Blood Sugar Control and Selenium Supplementation

Blood sugar levels. Insulin sensitivity. Risk of diabetes. What, if anything, is the likely effect of selenium supplementation on glycemic control?

Blood sugar monitor
To maintain blood sugar levels within the normal range, the CDC recommends eating at regular times, not skipping meals, eating foods lower in calories, saturated fat, trans fat, sugar, and salt, drinking water instead of juice or soda, limiting alcohol intake, and exercising. Adequate intakes of selenium are also important.

Glycemic control is the maintenance of blood sugar levels within an acceptable range to prevent the adverse effects of low blood sugar and high blood sugar.

The best measure of glycemic control is the HbA1c test. This blood test HbA1C gauges the average glucose level in the blood over a period of approximately three months. It is considered a good predictor of diabetic complications.

Checking Blood Sugar

The US Center for Disease Control and Prevention suggests that logical times for testing blood sugar levels are as follows [CDC 2022]:

  • When first awake and before eating or drinking anything
  • Before a meal
  • Two hours after a meal
  • At bedtime
Target Blood Sugar Levels

The CDC suggests the following desirable blood sugar levels [CDC 2022]: read more

Selenium and Type 2 Diabetes

Type 2 Diabetes. Some news reports have suggested that high selenium intakes and status may be potential risk factors for the development of type 2 Diabetes mellitus. However, current data show that supplemental selenium does not cause diabetes [Schomburg 2020].

Diabetes symptoms
It seems likely that diabetes causes elevated blood selenium levels rather than the other way around [Schomburg 2020].
Two large randomized controlled trials using selenium supplements have shown no diabetes risk caused by 1) a selenomethionine product [Lippman 2009] and 2)   a selenium-enriched yeast product [Thompson 2016; Jacobs 2019]. In neither study was there any significant risk of diabetes  at the recommended dosage, not even among selenium-replete individuals of various ages and both genders [Schomburg 2020].

Moreover, in the Selenium Trial, the researchers saw no causal role for selenium in the development of insulin resistance or diabetes. Instead, they observed decreased fasting blood glucose levels in the selenium supplemented group compared to the control group [Jacobs 2019]. 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 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