TikTok has gone all in on selenium due to its impressive benefits, largely thanks to one food that packs the nutrient in spades. But how much selenium do you really need… and how much is too much?
If you’ve seen TikToks touting the magic packed into Brazil nuts, you’re probably thinking pretty highly about a certain nutrient right now: selenium. The reason why everyone’s abuzz about Brazil nuts is that just one nut packs more than 100 percent of the selenium you need in a day, which basically makes them a supplement in food form.
But what’s so great about selenium anyway, and do you need more? These questions, answered below.
What Is Selenium?
Selenium is an essential trace mineral found in foods (including fortified foods) and supplements, according to the National Institutes of Health (NIH). The nutrient affects many systems in the body and assists many crucial functions.
“Selenium is important for cognition, the immune system, reproduction, as well as thyroid hormones,” says Courtney Smith Dorchak, RD, owner of Keys to Nutrition, a virtual nutrition consulting practice based in the Florida Keys. Clearly, you need it to function and feel your best.
5 Benefits of Selenium
Your body relies on this nutrient to function from head to toe. Here are some of the most notable health benefits of selenium.
1. It Supports Thyroid Health
Your thyroid—the small, butterfly-shaped gland at the base of your neck—relies on two important nutrients to support its function: iodine and selenium. In fact, per the NIH, your thyroid houses more selenium compared to any other organ in your body.
Your thyroid churns out two main hormones: T3 (triiodothyronine) and T4 (thyroxine). T4 needs to be converted into T3, which is the active form of the hormone.
Selenium steps in here to help convert T4 to T3, says Dorchack. With that mission accomplished, T3 can then travel through the body and do its work to support the function of your metabolism, heart rate, body temperature, and digestion. (Truly, a big job.)
2. It Supports Fertility
For men looking to start or grow your family, Dorchak points out that there’s some research to suggest that selenium may help shore up sperm concentration and sperm motility. (One review of randomized controlled trials backs up the notion that selenium may help boost male fertility.) Selenium may quell oxidative stress that harms the number and speediness of swimmers.
Note: Be sure to ask your doctor if there are nutritional or lifestyle changes that may support your or your partner’s fertility.
3. It Acts as an Antioxidant
Selenium has antioxidant properties, which means it can help fight off damaging free radicals that, over time, contribute to aging and poor health. The nutrient may also aid in DNA repair, according to the NIH.
What does this all mean? Ultimately, selenium can help bolster your body’s natural defense system and help shore up your immunity to potentially offer protection against certain health issues, according to a 2022 review in the journal Molecules.
However, selenium can’t do it all. There are other nutrients that have antioxidant properties (vitamin C, anyone?) that work to keep your immune system zipping along. So think of your immune system as an ensemble, filled with various elements that make it strong. Selenium may be one supporting actor amongst the full cast.
4. It Promotes Heart Health
To keep your ticker strong, it’s important to eat the RDA for selenium on the regular. (Keep reading to see how much selenium you need.) Again, selenium helps protect cells against damage from free radicals, and this may, in turn, safeguard your heart.
Consuming adequate or higher-than-adequate (but still safe) amounts of selenium may help decrease the overall risk of heart complications compared to having low levels, according to a 2021 meta-analysis in Critical Reviews in Food Science and Nutrition. Still, loading up on much more selenium than is necessary isn’t the best option, as we’ll see below.
5. It Supports a Healthy Pregnancy
Women who are pregnant or breastfeeding need just a bit more selenium in their diet. As an antioxidant, selenium may reduce oxidative stress, which is associated with pregnancy complications, a research review in the Journal of Nutrition and Metabolism points out. Selenium may also affect your thyroid hormones, which are needed for a baby’s developing brain and nervous system.
While it’s important to aim for the recommended intake of selenium during pregnancy and breastfeeding, researchers are still exploring if supplementing with selenium during this time is needed or entirely safe. (This invites another important opportunity to talk to your OB-GYN.)
How Much Selenium Do I Need?
According to the NIH, adults should get 55 micrograms of selenium per day to reap its benefits. You’ll need 60 and 70 micrograms, respectively, if you are pregnant or breastfeeding.
The NIH also noes that selenium deficiency is rare. However, Dorchak says that people who follow primarily plant-based diets may be more at risk of deficiency, as well as those who have thyroid issues. That’s because some of the best dietary sources of selenium include meat, fish, and shellfish. However, decent plant-based sources of selenium include grains like brown rice and oatmeal.
But there’s one plant food that tops all other foods for selenium—and that’s Brazil nuts. But there’s one caveat. Since these nuts are so rich in selenium, it’s easy to eat too many and exceed the recommended upper intake, which is 400 micrograms per day. (Upper intake is the maximum you can take that’s known to be safe.) After all, one ounce of Brazil nuts—or six to eight nuts—packs 544 micrograms.
You can find out if you may be consuming too much selenium if your breath smells garlicky (and you did not just feast on a garlic-rich pasta) or you have a metallic taste in your mouth, per the NIH. Overdoing it on the selenium long-term can contribute to hair loss, as well as nausea, diarrhea, fatigue, and irritability, among other side effects.
That’s why it’s best not to buy into TikTok’s Brazil nut excitement too much, since more is not better. If you are going the Brazil nut route to benefit from selenium, Dorchak advises eating one per day. In addition, buying a bag and roasting them yourself can bring out an enjoyable, nuttier taste. If you’re purchasing the nuts already roasted and salted, be sure to watch the sodium content, as nuts can pack a lot of salt.
How to Get More Selenium in Your Diet
Of course, not everyone thinks that Brazil nuts are delicious. They can be bitter, which is why they’re often neglected in nut medleys. According to the NIH, other foods that are excellent sources of selenium include:
- Yellowfin tuna and halibut
- Canned sardines
- Boneless roasted turkey
- Cottage cheese
- Hard-boiled eggs
- Long-grain brown rice
- Whole-wheat bread