In an online article in the Cleveland Clinic’s Health Essentials series, the registered dietician Kayla Kopp explains that selenium is an essential trace element that helps thyroid gland function and reproductive function, among other health benefits [Cleveland Clinic 2023].
What does it mean that selenium is an essential trace element? Answer: our bodies need adequate selenium to function well. However, our bodies cannot synthesize selenium. We have to get our selenium from our food.
What are the health benefits of adequate selenium intake and adequate selenium status? Answer: Kopp says that selenium is important for the following reasons [Cleveland Clinic 2023]:
- helps to protect our cells from damage
- promotes good thyroid function
- promotes good reproductive function
- plays a role in DNA synthesis
Selenium Supports Thyroid Health
The thyroid gland is responsible for producing and releasing the hormones that control our metabolism. The metabolism rate is what determines how rapidly or slowly our bodies convert food into energy. The selenium we absorb from our food or from supplements gets converted into selenoproteins. These selenoproteins then help to regulate our thyroid hormones [Cleveland Clinic 2023].
Selenium Protects Reproductive Health
Unstable molecules called free radicals cause damage to our cells and our DNA. Not all free radicals are harmful, but too many free radicals cause a condition known as oxidative stress. Oxidative damage contributes to infertility.
Selenium in the form of selenoproteins protects against oxidation damage and infection. There is some evidence from clinical research that selenium supplementation may be beneficial in people who are trying to conceive, according to dietician Kopp [Cleveland Clinic 2023].
Selenium for Asthma Management
Dietician Kopp also mentions that selenium could play a role in managing chronic asthma. She points to the antioxidant role of selenoproteins in reducing oxidative stress in lung tissue. However, the possible benefit of selenium supplementation in the management of asthma has not yet been conclusively demonstrated [Cleveland Clinic 2023].
Selenium May Protect Against Cancer
Some studies have shown that lower selenium intakes have been associated with increased risk of certain forms of cancer. One possible explanation is that we need selenium to repair DNA damage. The Cleveland Clinic Staff writers specifically mention the following forms of cancer for which an inverse relationship with selenium intake and status has been seen:
- Breast cancer
- Esophageal cancer.
- Gastric cancer
- Lung cancer
- Prostate cancer
Note that the KiSel-10 Study conducted by Prof. Urban Alehagen et al has shown that daily selenium supplementation of elderly individuals with low selenium status also reduces the risk of cardiovascular disease [Alehagen 2013].
Selenium Intake and Status
The Cleveland Clinic article makes the point that we definitely need sufficient selenium for good health but that we do not need too much of it.
In a 2021 review article, Professor Lutz Schomburg, Charité Berlin, finds it “unfortunate that the health risks of selenium deficiency are often
neglected while the possible side effects of selenium supplementation are exaggerated, leading to a disregard for this safe and promising preventive and adjuvant treatment option.”
Where one lives affects the need for selenium supplementation. It is estimated that the selenium status in the selenium-poor regions of
Europe is 80–90 mcg/L, on average. In the USA with its many selenium-rich regions, the estimated selenium status, on average, is greater than 120 mcg/L [Alehagen 2024].
What do these numbers mean?
Optimal serum selenium levels
Larsen et al maintain that the serum selenium concentration should be in the range of 120-130 mcg/L to optimize the concentration of selenoprotein P. Selenoprotein P is the primary transporter of selenium in the blood circulation. It is one of the most valid biomarkers of the selenium status. To
reach the selenoprotein P level of 120-130 mcg/L, it is estimated that a daily selenium intake of at least 100 mcg is required [Larsen 2024].
Selenium deficiency and sub-optimal serum selenium levels
Al-Mubarak, van der Meer, and Bomer have defined serum selenium concentrations below 70 mcg/L as deficiency levels. They have noted that serum selenium concentrations below 100 mcg/L are sub-optimal levels [Al-Mubarak 2021].
Tolerable upper intake levels
In 2023, EFSA established the tolerable upper intake level for selenium at 255 mcg/day. That amount includes dietary and supplemental selenium intakes.
Conclusion: Selenium is an Essential Trace Element
An article on the Cleveland Clinic website makes clear that we need steady daily intakes of selenium, in our food and, where necessary, from supplements.
According to the Cleveland Clinic Staff writers, adequate selenium intakes are needed to promote good thyroid gland health and good reproductive function. Moreover, sufficient selenium status may improve the management of chronic asthma and may help to prevent the development and progression of certain forms of cancer.
Sources
Alehagen U, Alexander J, Aaseth JO, Larsson A, Opstad TB. Supplementation with selenium and coenzyme Q10 in an elderly Swedish population low in selenium – positive effects on thyroid hormones, cardiovascular mortality, and quality of life. BMC Med. 2024 May 7;22(1):191.
Alehagen U, Johansson P, Björnstedt M, Rosén A, Dahlström U. Cardiovascular mortality and N-terminal-proBNP reduced after combined selenium and coenzyme Q10 supplementation: a 5-year prospective randomized double-blind placebo-controlled trial among elderly Swedish citizens. Int J Cardiol. 2013 Sep 1;167(5):1860-6.
Al-Mubarak AA, van der Meer P, Bomer N. Selenium, selenoproteins, and heart failure: current knowledge and future perspective. Curr Heart Fail Rep. 2021 Jun;18(3):122-131.
Cleveland Clinic Staff. What Selenium Is and Why You Need It (But Not Too Much of It). 31 May 2023. Retrieved from
https://health.clevelandclinic.org/selenium-benefits
EFSA Panel on Nutrition, Novel Foods and Food Allergens. Scientific opinion on the tolerable upper intake level for selenium. EFSA J. 2023 Jan 20;21(1):e07704.
Hurst R, Armah CN, Dainty JR, Hart DJ, Teucher B, Goldson AJ, Broadley MR, Motley AK, Fairweather-Tait SJ. Establishing optimal selenium status: results of a randomized, double-blind, placebo-controlled trial. Am J Clin Nutr. 2010 Apr;91(4):923-31.
Larsen C, Winther KH, Cramon PK, Rasmussen ÅK, Feldt-Rasmusssen U, Knudsen NJ, Bjorner JB, Schomburg L, Demircan K, Chillon TS, Gram J, Hansen SG, Brandt F, Nygaard B, Watt T, Hegedus L, Bonnema SJ. Selenium supplementation and placebo are equally effective in improving quality of life in patients with hypothyroidism. Eur Thyroid J. 2024 Jan 1;13(1):e230175.
Schomburg L. Selenium deficiency due to diet, pregnancy, severe illness, or covid-19-a preventable trigger for autoimmune disease. Int J Mol Sci. 2021 Aug 8;22(16):8532.
The information presented in this review article is not intended as medical advice. It should not be used as such.