Effects of dietary polyphenols on metabolic syndrome features in humans: a systematic review

Abstract

SummaryDietary polyphenols constitute a large family of bioactive substances potential beneficial effect on metabolic syndrome (MetS). This review summarizes the results of clinical studies on patients with MetS involving the chronic supplementation of a polyphenol-rich diet, foods, extracts or with single phenolics on the features of MetS (obesity, dyslipidemia, blood pressure and glycaemia) and associated complications (oxidative stress and inflammation). Polyphenols were shown to be efficient, especially at higher doses, and there were no specific foods or extracts able to alleviate all the features of MetS. Green tea, however, significantly reduced body mass index and waist circumference and improved lipid metabolism. Cocoa supplementation reduced blood pressure and blood glucose. Soy isoflavones, citrus products, hesperidin and quercetin improved lipid metabolism, whereas cinnamon reduced blood glucose. In numerous clinical studies, antioxidative and anti-inflammatory effects were not significant after polyphenol supplementation in patients with MetS. However, some trials pointed towards an improvement of endothelial function in patients supplemented with cocoa, anthocyanin-rich berries, hesperidin or resveratrol. Therefore, diets rich in polyphenols, such as the Mediterranean diet, which promote the consumption of diverse polyphenol-rich products could be an effective nutritional strategy to improve the health of patients with MetS.

Antiobesity Effects of Anthocyanins in Preclinical and Clinical Studies

“…Few interesting reviews have been published in recent years on this topic, and all of them concluded that further interventional studies are needed to assess the preventive effects of anthocyanin-containing foods in obesity, diabetes, and metabolic syndrome due to the difficulty to establish the optimal dose and to identify the ideal food matrix for the best anthocyanin supplementation [27, 61]. Observational studies are more prone to suggest an antiobesity role of this class of polyphenols.…”

Paradoxical Effects of Fruit on Obesity

“…Plant phytochemicals can be categorized into six main classes, but fruit phytochemicals are primarily phenolic compounds. Specific isolated phenolic compounds such as resveratrol, caffeic acid, naringenin, proanthocyanidins, catechins, and cyanidin are known anti-obesity compounds found in fruit [17,85,86,87,88]. A previous study performed phenolic phytochemical profiling in 25 of the most commonly consumed fruits, and found that each fruit contained unique phenolic constituents in substantial amounts as well as in proportion to others [89].…”

Dietary Strategies Implicated in the Prevention and Treatment of Metabolic Syndrome

“…Anthocyanins are water-soluble polyphenolic compounds responsible for the red, blue and purple colors of berries, black currants, black grapes, peaches, cherries, plums, pomegranate, eggplant, black beans, red radishes, red onions, red cabbage, purple corn or purple sweet potatoes [165,166,167]. Actually, they are the most abundant polyphenols in fruits and vegetables [167].…”