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What Is Selenium And What Affects Does It Have On My Health?

Selenium is a great antioxidant. Antioxidants keep free radicals in check within the body and reduce inflammation, which is important because an excess number of free radicals and inflammation can lead to Alzheimer’s disease, thyroid problems, immune system issues, heart disease, and cancer. Selenium also protects DNA and bolsters the immune system. Interestingly, selenium has been found to decrease the likelihood of Alzheimer’s disease and increase mental functioning in people that have already undergone some mental degeneration. Lastly, selenium has been found to reduce symptoms within Asthmatic people as well [1][3].

Supplementing selenium has less dramatic benefits but has been found to help bolster some cancer patient’s gastrointestinal functioning, specifically those who are undergoing radiation for cervical and uterine cancer. Additionally, supplementing selenium can aid the immune function of HIV positive individuals and help people with thyroid issues. It is important to note, that a study done by Jenkins, Kitts, Giovannucci, etc. (2020) found that selenium supplements were only effective at reducing health risks when working as an additive to other antioxidant supplements, like vitamin E and C [1][2].

Selenium deficiencies are often uncommon in people in the US, because North America typically has selenium rich soil. People at the highest risk of having a selenium deficiency, who are living in the US, are people with HIV and people that are currently undergoing dialysis. This is because people with HIV have difficulty absorbing nutrients and people undergoing dialysis tend to have some selenium filtered out of their blood [1].

Selenium is a very potent nutrient that can be found within oysters, brazil nuts, halibut, yellowfin tuna, eggs, red meat, sardines, sunflower seed, chicken breast, and shiitake mushrooms; There is often even selenium in fortified breads and cereals. Mediterranean people have an increased amount of selenium in their blood opposed to other regions, thus following a Mediterranean diet has been found to be very beneficial for the body. You can take selenium supplements, as aforementioned, but you should first get approval from your doctor [1][3].

Selenium, thus far, sounds like a miracle mineral that everyone should consume as much as they possibly can, but selenium toxicity is very dangerous and can be lethal. Only about 55 micrograms (mcg) of selenium should be consumed a day, and only 400 mcg of selenium can be tolerated within the body before it reaches toxic levels. Selenium toxicity is commonly caused by Selenium supplements, and not often due to the consumption of selenium in food, but it is important to note that only 3 ounces of oysters has 238% of your daily value of selenium, one brazil nut has 174% of your daily value, and 6 ounces of halibut has 171% of your daily value. So, a single brazil nut can provide you with all the selenium you need in a day and then some [1][3].

[1] Harvard T.H. Chan: The Nutrition Source. (2021). Retrieved from

[2] Jenkins, D. Kitts, D. and Giovannucci, E. etc. (2020). Selenium, antioxidants, cardiovascular disease, and all-cause mortality: a systematic review and meta-analysis of randomized controlled trials. The American Journal of Clinical Nutrition.

[3] Kubala, Jillian. (2019). 7 science-based health benefits of selenium. Healthline. Retrieved from

Blog Contributors

Author- Katrina Peavy

Editor- Sophia Galvez

Public Health Scientist- Hira Mughal


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