Polyphenols are chemical substances and have a number of antioxidant properties. It has capacity to neutralize the oxidization caused due to presence of free radicals (unstable molecules). Atmospheric pollution, inhalation of tobacco smoke, certain fats and ingestion of pesticides are the major path through which free radicals enter your body. It is harmful for your body as it damages cell membranes, destroy cells and mutate DNA of the cells. This results in the number of health-related issues in humans along with the risk of diseases like cancer. It can also cause cardiovascular disease and cause oxidation of LDL cholesterol and results in thickening of arteries.