Selenium is an essential trace mineral that functions as an antioxidant in the body, meaning it helps protect cells from damage caused by free radicals. Free radicals are unstable molecules that can damage cells and contribute to the development of chronic diseases like cancer, heart disease, and Alzheimer’s disease.

Selenium helps prevent damage caused by free radicals by participating in the body’s antioxidant defense system. Specifically, selenium is a component of an enzyme called glutathione peroxidase, which helps break down harmful hydrogen peroxide and lipid peroxides in the body.

Additionally, selenium can stimulate the production of other antioxidant enzymes and molecules, including superoxide dismutase and catalase, which work together to neutralize free radicals.

Studies have shown that selenium supplementation can increase the activity of antioxidant enzymes and reduce oxidative stress in the body. For example, a study published in the Journal of Nutrition found that daily supplementation with 200 mcg of selenium for 15 weeks improved antioxidant capacity and reduced levels of oxidative stress markers in the blood of healthy adults.

Selenium is an important mineral for immune system support. It plays a vital role in the function of white blood cells, which are key players in the body’s immune response.

One way that selenium supports the immune system is by enhancing the activity of natural killer cells, which are white blood cells that help identify and destroy infected or cancerous cells in the body. Selenium can also improve the production and activity of other immune cells, such as T cells and B cells.

Additionally, selenium helps regulate the production of cytokines, which are proteins that help coordinate the immune response. Certain cytokines, such as interleukin-2 and interferon-gamma, are important for activating immune cells and promoting an effective immune response.

Selenium deficiency has been associated with increased susceptibility to viral infections, such as HIV, influenza, and the Coxsackie virus, as well as bacterial infections, such as tuberculosis and pneumonia. Studies have shown that selenium supplementation can improve immune function in people with low selenium levels, and may reduce the risk of infections.

For example, a study published in the Journal of Nutrition found that daily supplementation with 200 mcg of selenium for 12 weeks increased the activity of natural killer cells and improved immune function in elderly individuals.

Selenium is important for the proper functioning of the thyroid gland, which is responsible for producing and releasing thyroid hormones. Thyroid hormones play a crucial role in regulating metabolism, growth, and development throughout the body.

Selenium is a component of several enzymes involved in thyroid hormone metabolism. For example, it’s required for the activity of an enzyme called iodothyronine deiodinase, which converts the inactive form of thyroid hormone (T4) to the active form (T3) that can be used by the body.

Studies have shown that selenium deficiency can impair thyroid function and lead to a range of thyroid disorders, such as hypothyroidism (underactive thyroid) and autoimmune thyroiditis (inflammation of the thyroid gland).

In areas where selenium intake is low, such as certain parts of China and Europe, selenium deficiency is a common cause of thyroid disorders. However, studies have also shown that selenium supplementation can improve thyroid function in individuals with low selenium levels.

For example, a study published in the Journal of Clinical Endocrinology and Metabolism found that daily supplementation with 200 mcg of selenium for six months improved thyroid function and reduced levels of thyroid antibodies in women with autoimmune thyroiditis.

Selenium is an important mineral for cognitive function, particularly in older adults. Several studies have suggested that selenium may help improve cognitive function and reduce the risk of cognitive decline.

One way that selenium may help support cognitive function is through its antioxidant properties. As an antioxidant, selenium helps protect cells from oxidative stress, which is a major contributor to age-related cognitive decline. Additionally, selenium can improve the production and activity of antioxidant enzymes, which can further reduce oxidative stress in the brain.

Selenium may also play a role in regulating inflammation, which can contribute to cognitive decline. Studies have shown that selenium supplementation can reduce levels of inflammatory markers in the blood and improve cognitive function in older adults.

For example, a study published in the American Journal of Clinical Nutrition found that daily supplementation with 200 mcg of selenium for six months improved cognitive function and reduced levels of inflammatory markers in older adults.

Additionally, selenium may be important for the prevention of neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. Studies have shown that selenium supplementation can improve cognitive function and reduce the risk of Alzheimer’s disease in individuals with low selenium levels.

Selenium may have several benefits for heart health, including reducing inflammation and improving blood vessel function.

One way that selenium may help support heart health is through its antioxidant properties. As an antioxidant, selenium helps protect cells from oxidative stress, which can contribute to the development of heart disease. Additionally, selenium can improve the production and activity of antioxidant enzymes, which can further reduce oxidative stress in the body.

Selenium may also help reduce inflammation in the body, which is a risk factor for heart disease. Studies have shown that selenium supplementation can reduce levels of inflammatory markers in the blood and improve markers of endothelial function, which is important for maintaining healthy blood vessel function.

For example, a study published in the Journal of the American Medical Association found that daily supplementation with 200 mcg of selenium for 5 years reduced the risk of cardiovascular disease in individuals with low selenium levels.

Additionally, some studies suggest that selenium may have a protective effect against certain types of heart disease, such as atherosclerosis and heart failure. However, more research is needed to fully understand the role of selenium in preventing heart disease.

Selenium has been studied for its potential role in cancer prevention, particularly for certain types of cancer such as prostate, lung, and colorectal cancer. The mechanisms by which selenium may help prevent cancer are not fully understood, but it is believed to be related to its antioxidant and anti-inflammatory properties, as well as its role in DNA repair and cell growth regulation.

Selenium is an essential component of several antioxidant enzymes, including glutathione peroxidase, which helps protect cells from oxidative damage caused by free radicals. Oxidative damage to cells is believed to be a key contributor to the development of cancer.

Selenium may also help regulate inflammation in the body, which can contribute to the development and progression of cancer. Studies have shown that selenium supplementation can reduce levels of inflammatory markers in the blood and improve markers of immune function.

Additionally, selenium may play a role in DNA repair and cell growth regulation, which are important processes for preventing the development of cancer. Studies have shown that selenium can regulate the expression of certain genes involved in these processes, and may help prevent the formation of cancerous cells.

For example, a large-scale study called the Nutritional Prevention of Cancer Trial (NPC) found that daily supplementation with 200 mcg of selenium for 7 years reduced the risk of prostate cancer by 63% in men with low selenium levels.

However, it’s important to note that not all studies have found a significant association between selenium supplementation and cancer prevention, and some studies have even suggested that high levels of selenium intake may increase the risk of certain types of cancer.

Selenium plays an important role in reproductive health, particularly in men. Selenium is necessary for the production and function of sperm, and low selenium levels have been associated with impaired fertility and an increased risk of birth defects.

Selenium is a component of several enzymes involved in sperm production and function. For example, it’s required for the activity of an enzyme called glutathione peroxidase, which helps protect sperm from oxidative damage caused by free radicals. Selenium also plays a role in the metabolism of testosterone, which is important for male fertility.

Studies have shown that selenium supplementation can improve sperm motility and reduce the risk of birth defects. For example, a study published in the Journal of Andrology found that daily supplementation with 200 mcg of selenium for 26 weeks improved sperm motility and reduced DNA damage in infertile men.

Additionally, some studies suggest that selenium may have a protective effect against prostate cancer, which is the most common cancer among men. Selenium may help prevent the development of prostate cancer by reducing oxidative stress and inflammation in the prostate gland.

When the body has excess amounts of selenium, it stores the mineral primarily in the liver, kidneys, and muscles. However, if selenium intake continues to exceed the body’s needs over a long period of time, it can lead to a condition called selenosis, which can cause a range of symptoms and health problems.

The body has a limited capacity to excrete excess selenium, and it’s mainly eliminated through urine and feces. However, this process is not very efficient, and excess selenium can accumulate in the body’s tissues over time.

In cases of acute selenium toxicity, such as accidental ingestion of high doses of selenium supplements or industrial exposure to selenium, the excess selenium can cause more immediate and severe symptoms, including gastrointestinal upset, respiratory distress, and neurological symptoms.

Selenium works in conjunction with several other nutrients in the body, including:

1. Vitamin E: Vitamin E is a powerful antioxidant that works synergistically with selenium to protect cells from oxidative damage caused by free radicals.
2. Vitamin C: Vitamin C is another antioxidant that can enhance the activity of selenium-containing enzymes in the body.
3. Zinc: Zinc is necessary for the production of the enzyme that converts inactive thyroid hormone to its active form, which requires selenium.
4. Vitamin D: Vitamin D is important for the regulation of calcium and bone metabolism, and studies have shown that adequate levels of selenium may enhance the effect of vitamin D on bone health.
5. Omega-3 fatty acids: Omega-3 fatty acids, found in fish and certain nuts and seeds, can enhance the activity of selenium-containing enzymes involved in inflammation and oxidative stress.
6. Iron: Iron is necessary for the production of red blood cells and immune function, and studies have shown that selenium may enhance the absorption of iron from plant sources.

While selenium is an essential nutrient for the body, excessive intake of selenium can be toxic and cause a range of symptoms and health problems. However, it’s rare for the body to be unable to break down selenium, as the body has several mechanisms in place to regulate selenium levels and excrete excess selenium.

One possible reason for selenium toxicity is excessive selenium intake from supplements. Supplements can contain high doses of selenium, and taking too much selenium from supplements can lead to toxicity.

Another possible reason for selenium toxicity is exposure to high levels of selenium in the environment. For example, selenium levels in soil and water can vary widely depending on geological factors, and some areas may have higher levels of selenium than others. People living in areas with high levels of selenium may be at higher risk of selenium toxicity.