Polyphenols are a combination of chemicals found in the body. Flavonoids, which are another type of polyphenol, are often found in high concentrations in cocoa and dark chocolate. You will not find flavonoids in regular chocolate because most of the flavonoids are lost during the chocolate making process. Dark chocolate is the only type of chocolate that retains flavonoids, but why and how is not really known. Since dark chocolate retains the flavonoids, you can use the excuse of eating it as being healthy because the flavonoids in the dark chocolate can help you lower your risk of cardiovascular disease.
Nuts are another type of food that is high in polyphenols; the polyphenols that you find in nuts are carotenoids, phenols, and phytosterols. The nuts that contain the highest amounts of these polyphenols are hazelnuts, almonds, and walnuts. Eating these nuts can help you reduce the chances of falling victim to numerous chronic diseases because they help improve your overall health. As an added bonus most nuts, including pistachios and pecans also contain high levels of flavonoids, so they can also help keep your heart healthy.
Resveratrol is also considered a polyphenol
Resveratrol is also considered a polyphenol and it is mainly found in red wine, but can also be found in grapes. Red wine contains a higher amount of resveratrol because the antioxidant resveratrol is found in the skin of the grapes and the longer the skins are present during the wine making process the higher amounts of resveratrol. Resveratrol helps keep your neurological and cardiovascular systems functioning properly, but can also help remove free radicals from your body. Wine is only helpful in moderate amounts, too much wine and you can cause damage to your organs and body cells.
National Library of Medicine: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6160559/
Journal of Agriculture: https://pubs.acs.org/page/jafcau/vi/polyphenols-research.html?ref=vi_collection&