Polyphenol is not a term that many American's are familiar with. Polyphenols are things in food, often colorful, that have been shown over and over in research to provide health benefits to humans. Unfortunately, no one is sure why or how. Originally, it was thought that there primary benefit was functioning as antioxidants, but further research seems to show that this isn't the truth. There are so many different polyphenols in so many different groups of fruits and vegetables that it is really hard to isolate them and pinpoint what exactly they do.
The moral of the story equals eat a wide variety of fruits and vegetables from different groups and families and of different colors and properties to make sure that you are getting as many healthy polyphenols as possible. I have a list that I use that divides fruits and vegetables into groups based on the polyphenols in them. I try to eat foods from every group on a regular basis. This is one of the keys to healthy eating in my opinion.