Selenium Supplementation and Insulin Resistance

by | Feb 8, 2021 | 2019, Diabetes, Minerals, Selenium

Written by Jessica Patella, ND. This study did not find an association between selenium supplementation and the development of type 2 diabetes.

seleniumThe CDC estimates about 1 in 10 Americans have diabetes, with 90-95% of those cases being type 2 diabetes 1. There have been mixed reviews on the effects of selenium in relation to type 2 diabetes, but much of the research has been correlational.  To determine if selenium could possibly be associated with developing type 2 diabetes, a randomized, placebo-controlled trial was conducted over a period of almost 3-years and found there was no effect of selenium on type 2 diabetes 2.

Selenium was originally thought to be helpful for diabetes when supplementing selenium in mice showed improvement in insulin response 2,3.  However, the form of selenium used was selenate, an inorganic form that is rarely found in the human diet.  More recent research with selenium has been with selenoproteins, which are a family of proteins that contain selenium and are more common in the human diet.  Glutathione peroxidase-1 is a selenoprotein that plays an important role in protecting against oxidative damage 2,4.  Although, some studies have shown overexpression of glutathione peroxidase-1 results in elevated glucose and insulin levels 2,5.  Because of these mixed results researchers wanted to investigate the effects of selenium in a randomized clinical trial 2.

The research included 400 individuals (40-80 years of age) that were in a randomized, placebo-controlled trial taking 200 micrograms of Selenium daily (as selenized yeast, n=205) or placebo (n=195) for colorectal adenomatous polyps 2. Beta-cell function and insulin sensitivity were used as the outcome measures in the sub-study and participants were followed for an average of 2.9 years.  Beta-cell functioning evaluates the beta cells in the pancreas and their ability to produce insulin.  With type 2 diabetes the beta cells eventually lose their ability to produce insulin.  The test for insulin sensitivity determines how well the cells in the body respond to insulin. An oral glucose tolerance test was also assessed as a secondary measure at the final follow-up visit to determine how the body responds to sugar in food 2.

There were no statistically significant differences observed for Beta-cell functioning or insulin sensitivity in either group.  There were some observable differences in the oral glucose tolerance test:

  • Fasting glucose was higher in the placebo group (96.6 +/-14.6 mg/dL) than in the selenium group (92.3 +/-12.0 mg/dL; p=0.04) and remained higher during the 10-minute (p=0.07) and 20-minute intervals (p=0.05), but for the remaining times of 30, 60, 90, 120, 180 minutes, there were no differences between groups.

In conclusion, the results of this clinical trial showed no effect of selenium supplementation on insulin action or secretion for up to 3 years.  The main difference is previous studies that found opposite results were merely observational studies, compared to this study which was a randomized, double-blind placebo controlled trial.  This suggests there may be a confounding or third variable that resulted in previous correlations.  Researchers suggest investigating genotypes in the future, in regards to selenium 2.

Source: Jacobs, Elizabeth Theresa, Peter Lance, Lawrence J. Mandarino, Nathan A. Ellis, HH Sherry Chow, Janet Foote, Jessica A. Martinez et al. “Selenium supplementation and insulin resistance in a randomized, clinical trial.” BMJ Open Diabetes Research and Care 7, no. 1 (2019).

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Posted February 8, 2021.

Jessica Patella, ND, is a naturopathic physician specializing in nutrition and homeopathic medicine and offers a holistic approach to health. She earned her ND from Southwest College of Naturopathic Medicine in Tempe, AZ, and is a member of the North Carolina Association of Naturopathic Physicians. Visit her website at www.awarenesswellness.com.

References:

  1. CDC. Type 2 Diabetes. 2019; https://www.cdc.gov/diabetes/basics/type2.html. Accessed February 1, 2021.
  2. Jacobs ET, Lance P, Mandarino LJ, et al. Selenium supplementation and insulin resistance in a randomized, clinical trial. BMJ open diabetes research & care. 2019;7(1):e000613.
  3. McNeill JH, Delgatty HL, Battell ML. Insulinlike effects of sodium selenate in streptozocin-induced diabetic rats. Diabetes. 1991;40(12):1675-1678.
  4. Papp LV, Lu J, Holmgren A, Khanna KK. From selenium to selenoproteins: synthesis, identity, and their role in human health. Antioxid Redox Signal. 2007;9(7):775-806.
  5. Loh K, Deng H, Fukushima A, et al. Reactive oxygen species enhance insulin sensitivity. Cell Metab. 2009;10(4):260-272.