Antioxidants protect your body from free radicals, which are unstable molecules that can damage your cells and contribute to aging and diseases, such as cancer. Blueberries are believed to have one of the highest antioxidant levels of all common fruits and vegetables. The main antioxidant compounds in blueberries belong to a family of polyphenols antioxidants called flavonoids. One group of flavonoids in particular — anthocyanins — is thought to be responsible for much of these berries’ beneficial health effects. Blueberries have been shown to directly increase antioxidant levels in your body.