Page 28 - GTM-3-2

Global Translational Medicine Impact of flavonoids on vascular health

Table 1. Studies ınvestigating the effects of quercetin, a flavonoid variety, on blood pressure regulation
Study Details and findings of the study
Dehghani et al. 79 (i) The study involved 88 post-MI patients who were randomly assigned to receive either 500 mg/day of quercetin or
a placebo for eight weeks in a double-blind, placebo-controlled trial. The researchers aimed to assess the effects of
quercetin supplementation on inflammatory factors, total antioxidant capacity (TAC), and quality of life in these
patients.
(ii) Results indicated that quercetin supplementation significantly increased serum TAC levels compared to the placebo group.
Levels of TNF-α, an inflammatory marker, decreased in the quercetin group.
Dower et al. 80 (i) In this study, researchers investigated the effects of supplementation with pure epicatechin and quercetin on vascular
function and cardiometabolic health in apparently healthy individuals with moderately elevated blood pressure.
(ii) Study participants, aged 40 – 80 years, were enrolled in a randomized, double-blind, placebo-controlled crossover trial. They
received either (-)-epicatechin (100 mg/d), quercetin-3-glucoside (160 mg/d), or placebo capsules for four weeks in random
order. The primary outcome measured was the change in flow-mediated dilation, a marker of vascular function, from pre- to
post-intervention.
(iii) Results indicated that epicatechin supplementation did not significantly change flow-mediated dilation but improved fasting
plasma insulin levels and insulin resistance.
Edwards et al. 81 (i) In this study, researchers investigated the potential of quercetin supplementation to lower blood pressure in hypertensive
patients based on prior epidemiological studies linking quercetin intake to reduced risk of coronary heart disease and
stroke.
(ii) The study enrolled men and women with prehypertension and stage 1 hypertension in a randomized, double-blind,
placebo-controlled crossover trial. Participants received either 730 mg of quercetin daily or a placebo for 28 days.
(iii) Results showed that quercetin supplementation did not significantly alter blood pressure in prehypertensive patients.
However, in patients with Stage 1 hypertension, quercetin treatment led to reductions in systolic, diastolic, and mean arterial
pressures. Notably, these reductions were observed without significant changes in systemic markers of oxidative stress,
contrary to findings in animal studies.
Nishihira et al. 82 (i) In this randomized, double-blind, placebo-controlled clinical trial, researchers investigated the potential cognitive benefits of
quercetin-rich onion intake in healthy Japanese individuals aged 60 – 79 years old.
(ii) Seventy participants were divided into two groups: one receiving quercetin-rich onion (the active test food) and the other
receiving quercetin-free onion as a placebo for 24 weeks. The cognitive function of participants was assessed using various
tests, including the Mini-Mental State Examination, Cognitive Assessment for Dementia iPad version, and Neuropsychiatric
Inventory Nursing Home version.
(iii) Results showed that the group consuming quercetin-rich onion experienced significant improvements in Mini-Mental
State Examination scores compared to the placebo group after 24 weeks. In addition, the active test food group showed
improvements in emotional function evaluation, suggesting a reduction in depressive symptoms and increased motivation.
Shatylo et al. 83 (i) In this randomized, placebo-controlled, double-blind clinical trial, researchers investigated the effects of quercetin
supplementation on various aspects of metabolic syndrome (MetS) in patients aged 60 and above.
(ii) Participants consumed two quercetin-containing or placebo tablets three times per day for a duration of 3 months, resulting
in a daily quercetin dose of 240 mg.
(iii) Results showed that quercetin administration led to significant improvements in several parameters of MetS. These included
reductions in body weight and body mass index, as well as decreases in systolic and diastolic blood pressure. Quercetin
intervention also improved cholesterol metabolism, as evidenced by reductions in serum total cholesterol and low-density
lipoprotein cholesterol levels. In addition, fasting plasma insulin and glucose levels at the 2-h oral glucose tolerance test were
reduced following quercetin supplementation.
Shi and Williamson 84 (i) In this randomized, double-blinded, placebo-controlled, cross-over trial, researchers investigated the effects of oral
supplementation of quercetin on plasma uric acid, blood pressure, and fasting glucose levels.
(ii) Twenty-two healthy males aged 19 – 60 years with baseline plasma uric acid concentrations in the higher, yet still considered
healthy, range was recruited for the study.
(iii) Participants received one tablet containing 500 mg of quercetin daily for 4 weeks, compared to placebo, with a 4-week
washout period between treatments. The primary outcome measured was the change in plasma uric acid concentrations
after 2 and 4 weeks, while secondary outcome measures included changes in fasting plasma glucose, 24-h urinary excretion
of uric acid, and resting blood pressure.
(iv) Results showed that after quercetin treatment, plasma uric acid concentrations were significantly lowered by−26.5 µmol/L
compared to placebo (95% CI, −7.6 – −45.5; P=0.008).
(v) The study concluded that daily supplementation of 500 mg of quercetin for 4 weeks, equivalent to the bioavailable amount
found in approximately 100 g of red onions, significantly reduces elevated plasma uric acid concentrations in healthy males.
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Volume 3 Issue 2 (2024) 8 doi: 10.36922/gtm.2458