Selenium: Trace Mineral for Antioxidant Enzymes

The Tiny Mineral Doing Heavy Lifting Inside Your Cells

Ask most people to name a mineral their body needs and you’ll hear calcium, iron, maybe magnesium if they’ve been paying attention to supplement ads. Selenium rarely makes the list, and honestly, that’s a little unfair. This is a mineral that shows up in vanishingly small amounts in the body, we’re talking micrograms, not milligrams, and yet it’s woven into some of the most important defense systems your cells have.

I’ve spent a long time looking at trace minerals, and selenium keeps surprising me. Unlike a lot of nutrients that just get incorporated into structures or float around doing generic support work, selenium gets written directly into the genetic code of specific proteins. It’s not decoration. It’s a functional, non-negotiable component of enzymes your body cannot build without it. That’s a different kind of relationship than, say, potassium has with your nerves.

Here’s the part that tends to get people’s attention: selenium is the raw material for an amino acid called selenocysteine, which your body slots into at least 25 different selenoproteins. Several of these are antioxidant enzymes, glutathione peroxidases and thioredoxin reductases among them, and they spend their entire existence neutralizing the kind of oxidative damage that, left unchecked, chips away at cells over time. Selenium also plays a starring role in thyroid hormone metabolism, which is a connection almost nobody makes until they’ve had a weird thyroid panel and started digging.

What makes selenium particularly interesting from a nutrition standpoint is how geography-dependent it is. Unlike vitamin C or calcium, which you can find reliably across food categories no matter where you live, selenium content in plant foods swings wildly depending on how much selenium was in the soil where that plant grew. Some regions of the world, parts of China and areas of Central Africa in particular, have soil so low in selenium that entire populations historically developed deficiency-related diseases. Meanwhile, someone eating a handful of Brazil nuts in a selenium-rich region could blow past their daily needs in one sitting without realizing it.

That contrast, deficiency in one corner of the globe and potential overconsumption in another, is part of what makes selenium worth understanding properly rather than just tossing back a supplement because a label mentioned antioxidants. Minerals in general get treated as interchangeable in the wellness world, lumped together under vague promises of “immune support” or “cellular health.” Selenium deserves more precision than that. It has a defined biochemical job, clear food sources, a narrow window between adequate and excessive intake, and a body of research that’s more nuanced than most supplement marketing lets on.

I also want to be upfront that selenium research has had its share of reversals. Early studies looked promising for cancer prevention, and then larger, better-designed trials walked a lot of that back. That’s not a knock against the mineral, it’s actually a pretty good illustration of how nutrition science evolves, and I think it’s worth walking through honestly rather than cherry-picking the flattering older studies, which a lot of health content still does.

So here’s where we’re headed. We’ll get into what selenium actually does for your health, where you can realistically get enough of it from food, how much you need at different life stages, what deficiency looks like when it happens, and where the line sits between “beneficial” and “you’ve now made yourself sick.” Selenium is a classic Goldilocks nutrient, and I think once you see the range involved, you’ll understand why I get a little twitchy when people mega-dose minerals without knowing their numbers first.

There’s also a cultural piece to this that doesn’t get discussed enough. Selenium status varies not just by country but by whether someone follows a vegetarian or vegan eating pattern, whether they smoke, whether they’re on dialysis, even by which region of the United States they live in. It’s one of those minerals where “eat a balanced diet” is genuinely good advice for most people, but it’s not universal advice, and I’d rather walk you through the nuance than hand you an oversimplified rule that doesn’t apply to your situation.

One more thing before we get into the substance of it. Selenium sits at an interesting intersection of old-school deficiency disease, the kind you’d read about in a mid-century medical journal, and modern trace-mineral science built on genome sequencing and selenoprotein identification. Few nutrients let you see both eras of nutrition science stacked on top of each other quite so clearly. That’s part of why I find it genuinely interesting to write about, rather than just another entry on a supplement facts label.

Key Health Benefits

Let’s talk about what selenium is actually doing in there, because “antioxidant” gets thrown around so loosely these days that it’s practically lost meaning. Selenium’s antioxidant role isn’t abstract. It’s built into specific enzymes with specific jobs, and understanding that structure helps explain why selenium keeps showing up in research on thyroid function, immune defense, fertility, and chronic disease risk.

The Antioxidant Enzyme Connection

The headline function of selenium is its role in glutathione peroxidases, a family of enzymes that neutralize hydrogen peroxide and other reactive molecules before they can damage lipids, proteins, and DNA. Selenium is also required for thioredoxin reductases, another enzyme family involved in maintaining the cell’s internal redox balance, essentially keeping the ratio of oxidizing and reducing molecules in a livable range. Without adequate selenium, these enzymes simply cannot be built correctly, and the antioxidant defense system that depends on them gets weaker.

I think the reason this matters practically, beyond the biochemistry, is that oxidative stress isn’t some fringe concern. It’s implicated in aging processes, cardiovascular changes, and a long list of chronic conditions. Selenium isn’t a magic shield against any of that, but it is a structural requirement for one of the body’s core defense mechanisms, and that’s worth taking seriously.

Thyroid Function

If there’s one organ where selenium’s importance is impossible to ignore, it’s the thyroid. Selenium concentration in thyroid tissue is higher than in any other organ in the body, and selenoproteins there do two jobs simultaneously: they help convert the storage form of thyroid hormone, T4, into its active form, T3, and they protect thyroid tissue from the hydrogen peroxide that gets generated as a natural byproduct of hormone synthesis. That second point is almost ironic. The thyroid needs hydrogen peroxide to make hormones, but too much of it damages the gland, so selenium is essentially there as cleanup crew for a mess the thyroid itself creates.

Research on selenium and chronic autoimmune thyroiditis, often called Hashimoto’s thyroiditis, has found that selenium supplementation can meaningfully lower levels of thyroid antibodies in people undergoing treatment, though its effect on overall thyroid function and quality of life has been more inconsistent across trials. A systematic review and meta-analysis of trials in people with chronic autoimmune thyroiditis treated with levothyroxine found that selenium supplementation lowered thyroid peroxidase antibody levels, with selenomethionine outperforming sodium selenite, likely due to better absorption. That’s a fairly specific, well-supported finding, not a sweeping claim, and I appreciate that the nuance holds up under scrutiny.

Immune Function and Infection Response

Selenium’s antioxidant enzymes also support immune cell function, partly by protecting immune cells themselves from the oxidative stress they generate while fighting off pathogens. This is part of why selenium status keeps coming up in research on infections, including HIV, where deficiency has been associated with worse outcomes in observational studies, even though supplementation trials haven’t consistently shown it reverses those outcomes once someone is already infected.

Fertility, Particularly Male Fertility

One selenoprotein, phospholipid hydroperoxide glutathione peroxidase, is a structural component of mature sperm cells, not just a background antioxidant but literally part of the sperm’s physical architecture. Some clinical trials have found that selenium supplementation improves sperm motility in men with low baseline selenium status, while other trials in men who already had adequate selenium found no additional benefit. That pattern, benefit mainly in people who were deficient to begin with, comes up again and again in selenium research, and it’s an important detail that a lot of supplement marketing conveniently skips.

Where the Evidence Gets Weaker

I’d be doing you a disservice if I only listed the flattering findings. Selenium’s relationship with cancer prevention looked genuinely promising in early observational studies and one notable early trial, but larger, more rigorous randomized trials, including a massive study involving more than 35,000 men, failed to confirm a protective effect against prostate cancer, and one analysis even flagged a possible increased risk of aggressive prostate cancer in men who already had high selenium status and kept supplementing anyway. Cardiovascular disease research tells a similar story. Selenium alone hasn’t held up as a way to reduce heart disease risk in people who already get enough from food, though there’s some intriguing signal that selenium combined with other antioxidants in a formula might reduce cardiovascular mortality, a finding that needs more investigation before anyone builds a health strategy around it.

I bring this up not to undercut selenium’s value, but because I think a decade-plus of reading nutrition research has taught me that the nutrients worth respecting are the ones with real, sometimes unglamorous evidence, not the ones with the flashiest early headlines. Selenium’s antioxidant enzyme role and its thyroid function are rock solid. Its role in preventing cancer or heart disease through supplementation is, at best, unproven, and at worst, actively risky at high doses, which we’ll get into later.

Dietary Sources

Here’s where selenium gets genuinely interesting from a practical standpoint, because unlike most minerals, its concentration in food is less about the food category and more about geography. A carrot grown in selenium-rich soil in one state could have measurably more selenium than the same variety grown a thousand miles away.

Animal-Based Sources Are the Most Reliable

Because selenium in food is bound to protein, high-protein foods tend to be the richest and most consistent sources. Seafood, meat, poultry, and organ meats top the list, and unlike plant foods, animal products maintain fairly predictable selenium levels regardless of regional soil variation. That’s because animals regulate their own tissue selenium concentrations through homeostatic mechanisms, and livestock feed is typically formulated with consistent selenium content. So if you’re eating a reasonably varied diet that includes some animal protein, you’re probably not thinking much about selenium, and that’s by design, not luck.

Brazil Nuts Deserve Their Own Paragraph

I can’t talk about selenium sources without singling out Brazil nuts, because the numbers are almost comical. A single ounce, roughly six to eight nuts, can contain several hundred micrograms of selenium, several times the daily recommended amount for an adult. Some individual nuts alone can pack close to 100 micrograms. This isn’t a “eat more of this superfood” situation, it’s closer to a “know exactly how many you’re eating” situation, because a habit of snacking on a handful of Brazil nuts daily can push you toward excessive intake territory faster than almost any other food.

Seafood and Fish

Tuna, sardines, shrimp, and other seafood provide substantial selenium, often in the range of 40 to over 90 micrograms per serving depending on the type. If you eat fish regularly, there’s a good chance you’re already meeting a meaningful chunk of your selenium needs without ever thinking about it.

Meat, Poultry, and Eggs

Pork, beef, turkey, chicken, and eggs all contribute moderate but reliable amounts of selenium, generally somewhere between 15 and 40 micrograms per typical serving. Organ meats, like beef liver, add a bit more. None of these are selenium powerhouses on their own, but they add up across a day of eating in a way that’s easy to underestimate.

Grains and Plant Foods

Here’s where things get regionally messy. Whole wheat bread, oats, brown rice, and legumes can all contribute selenium, but the amount depends heavily on where the grain was grown. Spaghetti made from wheat grown in selenium-rich soil, for instance, can provide a surprisingly solid dose, while produce grown in low-selenium regions may barely register. This regional inconsistency is precisely why populations that eat mostly locally grown plant foods in low-selenium areas, certain parts of China being the most studied example, historically ran into deficiency-related disease, while people eating food sourced from a wide geographic area, as is common in North America thanks to extensive food distribution networks, tend to average out just fine.

Dairy

Milk, yogurt, and cottage cheese offer smaller but steady amounts of selenium, generally in the single digits to low teens of micrograms per serving. Not a primary source, but a contributor in a well-rounded diet.

Practical Takeaways for Getting Selenium From Food

• If you eat seafood a couple of times a week, you’re likely covering a large share of your needs without supplementing.
• One or two Brazil nuts, not a whole handful, is plenty if you’re using them as a selenium source; treat the rest of the bag with some caution.
• Vegans and strict vegetarians should pay closer attention to selenium intake, since plant sources are the most variable and animal products are typically the most consistent contributors.
• If you’re curious about your own status, a conversation with a healthcare provider about testing is more useful than guessing based on diet alone, particularly if you fall into a higher-risk group like people undergoing dialysis or those with limited dietary variety.

Supplements, Briefly

Selenium shows up in multivitamins, in combination antioxidant formulas paired with vitamin E, and as standalone supplements. Multivitamins commonly include around 55 micrograms, while standalone selenium supplements can run anywhere from 100 to 400 micrograms, a range that starts brushing up against the upper intake limit for adults fairly quickly. The forms most commonly used, selenomethionine, selenium-enriched yeast, sodium selenite, and sodium selenate, are all reasonably well absorbed, with the body taking up close to 90 percent of selenium from these forms. I’ll go deeper into dosing specifics in the next section, but the short version is: most people eating a varied diet don’t need a standalone selenium supplement, and if you’re considering one, it’s worth knowing your baseline status first rather than assuming more is automatically better.

Dosage & Deficiency

This is the section where I think a lot of people’s assumptions about minerals get challenged, because selenium operates within a genuinely narrow range between “not enough” and “too much.” It’s not a nutrient where you can shrug and say more is probably fine.

How Much Do You Actually Need

For most adults, the recommended dietary allowance sits at 55 micrograms per day, a number that climbs slightly during pregnancy to around 60 micrograms and further during lactation to about 70 micrograms, reflecting the added demand of supporting a developing infant. Children and adolescents need considerably less, with recommendations scaling up gradually from 15 micrograms in early infancy to 40 micrograms by early adolescence, before reaching the adult level around age 14. These aren’t arbitrary numbers, they’re based on the intake levels needed to maintain the enzyme systems selenium supports, particularly the antioxidant selenoproteins we’ve already talked about.

What surprises people most, in my experience, is how little food it actually takes to hit these numbers. A few servings of seafood or meat across a day, or one modest serving of Brazil nuts, can meet or exceed daily needs without any deliberate effort. This is part of why selenium deficiency is genuinely rare in places like the United States and Canada, even in regions where local soil selenium is lower than average, because food distribution networks mix selenium sources from all over the country onto the same grocery shelves.

What Deficiency Actually Looks Like

Selenium deficiency on its own rarely causes obvious illness in an otherwise healthy person. It’s more of a slow biochemical shift that leaves someone more vulnerable to other stressors. That said, there are two specific, well-documented deficiency diseases worth knowing about, both first identified in regions of China with extremely low soil selenium.

Keshan disease is a form of heart muscle disease that mainly affects women of childbearing age and young children in low-selenium regions where dietary intake drops to around 10 micrograms per day or less. Research has shown that even modest selenium supplementation, providing at least 20 micrograms daily, offers meaningful protection, and a large meta-analysis found selenium supplementation reduced Keshan disease risk dramatically in populations where it was studied.

Kashin-Beck disease is a joint condition, a form of osteoarthritis that tends to appear during childhood and adolescence in certain low-selenium, low-iodine regions spanning parts of China, Tibet, Siberia, and North Korea. It’s less about selenium deficiency alone and more about the combination of low selenium and low iodine acting together.

Speaking of iodine, this is a connection I think deserves more attention than it usually gets. Selenium deficiency can worsen the effects of iodine deficiency, because certain selenoproteins are involved in thyroid hormone processing. In regions with severe combined deficiency, this contributes to a serious condition affecting thyroid hormone production in infants and young children. It’s a good reminder that minerals rarely work in isolation, and looking at selenium status without considering iodine status tells an incomplete story.

Who’s Actually at Risk

A handful of groups face a meaningfully higher risk of inadequate selenium, even in places where deficiency is generally uncommon.

• People living in regions with genuinely low soil selenium and limited access to food from other regions, most notably certain rural parts of China.
• Vegans and vegetarians, whose plant-heavy diets are more exposed to the regional variability in plant selenium content, and who miss out on the more consistent selenium contribution from animal products.
• People undergoing long-term hemodialysis, since the dialysis process itself removes selenium from the blood, compounded by appetite changes that often accompany kidney disease.
• People living with HIV, where selenium deficiency appears more common, possibly related to malabsorption, and has been associated in observational research with worse outcomes, though supplementation hasn’t reliably reversed those associations in trials.
• People who smoke, who tend to show lower selenium status than nonsmokers, likely connected to the added oxidative stress smoking places on the body.

If you fall into one of these categories, I’d say it’s worth an actual conversation with a healthcare provider about testing rather than self-supplementing based on a general recommendation, mainly because the therapeutic window for selenium is narrow enough that guessing isn’t a great strategy.

A Quick Word on Testing

Selenium status is typically assessed through blood plasma or serum concentration, with levels used as a marker of whether someone has enough selenium for their antioxidant enzyme systems to function properly. Long-term status can also be estimated through hair or nail selenium content, which reflects intake trends over months rather than days. None of this is something you need to track obsessively if you’re eating a varied diet, but it’s useful context if you’re already dealing with a condition that puts you at higher risk.

Toxicity & Risks

I mentioned earlier that selenium sits in a narrow range, and this is the section where that becomes concrete. Selenium toxicity, called selenosis, is a real and documented condition, and it happens at doses that aren’t actually that hard to reach if someone is stacking a supplement on top of a selenium-rich diet or overdoing foods like Brazil nuts.

The Upper Limit

For adults, the tolerable upper intake level is set at 400 micrograms per day, more than seven times the recommended daily allowance. That gap sounds like a comfortable margin until you realize how concentrated selenium is in certain foods. A serving of Brazil nuts alone can approach or exceed that upper limit, and stacking a standalone selenium supplement, which can contain 100 to 400 micrograms on its own, onto an already selenium-rich diet is a genuinely easy way to cross that threshold without noticing. Interestingly, a separate scientific opinion published by European food safety regulators set a more conservative upper limit of around 255 micrograms per day for adults, which suggests there’s still some active debate about exactly where that ceiling should sit, and I’d lean toward the more cautious interpretation if you’re the type who likes a wide safety margin.

What Selenosis Looks Like

Chronic selenosis has a fairly recognizable symptom pattern, and it tends to show up before things get dangerous, provided someone is paying attention. Early indicators include a garlic-like odor on the breath and a persistent metallic taste in the mouth, oddly specific symptoms that come up again and again in the literature. The hallmark signs are hair loss and brittle or splitting nails, sometimes progressing to actual nail loss. Beyond that, people can experience skin rashes, nausea, diarrhea, fatigue, irritability, and in more severe or prolonged cases, nervous system abnormalities.

Acute Toxicity Is a Different, More Dangerous Animal

Chronic selenosis from overdoing supplements or Brazil nuts is uncomfortable but generally reversible once intake is reduced. Acute selenium toxicity, from ingesting a large dose all at once, is a much more serious event. There’s a documented case where over 200 people experienced severe adverse reactions after taking a liquid supplement that was manufactured with 200 times its labeled selenium content, a genuinely alarming manufacturing failure. Acute toxicity at that scale can cause severe gastrointestinal and neurological symptoms, respiratory distress, cardiac complications, muscle tenderness, tremors, and in rare instances, death. This is an extreme scenario tied to a product defect rather than typical dietary behavior, but it’s a useful illustration of why selenium isn’t a mineral to treat casually, especially when buying supplements from less scrupulous manufacturers.

The Prostate Cancer Wrinkle

I touched on this earlier, but it’s worth repeating here because it’s specifically a toxicity-adjacent concern rather than a benefit question. In a large trial analysis, men who already had higher baseline selenium status before starting supplementation showed an increased risk of high-grade prostate cancer when they supplemented anyway, leading researchers to specifically recommend that men over 55 avoid selenium supplementation beyond typical dietary intake levels. That’s a pretty direct, actionable finding, and it’s the kind of nuance that gets lost when selenium gets marketed as a blanket antioxidant booster without regard for who’s taking it or what their existing status looks like.

Medication Interactions Worth Knowing

Selenium status can also be affected by certain medications, most notably cisplatin, a chemotherapy drug used for several cancer types, which can lower selenium levels in the blood and hair. Some smaller studies have suggested selenium supplementation might reduce cisplatin’s toxic side effects, but a formal review of the evidence concluded it isn’t strong enough yet to recommend selenium for that purpose. If you’re undergoing chemotherapy or taking other medications regularly, selenium status is worth discussing with your care team rather than adding a supplement independently.

Practical Risk Management

• Don’t combine a standalone selenium supplement with regular, generous servings of Brazil nuts; that combination adds up faster than most people expect.
• If you notice a garlic smell on your breath that isn’t diet-related, or your nails start becoming unusually brittle, it’s worth mentioning to a healthcare provider along with your supplement habits.
• Multivitamins with modest selenium content, around 55 micrograms, are unlikely to push most people toward toxicity on their own; it’s the standalone high-dose products layered on top of food sources that create the real risk.
• Men over 55 in particular should be cautious about selenium supplementation beyond what a normal diet provides, given the prostate cancer signal from higher-quality trial data.

What Selenium Teaches Us About Getting Nutrition Right

After spending this much time with selenium, I keep coming back to the same thought: this is a mineral that rewards precision and punishes assumption. It’s not a nutrient you can approach with a “more is better” mentality, and it’s also not one you can safely ignore, particularly if you’re vegan, undergoing dialysis, living with HIV, or eating a diet built almost entirely around locally grown plants in a low-selenium region.

What I find genuinely compelling about selenium is how directly its biochemistry explains its health effects. This isn’t a mineral with a vague, hand-wavy connection to wellness. It gets written into specific antioxidant enzymes, glutathione peroxidases and thioredoxin reductases, that do a defined job protecting cells from oxidative damage, and it plays an equally specific, well-documented role in thyroid hormone metabolism. When the evidence is that concrete, I trust it more than nutrients whose benefits seem to shift depending on which supplement company is funding the latest study.

At the same time, selenium is a great case study in why nutrition science needs time and repetition to get things right. The early cancer prevention enthusiasm didn’t hold up under more rigorous trials, and in some cases, the picture flipped toward actual concern for people who supplemented despite already having adequate status. That’s not a failure of selenium research, it’s exactly how good science is supposed to work, and I’d rather you know that nuance than walk away thinking selenium is a cancer-fighting silver bullet, because it isn’t.

If I had to boil this down into practical guidance, it would look something like this. Most people eating a reasonably varied diet that includes some seafood, meat, or eggs are already getting enough selenium without thinking about it, and that’s genuinely good news, not a letdown. Brazil nuts are a legitimate selenium source but need portion awareness, not enthusiasm. Standalone selenium supplements make sense for specific situations, documented deficiency, certain medical conditions, or a diet that’s genuinely low in selenium sources, rather than as a default addition to a supplement routine. And if you fall into one of the higher-risk categories we covered, vegan or vegetarian, on dialysis, living with HIV, or in a region with documented low soil selenium, that’s worth a real conversation with a healthcare provider rather than a guess based on a blog post, mine included.

Selenium doesn’t need hype to be interesting. The actual biochemistry, a trace mineral quite literally built into the genetic code of specific protective enzymes, is compelling enough on its own. I’d rather you walk away from this understanding why selenium matters and where its limits are than with an oversimplified takeaway that either dismisses it or oversells it. Somewhere in that narrow, well-documented middle ground is where the real value of this mineral lives.

Article Sources

At AncientHerbsWisdom, our content relies on reputable sources, including peer-reviewed studies, to substantiate the information presented in our articles. Our primary objective is to ensure our content is thoroughly fact-checked, maintaining a commitment to accuracy, reliability, and trustworthiness.

1. Gladyshev, V. N., Arnér, E. S., Berry, M. J., Brigelius-Flohé, R., Bruford, E. A., Burk, R. F., Carlson, B. A., Castellano, S., Chavatte, L., Conrad, M., Copeland, P. R., Diamond, A. M., Driscoll, D. M., Ferreiro, A., Flohé, L., Green, F. R., Guigó, R., Handy, D. E., Hatfield, D. L., Hesketh, J., … Zhang, Y. (2016). Selenoprotein gene nomenclature. Journal of Biological Chemistry, 291(46), 24036-24040. https://doi.org/10.1074/jbc.M116.756155 
2. Institute of Medicine, Food and Nutrition Board. (2000). Dietary reference intakes: Vitamin C, vitamin E, selenium, and carotenoids. National Academy Press.
3. MacFarquhar, J. K., Broussard, D. L., Melstrom, P., Hutchinson, R., Wolkin, A., Martin, C., Burk, R. F., Dunn, J. R., Green, A. L., Hammond, R., Schaffner, W., & Jones, T. F. (2010). Acute selenium toxicity associated with a dietary supplement. Archives of Internal Medicine, 170(3), 256-261. https://doi.org/10.1001/archinternmed.2009.495 
4. National Institutes of Health, Office of Dietary Supplements. (2025). Selenium: Fact sheet for health professionals. https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/ 
5. National Institutes of Health, Office of Dietary Supplements. (2024). Selenium: Fact sheet for consumers. https://ods.od.nih.gov/factsheets/Selenium-Consumer/
6. Rayman, M. P. (2012). Selenium and human health. The Lancet, 379(9822), 1256-1268. https://doi.org/10.1016/S0140-6736(11)61452-9 
7. Rees, K., Hartley, L., Day, C., Flowers, N., Clarke, A., & Stranges, S. (2013). Selenium supplementation for the primary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews, 2013(1), CD009671. https://doi.org/10.1002/14651858.CD009671.pub2 
8. Thomson, C. D., Chisholm, A., McLachlan, S. K., & Campbell, J. M. (2008). Brazil nuts: An effective way to improve selenium status. American Journal of Clinical Nutrition, 87(2), 379-384. https://doi.org/10.1093/ajcn/87.2.379 
9. Vinceti, M., Filippini, T., Del Giovane, C., Dennert, G., Zwahlen, M., Brinkman, M., Zeegers, M. P., Horneber, M., D’Amico, R., & Crespi, C. M. (2018). Selenium for preventing cancer. Cochrane Database of Systematic Reviews, 1, CD005195. https://doi.org/10.1002/14651858.CD005195.pub4 
10. Wichman, J., Winther, K. H., Bonnema, S. J., & Hegedüs, L. (2016). Selenium supplementation significantly reduces thyroid autoantibody levels in patients with chronic autoimmune thyroiditis: A systematic review and meta-analysis. Thyroid, 26(12), 1681-1692. https://doi.org/10.1089/thy.2016.0256