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Selenium is a mineral needed for several functions within the body. Research shows that getting the recommended daily value of selenium can support your immune system, help underactive thyroid and may even protect you against colds or flu.

What Is Selenium?

Selenium can be taken in supplement form, or you can get it from your diet. Selenium-rich foods include lean red meat, liver seafood and some grains (if they're grown in soil with the mineral).


The recommended intake for adult women is 45-55 mcg per day, while the amount is slightly higher for men—40-70 mcg per day. Selenium is good for the immune system, underactive thyroid and may even benefit you during cold and flu season. 

Although rare in the U.S., selenium deficiency is possible and can lead to illnesses when combined with other factors. For example, selenium deficiencies in Chinese populations have led to Keshan disease, which causes heart failure and the deterioration of joints.

If you aren’t getting enough selenium in your diet, you can supplement this trace mineral with daily tablets or multivitamins.

Selenium Immune System Benefits

Your immune system is designed to keep your body healthy by recognizing threats, like infections, and fighting them off. Selenium is important in your body’s natural defense, producing more immune cells and managing oxidative stress.

Promotes Immune Cell Production

Selenium can boost the immune system by promoting white blood cell production—T-cells in particular. T-cells are white blood cells, and their job is to search the body for infections and kill infected cells. In one Italian study, participants received a selenium supplement or a placebo. After 10 weeks, researchers found that moderate doses increased T-cell levels in the blood. The cells also used fewer molecules to kill infected cells, meaning they became more efficient.


On the other hand, a selenium deficiency can make you more susceptible to infections by interfering with your body’s ability to fight pathogens. Low levels of selenium can harm the way your immune cells function and lead to a weaker response to the threat. For example, researchers looked at how the bacteria candida albicans affected mice. They found that, compared to mice given a supplement, those with selenium deficiencies were less able to fight the bacteria. This suggests that low selenium levels could lead to a higher susceptibility for bacterial infections.


A selenium deficiency may cause even more immune problems for people with HIV. Patients taking a supplement reduced their hospitalizations while improving their symptoms. Those who didn't have enough in their diet were at an increased risk of disease progression and shortened lifespan.

Getting the right level of selenium not only boosts your body’s ability to fight pathogens, it also prevents the risk of infection that can occur when you’re deficient in this mineral.

Reduces Oxidative Stress

Selenium is an antioxidant, meaning it combats free radicals. Although free radicals are essential for health and are naturally occurring in the body, too many causes an unhealthy imbalance. Risk factors, such as drinking alcohol and smoking, can cause free radicals to increase, weakening your body's ability to stop them. An overabundance of free radicals causes oxidative stress.


Oxidative stress damages good cells and has been associated with chronic conditions, like Parkinson's and Alzheimer's diseases, heart disease and cancer.


Antioxidants, like selenium, can help restore oxidative balance. A 2008 study found that selenium increases antioxidant activity in coronary artery patients. Other research shows that a lack of the mineral can lead to the opposite. In one study on how selenium deficiency can impact cells during the flu, the authors found that there was reduced antioxidant activity during infection. Similarly, taking below the daily recommended value can put you at a higher risk for diseases associated with oxidative stress.


The good news is that, at higher levels, Selenium antioxidant boosts immune system function. Taking more than your daily requirement has been shown to help your body resist viral infections. Selenium for immune systems can also allow your body to respond to threats in the most effective way.

Selenium Uses

Thanks to selenium’s immune system benefits, the mineral can also help problems linked to immune function. Some people take a selenium vitamin for underactive thyroid and the problems this condition causes. Others take it to help protect cells from the flu. 

Underactive Thyroid

Selenium deficiency is linked to an underactive thyroid. The thyroid gland produces hormones that control a variety of functions, including your metabolic rate, digestion, brain development, muscles and bones. Several disorders are linked to improper thyroid function. The most common are hyperthyroidism—when too many hormones are being produced—and hypothyroidism—when there’s a lack of hormones. Hypothyroidism (underactive thyroid) causes your body to burn energy slower than normal. This can mean weight gain, fatigue and being overly sensitive to cold.


Iodine is known as a key mineral for a healthy thyroid, but there’s also evidence that selenium plays an important role. When researchers studied people with iodine deficiency, they found that participants also had low selenium levels. Participants with low selenium tended to have enlarged thyroid glands.


Given this information, some people take selenium for thyroid issues. Although the results of studies vary, one study found that when compared to a placebo, selenium improved quality of life in patients with thyroid issues. The biggest selenium health benefit may be for patients who experience complications with their vision due to thyroid issues. When patients took a selenium supplement, their eye health improved by 61% compared to a 36% improvement in the placebo group(2)

Given selenium’s role as a hormone cofactor, people with thyroid imbalances may benefit from increasing their intake of this essential trace mineral.

Cold and Flu

People with nutrient deficiencies or poor diets tend to get sick more often. While proper nutrition is vital for preventing viral infections, there’s some evidence that selenium supplements specifically may help protect you against a cold or flu.


Research has found that in healthy adults, supplementing with selenium helped the immune system defend against the flu virus. Other research found that people aged 50-64 took supplements with selenium and, as a result, had increased T-cell levels after a flu shot(5).


Another study looked at combining selenium with zinc. They found that zinc and selenium for immune system function seemed to protect elderly people against colds and respiratory tract infections. After being given a flu shot, researchers noted the combination created more antibodies, and the number of infections was considerably lower when compared to those who received only a vaccine. Since nutrient deficiencies are common in elderly people, the supplement is thought to help provide nutritional balance and strengthen the immune system.


Researchers also note that it's possible selenium supplementation can also have negative effects on cell immunity. Because of that, people who are especially susceptible to the flu should consult their doctor and weigh the potential benefits against the possible risk.

Selenium in Summary

Selenium and the immune system are closely linked. For that reason, the mineral may help prevent or treat a variety of issues. Selenium benefits immune cells by encouraging their production. Since it’s an antioxidant, selenium plays a role in balancing free radicals. These advantages extend to people with an underactive thyroid or for those who just want a little extra help preventing a common cold.




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