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Selenium and Mercury Toxicity

A plate of salmon.
Eating fish will give pregnant women and children selenium and other nutrients that will promote the children’s growth and development. Eating fish may give adults heart health benefits. However, some ocean fish contain more mercury than selenium and should therefore be avoided. Consequently, the US Food and Drug Administration advises against eating meals from predatory whales, sharks, swordfish, king mackerel, marlin, orange roughy, tilefish, and big-eye tuna. Most other ocean fish will have more selenium than mercury in their tissues and should be safe, even advisable, to eat.

The selenium in our cells is the molecular “target” of toxic mercury. Inhibition of the normal biological activity of seleno-enzymes is the mechanism by which mercury damages our cells, most particularly our brain and nerve cells [Ralston & Raymond 2018].

Conceiving of selenium as the “target” of mercury leads to a better understanding of mercury toxicity than the old theory of selenium as the “tonic” that binds toxic mercury in a form that is no longer harmful [Ralston & Raymond 2018].

Professor Nicholas Ralston and consultant Lisa Raymond have done a review of the research literature about the characteristics of mercury toxicity to identify the selenium-dependent aspects of mercury’s biochemical mechanisms and effects. Their conclusions [Ralston & Raymond 2018]: read more

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Selenium Status and Major Trauma Patients

Abnormally low selenium status is characteristic of critical illness and major trauma. The fall in selenium status occurs very rapidly after major trauma and is associated with poor survival odds. For it to be effective, adjuvant treatment with selenium must be initiated as soon as possible.

Serum selenium and selenoprotein P concentrations drop to very low levels very quickly following major traumatic injury. The very low selenium and selenoprotein P levels are associated with poor survival odds [Braunstein].

These findings in a study done at the University Hospital in Munich, Germany, suggest that selenium supplementation may be a meaningful adjuvant treatment strategy for patients who have suffered major trauma [Braunstein].

Selenium and Critical Illness

Lower than normal selenium status is characteristic of critical illness. Low selenium status can affect the course and the outcome of various diseases [Braunstein].

For example, Bomer et al [2019] found that heart failure patients with serum selenium levels below 70 micrograms per liter had poorer quality of life, poorer exercise capacity, and poorer prognosis than heart failure patients with higher serum selenium levels. read more

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Selenium Supplementation and Graves’ Disease

Low selenium status is associated with increased risk of Graves’ Disease. Graves’ Disease is an autoimmune disease of the thyroid. It is the most common cause of hyperthyroidism. It often results in an enlarged thyroid.

A 2018 meta-analysis of randomized controlled trials shows that adjuvant selenium supplementation may enhance the restoration of normal thyroid function in patients with Graves’ Disease [Zheng].

Graves’ Disease is the most common cause of hyperthyroidism in adults. It is characterized by below-normal serum TSH levels and increased serum levels of free thyroxine (FT4) and/or triiodothyronine (T3). The basal metabolic status of Graves’ Disease patients is accelerated; the result is an increase in the production of harmful free radicals and reactive oxygen species [Zheng].

Intra-cellular antioxidant enzymes such as superoxide dismutase (SOD), glutathione reductase, and glutathione peroxidase (GPx) protect against the cellular damage caused by oxidative stress. read more

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Selenium Supplementation and Glucose Metabolism

The evidence from a randomized controlled trial shows that 2.9 years of supplementation with 200 micrograms per day had no effect on insulin sensitivity and no effect on pancreatic beta-cell function compared with placebo [Jacobs 2019]. The evidence from randomized controlled trials does not support a role for selenium in the risk of developing type-2 diabetes [Kohler 2018].
The findings from a 2018 meta-analysis show no consistent evidence that selenium supplementation plays a role in the development of type 2 diabetes among adults.

Researchers at the University of Arizona in Tucson, home of the Arizona Cancer Center, identified a statistically significant direct relationship between selenium and Type-2 diabetes in observational studies but no statistically significant relationship in randomized controlled trials [Kohler 2018].

Note: Randomized controlled trials are the gold standard for scientific evidence in the bio-medical field. The randomization of the study participants should produce comparable groups and should eliminate accidental bias.  In observational studies, the researchers do not randomly assign the study participants to groups and do not decide which treatments each group receives or does not receive. read more

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Selenium Status and Heart Failure

Heart failure patients with low serum selenium levels are much more likely to be re-hospitalized and/or to die than are heart failure patients with serum selenium levels above 100 micrograms per liter.

A multi-national cohort study has shown that selenium deficiency in heart failure patients is associated with impaired exercise tolerance and with a 50% higher mortality rate [Bomer].

In-vitro studies of cultured human heart muscle cells from the heart failure patients show that  low selenium levels in the heart muscle cells are associated with impaired mitochondrial function [Bomer].

Recent information shows that up to 50% of heart failure patients suffer from some form of micronutrient insufficiency, e.g. selenium, zinc, iron, or iodine [Bomer].

Selenium: An Essential Micronutrient

Selenium intakes and status vary considerably from geographical region to region according to the content of selenium in the soil and in the food.

Sufficient intakes of selenium are necessary for important biological functions: read more

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Selenium Supplementation and Sperm Quality Parameters

Supplementation with selenium and with Coenzyme Q10 has beneficial effects on sperm count, sperm motility, and sperm morphology. There seems to be a special interrelationship between selenium and Coenzyme Q10 such that sufficient concentrations of each are needed for the optimal function of the other.

Data from two randomized controlled trials have shown that selenium supplementation has the following significant beneficial effects [Salas-Huertos]:

  • improved sperm volume and concentration
  • improved sperm motility
  • improved sperm morphology

Selenium supplementation at 100 micrograms per day for 3 months improved sperm motility and increased the chance of conception.  Selenium supplementation at 200 micrograms per day for 6 months improved semen volume, total sperm count and concentration, and sperm morphology [Salas-Huertos].

Data from five other randomized controlled trials have shown that Coenzyme Q10 supplementation is significantly associated with the following beneficial effects:

  • improved sperm count
  • improved sperm concentration
  • improved sperm motility
  • improved sperm morphology

The Coenzyme Q10 supplementation was most effective when the supplementation was in the range of 200 – 300 milligrams per day (in divided doses) for at least 3 months and especially after 6 months [Salas-Huertos]. read more

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Selenium Status and Prostate Cancer Risk

The light blue ribbon is the prostate cancer awareness ribbon. Along with skin cancer, prostate cancer is the most common cancer among American men. The American Cancer Society estimates that one man in nine will be diagnosed with prostate cancer during his lifetime. Research shows that blood selenium status within a specific range is associated with reduced risk of prostate cancer.

One of the big challenges in selenium research is the optimizing of the daily selenium intake to reduce the risk of prostate cancer. We need more research results to answer the following questions about the use of selenium supplements to reduce the risk of prostate cancer [Waters & Chiang 2017]:

  • What is the optimal formulation of the selenium supplement?
  • What is the correct daily dosage?
  • What is the range of baseline blood selenium concentrations that indicates a need for selenium supplementation?
  • What is the blood selenium level above which selenium supplementation will not reduce the risk of prostate cancer further?

The idea that selenium intakes and selenium status are an important determinant of prostate cancer risk began to receive considerable attention after University of Arizona Professor Larry Clark published the results of the Nutritional Prevention of Cancer Trial in JAMA in December 1996 [Clark 1996].

High-Selenium Yeast Supplements in the Nutritional Prevention of Cancer Trial

The Nutritional Prevention of Cancer Trial (NPCT) was a supplementation trial using 200 micrograms of a selenized yeast preparation or placebo for an average duration of 4.5 years.  The study participants were 1312 men and women with an average age 63 years. read more

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Selenium and Longevity and Ageing

There are notable regional variations in the blood selenium concentrations in senior citizens. The differences range from 66 micrograms per liter in Brazil and Turkey to 126 micrograms per liter in Japan.  Below 85 micrograms per liter is poor selenium status.  The desirable range is thought to be 125-135 micrograms per liter.

We want, all of us, to stay as young and healthy as possible as late in life as possible.  Ageing is inevitable.  How can we delay the onset of ageing’s bio-chemical and physiological consequences?

  • Physical exercise?
  • Caloric restriction?
  • Ingestion of micronutrients?

Selenium Status and the Health of Senior Citizens

The authors of a 2019 review article have found that, overall, there is an inverse correlation between age and blood selenium levels. Higher age is associated with lower blood selenium concentrations [Robberecht 2019].

Inadequate dietary intakes of selenium and poor selenium status (< 85 micrograms per liter in blood) may increase the risk of following harmful health outcomes [Robberecht]:

  • oxidative stress (= imbalance of harmful free radicals and protective antioxidants)
  • destruction of nerve cells (neurons)
  • dementia

Selenium Status and Biological and Social Factors

A variety of factors must be taken into consideration when we investigate the relationship between ageing and selenium intake and status.  There are, first of all, considerable regional variations in the availability of selenium in the soil and in foodstuffs [Stoffaneller & Morse]. read more

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Selenium For Cancer Treatment

Pre-clinical studies suggest that selenium supplementation in the right formulation and the right dosage may enhance the effects of chemotherapy for certain forms of cancer. Selenium may help to protect normal cells and tissues against the toxicities of chemotherapy drugs.  Selenium may enable the administration of higher than normal doses of the chemotherapy drugs.

Chemotherapy and radiation continue to be the major forms of treatment for many types of cancer. The considerable toxicity of these treatments to normal cells is a problem in cancer treatment and management.

Selenium’s Role in Cancer Prevention

Selenium supplementation has already been associated with statistically significant reductions in the risk of various cancers and pre-cancerous conditions:

Possible Role for Selenium in Cancer Treatment

Selenium supplementation may be valuable in the treatment of cancer as well as in the prevention of cancer.  Selenium has the ability to protect against the formation and progression of some cancer cells and also the ability to selectively target some existing cancer cells.

Moreover, it may be that selenium can work in synergy with conventional cancer therapies.  Pre-clinical research data suggest that selenium may in some instances protect normal cells and tissues against the toxic effects of conventional cancer treatments on the cells [Evans 2017]. read more

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Metabolic Changes After Supplementation with Selenium and Coenzyme Q10

Professor Urban Alehagen’s research has shown that there is a relatively high mortality risk in elderly Swedish subjects with low selenium intakes and low selenium status. Senior citizens in Sweden had, on average, serum selenium concentrations of 67.1 micrograms per liter. The same increased mortality risk seen in Sweden may be typical of other selenium-poor regions of the world as well.

There are clear differences in the metabolic profiles of elderly men who took 200 micrograms of selenium and 2 x 100 milligrams of Coenzyme Q10 daily for at least 18 months as compared with the metabolic profiles of elderly men who took matching placebos [Alehagen 2019].

Drawing on data from a sub-analysis of the KiSel-10 Study, Professor Urban Alehagen reported that the major differences were seen primarily in the following biological pathways [Alehagen 2019]:

  • pentose phosphate pathway (the pathway for the generation of nicotinamide adenine dinucleotide phosphate, which is a substance that reduces ubiquinone Coenzyme Q10)
  • mevalonate pathway (the pathway for the synthesis of cholesterol, Coenzyme Q10, and dolichol)
  • beta-oxidation pathway (the pathway for the breaking down of fatty acid molecules to produce energy and to produce acetyl-CoA, FADH2 and NADH, which are needed for the citric acid cycle [Krebs cycle]

There were other significant metabolic changes associated with the selenium and Coenzyme Q10 supplementation of senior citizens as well [Alehagen 2019].

Changes in Metabolic Profile After Supplementation with Selenium and Coenzyme Q10

In this study, Professor Alehagen and his team of researchers analyzed the metabolic patterns of 95 metabolites in the plasma of elderly men. read more