Effects of whey protein on glycemic control and serum lipoproteins in patients with metabolic syndrome and related conditions: a systematic review and meta-analysis of randomized controlled clinical trials

Background This systematic review and meta-analysis aimed to assess the effects of whey protein on serum lipoproteins and glycemic status in patients with metabolic syndrome (MetS) and related disorders. Methods Online databases, such as Web of Science, Cochrane Library, PubMed and Scopus were systematically searched by two independent authors from inception until 30th April 2020 for English randomized clinical trials investigating the efficacy of whey protein administration in subjects with Mets or related conditions on the parameters of glycemic and lipid control compared to certain control. In order to evaluate the included studies' methodological quality, Cochrane Collaboration risk of bias tool was applied. Using Cochrane's Q test and I-square (I-2) statistic, the included trials' heterogeneity was also examined. Using a random-effects model, data were pooled, and weighted mean difference (WMD) was considered as the overall effect size. Results Twenty-two studies were selected to be included in this meta-analysis. Consumption of whey protein resulted in significant reduction of HbA1c (WMD: -0.15; 95% CI: - 0.29, - 0.01) insulin (WMD: -0.94; 95% CI: - 1.68, - 0.21) and homeostasis model assessment-estimated insulin resistance (HOMA-IR) (WMD: -0.20; 95% CI: - 0.36, - 0.05). A significant reduction in triglycerides levels (WMD: -17.12; 95% CI: - 26.52, - 7.72), total cholesterol (WMD: -10.88; 95% CI -18.60, - 3.17), LDL-cholesterol levels (WMD: -8.47 95% CI: - 16.59, - 0.36) and total cholesterol/HDL-cholesterol ratio (WMD: -0.26; 95% CI: - 0.41, - 0.10) was found as well. Conclusions This meta-analysis suggests that supplementation with whey protein had beneficial effect on several indicators of glycemic control and lipid parameters in patients with MetS and related conditions.