Antioxidants like selenium help reduce oxidative stress by keeping free radical numbers in check (7Trusted Source). Selenium is a powerful antioxidant that fights oxidative stress and helps defend your body from chronic conditions, such as heart disease and cancer. In addition to decreasing oxidative stress, selenium may help lower the risk of certain cancers. This has been attributed to selenium’s ability to reduce DNA damage and oxidative stress, boost your immune system, and destroy cancer cells (8Trusted Source).
A review of 69 studies that included over 350,000 people found that having a high blood level of selenium was associated with a lower risk of certain types of cancer, including breast, lung, colon, and prostate cancers (9Trusted Source). For example, one study found that oral selenium supplements improved overall quality of life and reduced radiation-induced diarrhea in women with cervical and uterine cancer (10Trusted Source). Higher blood levels of selenium may protect against certain cancers, while supplementing with selenium may help improve quality of life in people undergoing radiation therapy. A diet rich in selenium may help keep your heart healthy, as low selenium levels have been linked to an increased risk of heart disease. In an analysis of 25 observational studies, a 50% increase in blood selenium levels was associated with a 24% reduction in the risk of heart disease (11Trusted Source).
Selenium may also lower markers of inflammation in your body — one of the main risk factors for heart disease. For example, a review of 16 controlled studies including over 433,000 people with heart disease showed that taking selenium supplements decreased levels of the inflammatory marker C-reactive protein (CRP). This indicates that selenium may help lower heart disease risk by reducing inflammation and oxidative stress in your body. Selenium may help keep your heart healthy by keeping oxidative stress in check and reducing your risk of heart disease.
Several studies have shown that patients with Alzheimer’s disease have lower blood levels of selenium (15Trusted Source, 16). A diet rich in selenium may help prevent mental decline and improve memory loss in people with Alzheimer’s disease.
In fact, thyroid tissue contains a higher amount of selenium than any other organ in the human body (21Trusted Source). Selenium deficiency has been associated with thyroid conditions like Hashimoto’s thyroiditis, a type of hypothyroidism in which the immune system attacks the thyroid gland. An observational study including over 6,000 people found that low serum levels of selenium were associated with an increased risk of autoimmune thyroiditis and hypothyroidism (23).
Additionally, some studies have shown that selenium supplements may benefit people with Hashimoto’s disease. Selenium protects the thyroid gland from oxidative stress and is necessary for thyroid hormone production. Selenium may help people with Hashimoto’s disease and other types of thyroid disease, but more research is needed.
Additionally, selenium supplements may help strengthen the immune system in people with influenza, tuberculosis, and hepatitis C (27Trusted Source). Higher levels of selenium may help boost the immune systems of people with HIV, influenza, tuberculosis, and hepatitis C.
Due to selenium’s ability to reduce inflammation, some studies suggest that this mineral may help reduce asthma-related symptoms. In fact, one study showed that asthmatic patients with higher levels of blood selenium had better lung function than those with lower levels (30Trusted Source). For example, one study found that giving people with asthma 200 mcg of selenium per day reduced their use of the corticosteroid medications used to control their symptoms (31Trusted Source).
The amount of selenium in plant-based foods varies depending on the selenium content of the soil in which they were grown.
What’s more, selenium may help boost your immune system, slow age-related mental decline, and even reduce your risk of heart disease.Sources of Selenium