Efficacy of Dietary Polyphenols from Whole Foods and Purified Food Polyphenol Extracts in Optimizing Cardiometabolic Health: A Meta-Analysis of Randomized Controlled Trials

The evidence from clinical trials concerning the efficacy of dietary polyphenols on cardiometabolic health is divergent. Therefore, this review aimed to determine the pooled effect of dietary polyphenols on cardiometabolic risk markers and compare the difference in efficacy between whole polyphenol-rich foods and purified food polyphenol extracts. We conducted a random-effect model meta-analysis of ran-domized controlled trials (RCTs) on the effect of polyphenols on blood pressure, lipid profile, flow-mediated dilation (FMD), fasting blood glucose (FBG), waist circumference, and markers of inflammation. Effect size was expressed as weighted mean difference and 95% CI. RCTs published in English between 2000 and 2021 involving adult participants with cardiometabolic risks were searched in electronic databases. Forty-six RCTs involving 2494 participants with a mean age of 53.3 +/- 10 y were included in this review. Whole polyphenol-rich food but not purified food polyphenol extracts significantly reduced systolic blood pressure (SBP, -3.69 mmHg; 95% CI: -4.24, -3.15 mmHg; P = 0.00001) and diastolic blood pressure (DBP, -1.44 mmHg; 95% CI: -2.56, -0.31 mmHg; P = 0.0002). Concerning waist circumference, purified food polyphenol extracts led to a larger effect (-3.04 cm; 95% CI: -7.06, -0.98 cm; P = 0.14). Significant effects on total cholesterol (-9.03 mg/dL; 95% CI: -16.46, -1.06 mg/dL; P = 0.02) and TGs (-13.43 mg/dL; 95% CI: -23.63, -3.23; P = 0.01) were observed when purified food polyphenol extracts were considered separately. None of the intervention materials significantly affected LDL-cholesterol, HDL-cholesterol, FBG, IL-6, and CRP. When both whole food and extracts were pooled together, there was a significant reduction in SBP, DBP, FMD, TGs, and total cholesterol. These findings suggest that polyphenols both as whole food and purified extracts can be efficacious in reducing cardiometabolic risks. However, these results must be interpreted with caution because of high heterogeneity and risk of bias among RCTs. This study was registered on PROSPERO as CRD42021241807.

Automated summary

This review analyzed data from 46 clinical trials and found that whole polyphenol-rich foods can significantly reduce diastolic and systolic blood pressure, while purified food polyphenol extracts have a larger effect on waist circumference. Significant effects on total cholesterol and triglycerides were observed with purified extracts. These findings indicate that both whole food and purified extracts of polyphenols can reduce cardiometabolic risks, but caution is needed due to high heterogeneity and risk of bias among trials.