Selenium as a Nutritional and Preventive Medicine Substance

Berlin Brandenburger Tor
Professor Dr. Lutz Schomburg, affiliated with the Charité Institute of Experimental Endocrinology and with both the Humboldt University and the Free University in Berlin, has analyzed the research literature on selenium supplementation. He concludes that current data show that selenium supplementation does not cause diabetes.

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]. read more

Selenium Supplementation and Blood Sugar Levels

Testing blood sugar
The results of randomized controlled trials of selenium supplementation show beneficial effects or no effect on blood sugar levels and insulin sensitivity values. In this review, we summarize the study results.

The effect of selenium supplementation on blood sugar levels and on the risk of diabetes is still an open question. However, the data from randomized controlled studies show that selenium supplementation is associated with either a beneficial effect or no effect at all on blood sugar levels, insulin sensitivity, and glucose tolerance [Jablonska 2016].

Study Participants with Type-2 Diabetes

Beneficial effect. In a 2019 study, the participants were 72 male and 22 female patients aged 48 to 64 years old with diabetes mellitus type 2. They were smokers, all of them, and they all followed a Mediterranean diet.

The researchers administered selenium 200 microg/day once daily on an empty stomach. The study data showed a statistically significant reduction in the blood levels of glucose and in HbA1c values at both three months and six months after the beginning of the treatment. The administration of selenium to type-2 diabetic patients seemed to improve the patients’ glycemic profile [Karalis 2019]. read more

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

Selenium Supplementation: No Adverse Effect on Insulin Resistance

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

Selenium supplementation and insulin resistance: a clinical study

The latest clinical evidence shows that selenium supplementation of older adults with 200 micrograms of a high-selenium yeast preparation for up to three years does not adversely affect pancreatic beta-cell function or insulin sensitivity.

Results from a clinical trial comparing 200 micrograms of selenium supplementation with placebo supplementation show no effect of the selenium supplementation on measures of insulin secretion and insulin action [Jacobs]. 

These results can be regarded as important evidence that selenium supplementation for up to three years in older individuals has no diabetes causing effects in humans [Jacobs].

The researchers who conducted the selenium and insulin resistance study concluded that the results of the study do not show a causal role for selenium in the development of insulin resistance or in the development of type-2 diabetes [Jacobs].

Research design of the selenium and insulin resistance study

Background: In 2016, researchers at the Arizona Cancer Center in Tucson reported on the results of the Selenium Trial [Thompson]. read more

Serum selenium status and gestational diabetes

The prevalence of gestational diabetes varies from region to region of the world from below 5% of pregnancies to below 10% to as high as 20%. Gestational diabetes increases the risk of type 2 diabetes and metabolic syndrome for the mother and increases the risk of acute and long-term adverse metabolic disorders in the offspring. A recent meta-analysis reveals that women with gestational diabetes typically have significantly lower serum selenium concentrations.

Typically, the serum selenium concentration levels are significantly lower in women with gestational diabetes than in healthy pregnant women.  The differences are especially remarkable in non-Caucasian pregnant women and in pregnant women in the third trimester.  That is the finding of a recent meta-analysis and systematic review of the relevant literature from observational studies [Kong 2016].

Selenium and gestational diabetes

Gestational diabetes is defined as any degree of glucose intolerance that occurs with the onset of pregnancy.  A physiological insulin resistance beginning in the second trimester and progressing through the third trimester is fairly typical of pregnancies.  Expecting mothers generally need increased insulin secretion to maintain normal blood glucose levels.  Impairment of the needed compensatory increases in insulin secretion leads to a diagnosis of gestational diabetes [Kong 2016]. read more

Selenium and glucose metabolism

In our thinking about our diet and our fitness, scientific research must be our highest authority.  The results from randomized controlled studies are the best evidence for the possible existence of a cause-effect relationship between treatment with a selenium (or Coenzyme Q10) supplement and beneficial health outcomes.

Recently, I did a search of the Medline database on the subject of selenium supplementation and its effect or non-effect on glucose metabolism, insulin resistance, glycemic control, etc.  I limited my search to reports of data from randomized, controlled trials.

Altogether, the Medline search yielded 48 hits.  Reading through the abstracts of the 48 journal articles, I was able to eliminate 30 references from consideration.  These 30 eliminated studies were studies that included all of my search terms but did not actually measure the effect of an intervention with selenium on some aspect of glucose metabolism.

18 good selenium supplementation studies
I was left with 18 good intervention studies that met my search criteria.  I read these studies and separated them into three distinct categories related to the effect of selenium supplementation on glucose metabolism and insulin sensitivity: read more

Selenium intakes and type-2 diabetes

In many regions of the world, it may not be possible to get an optimal amount of selenium from meals. The content of selenium in our food depends on the availability of selenium in the soil. Known selenium-poor areas are found in much of Europe and the Middle East, China, Korea, Japan, and New Zealand. In the United States, the coastal areas tend to have lower selenium content than the middle of the country does.

In 2013, Dr. Margaret Rayman, University of Surrey, United Kingdom, reviewed the published reports of randomized controlled trials in which a selenium supplement had been used as a single-agent treatment option and in which there had been a follow-up or sub-group analysis of the effect of the selenium supplementation on the risk of type-2 diabetes.

Dr. Rayman found 5 such studies.  I want to summarize Dr. Rayman’s review, and then I want to see what studies have been done since 2013.

Selenium and diabetes studies
Nutritional Prevention of Cancer (NPC) study
In 2007, Dr. Saverio Stranges published the results of a post hoc analysis of the data from the Nutritional Prevention of Cancer study.  In the NPC study, supplementation for an average of 4.5 years with 200 micrograms of a high selenium yeast preparation resulted in significant reductions in the risk of lung cancer, colon cancer, and prostate cancer [Clark 1996].  The age of most participants in the study was 63 years, plus or minus 10 years. read more

The functions of selenium supplements

skin-cells antioxidant
Selenium is an important component of the antioxidant defense in the cells. It helps to protect against oxidative damage to both cells and DNA. It has been shown to have a protective effect against the damage to skin cells caused by ultraviolet radiation.

Why the interest in selenium facts?  Here, at the beginning of the website, we want to review in broad terms what we know about the functions of selenium supplementation. We are especially interested in selenium’s antioxidant and anti-inflammatory effects in the human body.

Selenium is an essential trace element in the human diet, and, in many regions of the world, it is an absolutely necessary nutritional supplement.  It has many and diverse functions in the human body.

One of the interesting things about selenium is that it does not perform its functions as an element or an ion.  Instead, it functions as a component of more complex compounds.  In particular, it is an essential component of the 21st amino acid, selenocysteine. read more