Does Quercetin Improve Cardiovascular Risk factors and Inflammatory Biomarkers in Women with Type 2 Diabetes: A Double-blind Randomized Controlled Clinical Trial

BACKGROUND: Quercetin has been distributed in a wide range of foods, but some of its known effects in vitro, are not proven in human studies. Therefore, the aim of this study was evaluation of the effects of quercetin intake on cardiovascular risk factors and inflammatory biomarkers in women with type 2 diabetes. METHODS: This double-blind randomized clinical trial was carried out on 72 women for 10 weeks. Subjects were assigned to quercetin and placebo groups using a permutated block randomization of size two. Quercetin was given to participants as a 500 mg capsule daily. Biochemical variables were measured at baseline and at the end of the study, and changes were compared using appropriate statistical methods. RESULTS: Compared with placebo, quercetin intake decreased systolic blood pressure significantly (−8.8 ± 9.3 vs. −3.5 ± 11.7, P = 0.04). Although changes in diastolic blood pressure between the groups was not significant (P = 0.19), high-density lipoprotein cholesterol (HDL-C) was significantly decreased in both groups while changes in total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglycerides (TG) and ratio of TG/HDL-C and LDL-C/HDL-C were not significant between and within groups. Quercetin supplementation significantly reduced the serum concentration of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) (P = 0.01 and P < 0.0001, respectively); however, the mean changes in serum levels of IL-6, TNF-α, and high-sensitivity C-reactive protein were not significant between the groups. CONCLUSIONS: Quercetin supplementation reduced systolic blood pressure significantly but had no effect on other cardiovascular risk factors and inflammatory biomarkers. Considering the biological effects of quercetin in vitro, we need more studies with a stronger design and sample size with different doses of quercetin.