Selenium is an antioxidant rich essential trace mineral that works in conjunction with other enzymes and proteins in the body (known as selenoproteins), which are involved in many antioxidant enzyme pathways. It is estimated that up to one billion people worldwide suffer from selenium deficiency. Selenium can be found in vary concentration in soil and naturally found in foods such as brazil nuts, garlic and tuna.
Selenium is nutritionally essential for humans and plays a role in more than two dozen selenoproteins, which are critical for reproduction, thyroid hormone metabolism, DNA synthesis and protection from oxidative and free radical damage.
Selenoprotein S, in particular, is involved in the protection against cellular stress and regulating the release of pro-inflammatory cytokine release. Having adequate selenium levels is essential for not only proper immune function, but also for regulating excessive immune response (found at the root cause of several autoimmune disease), chronic inflammation and protecting cells against free radical damage.
Signs of Deficiency
Analysis from the National Health and Nutrition Examination Study found that the average daily selenium intake in Americans aged 2 years and older from foods was roughly 100 mcg and 210 mcg from both food and supplements, concluding that most Americans consume adequate amounts of selenium.
Deficiencies of selenium is higher for people living in selenium deficient regions, which would include countries whose diets consist of vegetables grown in low-selenium soils, such as China. People who are undergoing kidney dialysis, those with HIV, autoimmune issues and cancer are at a higher risk of being deficient in selenium.
Signs of deficiency would include a decline in cognitive health, thyroid functioning and immune health, as well as heart disease and infertility. A blood test would be the best marker for showing deficient levels throughout the body.
10 Health Benefits
Immune Support—Selenium is widely known for its immune stimulating properties, which has made it an immune system superstar! Selenoproteins exert strong antioxidant effects throughout the entire body and can help to recycle vitamin C in the body, which can improve overall cellular, metabolic and immune function. Selenium also creates glutathione, the body’s master antioxidant, which can also support detoxification pathways, such as the liver.
Cancer Support—More and more research is coming out about selenium’s role in its ability to have anti-cancer effects, due largely in part to its antioxidant properties and its ability to support overall immune function. Selenium was actually first discovered to be related to cancer through its correlational research, which found higher cancer rates in areas with lower crop selenium content.
In 2015, research that was published in the International Journal of Cancer found that higher selenium levels were linked to a lower risk of colorectal cancer, particularly in women. While in a 2016 meta-analysis of 69 studies research found that high amounts of selenium (from food but not from supplements) had a protective effect on overall cancer risk and decreased the risk of breast, lung, gastric, esophageal and prostate cancer. Selenoprotein P being associated with both colorectal adenoma and prostate cancer, while Selenoprotein 15 has been associated with head, neck, breast and lung cancer.
Thyroid Support—Selenium is required for the proper functioning of the thyroid hormone and plays a major role in converting T4 to T3, which is the active thyroid hormone in the body. The body has receptors for thyroid hormones in almost every single cell, and thyroid health is required for metabolic health, ovarian health, libido and fertility. Selenium can also protect the thyroid against antibodies, which can create thyroid disease such as Hashimoto’s.
Antioxidant Support—Selenium forms a part of some anti-oxidant enzymes, such as glutathione, which is one of our body’s main antioxidants, which helps to recycle other antioxidants in the body. Selenium also helps to maximize the activity of glutathione peroxidase (GPx), which is a natural antioxidant that helps to protect cells from oxidative damage and helps the body naturally repair itself.
Cardiovascular Support—Increased production of reactive oxygen species (ROS) can cause damage to cellular lipids, proteins and DNAs, which has been linked to heart disease. Having high levels of ROS can cause the oxidation of LDL particles, which has been associated with a threefold increase in the development of Heart Disease. Selenium has been found to reduce the production of oxidized LDL particles and regulate blood plasma levels of cholesterol.
Asthma Support—Several observational studies have shown patients who have chronic asthma may also have lower levels of selenium. When people with asthma took selenium in a supplement form that experienced less asthma related symptoms, compared to those taking a placebo. This could be due to the fact that selenium levels can influence the release of various pro-inflammatory cytokines as well as boost overall immune function.
Fertility Support—Selenium is required for sperm health and motility and can be useful in increasing blood flow, all important aspects of conception. Selenium is actually incorporated in the sperms mitochondria and can affect its ability to move through the vaginal canal. There is even some research that shows having higher levels of selenium can reduce the risk of miscarriage, but the research is more focused on the infertility regarding men.
Bacterial and Viral Support—Many viral and bacterial infections are associated with micronutrient deficiencies, such as selenium. Supplementing with selenium has been shown to benefit those suffering from HIV and Influenza A virus infection, as selenium can help support the overall function of the innate and adaptive immune system, or the immediate term and long term immune system. Selenoproteins can regulate overall inflammation and immunity.
Oxidative Damage Support—Selenium plays a role in redux reactions in the body, which is a chemical reaction in the body that is important in regulating oxidative processes and oxidative damage to cells. Selenium has also been shown to play a role in cell proliferation and apoptosis, or programmed cell death. Selenoproteins (proteins with selenium in them) help to protect against endoplasmic reticulum (a network of organelles found in cells) stress and regulate the release of pro-inflammatory cytokine release.
Dietary Insurance—Eating foods rich in selenium can support overall health, as many of the foods that contain selenium are also rich in other critical vitamins and nutrients, such as B12, iron, zinc, B6 and various antioxidants such as C and E. This can be a nice way to give yourself some dietary insurance, while navigating your health journey!
How to Choose a Selenium Supplement and Dosage
Selenium exists mainly in two forms, inorganic (selenate and selenite) and organic (selenomethionine and selenocysteine). Generally soils contain the inorganic form. Most of the selenium that is found in the human tissues is in the selenomethionine form. The body stores most of its selenium in the skeletal muscles (roughly 28 percent-46 percent) of total selenium.
The main active dietary form is selenomethionine. General intake of selenium when it comes to supplement form ranges in the dosage of 200-300 mg daily. You can find selenium in a multivitamin form, as well as a standalone supplement. Research has shown that the human body absorbs more than 90 percent of selenomethionine.
Brianna Diorio is a clinical nutritionist with an MS in human nutrition. She is also a holistic lifestyle coach and NASM CPT. Diorio advocates a holistic and naturopathic approach toward health and wellness, placing importance on proper digestive health, gluten-free living, herbal supplementation and using food as functional medicine as information for our cells. She is the director of training and education at Vitamer Laboratories in Irvine, CA.