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
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
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
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
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].
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
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:
Selenium supplementation may be valuable in the treatment of canceras 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.
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
Dr. Margaret P. Rayman, Professor of Nutritional Science, University of Surrey at Guildford, said in 2002: ” Se deficiency is defined by Baum et al (1997) as a plasma level ≤ 85μg/liter, a level not attained in many northern European countries.”
Selenium is an important trace element that is needed for the proper functioning of our cells. It is needed in very small amounts, but it might be a good idea to have a blood test done to check the serum selenium level.
The Mayo Clinic Laboratories state that the normal concentration in adult human blood serum is 70 to 150 micrograms per liter (the same as 70 to 150 nanograms per milliliter). According to the Mayo Clinic, the US population mean value is 98 micrograms per liter [Mayo Clinic].
Variations in Serum Selenium Levels
Diet, geographic location, demographic factors, and environmental factors all influence serum selenium levels.
The following factors are independent predictors of higher selenium status in the United States [Park]:read more
Researchers at the Arizona Cancer Center report study results that do not support any significant adverse effect of daily supplementation with 200 micrograms/day of selenized yeast on beta-cell function or insulin sensitivity. High-selenium yeast preparations contain more selenium species with more biological functions than the 100% selenomethionine preparations do.
Researchers at the University of Arizona Cancer Center in Tucson have reported interesting findings with respect to selenium supplementation [Jacobs 2019]:
Supplementation with 200 micrograms/day of a selenized yeast preparation for 2.9 years had no effect on insulin sensitivity or beta-cell function as compared with the placebo group.
Further stratification of the data by sex and age showed no effect modification in response to the selenium supplementation.
The Take-Home Message from this Selenium Research
The Arizona Cancer Center research does not support the idea of a major role for selenium in insulin sensitivity or beta-cell function.
The University of Arizona researchers write that their results provide key information for clinicians to convey to patients in the USA about the use of selenized yeast dietary supplements.
The Selenium Supplementation Research Design
The researchers analyzed the data from a subset of 400 individuals who were participating in the Selenium Trial, a randomized, double-blind, placebo-controlled trial of the effect of selenium supplementation at 200 micrograms per day on colorectal adenomatous polyps [Jacobs 2019].
The data included the fasting plasma glucose and insulin measured both before randomization and within 6 months of completing the intervention.
The researchers compared changes in the homeostasis model assessment-beta cell function (HOMA2-%beta) and insulin sensitivity (HOMA2-%S) between the active selenium treatment group and the placebo control group.read more
The quantity of selenium in foodstuffs may be inadequate in many parts of the world. Sub-optimal selenium status is reported to be widespread throughout Europe, the UK, and the Middle East [Stoffaneller & Morse]. Coastal regions in the US tend to have selenium-poor soil. Vast regions in China, Korea, Siberia, Tibet, and New Zealand are low selenium regions. Low selenium status is associated with increased risk of cancer and cardiovascular disease and thyroid disorders [Tolonen].The research evidence to date suggests that there is a U-shaped relationship between selenium intake and health. According to a recent report by the long-time selenium researcher Professor Dr. Margaret P. Rayman, University of Surrey, UK, both selenium deficiency and selenium excess have been associated with adverse health effects.
Conditions Indicating a Need for Selenium Supplementation
Professor Rayman lists a number of conditions that have been associated in the research literature with selenium deficiency:
Keshan disease (a heart muscle disease caused by a selenium deficiency together with a strain of Coxsackie virus)
Kashin-Beck disease (a bone disease for which selenium deficiency is a factor)
Increased viral virulence
Increased mortality
Poorer immune function
Problematic fertility/reproduction
Thyroid autoimmune disease
Cognitive decline/dementia
Type-2 diabetes
Prostate cancer risk
Colo-rectal cancer risk (in women)
Increased risk of tuberculosis in HIV patients
Professor Rayman does not specify a plasma/serum selenium level for selenium deficiency.
She does mention a US National Health and Nutrition Examination Survey that measured the serum selenium levels in 13,887 adult participants and then followed up for mortality for up to 18 years. The mortality in that study showed a U-shaped association between serum selenium and death, with a serum selenium concentration of 135 micrograms per liter at the bottom of the U [Rayman 2019].read more
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