Lower selenium status during pregnancy means there is a greater risk of developing gestational diabetes [Hamdan 2022; Xu 2022]. Three different selenium biomarkers in early and late pregnancy show a quite strong association of selenium with 1) the risk of developing gestational diabetes mellitus and 2) the birth of large for gestational age offspring [Demircan 2022].
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.
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 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
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 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
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
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].
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
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
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
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
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