Selenium: The Benefits and Sources - Ask a Nutritionist

February 23, 2024

Today's episode of Ask a Nutritionist is about the lesser-known world of selenium. Dietitian Leah Kleinschrodt reveals how this crucial little mineral powers your thyroid, boosts immunity, and much more. Discover the surprising sources of selenium and learn practical tips to take advantage of its health benefits. Tune in!

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LEAH: Hello and welcome to Dishing Up Nutrition's “Ask a Nutritionist” podcast brought to you by Nutritional Weight and Wellness. My name is Leah Kleinschrodt. I'm a Registered and Licensed Dietitian, and we're thrilled to be celebrating 20 years of on air, discussing the connection between what you eat and how you feel while sharing practical real-life solutions for healthier living through balanced nutrition.

We thank all of you for your support and listenership over the years. And if you're enjoying the show, please let us know by leaving a rating or review on Apple podcast or Spotify. Providing feedback also helps others find these important real food messages. Now let's get started.

So on today's show, I will be answering one question that we received from our Dishing Up Nutrition listeners. Now this listener says, “I'm interested in learning more about selenium. What are the benefits and is it possible to be deficient?” So this is a great question. Selenium doesn't get much air time compared to a lot of our other vitamins and minerals like vitamin D or calcium or magnesium, but that certainly doesn't mean that it's not a critical nutrient for the body.

So we're going to dig a little deeper into selenium. So selenium is a mineral. There's actually several different forms of selenium in the body and that exist in nature, but just for the sake of this podcast, we'll just be referring to the umbrella term of selenium. And selenium plays several different critical roles in the body.

What roles does selenium play in the body?

Primarily the first one that comes to my mind is it is important for making our thyroid hormones. So it catalyzes some of the enzymes that are needed to make our thyroid hormones. Now, our thyroid gland is the organ in the body with the highest concentration of selenium, which really tells us something there.

And our thyroid is responsible for many, many different things, including our metabolism, our bone maintenance, our brain function, our digestive health, our temperature regulation, and so many different things. So anything we can do to keep our thyroid running well is usually worth the effort.

Selenium also is important for immune function, and one of the primary things it does in the immune system is it helps to fight off viral infections. So that's really important, thinking about the last four years, and it is also an important antioxidant.

So selenium has been postulated to have some impact in reducing cancer risk. There's a lot of studies out there that are still looking at that, but it is definitely one area that's a hot topic of research. And then lastly, selenium also plays a role in DNA synthesis and repair, and it also has been found to impact fertility in both men and women.

How much selenium does the body require?

So we have this one little mineral that has its hands in a lot of different areas. And to me, actually, what's more amazing is that selenium is required in very little amounts in the body. It is a required nutrient for the body, but it is required in a very small amount. We have some of our major minerals like sodium and potassium, they're required in gram amounts.

And then a lot of our other minerals like magnesium or zinc, they're required in milligrams amounts. Now, selenium is required in microgram amounts, so a hundred fold less than some of those other again, bigger player minerals. The RDA of selenium for adults is 55 micrograms per day. It's a little higher in pregnancy and in lactation around 60 to 70, but again, just very small amounts.

According to the NHANES data from 2009 to 2010, and this is a long running data collection of how Americans eat. That's what the NHANES data is. What that shows is that the average American consumes just a little over 100 micrograms of selenium per day. So actually, frank selenium deficiency is very rare.

Which groups of people may be at risk for selenium deficiency?

According to the NIH fact sheet for selenium, there are some groups that are a little higher risk for selenium inadequacy. But again, frank deficiency is rare. So, people who just might have inadequate selenium might be people who live in selenium deficient regions. So, thinking about the soil. The soil is where we get selenium from. So, if we're living in a region where it is not a high amount of selenium in the soil, then we can run into selenium inadequacy.

And there's some areas in China that really fit this category. Not only is the soil deficient in selenium, but the people who live in this region also primarily eat plants that are grown in that region. So again, like they just don't have access to foods that have a high amount of selenium.

People who are undergoing kidney dialysis might also run into selenium inadequacy because the dialysis removes some selenium from the blood during that cleaning process. And people living with HIV could also, again, just run a little low in selenium; HIV being a chronic viral infection. And that can result in selenium losses just mainly from like chronic diarrhea and malabsorption.

So if we think from that perspective also, so it's not limited potentially just to people with HIV. We see a lot of other conditions where we see chronic diarrhea or malabsorption, or that intestinal tract does not absorb things really well from the gut. So I think about celiac disease or inflammatory bowel disease, which is either Crohn's disease or ulcerative colitis.

So again, even if selenium deficiency is rare, it's good to be aware that there are certain groups of people that still might not clear that bar of having adequate selenium. So I'm going to take a pause right here, and we're going to take a quick break. When we return, I will be sharing more about how to get adequate selenium in the diet using a real food approach.


What are some selenium sources?

Now, where do we get selenium and how can we make sure we're getting enough to power our thyroid and to keep our immune system up to par? The food with the highest source of selenium are Brazil nuts. And so some of us may have heard of that before, but about an ounce of Brazil nuts, which is usually around six to eight Brazil nuts, provides about 550 micrograms of selenium.

So remember the RDA for selenium for most adults is 55 micrograms of selenium. So if we're eating an ounce of Brazil nuts a day, we're actually getting tenfold what that RDA recommendation is. And I've had clients use Brazil nuts like a tasty little selenium supplement. 550 micrograms of selenium is quite a bit.

So I'll have clients do two to three nuts per day, and that is their selenium supplement. It's a tasty way to add in some nutrition. And usually they use it as part of their balanced snack or might just tag on a little bit extra onto one of their meals during the day.

Now, the food category with the next highest selenium content is fish and seafood. So I know it's not everybody's cup of tea, but if we think about tuna, if we think about shrimp, sardines, oysters, things like that, these will get you somewhere in the range of 40 to 90 micrograms of selenium per three ounce serving. So that's actually quite a bit lower. If you think about Brazil nuts, one ounce of Brazil nuts has about 550 micrograms of selenium in it;

Versus if you have to eat three ounces of shrimp to get maybe 60 or 70 micrograms of selenium in there, but still we can get in a three ounce serving of shrimp or three ounces of tuna, and we're still going to clear that bar for the RDA requirements. So if you like shrimp stir fry, or I have a lot of clients who love tuna salad and using a good quality mayo, of course, you're well on your way to meeting and even exceeding those selenium needs for a day.

Most of our meats have a decent amount of selenium. So think chicken, pork, beef, things like that. Organ meats, liver, kidney, spleen, again, not super common or popular in this part of the world, but in other places it definitely is.

Dairy products have some selenium in it. Eggs, some grain products and vegetables. When it comes to plant foods, like the grains and the vegetables, the selenium content in these foods will be a lot more variable, meaning like broccoli grown in one part of the world might have a lot more selenium versus broccoli grown in another part of the world.

So it doesn't mean like broccoli across the board is going to have one amount of selenium. Again, it is due to the soil and selenium varies in where it is grown in the soil content. So, we kind of, we have to take our best guess, especially when it comes to the plant based foods like that.

Animal products will have some variation, but overall they tend to have a little more consistency in their selenium levels; just because there's processes in the body that keeps selenium levels in a tighter range. So we can predict a little bit better what those selenium levels are when it comes to animal products. So not that one is, is worse or better, but just know, again, when it comes to the plant foods, we have to kind of hedge our bets a little bit more.

Can you get too much selenium?

Now, you can get too much selenium. It's unlikely through food, unless you're eating a pound of Brazil nuts every single day for a long period of time. The tolerable upper limit for selenium in adults is 400 micrograms per day. It's usually only a problem if someone is supplementing long term with selenium.

And again, even if you had a day where maybe 1 day you had 600 micrograms of selenium, you're not going to get thrown into toxicity right then and there. It is more of a, like really overdoing it on selenium over the long term that might push you more into that range of selenium toxicity.

Supplementation: who might need it & how much?

If you choose to supplement with selenium either for some thyroid support or for a little bit extra immune support, again, you can go back and eat a few Brazil nuts every single day or most likely supplementing with 100 to 200 micrograms of selenium per day is a safe range that won't throw anything overboard.

So that is selenium in a nutshell. I hope this information was helpful and I want to thank you again so much for listening to Dishing Up Nutrition's “Ask a Nutritionist”, and if you found this episode helpful, please be sure to leave us a rating or review on your favorite podcast app.

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