Top 9 Selenium Benefits to Improve Health & Well-Being

Selenium Benefits Overview

What Is Selenium?

Selenium is an essential micronutrient that the body needs in small quantities. It is naturally found in many foods, with Brazil nuts being the richest source of dietary selenium. It is also available as a selenium supplement. 

Selenium is needed to make compounds called selenoproteins in the body. Selenoproteins, such as glutathione peroxidase and thioredoxin reductase, play a vital role in human health, including DNA synthesis, thyroid hormone metabolism, protection from oxidative stress and infections, and reproduction. The liver regulates selenium metabolism in the body.

Selenium Health Benefits: What Does Selenium Do For The Body?

Selenium has antioxidant and anti-inflammatory properties. Research suggests it has many potential health benefits, including: 

• Prevention of cancer and reduction in cancer risk.

• Reduction in cardiovascular risk.

• Reduction in the risk of cognitive decline and Alzheimer’s disease.

• Reduction in the risk of thyroid disease.

• Beneficial effects on reproductive health and fertility.

Antioxidant Properties: What Is The Main Use Of Selenium?

Reactive oxygen species (ROS) and antioxidants are substances in the body that participate in many processes and maintain a balance called the redox balance. Excess levels of either of these substances can be damaging. Excessive ROS can lead to what is called oxidative stress, which results in cell damage and cell death. The damage caused by ROS has been linked to many diseases in the human body, including heart disease and cancer. Excess antioxidants can lead to reductive stress and impaired cellular signaling. 

Antioxidants have the important function of scavenging ROS and helping to maintain healthy cells and tissues. Selenium is a key ingredient in antioxidant selenoproteins that protect the body against oxidative stress caused by excessive amounts of reactive oxygen species (ROS).

Signs of Selenium Deficiency

Selenium deficiency rarely causes obvious health effects or symptoms. However, it can lead to biochemical changes that can increase the risk of certain health conditions. Low plasma selenium levels are linked to the following illnesses: 

• Keshan disease, which affects the heart muscle in women of childbearing age and young children. This condition is rare after scientists discovered that taking selenium supplements can reduce the risk by nearly 90%. 

• Kashin-Beck disease, a condition that causes inflammation of the joints, most commonly in children and adolescents. 

• Worsening iodine deficiency and hypothyroidism (underactive thyroid) in infants and young children living in regions with very low selenium levels.

Health Effects of Selenium

Cancer Risk and Prevention

Because of its role in DNA repair, antioxidant effects, and support for the immune system, scientists believe selenium plays a role in preventing cancer, reducing cancer risk, and reducing the risk of death from cancer. Selenium supplementation has been extensively studied in prostate cancer, lung cancer, breast cancer, and colorectal cancer.

Cardiovascular Risk

Because selenoproteins have antioxidant and anti-inflammatory properties, these compounds can reduce inflammation and prevent platelet aggregation (when small blood cells stick together to form a clot) and lipid oxidation (when fat reacts with oxygen and breaks down). Research suggests selenium supplements reduce the risk of cardiovascular disease and all-cause cardiovascular mortality (death related to heart disease). 

Cognitive Function

Studies have found that older adults have lower selenium concentrations in their blood. Research also suggests that chronic selenium deficiency is linked to cognitive decline. In addition, older adults with higher blood selenium levels and higher selenium intake have been found to have better cognitive scores. Scientists, therefore, believe that increasing selenium intake could potentially lower the risk of cognitive decline and neurodegenerative disorders like Alzheimer’s disease.

HIV Infection

In adults and children with HIV infection, selenium deficiency is linked to a greater risk of morbidity and mortality (severe disease and death). However, larger, more comprehensive studies and reviews of clinical trials on whether selenium supplementation can affect disease outcomes in people with HIV have shown mixed results.

Reproductive Health

A selenoprotein called phospholipid hydroperoxide glutathione peroxidase is a key substance found in mature sperm. Research has shown that the lack of nutrients such as selenium, which reduces oxidative stress, may play a role in male infertility. Studies in infertile men suggest that both selenium deficiency and high blood selenium levels can result in male infertility.

In females, higher blood selenium concentrations are linked to improved female fertility, such as a higher number of oocytes and ovarian follicles (immature eggs). Studies also suggest that selenium deficiency could be linked to an increased risk of pregnancy complications such as gestational diabetes, preeclampsia, miscarriage, premature birth, and low birth weight. Taking selenium supplements during pregnancy may potentially lower the risk of these complications in women who are at a higher risk. Prenatal vitamins often include selenium, but review the ingredient list to be sure.

Healthy Thyroid Function

The thyroid gland has one of the highest concentrations of selenium among all the organs in the body. Selenium plays a critical role in thyroid health, including the synthesis and metabolism of thyroid hormones. Selenoproteins are essential in the conversion of the thyroid hormone thyroxine or T4 (which is not very active) into T3 (which is the active form). T3 helps regulate how your body utilizes energy. Additionally, selenoproteins such as thioredoxin reductase and glutathione peroxidase have a protective function for the thyroid gland. 

Researchers have found women with a low selenium level are at a higher risk of thyroid disorders. A randomized controlled trial found many people with chronic autoimmune thyroiditis were selenium-deficient or had a marginal selenium status. But more research is needed to find out if selenium supplements can prevent thyroid disease.

Effects on Immune Function

Selenium plays an important role in inflammation and immunity. Adequate selenium levels in the body are necessary for initiating an immune response and protecting the body against infectious microorganisms. Studies suggest adequate selenium levels are associated with higher amounts of white blood cells (T-cells or lymphocytes). 

In addition, research has found that selenium is involved in regulating the immune response. Selenoproteins prevent an excessive immune response and chronic inflammation, which is linked to a number of chronic health conditions.

Respiratory Health and Lung Function

Selenium has antioxidant effects that protect against oxidative stress. Studies have shown that people with asthma who have a lower amount of selenium in their blood tend to have more severe asthma attacks and more frequent inhaler use. Therefore, taking selenium supplements to raise blood selenium levels could potentially help manage symptoms and reduce respiratory distress in people with asthma. 

Autoimmune Diseases

Studies have found that people with autoimmune disorders such as collagen vascular diseases have lower selenium levels. Moreover, there is an improvement in symptoms of collagen vascular diseases when these individuals are treated with a selenium supplement. 

Researchers believe low levels of selenium may play a role in the development of inflammation and autoimmunity in people with autoimmune conditions. Studies have found that selenium supplementation reduces complications of autoimmune diseases and improves survival rates in people with these conditions. 

Recommended Selenium Intake

How Much Selenium Should You Take?

According to the National Institutes of Health - Office of Dietary Supplements, the recommended dietary allowance for selenium in micrograms (mcg) per day in different age groups is as follows:

• Birth to 6 months: 15 mcg 

• 7 to 12 months: 20 mcg

• 1 to 3 years: 20 mcg

• 4 to 8 years: 30 mcg

• 9 to 13 years: 40 mcg

• 14 to 18 years: 55 mcg

• 19 years and older: 55 mcg

• Pregnancy: 60 mcg

• Lactation: 70 mcg

Who Is At Risk of Selenium Inadequacy?

Selenium deficiency is rare in the United States, and most people consume enough selenium through their diet. The average dietary intake of selenium is 116 mcg per day (from foods, beverages, and supplements such as selenomethionine, selenate, selenite, and selenium yeast), which is well above the recommended dietary allowances for all age groups. However, some people may be at a higher risk of having lower selenium intakes and selenium deficiency, such as:

• People who eat a vegetarian or vegan diet.

• People who live in countries with low selenium exposure due to low soil levels of selenium, such as China, certain parts of Africa, and some European countries.

• People undergoing hemodialysis for kidney failure (selenium is removed from blood during kidney dialysis).

• People living with HIV (due to poor absorption of nutrients from dietary sources).

Tests for Selenium Levels in the Body

Doctors can measure selenium concentrations in plasma, whole blood, hair, and nail samples. Plasma selenium concentrations of 8 mcg/dL or higher are considered healthy and adequate for selenoprotein synthesis in the body. In addition, doctors can measure the levels of the two main selenoproteins (glutathione peroxidase 3 and selenoprotein P) to check a person’s selenium status.

Sources of Selenium

Foods Containing Selenium

Selenium binds to proteins and is, therefore, mainly found in protein-rich foods. Foods rich in selenium include Brazil nuts, seafood, meat, poultry, eggs, grains, and dairy products. The top 5 food selenium-rich foods are as follows:

• 1 ounce Brazil nuts: 544 mcg

• 3 ounces yellowfin tuna: 92 mcg

• 3 ounces canned sardines: 45 mcg

• 3 ounces cooked shrimp: 42 mcg

• 3 ounces pork chop: 37  mcg

Some of the plant-based foods that are selenium-rich include:

• 1 cup baked beans: 13 mcg

• 1 cup cooked oatmeal: 13 mcg

• ½ cup grilled Portobello mushrooms: 13 mcg

• 1 cup brown rice: 12 mcg

• 1 slice whole wheat bread: 8 mcg

• 1 cup low-fat plain yogurt: 8 mcg

Dietary Supplements: Selenium Supplements for Low Selenium Levels

Selenium is available alone or with other dietary supplements and antioxidant vitamins (vitamin C, vitamin E). It is present in many multivitamins and mineral supplements. 

Common forms of selenium in dietary supplements include selenomethionine, sodium selenite, sodium selenate, and selenium-enriched yeast. Most selenium supplements contain a dose of 55 mcg of selenium. The body absorbs about 90% of selenium from supplements. 

Potential Risks And Safety Considerations of High Selenium

Dangers of Excessive Selenium Supplementation

Eating too much selenium (organic and inorganic selenium) from dietary sources or selenium supplements can result in selenosis (selenium toxicity) and serious health risks. Remember, certain selenium-containing foods, such as Brazil nuts, contain a very high amount of selenium (70-90 mcg of selenium per nut). Selenium toxicity can also result from overconsumption of selenium supplements long-term. 

Signs and Symptoms of Excessive Selenium Intake and Selenium Toxicity

Side effects of too much selenium in the body include:

• Garlicky odor to the breath

• Metallic taste in the mouth 

• Hair loss 

• Brittle nails or nail loss

• Skin rash

• Fatigue

• Nausea

• Diarrhea

• Irritability

• Weight loss

Signs and symptoms of acute selenium toxicity include

• Muscle tenderness

• Tremors

• Dizziness or lightheadedness

• Facial flushing

• Severe gastrointestinal symptoms

• Neurological abnormalities

• Acute respiratory distress syndrome

• Myocardial infarction (heart attack)

• Kidney failure

• Heart failure 

• Death 

Who Should Not Take Selenium?

People with the following health conditions should check with their healthcare professional before taking a selenium supplement, either alone or with some other dietary supplement:

• Hypothyroidism (underactive thyroid)

• Skin cancer or high risk of skin cancer

• High cholesterol

• Diabetes

Is It Safe To Take Selenium Every Day?

You should not take selenium supplementation every day without talking to your healthcare provider first. The upper limit for selenium intake for adults is 255 mcg per day, and for children and adolescents, between 70 mcg and 230 mcg per day, depending on age.