Research from 2017 shows that men's sperm count has dropped by half over the last 40 years . This decline explains why we need to understand how selenium and testosterone work together. Selenium is a vital trace mineral that plays a substantial role in male reproductive health. It does more than provide simple nutrition—selenium actively supports spermatogenesis, sperm motility, and male fertility .
Selenium controls inflammation and oxidative stress through specialised proteins known as selenoproteins, including glutathione peroxidase (GPX) and thioredoxin reductase . Men can't ignore selenium's benefits, especially when it comes to reproductive health. Studies have shown that taking selenium supplements can improve sperm quality substantially. Research documents a 52.6% improvement in sperm motility, morphology, or both . On top of that, selenium connects with thyroid and testosterone to influence hormone production. Its antioxidant properties become especially valuable when men face age-related fertility challenges. Men who care about reproductive wellness should understand the right selenium dosage and how this mineral helps maintain prostate health.
The biological importance of selenium in male health
Selenium is a unique trace mineral that plays a vital role in male health. The human body needs most nutrients in gramme quantities, but selenium works in micrograms—just 40-70 μg per day for European populations [1]. These tiny amounts are a big deal as they affect male reproductive health and overall wellness.
Selenium as a trace mineral and antioxidant
Selenium is a key component of the 21st amino acid, selenocysteine (SeC), which forms the core of selenium-dependent enzymes [1]. These proteins, called selenoproteins, are the foundations of many biological processes that help maintain cellular redox balance [1]. The human body has 25 different selenoproteins, and each one has its own role in keeping our bodies running smoothly [2].
These selenoproteins give selenium its antioxidant properties, especially through glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) [1]. These enzymes fight off reactive oxygen species and free radicals that can damage cells [1]. Selenium acts as a powerful shield against oxidative stress, which can lower sperm quality and reduce testosterone production.
Your skeletal muscles hold 28% to 46% of your body's selenium [2]. The thyroid gland has the highest concentration because it needs various selenoproteins for proper function [2]. This creates the selenium thyroid testosterone connection, since thyroid hormones directly affect how much testosterone your body produces.
How selenium supports cellular redox balance
Selenium keeps cellular redox balance through selenoproteins that control oxidation-reduction reactions. These proteins:
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Fight reactive oxygen and nitrogen species to reduce ischemic injury [1]
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Shield proteins and lipids from damage through antioxidant activity [1]
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Control cell growth and death processes [1]
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Help with protein folding and calcium balance [1]
Selenoprotein P (SELENOP) makes up more than half of all plasma selenium and works as both a transport protein and antioxidant [1]. This makes it especially valuable for selenium benefits men since it moves selenium to tissues while protecting against oxidative damage.
Selenium's effect on redox balance follows a U-shaped curve—too little or too much can cause problems [1]. Healthy people typically have selenium serum levels between 80 and 120 μg/L [1]. Lower levels increase the risk of oxidative damage, which can lead to less testosterone and affect [selenium prostate health](https://goldmanlaboratories.com/blogs/blog/[andropause](https://goldmanlaboratories.com/fr/blogs/blog/andropause-men-over-60).
Overview of selenium's role in reproductive tissues
Male reproductive tissues need selenium to support fertility and reproductive function. Selenium is vital for sperm production and male fertility because it helps control antioxidant defences [3].
Your testes need the right amount of selenium to develop properly. Even small changes in selenium levels can lead to abnormal development [4]. Testicular tissue contains several selenoproteins including GPx1, GPx3, mGPx4, cGPx4, and GPx5 [4]. These proteins protect sperm from oxidative damage throughout their development.
GPx4 is exceptionally important for male reproductive health. It protects developing sperm from DNA damage caused by oxidative stress [3]. Later, it becomes part of the mitochondrial sheath around the flagellum, which helps sperm move properly [3]. Research shows that sperm structure and movement are directly related to GPx4 levels [3].
Selenoprotein P (SELENOP) also helps with male reproduction by moving selenium to vesicle-like structures in Sertoli cells [3]. Male mice without SELENOP show reduced fertility, lower selenium levels, and decreased GPx activity [3]. This makes selenium testosterone interactions especially relevant for older men interested in selenium antioxidant elderly benefits.
Selenoproteins and their role in testosterone and fertility
Selenoproteins work as molecular machines that help selenium improve male reproductive health. These specialised proteins contain selenium as selenocysteine and play vital roles in fertility and testosterone production. Men need these proteins to work properly as they age to keep their reproductive ability.
GPX4: antioxidant and structural role in sperm
GPX4 (also called PHGPx) is the main selenoenzyme in the testes and you need it to make sperm [5]. This amazing protein serves two key functions for male fertility. The protein first protects developing sperm from oxidative stress damage to DNA as an antioxidant enzyme [2]. Later, it becomes a structural part and makes up over 50% of the mitochondrial capsule in mature sperm's midpiece [2].
The GPX4 gene creates three different isoforms found in different cell locations:
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Mitochondrial GPX4 (mGPX4)
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Cytosolic GPX4 (cGPX4)
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Nuclear GPX4 (snGPX4)
The mitochondrial variant plays a vital role in male fertility. Research shows that removing mGPX4 lets embryos develop normally but makes males infertile, with poor sperm quality and serious structural problems in the sperm midpiece [6]. Clinical studies also reveal that approximately 10% of infertile men have much lower GPX4 in their sperm compared to healthy men [5].
GPX4's role goes beyond just structure—it guards against ferroptosis, which is iron-dependent cell death with high lipid peroxidation [7]. You need enough selenium to keep GPX4 working properly and maintain the right selenium testosterone balance.
SELENOP: selenium transport and testicular function
SELENOP serves as the main protein that moves selenium through the body and helps testicular selenium metabolism. This versatile protein reduces phospholipid hydroperoxides while delivering selenium from the liver to other tissues like the brain and testes [8]. SELENOP appears in vesicle-like structures in Sertoli cells' basal region and Leydig cells in the male reproductive system [2].
Studies of mice without SELENOP show how important this protein is. Male mice lacking SELENOP have reduced fertility, less selenium, and lower glutathione peroxidase activity [2]. Even diets high in selenium can't restore normal testis selenium or sperm in these mice, which proves SELENOP's essential role in testicular function [2].
X-ray fluorescence microscope studies show that removing SELENOP leads to a 77% drop in testicular tissue selenium [2]. This big loss explains why selenium benefits men during their reproductive years and why proper selenium dosage men need becomes more important with age.
Other selenoproteins involved in male reproduction
GPX1 and GPX3 join GPX4 and SELENOP in supporting male reproductive health. These prominent selenoproteins protect the epididymal parenchyma and maturing sperm from oxidative damage in the epididymal epithelia and sperm [2]. These proteins help maintain selenium prostate health and support reproduction as part of the complete antioxidant defence system.
Scientists have found about ten other selenoprotein transcripts in male gonads, though they appear at levels about ten times lower than GPX4 [1]. These include:
Thioredoxin/Glutathione Reductase (TGR), selenoprotein V, selenoprotein W, selenoprotein K, selenoproteins 15 and selenoprotein S [1]. We don't fully understand what many of these proteins do, but their presence shows how complex selenium's role is in male reproduction.
Research into the selenium thyroid testosterone link shows that selenium supplements can boost mRNA expression of certain selenoproteins in prostate cells, especially glutathione peroxidases GPX1, GPX2 and GPX3 [1]. This becomes especially important for selenium antioxidant elderly health since oxidative stress increases with age and affects testosterone production and reproductive ability.
Selenium’s influence on testosterone production
Selenium does more than act as an antioxidant - it plays a direct role in testosterone production through multiple mechanisms. The way this mineral affects male hormone synthesis explains why men need proper selenium levels as they age.
Selenium and Leydig cell function
The body's main testosterone factories are Leydig cells, which reside in the testes. These cells get vital support from selenium in multiple ways. The mineral shields them from oxidative damage that builds up with age. It also boosts steroidogenic enzymes inside Leydig cells to produce more testosterone.
Research shows how Leydig cells stop working properly in animals that lack selenium. Their testosterone drops and sperm production suffers. In fact, studies prove that low selenium cuts testosterone production by 15-35%, with older animals showing worse effects. The good news is that taking the right amount of selenium helps restore testosterone in people who need it.
Men dealing with andropause or age-related testosterone decline can benefit from selenium supplements. The mineral works well with other nutrients like vitamin D to boost hormone production.
Impact on steroidogenesis pathways
Selenium boosts testosterone creation by affecting several steroidogenesis pathways:
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Cholesterol transport enhancement - It raises steroidogenic acute regulatory protein (StAR) levels to move cholesterol into mitochondria—the first key step in making testosterone.
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Enzyme activity regulation - The mineral helps key enzymes work better in the testosterone production chain, including 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β-HSD).
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Protection from oxidative inactivation - Selenium-based enzymes shield steroidogenic enzymes from oxidative damage to keep them working well.
The mineral's antioxidant properties protect testes from oxidative stress—a big reason why testosterone drops with age. This protection helps older men the most since oxidative damage builds up over time and hurts hormone production.
Men at risk of prostate issues get double benefits from selenium. It supports both prostate health and testosterone levels. This makes getting the right selenium dose more crucial as men age.
Selenium thyroid testosterone connection
The sort of thing I love about selenium's hormone effects is how it links to thyroid function and testosterone. Selenium forms an essential part of iodothyronine deiodinases—enzymes that convert thyroid hormones. This means selenium levels directly affect how well the thyroid works.
This matters because thyroid hormones control testosterone production in several ways:
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They trigger gonadotropin-releasing hormone (GnRH) release
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They make Leydig cells more sensitive to luteinizing hormone (LH)
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They boost the activity of testosterone-making enzymes
Studies show that low thyroid function often leads to less testosterone. High thyroid levels can boost testosterone at first but damage the testes over time. This means you need a well-working thyroid—supported by enough selenium—to maintain healthy testosterone levels.
Selenium also helps bone density maintenance through its effects on testosterone and bone metabolism. This gives ageing men more health benefits.
Older men need this selenium-thyroid-testosterone connection even more. Both thyroid function and testosterone naturally drop with age. Add increased oxidative stress in seniors, and you can see why selenium's antioxidant properties help maintain reproductive health throughout ageing.
Selenium and spermatogenesis: protecting sperm health
The reproductive process of sperm faces many challenges. Oxidative stress is one of the biggest threats to male fertility. Selenium's protective role goes way beyond simple nutrition. It provides vital protection during spermatogenesis and maturation.
Oxidative stress and sperm DNA damage
Scientists have made important findings in male fertility research. They found that oxidative sperm DNA damage plays a vital role in poor semen quality and male infertility [9]. Sperm cells can easily get damaged by oxidation because their membranes have high levels of polyunsaturated fatty acids [10]. These cells become more vulnerable as they mature and lose much of their cytoplasm that contains important antioxidant enzymes.
Reactive oxygen species (ROS) attack sperm in multiple ways:
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They reduce sperm viability through membrane damage [9]
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They cause DNA fragmentation [4]
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They make oocyte-sperm fusion less effective [9]
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They trigger lipid peroxidation in sperm cellular membranes [9]
Selenium helps curb these threats by becoming part of selenoproteins that neutralise free radicals. Research shows that selenium can protect human sperm cells from oxidative DNA damage [9]. This protection becomes more important for men going through andropause, when natural antioxidant defences usually decline.
Selenium's role in sperm motility and morphology
Selenium has major effects on sperm characteristics that directly affect fertility. It helps sperm mature throughout development [11]. An important research study showed that selenium supplements improved sperm concentration, progressive motility, and normal morphology in patients with autoimmune thyroiditis, even though these men had normal thyroid function [4].
Selenium affects sperm motility through two key mechanisms:
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Structural support: Selenium helps form phospholipid-hyperoxide GSH-Px, which becomes a structural protein. This protein makes up over 50% of the mitochondrial capsule in the sperm mid-piece [9]. The structural component stabilises the mid-piece, which helps proper motility.
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Mitochondrial function protection: Selenium helps maintain mitochondrial membrane potential, which will give adequate energy for sperm movement [12]. Lab studies show that selenium supplements improve sperm viability and mitochondrial membrane potential while reducing malondialdehyde (MDA) levels—a marker of lipid peroxidation [12].
Selenium improves morphology by protecting developing sperm from oxidative damage [10]. Studies show that low selenium leads to abnormal sperm morphology, especially in the head and midpiece regions [13]. This connection between selenium and sperm quality shows why it's important to maintain proper selenium testosterone balance, similar to how vitamin D and testosterone work together.
Selenium antioxidant elderly: age-related fertility support
Men's fertility slowly declines with age due to increasing oxidative stress and damage to reproductive tissues. Selenium's antioxidant properties are especially valuable here. Older men usually have higher oxidative stress levels, so selenium supplements might help them more.
Elderly men who want to maintain their reproductive capacity can benefit from selenium in several ways:
Selenium helps protect testicular function from age-related decline. The testes can easily get oxidative damage because antioxidant enzyme activity naturally drops with age. Selenium helps by supporting glutathione peroxidase activity.
Selenium works better when combined with vitamin E to improve sperm motility [13]. This partnership becomes more important as we age because both nutrients become less available. Like the link between andropause and prostate health, selenium affects many aspects of male ageing.
Selenium's benefits for sperm health work alongside its support for bone density. The right selenium dose for men—usually 55 μg daily with an upper limit of 400 μg—helps maintain reproductive health while avoiding potential toxicity that could increase oxidative stress.
Selenium supplementation: dosage, forms, and safety
Getting selenium supplementation right means knowing both the best dosage and form. This mineral walks a fine line between being an essential nutrient and a potential toxin. The right amount can substantially affect testosterone levels and reproductive health.
Recommended selenium dosage for men
Different countries have their own guidelines for daily selenium intake. The UK sets its Reference Nutrient Intake (RNI) at 75 μg/day [14], while the US recommends a slightly lower amount at 55 μg/day [3]. These numbers vary because selenium levels in soil and eating patterns differ by region.
Americans generally get enough selenium - about 108 μg daily from food and drinks [15]. But some groups still risk deficiency. This includes people on kidney dialysis, those with HIV, and anyone eating mostly plants grown in selenium-poor soil [3].
Men who want to maintain their testosterone should stick to the recommended range rather than taking more. Men tend to get more selenium (132 μg from foods) than women (94 μg) [15], and this might explain the connection between selenium and testosterone.
Selenomethionine vs selenite: which is better?
You'll find selenium supplements in several forms: selenomethionine, selenium-enriched yeast, sodium selenite, and sodium selenate [15]. Research shows selenomethionine is the best option benefits for several reasons.
Your body absorbs selenomethionine twice as well as selenite [16]. While both forms have a 90% absorption rate [15], selenomethionine blends better with body tissues. Studies on animals show that selenomethionine keeps blood selenium levels higher when intake drops [17].
Selenomethionine matches the selenium found in natural foods [18]. It causes less oxidative stress than selenite, making it a great choice especially when you have selenium antioxidant elderly needs.
Toxicity concerns and U-shaped response
Selenium works like a U-shaped curve - too little or too much can harm your health [19]. The US caps safe intake at 400 μg daily [3], while European guidelines suggest a lower limit of 255-300 μg daily [20].
Taking too much selenium leads to selenosis with symptoms like:
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Hair and nail loss
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Garlic breath and metallic taste
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Nausea and digestive disturbances
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Skin rashes and fatigue
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Nervous system problems [5]
Research shows cancer risk follows this U-shaped pattern too. Low intake (27.8–77.2 μg/day) and high intake (169.1–331.7 μg/day) both link to higher cancer risk [21].
Selenium from Brazil nuts and other sources
Brazil nuts pack more selenium than any other food - one nut contains 68-91 μg [6]. Eating 1-3 Brazil nuts daily is enough to meet your selenium needs [6]. More than that could push you over safe levels since selenium content varies based on where the nuts grow.
Men looking to optimise their selenium testosterone through diet might want to mix up their selenium sources. This balanced approach supports both selenium prostate health and testosterone bone density.
Geographic and dietary factors affecting selenium status
The selenium in our food depends heavily on soil composition. This creates major differences in selenium levels across the world. These geographical variations affect testosterone production and reproductive health directly.
UK soil selenium deficiency and its implications
Selenium levels in UK soils have dropped steadily over 30 years [22]. A survey by Rothamsted Research in 2000 showed that UK soils lack adequate selenium. The grass from these soils cannot provide enough selenium to grazing animals [8]. Tests revealed that 74% of forage samples fell below the critical level of 0.1 mg/kg DM [8]. The country's selenium levels show regional differences - southern England has higher levels than northern regions [22]. This shortage mainly results from the UK's reduced imports of selenium-rich North American wheat after joining the European Economic Community in 1973 [23].
Global variations in selenium intake
Worldwide selenium intake shows extreme variations, ranging from 3 μg/day to 7000 μg/day in certain selenium-rich areas [23]. Finland now maintains moderate selenium levels (60-80 μg/day) through selenium-enriched fertilisers [24]. Some Chinese regions report dangerous lows below 11 μg/day [24], while others show toxic levels at 4990 μg/day [23]. America's selenium distribution follows geological patterns. Wyoming, North Dakota, and Washington state show the highest levels, while North Carolina and Kentucky have some of the lowest [25].
Who is at risk of selenium deficiency?
People most likely to have selenium deficiency include:
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Residents of selenium-poor regions who eat mostly plant-based foods [2]
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HIV patients with absorption issues [2]
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Patients with kidney failure on dialysis [2]
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Older adults, especially those in care homes [22]
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People recovering from trauma and burns [22]
Scientists estimate that nearly one billion people worldwide don't get enough selenium [26]. This problem could worsen as climate change reduces soil selenium levels gradually [26].
Conclusion
Selenium plays a crucial role in male reproductive health. It helps produce testosterone and improves sperm quality. This mineral works through selenoproteins that shield reproductive tissues from oxidative damage and help create hormones. Men who lack selenium often show lower testosterone levels and poor sperm quality. This shows the strong link between selenium and testosterone production.
Selenium also affects male fertility by becoming part of GPX4. This protein acts as both an antioxidant and a structural component in developing sperm. These dual roles explain why healthy selenium levels help improve sperm movement, shape, and survival. Men who face fertility challenges should check their selenium levels, especially when they live in selenium-poor soils across the UK and Europe.
The connection between selenium, thyroid, and testosterone needs attention as men age. Thyroid function relies heavily on selenium-containing enzymes that affect testosterone production in many ways. Good selenium levels support both thyroid health and testosterone production. This offers complete support during andropause.
Older men get more benefits from selenium's antioxidant properties as their bodies face more oxidative stress with age. These protective benefits go beyond reproductive health to support prostate health and bone density maintenance. This creates an all-encompassing approach for ageing males.
The right dosage and form of selenium supplements need careful thought. Most men need 55-75 μg each day. Selenomethionine works better in the body than selenite. Brazil nuts offer a natural source of selenium, though their content varies. One to three nuts daily are enough.
Soil content determines how much selenium appears in food across different regions. Men living in areas known for low selenium face higher risks of deficiency. They might need to adjust their diet or take supplements.
Good selenium balance is vital yet often overlooked in male reproductive health. Both too little and too much can cause problems. Selenium follows a U-shaped response curve where extremes harm health. Men who care about their reproductive health should ensure they get adequate selenium without excess. This approach helps maintain hormone and reproductive health throughout life.
Key Takeaways
Selenium plays a crucial role in male reproductive health through its antioxidant properties and support for testosterone production. Here are the essential insights every man should know:
• Selenium deficiency significantly impacts fertility: Men with low selenium levels experience reduced testosterone production and poor sperm quality, with studies showing 52.6% improvement in sperm parameters following supplementation.
• Geographic location affects selenium status: UK soils are selenium-deficient, meaning men consuming primarily local produce may require dietary adjustments or supplementation to maintain optimal levels.
• Optimal dosage follows a narrow window: Men need 55-75 μg daily—both deficiency and excess (over 400 μg) can harm reproductive health due to selenium's U-shaped response curve.
• Selenoproteins protect sperm throughout development: GPX4 serves dual roles as antioxidant and structural component, comprising over 50% of sperm mitochondrial capsule whilst protecting against DNA damage.
• Brazil nuts provide concentrated natural selenium: Just 1-3 Brazil nuts daily typically meet selenium requirements, though variable content necessitates moderation to avoid toxicity.
The selenium-thyroid-testosterone connection becomes particularly important for ageing men, as this mineral supports hormone production whilst combating age-related oxidative stress. Maintaining proper selenium balance represents a vital yet often overlooked aspect of comprehensive male reproductive health throughout the lifespan.
FAQs
Q1. How does selenium impact male fertility? Selenium plays a crucial role in male fertility by supporting sperm development, protecting against oxidative damage, and aiding testosterone production. It's essential for the formation and maturation of sperm cells, and adequate selenium levels have been linked to improved sperm quality parameters like motility and morphology.
Q2. Can selenium supplementation increase testosterone levels in men? Yes, selenium supplementation may help increase testosterone levels in men, especially when combined with other antioxidants. Selenium supports the function of enzymes involved in testosterone synthesis and protects Leydig cells (the primary testosterone producers) from oxidative damage.
Q3. What is the recommended daily intake of selenium for men? The recommended daily intake of selenium for adult men varies slightly by country. In the UK, the Reference Nutrient Intake (RNI) is 75 μg/day, while in the US, the Recommended Dietary Allowance (RDA) is 55 μg/day. It's important not to exceed 400 μg daily to avoid potential toxicity.
Q4. Are there any natural food sources rich in selenium? Brazil nuts are nature's richest source of selenium, with a single nut containing 68-91 μg. However, due to their high selenium content, it's recommended to limit intake to 1-3 Brazil nuts per day. Other good sources include seafood, poultry, and whole grains, though selenium content can vary based on soil conditions where the food was grown.
Q5. How does selenium benefit older men's reproductive health? For older men, selenium offers multiple benefits to reproductive health. It helps combat age-related oxidative stress, supports thyroid function (which indirectly affects testosterone production), and aids in maintaining prostate health. Selenium's antioxidant properties become particularly valuable as natural antioxidant defences decline with age, potentially helping to preserve fertility and hormonal balance.
References
[1] - https://www.nature.com/articles/s41598-022-08121-3
[2] - https://nutritionsource.hsph.harvard.edu/selenium/
[3] - https://ods.od.nih.gov/factsheets/Selenium-Consumer/
[4] - https://pubmed.ncbi.nlm.nih.gov/34442049/
[5] - https://www.hollandandbarrett.com/the-health-hub/food-drink/nutrition/spotlight-on-selenium-2/
[6] - https://hodmedods.co.uk/blogs/news/selenium-in-brazil-nuts-good-but-highly-variable?srsltid=AfmBOorTxHqMaCDIdOxS46XnFoj9SDI5Z4koORWsGZ4J6DacQWpcwT2w
[7] - https://www.mdpi.com/1420-3049/30/3/437
[8] - https://www.fwi.co.uk/livestock/grassland-management/uk-soils-are-deficient-in-selenium
[9] - https://pmc.ncbi.nlm.nih.gov/articles/PMC3048346/
[10] - https://proceive.com/blogs/hcp-blog/the-role-of-selenium-in-male-fertility-an-hcp-perspective?srsltid=AfmBOorQ_N5kHGEoqJYyBNmwapqc_v76keGeOcmI_AOw8C5op-mLNezV
[11] - https://fullwellfertility.com/blogs/knowledgewell/7-antioxidants-to-know-your-guide-to-boosting-fertility-preconception?srsltid=AfmBOookqcROObuxYHHNSkO67zZ8NzoN-ZDDU6W9meHJy6AlQjokhABa
[12] - https://onlinelibrary.wiley.com/doi/10.1111/and.12869
[13] - https://pmc.ncbi.nlm.nih.gov/articles/PMC3921845/
[14] - https://www.nutrition.org.uk/media/qu0hypl2/selenium-and-health-summary.pdf
[15] - https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/
[16] - https://www.supplysidesj.com/vitamins/selenomethionine-more-bioavailable-than-selenite
[17] - https://pmc.ncbi.nlm.nih.gov/articles/PMC8189389/
[18] - https://wearefeel.com/blogs/learn/best-form-of-selenium-selenite-vs-selenomethionine?srsltid=AfmBOoqtwp2OIgp7m9wITITVO5w-BuJAqClaZ0T8KuCPXHoJsVOIWwoU
[19] - https://pmc.ncbi.nlm.nih.gov/articles/PMC7033057/
[20] - https://www.efsa.europa.eu/en/efsajournal/pub/6134
[21] - https://www.nature.com/articles/s41598-024-66553-5
[22] - https://patient.info/doctor/nutrition/selenium
[23] - https://journals.sagepub.com/doi/10.1089/ars.2010.3275?int.sj-full-text.similar-articles.7
[24] - https://assets.publishing.service.gov.uk/media/5a7ea6b440f0b62305b824ce/SACN_Selenium_and_Health_2013.pdf
[25] - https://pmc.ncbi.nlm.nih.gov/articles/PMC3180687/
[26] - https://www.healthline.com/health/selenium-deficiency
