The berries have been used in traditional medicine since the first century, and contain phytonutrients called anthocyanidins and proanthocyanidins, antioxidants that have a variety of therapeutic effects including strengthening the walls of blood vessels. Extracts of hawthorn berries, leaves and blossoms also contain compounds that have a tonifying effect on the heart and vascular system. Hawthorn has been studied for its use in treating health concerns related to the heart and blood vessels. This includes congestive heart failure, irregular heartbeat, chest pain, low and high blood pressure, angina, atherosclerosis, and high cholesterol. A meta-analysis based on data from 14 studies concluded that a hawthorn extract offers “significant benefit” as an adjunct to conventional treatment of chronic heart failure. Specifically, symptoms including shortness of breath and fatigue were significantly alleviated, compared to placebo treatment.