Selenium: What is it and where can you get it?

Selenium is an essential trace mineral that’s vital for supporting many of the body’s normal functions, including thyroid health and immunity. Get ready to further explore what selenium is, why it’s needed, and importantly, where you can get it.

Content Outline

• What is selenium? 
• What is the function of selenium in the human body?  
• Selenium: Which is the active form? 
• Selenium-rich foods  
• Selenium recipe: Brazil nut and quinoa salad
• Selenium supplements
  • Which is the best selenium supplement?
• Why buy food-borne vitamins?

What is selenium? 

Selenium is an essential mineral that is naturally present in many foods and in supplements1. It has numerous roles in many processes, including antioxidant defence, immunity, and thyroid regulation. Selenium, like iodine, is naturally found in soil and water, so how much selenium is found in food depends on where it was grown and sourced. 

Selenium is an essential trace mineral, but it is only needed in very small amounts. Despite its small requirements, its role in bodily functions is crucial. 

What is the function of selenium in the human body?  

Although only required in small amounts, selenium has a big impact on the body’s functions, contributing to thyroid health, supporting the immune system, and acting as an antioxidant. Here are some of selenium’s important functions:

Figure 1. Some of the key functions of selenium in the human body.

• Antioxidant properties: Research shows that selenium acts as an antioxidant, protecting the body’s cells from oxidative stress2, which could potentially prevent disease and contribute to healthy aging3.

• Fat-lowering potential: Although results are mixed, some evidence suggests that an adequate selenium intake can lower lipid levels in groups where selenium levels are otherwise low. One study found that selenium reduced total cholesterol and triglycerides and increased high-density lipoprotein (HDL) or good cholesterol after 7 years compared to those with a low selenium intake4.

• Thyroid function: Selenium, like iodine, is critical for maintaining thyroid function because it is a common component in the conversion of the less active hormone thyroxine (T4) into its active counterpart triiodothyronine (T3). Low selenium levels increase the risk of several thyroid conditions, with supplementation delaying the progression of Graves’ disease, improving outcomes in Hashimoto’s thyroiditis, and even having anticancer properties in thyroid cancer5.   

• Immunity: Selenium is crucial for a healthy immune system, with deficiency associated with impaired immune function6. It also lowers inflammation and regulates exaggerated immune responses7.

• Reproductive health: Alongside immunity and thyroid function, selenium has vital roles in reproductive health in both men and women. In men, it is important for sperm formation, motility, and testosterone production8, while in women, selenium can prevent pregnancy complications9. 

Selenium: Which is the active form? 

Selenium is found in foods usually in two main forms:

1. Selenomethionine

2. Selenocysteine 

These are readily absorbed in the body and metabolized into an intermediary that’s used for making selenocysteine. Between 28% to 46% of the body’s total selenium stores are found in skeletal muscle10. 

Selenium-rich foods  

Selenium is found in many foods, so following a balanced diet will help you to consume the levels that you need to function. Some of the richest selenium food sources are:

Figure 2. Selenium-rich food sources. Brazil nuts, salmon, chicken, spinach, brown bread, brown rice, sunflower seeds, broccoli, and mushrooms.

Selenium recipe: Brazil nut & quinoa salad

Incorporating selenium-rich foods into your diet, with delicious Brazil nuts and quinoa salad. Brazil nuts have some of the richest selenium contents of all foods, and quinoa, another rich source, makes a great pairing for a nutty, savoury, and nutritious salad. Its versatility is also attractive. Simply add some roasted vegetables or some lean chicken breast for a flavoursome meal.

Ingredients: 

• 1 cup quinoa (cooked)

• ¼ cup chopped Brazil nuts

• 1 cup roasted sweet potatoes

• 1 cup steamed broccoli

• 1 tbsp salad dressing of your choice, such as lemon-tahini, chilli and lime, or lemon and herb 

Method:

1. In a large salad bowl, add the quinoa, chopped Brazil nuts, sweet potatoes, and broccoli.

2. Toss all the ingredients together.

3. Serve on a plate and drizzle over your preferred dressing. Top with chicken breast, fish, or tofu for added nutrition. 

This selenium-rich salad is super easy and quick to prepare, making it perfect for lunch or as a side for your main evening meal. 

Selenium supplements

While selenium is easily obtained through a balanced diet, some groups may be at a greater risk of deficiency and could benefit from supplementation. These include:

• People with thyroid disorders: Selenium is crucial for the production of thyroid hormones, particularly the conversion of T4 into the active T3. So, under a physician’s guidance, those with thyroid disorders may benefit from selenium supplementation to support their thyroid health and hormone metabolism.

• Pregnant women: Selenium may lower maternal oxidative stress during pregnancy, which may benefit both the mother and baby. However, it is important to speak with your doctor or midwife before taking any new supplements during pregnancy11. 

• Men trying to conceive: If you are trying to conceive with your partner, you may consider selenium supplementation because it plays a vital role in male fertility. Selenium is an antioxidant that can improve sperm motility and morphology, contributing to improved reproductive health12.

• Elderly individuals: Some evidence suggests that selenium has anti-aging properties and may even improve cognitive function13. So, supplementation in older adults may have some benefits.

• Vegans and vegetarians: Although plant-based diets can provide selenium, as our delicious recipe shows, the levels in these foods are typically lower than in animal-based foods, especially in regions where there are selenium-deficient soils. Vegans and vegetarians may need supplementation to meet their daily needs.

Selenium supplements are available in many forms, offering different benefits. The most common types include:

• Selenomethionine: The most bioavailable and commonly used form of selenium. It is readily absorbed in the body, making it a highly effective option for inclusion in supplements. It’s an ideal option for those looking for a highly absorbable selenium form. 

• Sodium selenite: An inorganic form of selenium commonly found in supplements. It is less bioavailable than selenomethionine, but can be a more affordable option for some people.

• Selenium-enriched yeast:  Yeast that has been grown in a selenium-rich environment. It closely mimics the natural state of selenium in food and is often included in food-based selenium supplements. 

• L-selenocysteine: Another highly bioavailable form of selenium, primarily found in the body as part of the selenoproteins that are crucial for antioxidant activity and other essential functions. These supplements may offer additional benefits for antioxidant protection.

Which is the best selenium supplement?

The best selenium supplement for you will depend on your individual needs and preferences. For example, the most effective and easily absorbed form is thought to be selenomethionine, making it the right choice for most people. However, for people with specific needs, such as supporting thyroid function or boosting antioxidant defences, supplements containing L-selenocysteine may be helpful. While selenium-enriched yeasts or food-born types may be the preferable choice for those looking for a natural option.

Why buy food-born vitamins?

Selenium is an essential trace mineral that is critical for maintaining good health. It acts as a powerful antioxidant, helping to protect cells from oxidative stress, supporting thyroid function, and boosting the immune system. It also has an important role in boosting and maintaining reproductive health in men and women. 

Although most people will get all the selenium they need by following a healthy, balanced diet and eating foods like Brazil nuts, fish, and whole grains, supplementation should be considered by some groups. 

If you’re looking for a selenium supplement, our Food-Born Multivitamin for Women with Iron can provide 75% of your daily value, alongside 20 other important vitamins and minerals required for optimal female health.

Check out our shop to explore our full range.

Written by: Leanne Edermaniger MSc