Onion skins
In the skin, there’s a high content of “quercetin, a flavonoid polyphenol-type of phytonutrient that fights inflammation, reduces blood pressure, prevents arterial plaque, and keeps the heart healthy,” says Popeck. Red onions contain more quercetin than yellow ones. “Add whole onions to soup, stock, chili, or sauce, then discard skins before eating,” says Popeck.