Reduced risk of heart disease and reduced risk of some cancers. Increasing the daily intake of selenium among individuals with low selenium status may reduce the risk of cardiovascular disease and some cancers. The available data seem to show that most adults in the Nordic and Baltic countries, with the exception of adults in Finland, have low selenium intakes and low selenium status [Alexander & Olsen 2023].
Selenium is an essential trace element. The human body cannot synthesize it. It must come from the diet and supplements. Selenium is a vital component of selenoproteins that are critical to normal health and physiological functioning. This is the fundamental message from a 2023 selenium scoping review conducted for the Nordic Nutritional Recommendations 2023 [Alexander & Olsen 2023].
Selenium is needed for the synthesis and maintenance of the 25 known selenoproteins. These selenoproteins have numerous biological functions in the body. Prominent among these biological functions are antioxidant activity and regulation of thyroid hormones [Alexander & Olsen 2023].
Selenium intakes and selenium status
The content of selenium in food varies with the richness or poorness of the selenium content of soil. Consequently, the selenium content of crops and fruits is low in selenium-poor regions of the world. In most of the Nordic and Baltic countries, the soil selenium content is poor. Selenium intakes from food are low [Alexander & Olsen 2023].
Selenium intake from food in the Nordic and Baltic countries ranges from 39 to 88 mcg/day in men and 22 to 68 mcg/day in women [Alexander & Olsen 2023]. Men and women in Finland have the highest selenium intakes. The explanation is that Finland has added selenium to soil fertilizers [Alfthan 2015].
In Finland with its selenium-enriched soil fertilizer, the intake of 88 mcg selenium/day in men and 68 mcg selenium/day in women has yielded an average selenium concentration in plasma of 110 mcg/L [Alexander & Olsen 2023].
Larsen et al have estimated that a selenium intake of 100 mcg/day is needed to raise and maintain serum selenium concentrations in the range 120-130 mcg/L [Larsen 2024].
Note that the European Food Safety Authority (EFSA) has established the
upper tolerable level in adults to be of 255 mcg selenium/day [EFSA 2023].
Selenoprotein P as a biomarker of selenium status
The three most commonly measured bio-markers of selenium status are the concentrations of total selenium, selenoprotein P, and glutathione peroxidase 3 in plasma or serum. The three blood bio-markers have shown a positive correlation. Prediction of mortality in breast cancer patients based on all three bio-markers gave a truer result than did prediction based on tumor histologic grade, tumor size, and number of involved lymph nodes [Demircan 2021].
Given selenoprotein P’s role in the regulation and transport of selenium in the body and given its response to selenium intake, the concentration of selenoprotein P measured in plasma or serum is considered the single most informative biomarker of selenium status. Maximum expression of selenoprotein P in plasma or serum is thought to occur at a level consistent with plasma/serum selenium concentrations of 120-130 mcg/L [Larsen 2024]. Maximum expression of selenoprotein P, then, represents adequate
supply of selenium to all tissues and a saturation of the “regulated body pool of selenium” [Alexander & Olsen 2023].
It is not known whether the maximized expression of selenoprotein P yields optimal health benefits. What has been shown, however, is that the plasma/serum level of selenium below which selenium concentration is inversely correlated with the risk of disease and mortality is 100 mcg/L [Bomer 2020; al-Mubarak 2021, 2022].
Low selenium status and degenerative disease risk
In individuals with low selenium status but not in selenium-replete individuals, the available clinical evidence indicates that increased selenium intake may reduce the risk of cardiovascular disease [Kuria 2021] and the risk of some cancers [Kuria 2020].
Most studies of the effect of selenium supplementation on health outcomes have been carried out in selenium-replete individuals. Not surprisingly, these studies show no beneficial effect. That should not be expected. However, some selenium supplementation studies that have been conducted in individuals with low selenium status have shown beneficial health outcomes [Alexander & Olsen 2023].
Conclusions: Heart disease and cancer in individuals with low selenium intakes and status
Needed are studies to address the following questions:
- To what extent does the daily requirement for selenium depend upon body size? How many micrograms of selenium per kilogram of body weight are optimal?
- Which intake forms of selenium achieve optimal serum/plasma selenium concentrations and improved health outcomes?
- What are the long-term outcomes of selenium supplementation in adults with a selenium status less than 45 mcg/L? Less than 70 mcg/L? Less than 100 mcg/L?
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The information presented in this review article is not intended as medical advice and should not be used as such.
28 February 2024