Is selenium supplementation beneficial for glycemic control?

There has been a dramatic rise in the prevalence of diabetes mellitus over the last few decades. Additionally, diabetes is closely related to cardiovascular disease (CVD). Impaired glycemic control is one of the major risk factors contributing to type 2 diabetes and CVD. Therefore, the reversal of this risk factor results in a substantial reduction in the risk of chronic diseases. Therefore there is evidence that drug therapy, lifestyle management, and dietary supplements can improve glycemic indices.

Researchers have focused on selenium as one of the dietary supplements for improving glycemic indices. Selenium as a trace element is crucial; for immune system function and antioxidant defenses. However, there is an ongoing debate on the effects of selenium supplementation on glycemic control on results from different studies.

To fill this knowledge gap, Mahdi Vajdi, Isfahan University of Medical Sciences, Isfahan, Iran, and colleagues investigated the overall effects of selenium supplementation on some glycemic parameters such as FBS, HbA1c, fasting insulin, QUICKI, and HOMA-IR in a GRADE-assessed systematic review and dose-response meta-analysis of RCTs.

For this purpose, the researchers conducted a comprehensive literature search from inception to April 2023 on online databases. It included all RCTs which reported an effect of selenium supplementation on glycemic parameters. The weighted mean difference (WMD) was estimated for each outcome using a random-effects model. Heterogeneity between studies was evaluated by the I2 and Cochran’s Q test. The meta-analysis included 20 trials.

The authors reported the following findings:

• Pooled analysis showed that selenium intake significantly reduced fasting insulin (WMD: −3.02 µIu/mL) and increased QUICKI levels (WMD: 0.01).
• Selenium supplementation did not change FBS (WMD: −1.32 mg/dL), HbA1c (WMD = 0.05%), and HOMA-IR (WMD: −0.82).
• There was a non-linear association between selenium supplementation dosage and FBS.

"After selenium supplementation in the meta-analysis, we observed a significant decrease in insulin level and a significant rise in QUICKI score," the researchers wrote. "There was also an improvement in fasting blood sugar and HOMA-IR among some subgroups of participants."

The researchers noted the close association between meta-analyses and evidence-based management practices in the clinic. Different doses of selenium supplements and baseline levels of serum selenium must be considered in future clinical trials to gain a better understanding of the therapeutic effects of selenium supplements.

"Conducting further prospective studies with larger sample sizes will be necessary, from different countries, and also longer follow-up periods to confirm whether selenium has effective anti-diabetic properties," they concluded.

Reference:

Vajdi, M., Hassanizadeh, S., Gholami, Z., & Bagherniya, M. (2023). Selenium supplementation effect on glycemic control: A GRADE-assessed systematic review and dose-response meta-analysis of randomized controlled trials. Pharmacological Research, 195, 106888. https://doi.org/10.1016/j.phrs.2023.106888