Here are the main points from a recent review article on the topic of aging and exposure to heavy metals and kidney function:
Professor Jan Aaseth and his colleagues have reviewed the research literature about the response of the aging kidney to environmental toxicants like mercury, cadmium, and lead. Selenium may have a protective effect in that it binds to and sequesters the harmful heavy metals and also serves to reduce the level of oxidative stress.
The efficiency with which the kidneys remove waste and excess fluid from the blood declines with age in individuals who are older than 50–60 years.
Exposure to metal pollutants may be detrimental to the kidneys of normal healthy adults and exacerbates the functional decline of the kidneys in seniors. Given the prevalence of these heavy metal toxicants in the environment, it is nearly impossible for people to avoid exposure.
Studies have shown that exposure to mercury, cadmium, and/or lead is associated with an increase in the incidence and the severity of kidney disease in elderly individuals. There is some reason to think that adequate selenium status helps to protect against the damage of heavy metal toxicants.
Unfortunately, the early signs of kidney dysfunction often go unnoticed.
Mercury, Cadmium, Lead – Difficult to Avoid
Prof. Aaseth et al. write that toxic metals are so abundant in the environment that it is almost impossible for humans to avoid contact with them.read more
Selenium is an essential trace element, essential in the sense that our bodies cannot synthesize it, and we must get what we need of it in our diets.
Professor Schomburg distinguishes between selenium substitution – supplying selenium to correct a nutritional deficit – and selenium supplementation – supplying selenium on top of a sufficient baseline status for therapeutical purposes. Here, elderly people with joint pain.
Suboptimal intakes of selenium, i.e., intakes below the recommended intake levels, are associated with increased disease risks, in particular increased risk of autoimmune diseases, chronic diseases, inflammation, etc.
Unfortunately, the health risks of selenium deficiency are often neglected. Here are some facts:
Preventable endemic diseases are known in regions with selenium deficiency, e.g., in certain parts of China.
Sufficiently high selenium status is a prerequisite for adequate immune system response.
Individuals living in regions with selenium-poor soil, women who are pregnant, individuals with autoimmune thyroid disease, and individuals with a severe illness, e.g. COVID-19, are known to have sub-optimal selenium intakes and status.
Improved dietary choices and/or selenium supplementation are efficient ways to avoid severe selenium deficiency.
These are the major points in a recent journal article published by Professor Lutz Schomburg, Charité–Universitätsmedizin Berlin, Freie Universität Berlin, and Humboldt Universität zu Berlin.
Selenium and Selenoproteins
The micronutrient selenium is a component of the amino acid selenocysteine, which is itself an essential part of some 25 selenoproteins identified in human biology. Some selenoproteins are known to be essential for life; accordingly, they are preferentially synthesized and distributed. The brain, for example, has high priority for selenium in times of scarcity.read more
The individual’s status of selenium and Coenzyme Q10 may be a decisive factor in his or her immune system’s response to the SARS-CoV-2 virus that causes the acute respiratory distress of a Covid-19 infection.
A research review shows that selenium and CoQ10 supplementation has positive effects on the free radical-induced oxidative stress and the inflammation associated with patients with COVID-19 disease.
In particular, immune system cells require adequate selenium and Coenzyme Q10 to protect against oxidative stress and to modulate the inflammatory effect.
This is the conclusion of the authors of a 2021 review of the relevant research literature [Hargreaves & Mantle].
Iain R. Hargreaves, a biochemistry faculty member in the Pharmacy and Biomolecular Sciences Department of the Liverpool John Moores University, together with the medical doctor David Mantle, has written that adequate selenium status and adequate Coenzyme Q10 status may be important factors:read more
Sufficient selenium is required for the formation of the amino acid selenocysteine, which is, in turn, an essential component of selenoproteins.
Low selenium status over longer periods of time can put individuals at greater risk of cardiovascular disease, cancer, and autoimmune thyroid disorders.
Adequate selenium intake and status are necessary for good immune function and protection against infectious diseases.
Particularly vulnerable to have low selenium status are individuals who are vegetarians and vegans, pregnant and breastfeeding women, overweight or obese individuals, HIV-patients, kidney-dialysis patients, and individuals on parenteral nutrition as well as individuals living in selenium-poor regions.
Where is selenium status likely to be low?
Stoffaneller and Morse conducted a comprehensive study – 143 references – of selenium status in Europe, the UK, and the Middle East. They concluded that selenium intake and status are generally suboptimal in European and Middle Eastern countries, with somewhat more variation in the Middle East. They reported that suboptimal selenium status is widespread throughout Europe and the UK, with Eastern European countries having lower selenium intakes than Western European countries. In the Middle Eastern countries, they found varying results, which were possibly caused by different food habits and different imports in different regions and within differing socioeconomic groups [Stoffaneller & Morse].read more
Selenium supplements come in many forms, both organic and inorganic. The advantage of the selenium-enriched yeast preparations is that they contain 20-30 different species of selenium in addition to selenomethionine. Some of these selenium species may have important biological effects.
Here we summarize their findings with respect to selenium in selenium-enriched yeast supplements. We do this for two reasons:
Selenium-enriched yeast supplements have been shown to reduce bio-markers of oxidative stresswhereas pure selenomethionine supplements have not [Richie 2014].
Absorption of selenium from selenium-enriched yeast preparations
In a 2008 paper, researchers reported having given healthy elderly individuals 100, 200 or 300 mcg selenium in a selenium-enriched preparation daily for a period of 5 years. The supplementation resulted in mean plasma levels of 165, 221, and 260 mcg/L,respectively. In the control group, given a placebo for 5 years, the plasma selenium concentration was 92 mcg/L [Ravn-Haren 2008].read more
Sufficient selenium status is necessary for good thyroid health.
Selenium-containing drugs are effective for treating patients with autoimmune thyroid disorders [Zuo 2021].Zuo et al [2021] have investigated selenium status and the effects of selenium supplementation in patients with autoimmune thyroid disease.
They analyzed the data from 17 journal articles based on studies of 1,911 subjects. Their meta-analysis results showed the following statistically significant associations:
Serum free triiodothyronine (FT3) levels in patients were reduced after selenium supplementation compared to placebo treatment.
Serum free thyroxine (FT4) levels and anti-thyroid peroxidase antibody (TPOAb) levels were reduced after selenium supplementation compared to placebo treatment.
Anti-thyroid peroxidase antibody (TPOAb) levels were decreased after selenium supplementation compared to placebo treatment.
However, the thyroid stimulating hormone (TSH) levels and the anti-thyroglobulin antibody (TGAb) levels were not significantly different between the selenium treatment group and the control group.
The researchers concluded that selenium-containing drugs were effective in treating patients with autoimmune thyroid disease and greatly reduced the levels of free triiodothyronine, free thyroxine, and anti-thyroid peroxidase antibody in these patients.read more
Data from an observational study done in the United States have shown the following relationships [Reja 2020]:
Liver pain is usually felt as a dull, throbbing pain in the upper right abdomen. NAFLD is the most common form of liver disease. It is characterized by the storing of too much fat in liver tissues, by inflammation, and by fibrosis. Liver fibrosis is a degenerative disease in which liver tissue is damaged and replaced by scar tissue.
Higher serum selenium status is correlated with lower risk of advanced liver fibrosis.
This correlation is especially strong in liver disease patients who are elderly, who are non-Hispanic white, or who are female.
The patients with non-alcoholic fatty liver disease (NAFLD) who had higher serum selenium levels also had a 28% lower hazard ratio of death from all causes compared to the NAFLD patients with the lowest serum selenium levels.
Serum Selenium Levels and the Risk of Advanced Liver Fibrosis and All-Cause Mortality in NAFLD Patients
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:
selenium’s role in DNA repair
selenium’s role in apoptosis
selenium’s role in the endocrine and immune systems
the antioxidant properties of certain selenoproteins
It is not possible to draw any conclusions regarding a causal link between selenium exposure/status and the prevention of cancer. However, numerous observational studies show an inverse relationship between serum selenium status and the risk of cancer.
Different Selenium Compounds Have Different Effects on Cancer
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).read more
Clinical studies show that daily supplementation with selenium can improve male fertility [Moslemi et al.; Safarinejad & Safarinejad; Scott et al.].
Sperm motility is a parameter of sperm analysis used to evaluate the ability of sperm to move in a forward direction. Poor sperm motility is associated with diminished male fertility. Adequate serum selenium status (> 90-100 mcg/L) is associated with improved sperm quality and improved sperm motility.
Selenium is essential for sperm function and male fertility.
Selenium deficiency has been associated with reproductive difficulty in cattle, chickens, mice, pigs, rats, and sheep; selenium supplementation has improved reproductive performance in mice and sheep and mice [Moslemi 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]:
selenium supplementation group (n=116; dosage = 200 mcg/day)
N-acetyl-cysteine group (n=118; dosage = 600 mg/day)
selenium supplementation group (n=116; dosage = 200 mcg/day) plus N-acetyl-cysteine (dosage = 600 mg/day)
Administering selenium plus N-acetyl-cysteine resulted in additive beneficial effects.
There was a significant positive correlation between the seminal plasma concentrations of selenium and N-acetyl-cysteine and the semen parameters.
There was a strong correlation between the sum of the selenium and N-acetyl-cysteine concentrations and the mean sperm concentration, sperm motility, and percentage of normal morphology sperm.
Selenium Supplementation of Men in Iran 2011
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.].read more
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].
Heart failure is a form of heart disease with high morbidity and mortality and with increasing prevalence. It is estimated that there are more than 26 million heart failure patients worldwide. Suboptimal selenium intakes and status adversely affect heart muscle function.
The key points in their review are as follows:
Selenium is an essential micronutrient. It is incorporated into 25 different selenoproteins that have many biological functions in the body.
Suboptimal selenium intakes and status lead to the impaired cellular synthesis of these selenoproteins and to the diminished function of selenoproteins, which may aggravate oxidative stress and inflammation, both of which are associated with greater severity of heart failure.
The heart failure patients with suboptimal serum selenium concentrations have lower exercise capacity, lower quality of life, and a worse prognosis than heart failure patients with serum selenium concentrations above 100 mcg/L.
Clinical trials of the efficacy of selenium supplementation in patients with heart failure have shown improved clinical symptoms such as improvements in NYHA function class, in left ventricular ejection fraction, and in lipid profile.
The Dutch cardiologists suggest that patients with serum selenium levels below 100 mcg/L should be considered to have suboptimal concentrations [Bomer 2020].
Observational Studies of Selenium Concentration and Heart Failure
Three meta-analyses have provided evidence of a relationship between selenium status and the risk of heart disease:
Studies of Selenium Supplementation – the KiSel-10 Study
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.read more
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