Selenium (Se) is an essential trace mineral which is vital for good health. Low selenium is linked to increased risk of mortality, poor immunity, and cognitive problems (1). The benefits of selenium are numerous.

Antioxidant

Se helps fight oxidative stress. Oxidative stress can damage healthy cells and is linked to heart disease, cancer and Alzheimer’s. Se decreases oxidative stress by neutralizing free radicals and protecting cells from the damage they can do (2). Glutathione is a key antioxidant.

Selenium is a glutathione cofactor, needed for glutathione activity. Glutathione is the first enzyme to be affected in the case of selenium deficiency (3).

Immunity

Within the immune system, Se stimulates antibody formation and the activity of T cells and other immune cells. Glutathione is also involved in immune and inflammatory responses, and Se helps promote glutathione activity (4).

Antiviral

One study in China found selenium was significantly higher in surviving COVID-19 inpatients compared with non-survivors.

Low selenium and higher oxidative stress can allow a virus to change from normally mildly pathogenic to highly virulent or damaging once it enters the body.

Se deficiency could be involved in the severity of SARS-CoVid-19. This potential protective effect of selenium is explained by its role in reducing oxidative stress. Selenium supplementation in people with low levels can help reduce viral infections (5).

Anti-inflammatory

A deficiency in selenium is associated with diseases involving chronic inflammation (inflammatory bowel diseases, rheumatoid arthritis and atherosclerosis) (6). Low Se can increase inflammatory cytokine immune cells (7).

In the inflammatory condition SIRS (Systematic Inflammatory Response Syndrome), there is an early decrease in blood levels of Se and reduced glutathione (8).

Genetics

Se affects gene expression related to the modulation of DNA behavior. Se defends against DNA adducts (when DNA becomes stuck to a cancer-causing agent, which could be the start of a cancerous cell), DNA or chromosome breakage, and chromosome gain or loss.

It is protective for mitochondrial DNA and telomere length and function, which are related to aging and longevity (9).

Thyroid

Proper selenium levels are required for a healthy and functional thyroid. The production, secretion, and action of thyroid hormones depend partially on adequate selenium.

Selenium status is lower in benign and malignant thyroid diseases (10). Low Se levels are associated with an increased risk of autoimmune thyroiditis and hypothyroidism (11).

Another benefit of selenium is its use to prevent and treat thyroid diseases including goiter, autoimmune thyroid disease, and thyroid cancer (12).

Cancer

Because Se is so pivotal in DNA health, the immune system, and oxidative stress, it is involved in the prevention of cancer (13). According to research, the risk of cancer was 2–6 times lower in those with high-selenium blood levels compared to those with low levels, or with low selenium intake (14).

High selenium levels have a protective effect on cancer risk, decreasing the risk of breast, lung, esophageal, gastric and prostate cancers (15).

Cardiovascular Disease

Selenium concentrations were significantly lower in patients suffering from heart attacks (16).  There is an inverse relationship between selenium levels and heart disease incidences, particularly in people with low selenium intake or low blood levels (17).

A 50% increase in selenium levels was associated with a 24% decrease in heart disease risk (18). It is believed this is partially due to lower inflammation and oxidative stress associated with selenium.

Exercise

Selenium is found abundantly in the muscles. Intense physical activity increases free radicals and oxidative damage in muscle tissue, and selenium’s antioxidant activity helps combat this oxidative stress (19).

Cognitive Function

Se is important for optimal brain function. Decreased selenium is associated with neurodegenerative diseases like Parkinson’s, Alzheimer’s, and epilepsy. So just one more benefit of selenium is it can protect against and delay the onset of neurodegeneration (20).

Contraindications

Some clinical trials have shown negative effects from too much Se (21). Excess selenium might increase risk of type 2 diabetes. Additional selenium intake helps people with low Se status, but those with adequate-to-high status might be affected adversely and should not take selenium supplements (22).

Foods with Selenium

Dosage

The Recommended Dietary Allowance (RDA) for selenium for adults is 55 mcg per day. Do not exceed 400 mcg per day. People with low Se levels, certain thyroid conditions or other issues may benefit from 200 mcg per day.

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