Data from an observational study done in the United States have shown the following relationships [Reja 2020]:
Higher serum selenium status is correlated with lower risk of advanced liver fibrosis.
The data analyzed in the study came from 33,944 NAFLD patients identified in the Third National Health and Nutrition Examination Survey (NHANES).
On its Selenium: Fact Sheet for Health Professionals website, the US Office of Dietary Supplements, an agency of the National Institutes of Health, writes that selenium might play a role in the prevention of cancer for the following reasons:
The evidence from scientific research into the effect of selenium on cancer prevention can be confusing. Two observations about selenium supplementation may help to explain the confusing results from existing selenium and cancer studies:
1. Different selenium containing compounds differ widely in their ability to prevent cancer. Study results may vary according to the form of the selenium supplement tested.
2. Selenium supplementation may be more effective at cancer prevention in study participants with low baseline selenium status (below 100 mcg/L) and less effective in study participants with high baseline selenium status (above 135 mcg/L).
Clinical studies show that daily supplementation with selenium can improve male fertility [Moslemi et al.; Safarinejad & Safarinejad; Scott et al.].
In a 2009 study lasting 26 weeks, researchers in Teheran randomly assigned infertile men, average age 31 years, range 25-48 years, to the following groups [Safarinejad & Safarinejad]:
In an open-label study of 690 infertile men, average age 28.5 years, range 20-45 years, who received a daily selenium supplement (200 mcg) together with a daily synthetic vitamin E (400 units, α-tocopherol) for at least 100 days, the researchers concluded that supplemental selenium and vitamin E improve semen quality and have beneficial effects on sperm motility [Moslemi et al.].
Cardiologists at the University of Groningen in The Netherlands have published a comprehensive review of the current knowledge about selenium deficiency and the role of selenoproteins in heart failure patients [Al-Mubarak 2021].
The key points in their review are as follows:
Three meta-analyses have provided evidence of a relationship between selenium status and the risk of heart disease:
The most interesting clinical study is the KiSel-10 study in which elderly community living citizens, average age 78 years, with low selenium status (mean baseline status: 67.1 mcg/L), were treated with a combination of 200 mcg of an organic high-selenium yeast preparation and 200 mg of Coenzyme Q10 daily for four years.
Selenium is a natural trace element that has an important role in the functioning of the immune system (summarized in an earlier seleniumfacts.com article).
SARS-CoV-2 is a single-stranded RNA virus responsible for COVID-19 infections. Covid-19 infections have a complex metabolism that is comparable to RNA virus infections such as coxsackievirus, influenza virus, Hanta virus, and HIV virus infections.
Selenium deficiency – frequently defined as serum selenium status below 70 mcg/L – increases the risk of infection with RNA viruses:
In people with selenium deficiency (variously defined as serum selenium status below 60 mcg/L or 70 mcg/L), the responses of the innate and adaptive immune systems may be impaired.
Selenium deficiency can lead to an immune-incompetence that is associated with increased susceptibility to infections [Avery & Hoffmann 2018; Hiffler et al. 2020].
In cell culture models, in rodent models, in livestock and poultry studies, and in human studies, researchers have found evidence that adequate levels of dietary selenium and the efficient incorporation of selenium into selenoproteins are important for immune system function [Avery & Hoffmann 2018].
Studies of selenium supplementation to boost immunity against pathogens have not provided entirely clear-cut results; however, selenium and selenoproteins do play a role in regulating immune cell functions. Dysregulation of these immune cell processes can lead to inflammation and immune-related diseases [Avery & Hoffmann 2018].
Herewith the conclusions from a review of the available research literature about selenium and inflammatory bowel disease [Ala & Kheyri 2021].
How does Adequate Selenium Status Help Inflammatory Bowel Disease patients?
Adequate intakes of selenium are needed for the biosynthesis of selenoproteins, which contribute to antioxidative protection of cells and to the effective functioning of the immune system.
The dietary intake and individuals’ serum level of selenium varies from region to region. For example, the US population has higher serum level of selenium (ca. 124 – 193 mcg/L) compared to most of the European and Middle Eastern populations (ca. 50-120 mcg/L) simply because the soil in many regions of North America is rich in selenium.
One thing that the Covid-19 infections have taught us is that biological sex differences affect the way we respond to the virus. The Johns Hopkins University biologist Dr. Sabra Klein says that men are more likely to die from Covid-19 and more likely to be hospitalized with severe cases of the disease.
This seems to hold true even though women are just as likely to be infected and even when researchers control for the effect of factors such as age and region.
Women seem to have a stronger immune response to pathogens – bacteria, viruses, parasites – and to have a higher antibody production after vaccination. On the other hand, women are at greater risk for the development of auto-immune diseases.
Results from an Italian study have added to the evidence that adequate selenium status is necessary to prevent heart disease, especially in elderly individuals.
The Italian study data showed that study participants with plasma selenium concentrations below 60 micrograms per liter were 1.9 times more likely to suffer from cardiovascular disease compared to study participants with higher selenium status [Giacconi 2021].
Reduced plasma selenium status was associated with elevated levels of biomarkers of inflammation, increased expression of cytokines, and down-regulation of sirtuins in peripheral blood mononuclear cells [Giacconi 2021].
In a clinical trial with combined selenium and Coenzyme Q supplementation of elderly citizens, average age: 78 years, with low selenium status (mean: 67.1 micrograms per liter), for 48 months, researchers found reduced cardiovascular mortality after 10 and 12 years of follow-up [Alehagen 2018, 2015).
The long-time selenium researcher Professor Dr. Lutz Schomburg has reviewed the nutritional and preventive medicine aspects of selenium supplementation. In his mind, a selenium deficiency in and of itself constitutes a health risk that should be corrected by dietary measures or by supplemental selenium intake [Schomburg 2020].
He interprets the available evidence for positive health effects of selenium supplement as the outcome of correcting a deficiency or insufficiency of selenium.
His review of the research literature indicates that selenium supplement does not cause diabetes. Instead, the current evidence suggests that the development of type 2 diabetes with low insulin levels and high glucose levels may be causing increases in selenium levels; hence, the perceived association between the incidence of diabetes and the higher selenium status [Schomburg 2020].
