The development of chronic diseases such has heart disease, diabetes, cancers, Alzheimer’s and Parkinson’s has been theorized to be caused by oxidative stress.  Antioxidants reduce oxidative stress. 
Include foods in your diet on a daily basis that have a high ORAC value.  Some of the highest are:  apples with skin, artichokes, dark chocolate, black beans, dark red kidney beans, blueberries, cranberries, ginger root, fresh marjoram, almonds, hazelnuts, pecans, walnuts, fresh oregano and peppermint. 

There are many more high antioxidant foods.  For the most part, choose a wide variety of fruits, veggies and fresh herbs and spices to fight disease.