Maintaining adequate selenium status is an acknowledged anti-aging strategy. We need selenium to live longer and to be healthier as we age. Adequate intakes of selenium and adequate bio-synthesis of selenoproteins contribute to healthy aging and to reduced vulnerability to various disorders. Selenium and selenoproteins are important for the following biological activity [Bjorklund 2022]:
- antioxidant protection
- enhancement of immune system function
- metabolic homeostasis
One characteristic of aging is oxidative stress.
Oxidative stress is defined as an imbalance between the damage caused by harmful free radicals and the protection offered by antioxidants. Inadequate selenium status can reduce the longevity and the health of senior citizens by accelerating the aging process and/or increasing vulnerability to immune system dysfunction, cardiovascular disease, and cancer [Bjorklund 2022].
Much of Europe and the Middle East is known to have selenium-poor soil and selenium-poor foodstuffs [Stoffaneller & Morse 2015]. An optimal dietary and supplemental intake of selenium will raise serum selenium status to about 125 mcg/L [Winther 2020].
Defense Against Harmful Free Radicals
Bjorklund et al [2022] list several potential causes of an overproduction of free radicals:
- By-products of metabolized drugs
- Cellular respiration
- Environmental pollutants
- Metal ions
- Radiation
- Strenuous exercise
Note: Not all free radicals are harmful. Some free radicals are necessary for cell signaling purposes. However, excessive production of free radicals – called reactive oxygen species – can result in oxidative damage to lipids, nucleic acids, and proteins. This oxidative damage, in turn, provides an environment in which age-related diseases can develop more readily.
In such cases, the defense mechanisms of the immune system need help from dietary antioxidants. Supplementation with selenium in selenium-poor regions is important in this regard [Bjorklund 2022]. A comparative study has showed that an organic selenium yeast product is more effective at reducing oxidative stress than a pure selenomethionine product is [Richie 2014].
Antioxidant Effects of Selenoproteins
The selenium-dependent glutathione peroxidases and thioredoxin reductases suppress oxidative stress and detoxify harmful free radicals. Bjorklund et al cite a review by Avery and Hoffmann who conclude that selenium deficiency can cause immune dysfunction and increase vulnerability to pathogens and to the development of cancer [Avery & Hoffmann 2018].
Beck et al [2004] have shown that deficient selenium intake and status can adversely influence not only the immune response to pathogens but can also influence the virulence of pathogenic viruses. Beck suggested that adequate nutrition of the population, especially adequate selenium intake, is an important form of protection against the emergence of new viral pathogens.
Selenium Supplementation and Elderly Swedish Citizens
Sweden is in one of the selenium-poor regions of the world. An evaluation of healthy elderly Swedish citizens, average age 78 years, revealed two important facts [Alehagen 2016]:
- The elderly Swedish citizens had a low mean serum selenium concentration of 67 mcg/L. The rate of death from heart disease was higher in the subgroup with lower selenium concentrations (less than 65 mcg/L). The rate of death from heart disease was lower in the subgroup having a selenium concentration greater than 85 mcg/L.
- In the subgroup with low selenium levels (less than 65 mcg/L), combined selenium and Coenzyme Q10 supplementation significantly reduced the rate of death from heart disease. By comparison, the effect of the supplementation was statistically significant in the subgroup with selenium levels above 85 mcg/L.
In a review article, Alehagen et al show that selenium has antioxidant, anti-inflammatory, and immune stimulating properties {Alehagen 2021].
Recommended Selenium Intake and Upper Limit
Selenoprotein P in plasma represents a saturable pool of selenium and is maximized at a plasma selenium concentration of about 110 mcg/L or at an intake of about 1.2 mcg/kg body weight. The Nordic Nutrition Recommendations 2023 set the Adequate Intake at 75 mcg/day (females) and 90 mcg/day (males) [Blomhoff 2023].
At intakes above 330 to 450 mcg/day, selenium may cause toxic effects affecting liver, peripheral nerves, skin, nails, and hair. The Nordic Nutrition Recommendations 2023 have adopted EFSA’s Upper Limit of 255 mcg/day [Blomhoff 2023; EFSA 2023].
Conclusion: Selenium Deficiency and Aging and Disease
Oxidative damage to DNA, lipids, and proteins in the human body creates a suitable environment for the development of age-related diseases.
Selenium incorporated into selenoproteins improves antioxidant defense, immune function, and metabolic homeostasis.
The health effect of dietary and supplemental selenium are dose-dependent.
There is a relatively narrow margin between the essential intake levels of selenium and the intake levels that are potentially toxic.
Sources
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Richie JP Jr, Das A, Calcagnotto AM, Sinha R, Neidig W, Liao J, Lengerich EJ, Berg A, Hartman TJ, Ciccarella A, Baker A, Kaag MG, Goodin S, DiPaola RS, El-Bayoumy K. Comparative effects of two different forms of selenium on oxidative stress biomarkers in healthy men: a randomized clinical trial. Cancer Prev Res (Phila). 2014 Aug;7(8):796-804.
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The information presented in this review article is not intended as medical advice and should not be used as such.
30 October 2023