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 Intake and Status Related to Health

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