatively few participants, use different selenium doses, and assess different fertility outcomes. In addition, improvements in semen parameters do not necessarily translate into higher pregnancy or live birth rates.

Not all studies have reported positive findings either. For example, Hawkes and colleagues supplemented healthy men with 300 micrograms of selenium per day for 11 months and found no meaningful improvements in conventional semen parameters or reproductive hormone levels (Hawkes et al., 2009). These conflicting findings highlight an important challenge in fertility research. While selenium clearly plays an important role in normal reproductive physiology, demonstrating that additional selenium improves fertility outcomes has proven much more difficult.

What Do the Most Recent Evidence Reviews Conclude?

As additional studies have been published, researchers have attempted to reassess the overall evidence for selenium and other fertility supplements. One of the most comprehensive and recent reviews was published by Michaelsen and colleagues. After examining randomised controlled trials investigating a wide range of dietary supplements for male infertility, the authors concluded that there was no convincing evidence that supplementation improved pregnancy rates, live birth rates, or most semen parameters with a high degree of certainty (Michaelsen et al., 2025). This does not mean selenium was ineffective. In fact, selenium supplementation was associated with improvements in total sperm motility in the studies included in the review. However, the evidence was based on a small number of trials and the overall certainty of the evidence was judged to be low due to issues such as small sample sizes, risk of bias, and differences between studies (Michaelsen et al., 2025).

When discussing male fertility, improvements in sperm concentration, motility, or morphology are often presented as though they automatically translate into improved fertility outcomes. While semen parameters are certainly relevant, they are ultimately surrogate markers. The outcomes that matter most to couples are pregnancy and live birth. And at present, the evidence that selenium supplementation improves these outcomes remains limited. This is not unique to selenium. Many fertility supplements have strong biological mechanisms and show promising results in small studies, only for the overall evidence to become less convincing when larger studies and systematic reviews are performed. This pattern has been observed across several antioxidant nutrients commonly used in male fertility practice.

Taken together, the current evidence suggests that selenium may improve certain sperm parameters in some men, particularly sperm motility. However, the evidence is not strong enough to conclude that routine selenium supplementation improves fertility outcomes for all men trying to conceive.

So if selenium is clearly important, but supplementation does not consistently produce better outcomes, how should we interpret this apparent contradiction?

Selenium, Deficiency, and the Problem with "More Is Better"

One possible explanation for the conflicting findings is that selenium may behave differently from many nutrients people associate with supplementation. For some nutrients, increasing intake from a low level may produce meaningful benefits. However, once requirements are met, additional intake may provide little further advantage. Selenium appears to fit this pattern.

The Recommended Dietary Intake for adult Australian men is 70 micrograms per day, while the Upper Level of Intake is 400 micrograms per day (NHMRC, 2006). Unlike some nutrients with a very wide margin of safety, the gap between recommended intake and excessive intake is relatively narrow. This means selenium may be particularly vulnerable to a "more is better" mindset.

Severe selenium deficiency is unquestionably harmful. Selenium deficiency has been linked to impaired antioxidant defence, thyroid dysfunction, and reproductive abnormalities in both animal and human research (NHMRC, 2006; Patel et al., 2026). However, there is little evidence that pushing selenium intake progressively higher continues to improve fertility outcomes. In fact, some researchers have proposed that selenium may exhibit a U-shaped relationship with health outcomes. In this model, both insufficient and excessive selenium exposure may be undesirable, with the greatest benefit occurring somewhere in the middle (Patel et al., 2026). This concept may also help explain some of the inconsistent findings seen in supplementation trials. A man with inadequate selenium intake may benefit from improving his selenium status. A man who already consumes sufficient selenium from food, however, may have little to gain from additional supplementation.

More recently, researchers have also begun discussing the concept of reductive stress. While excessive oxidative stress can damage sperm, small amounts of reactive oxygen species are necessary for normal sperm maturation, capacitation, and fertilisation. The goal is not to eliminate oxidative activity altogether, but to maintain an appropriate balance (Moustakli et al., 2025). Although the practical significance of reductive stress remains uncertain, it provides another reminder that biological systems rarely respond in a simple linear fashion. More antioxidant activity is not always better, just as more supplementation is not always better.

For men trying to conceive, the practical takeaway is that selenium should be viewed as an essential nutrient rather than a fertility shortcut. The goal is to achieve adequate intake and avoid deficiency, not necessarily to maximise intake as much as possible.

Food Sources of Selenium

Fortunately, selenium is found naturally in a variety of foods.

In Australia, some of the richest dietary sources include seafood, eggs, poultry, and meat. Selenium is also present in cereals, grains, nuts, and seeds, although the amount can vary considerably depending on the selenium content of the soil in which the food was grown (NHMRC, 2006).

Brazil nuts are often highlighted because of their exceptionally high selenium content. While they can be a useful dietary source of selenium, they also illustrate why more is not always better. The selenium content of Brazil nuts varies substantially depending on where they are grown, meaning the amount provided by a single nut can differ considerably. As a result, even a small serving may contribute a large proportion of an adult's daily selenium requirements. For most people, one or two Brazil nuts can provide a meaningful contribution to selenium intake. Regularly consuming large quantities, particularly alongside selenium-containing supplements, may increase the risk of excessive selenium intake over time.

This uncertainty highlights an important point that applies throughout the selenium literature. The question is not simply whether selenium is important. The question is whether an individual man is obtaining enough selenium to meet his needs. For many men, achieving adequate selenium intake may be less about adding supplements and more about maintaining a varied, nutrient-dense dietary pattern that includes selenium-rich foods.

Selenium is just one component of a broader dietary pattern. For a more comprehensive overview of the foods and eating patterns associated with better sperm health, see our guide to the Fertility Diet for Men. And if you're looking for practical examples of how this can look in everyday life, you may find our 7-Day Men's Fertility Meal Plan helpful. It includes many of the foods that support sperm health and provides a practical starting point for improving overall diet quality.

Should Men Trying to Conceive Take a Selenium Supplement?

Based on the current evidence, there is little reason to assume that every man trying to conceive needs a selenium supplement.

Selenium is clearly important for male reproductive health. It plays essential roles in antioxidant defence, sperm development, and normal reproductive function. Severe deficiency is undesirable, and observational studies consistently report lower selenium status among men with infertility compared with fertile controls. However, the leap from "selenium is important" to "more selenium improves fertility" is not supported as strongly as many supplement marketing claims suggest. Some clinical trials have reported improvements in sperm concentration, motility, and morphology following selenium supplementation. Yet other studies have found little or no benefit, and more recent evidence reviews have concluded that there is currently insufficient evidence to confidently state that selenium supplementation improves pregnancy or live birth rates (Michaelsen et al., 2025). For most men, the priority should be ensuring adequate selenium intake through a varied, nutrient-dense diet rather than automatically reaching for a supplement.

Supplementation may be reasonable in certain circumstances, particularly where dietary intake is poor, selenium status is suspected to be inadequate, or supplementation forms part of a broader evidence-based fertility plan developed with a qualified healthcare professional.

What the current evidence does not support is the idea that progressively increasing selenium intake will necessarily lead to better fertility outcomes.

In many ways, selenium illustrates an important principle in fertility nutrition. The goal is not to maximise every nutrient.m The goal is to create an environment that supports normal sperm development and function. Sometimes that means correcting a deficiency. Sometimes it means improving overall diet quality. And sometimes it means recognising that more is not always better.

For selenium, the most evidence-based approach appears to be finding the sweet spot between too little and too much.

Key Takeaways

• Selenium is an essential nutrient involved in sperm development, antioxidant defence, and normal reproductive function.

• Observational studies have reported lower selenium levels in men with infertility, but this does not prove that selenium deficiency causes fertility problems.

• Some clinical trials suggest selenium supplementation may improve sperm motility and other semen parameters.

• More recent evidence reviews have found limited evidence that selenium supplementation improves pregnancy or live birth rates.

• Selenium appears to have a relatively narrow therapeutic window, meaning both inadequate and excessive intake may be undesirable.

• For most men, achieving adequate selenium intake through a varied diet is likely to be more important than automatically taking a selenium supplement.

Final Thoughts

Selenium is one of the more interesting nutrients in male fertility nutrition.

Unlike some supplements that have little biological rationale, selenium clearly plays important roles in sperm development and reproductive function. Yet despite this strong biological foundation, the clinical evidence remains less convincing than many supplement marketing claims suggest.

For men trying to conceive, the most evidence-based approach is unlikely to involve chasing ever-higher selenium intakes. Instead, the goal should be ensuring adequate intake through a nutrient-dense diet and considering supplementation only within the context of an individual's overall health, diet, fertility history, and clinical circumstances.

As is often the case in fertility nutrition, the answer may be less about finding a miracle nutrient and more about creating the right environment for healthy sperm development.

Disclaimer: This article is intended for educational purposes only and should not be considered personalised medical or nutrition advice. If you have concerns about your fertility, diet, or supplement use, speak with your doctor, fertility specialist, or Accredited Practising Dietitian.

If you'd like personalised guidance on nutrition, supplements, and lifestyle factors that may be affecting sperm health, you can book a Sperm Health Assessment through Axis Dietetics.

References

1. National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes. Canberra: Commonwealth of Australia; 2006.

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3. Michaelsen MP, Poulsen M, Bjerregaard AA, Borgstrøm M, Poulsen LK, Chortsen MB, et al. The Effect of Dietary Supplements on Male Infertility in Terms of Pregnancy, Live Birth, and Sperm Parameters: A Systematic Review and Meta-Analysis. Nutrients. 2025;17(10):1710. doi:10.3390/nu17101710.

4. Unar A, Afridi HI, Ali A, Ali N, Qureshi T. Determination of electrolytes and trace elements in biological samples from patients with altered semen parameters: a correlational analysis. Biol Trace Elem Res. 2025;203:1383-1394. doi:10.1007/s12011-024-04281-7.

5. Scott R, MacPherson A, Yates RW, Hussain B, Dixon J. The effect of oral selenium supplementation on human sperm motility. Br J Urol. 1998;82(1):76-80.

6. Salas-Huetos A, Rosique-Esteban N, Becerra-Tomás N, Vizmanos B, Bulló M, Salas-Salvadó J. The effect of nutrients and dietary supplements on sperm quality parameters: a systematic review and meta-analysis of randomized clinical trials. Adv Nutr. 2018;9(6):833-848. doi:10.1093/advances/nmy057.

7. Hawkes WC, Alkan Z, Wong K. Selenium supplementation does not affect testicular selenium status or semen quality in North American men. J Androl. 2009;30(5):525-533. doi:10.2164/jandrol.108.006940..

8. Moustaki E, Christopoulos P, Potiris A, Zikopoulos A, Matsas A, Arkoulis I, et al. Reductive stress and the role of antioxidants in male infertility: a narrative review. Arch Gynecol Obstet. 2025;312(5):1503-1514. doi:10.1007/s00404-025-08184-3.