The effects of the flavonol are most likely related to its activity against oxidative stress and inflammation, report researchers in the Journal of Nutrition.
“Quercetin supplementation attenuated the changes in expression of markers for oxidative stress and inflammation in the liver and the heart,” wrote researchers, led by Lindsay Brown from the University of Southern Queensland in Australia.
“Thus, quercetin can be considered as a nutraceutical with potential [against] metabolic syndrome; clinical trials of this relatively safe natural compound should be undertaken.”
Metabolic syndrome (MetS) is a condition characterised by central obesity, hypertension, and disturbed glucose and insulin metabolism. The syndrome has been linked to increased risks of both type-2 diabetes and cardiovascular disease (CVD).
Fifteen per cent of adult Europeans are estimated to be affected by MetS, while the US statistic is estimated to be a whopping 32 percent. Obesity is established to be the main risk factor for MetS.
The compound
Quercetin is an antioxidant flavonoid found in fruits and vegetables. Potential health benefits include lowering of inflammatory markers, cholesterol reduction, and improving blood pressure.
However, many of these potential benefits are the result of in vitro or animal studies and data from human studies is rare.
One such human study by researchers from the University of Utah did indicate that a daily 730 milligram supplement of quercetin led to significant reductions in blood pressure.
The study, said to be the first to report the blood pressure-lowering activity of this flavonol, was published in the Journal of Nutrition (Nov. 2007, Vol. 137, pp. 2405-2411).
Study details
The new study involved four groups of lab mice: One group received a corn starch-rich diet for 16 weeks; one group received a high-carbohydrate, high-fat diet for 16 weeks; the third group was fed a corn starch-rich diet for 8 weeks and then the same diet fortified with quercetin (0.8 grams per kg of food); and the final group was fed the high-carb, high-fat diet for 8 weeks and then the same diet fortified with quercetin (0.8 g/kg).
Results showed that animals consuming the high-carbohydrate, high-fat diet gained more weight and body fat, had unhealthy blood lipid profiles and glucose concentrations, exhibited increased blood pressure, and developed fattier livers, compared with the corn starch-fed animals.
Addition of quercetin to the high-carbohydrate, high-fat diet, however, reversed most of these negative outcomes.
“Quercetin was effective against the symptoms of metabolic syndrome in a diet-induced rat model. The trafficking of fat away from the abdomen did not lower body weight and blood lipids, while the cardiovascular and liver complications of metabolic syndrome were attenuated,” concluded the researchers.
Source: Journal of Nutrition
Volume 142, Pages 1026-1032, doi: 10.3945/jn.111.157263
"Quercetin ameliorates cardiovascular, hepatic, and metabolic changes in diet-induced metabolic syndrome in rats”
Authors: S.K. Panchal, H. Poudyal, L. Brown