Selenium: The Trace Mineral with Macro Impact on Your Health

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Selenium is an essential trace mineral that acts as an antioxidant. Though required in tiny quantities, selenium plays a fundamental role in our health, contributing to everything from immune function to the health of our heart. Despite its trace status, the benefits of selenium are anything but minor, making it a crucial player in human wellness.

If Selenium supplements are right for you, this article will show you the best place to order Selenium online. This article is your basic guide to selenium, offering a deep-dive into its essential benefits, the science behind its role in our bodies, and the importance of maintaining adequate levels.

What Is Selenium?

Selenium is a trace element and essential micronutrient that is important for various physiological functions in the human body. It is a mineral that is naturally present in soil, water, and some foods. Small amounts of selenium are needed for the proper functioning of the immune system, thyroid gland, and reproductive system. It also has antioxidant properties that help to protect cells from oxidative damage caused by free radicals. Selenium is found in many foods such as seafood, meat, poultry, grains, and vegetables, and can also be taken as a dietary supplement. However, excessive intake of selenium can be toxic and may lead to health problems, so it’s important to consume it in appropriate amounts. The recommended daily intake of selenium for adults is around 55 micrograms per day.

What are the Benefits of Selenium?

Selenium is essential for human health and has been associated with various health benefits, including:

  • Acts as an antioxidant: Selenium has powerful antioxidant properties that help to protect cells from oxidative damage caused by free radicals, which can lead to chronic diseases such as cancer, heart disease, and Alzheimer’s. [PMC2698273]
  • Boosts the immune system: Selenium is necessary for the proper functioning of the immune system, and studies have shown that it can help to increase the production of antibodies and enhance the activity of white blood cells. [PMC3277928]
  • Helps with thyroid function: Selenium is required for the production of thyroid hormones, which are essential for regulating metabolism and maintaining normal growth and development. [PMC2698273]
  • Improves male fertility: Selenium is important for male fertility, and studies have shown that it can help to improve sperm motility. [PMC3048346] However, both high and low selenium may impair male fertility. [PMID: 36731804]
  • Helps with cognitive function: Selenium may play a role in cognitive function, and studies have shown that low selenium levels may be associated with an increased risk of cognitive decline and dementia. [PMC9370215]

Selenium May Not Reduce Cancer Risk

Older studies had suggested that selenium reduced the risk of certain cancers, however, a Cochrane review has stated that well-done studies haven’t found that selenium supplements lower cancer risk. Some even showed more severe prostate cancer and type 2 diabetes in those taking selenium. No clear pattern shows more selenium leads to less cancer risk. These studies may have flaws, like inaccurate selenium measurement and not considering other factors. More research is needed to understand if selenium affects cancer risk differently in people with certain genes or diets. [PMC6491296]

Early observational studies reported an inverse relation between selenium exposure and cancer risk. Subsequently, randomized controlled trials showed that selenium supplementation does not reduce the risk of cancer and may even increase it for some types, including advanced prostate cancer and skin cancer...The study of selenium and cancer is complicated by the existence of a diverse array of organic and inorganic selenium compounds, each with distinct biological properties.

The Epidemiology of Selenium and Human Cancer [PMID: 29054414]

How Much Selenium Do We Need?

The recommended dietary allowance (RDA) for selenium varies depending on age, sex, and life stage:

  • Adults 19 years and older: 55 micrograms/day
  • Children 1-3 years: 20 micrograms/day
  • Children 4-8 years: 30 micrograms/day
  • Children 9-13 years: 40 micrograms/day
  • Teens 14-18 years: 55 micrograms/day
  • Pregnant women: 60 micrograms/day
  • Breastfeeding women: 70 micrograms/day

These amounts are sufficient for most healthy people to prevent deficiency. It’s important to note that while selenium is a crucial trace mineral, excessive intake can be toxic, so it’s generally not recommended to exceed the upper limit of 400 micrograms per day for adults.

Food Sources of Selenium

Selenium is found in both vegetarian and animal foods. Its amount vary based on the soil where food is grown or animals are raised. Vegetarian sources include Brazil nuts, whole grains, seeds, and some vegetables like mushrooms and spinach. Animal sources with high selenium include seafood, meats like chicken and beef, and dairy products. The selenium content can vary widely depending on factors like soil content and processing methods.

Food selenium content depends on soil selenium levels where crops grow or animals graze. Low-selenium soil yields less selenium in local produce and meat, while selenium-rich soil results in higher levels in these foods. This makes local soil selenium a key factor in dietary intake. With this in mind, here is a table listing some common food sources of selenium and the approximate amount of selenium in each:

Food (Serving Size)Estimated Selenium Content (mcg)
Brazil Nuts (1 Nut)90 mcg
Tuna (3 ounces)64 mcg
Halibut, Sardines (3 ounces)46 mcg
Meat, poultry, pork Ham (3 ounces)20 – 40 mcg
Cottage Cheese (1 cup)20 mcg
Eggs (1 large)15 mcg

Brazil Nuts As A Selenium Supplement: Caution

Brazil nuts are often recommended as a way to assure adequate selenium, but be careful not to eat more than 1 or 2 per day to average to avoid excessive selenium intake. The daily value for selenium is set at 55mcg per day, and the tolerable upper limit for this mineral is set at 400mcg per day. * As you can see, brazil nuts, with an estimated 90mcg PER NUT, can make an excellent selenium supplement. But, along with such a high level of selenium, it is important to be careful to limit intake to 4 brazil nuts per day to avoid toxicity.

Are Selenium Supplements Safe

Selenium is essential for several biological functions, including supporting immune system and thyroid function.

Selenium is generally considered safe when taken in appropriate doses. However, the tolerable upper intake level (UL) for selenium is 400 mcg and excessive intake can lead to toxicity. High intakes in the first trimester of pregnancy increase the risk of birth defects. [PMID: 31461777] That being said, when selenium supplements are taken in accordance with these recommendations, they pose minimal risk.

Medication Interactions with Selenium

  • Anticoagulants (blood thinners) – Selenium can increase the risk of bleeding when taken with blood thinners, potentially leading to serious complications.
  • Chemotherapy drugs – Selenium may reduce the effectiveness of some chemotherapy drugs used to treat cancer.
  • Cholesterol-lowering medications – Selenium may reduce the effectiveness of some cholesterol-lowering medications, including statins.
  • Immunosuppressants – Selenium may reduce the effectiveness of immunosuppressive drugs used to prevent rejection of transplanted organs.
  • Hormone replacement therapy – Selenium may reduce the effectiveness of hormone replacement therapy used to treat menopause symptoms.
  • Contraceptives – Selenium may reduce the effectiveness of hormonal contraceptives, potentially leading to unintended pregnancy.

Supplement Interactions with Selenium

  • Vitamin C – High doses of vitamin C may reduce the absorption of selenium and lead to a selenium deficiency.
  • Vitamin E – High doses of vitamin E may reduce the absorption of selenium and lead to a selenium deficiency.
  • Iron – High doses of iron may reduce the absorption of selenium and lead to a selenium deficiency.
  • Zinc – High doses of zinc may reduce the absorption of selenium and lead to a selenium deficiency.
  • Calcium – High doses of calcium may reduce the absorption of selenium and lead to a selenium deficiency.

Selenium by Pure Encapsulation

Amount Per 1 Capsule Serving
Selenium … 200mcg
(as selenomethionine)

Other Ingredients: hypoallergenic plant fiber (cellulose), ascorbyl palmitate, vegetarian capsule (cellulose, water)

Food First!

Although this article discusses supplements in detail, don’t forget that we are absolutely committed to the “Food First” approach to nutrition. When it comes to your health, the totality of your eating habits far surpasses the impact of individual nutrients or any single supplement you consume. Even though this article doesn’t delve into the broader picture of your overall diet, it’s crucial to keep this element at the forefront of our minds. Your food needs to provide all the vitamins, minerals, fiber, and phytochemicals to nourish your body systems down to the cellular level.

Food choices, rather than supplements, are the most critical factors for a healthy gut microbiome. These trillions of tiny inhabitants in your gut affect your brain waves; they orchestrate your immune system. They possess the power to create molecules that can switch genes on or off and are even capable of synthesizing neurotransmitters. Opting for organic foods and steering clear of plastic packaging (including those labeled BPA-free) is a smart move to limit toxin exposure. The sum of all these parts leads to a powerful conclusion: the ultimate key to your health lies in the quality and balance of the food you consume. Supplements are secondary.

To Sum It Up

Selenium through foods or through supplements offers a boost to your health. Selenium supports a robust immune system, plays a crucial role in metabolism, and is key for thyroid function. Adequate selenium intake can contribute to heart health and may protect against certain types of cancers. While selenium is found in a variety of foods, supplements ensure you meet your daily needs, especially important in areas where soil selenium levels are low. Remember, balance is key, as too much can have adverse effects.

This Article is Not a Substitute for Medical Advice

Dietary supplements are not designed to diagnose, treat, cure, or prevent any disease. The Supplement Sciences website seeks to provide comprehensive access to the most relevant supplement information along with convenient online ordering. We do not provide medical advice and cannot guarantee that every product suggested is completely without risk. Since each person is unique in their health history and medication use, it is important to discuss supplements with your personal physician. Specifically, pregnant women and individuals being treated for cancer or liver or kidney problems must consult their physician about every nutritional supplement they plan to take. People taking medications for the treatment of HIV or with a history of organ transplant must not take supplements without consulting with their physician.

About the Author

Stephanie Figon, MS, RDN, LD

Creator of Supplement Sciences and NutriScape.NET. As a dietitian since 1992, Steph has had experiences in consulting, 15 years in clinical, and has operated a private practice nutrition counseling office for since 2011. Log in to comment and save this article on your board or send your comments to

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