Free radicals (oxidants) are active throughout the body and are responsible for many chronic diseases. These oxidants are acquired through food preservatives. Also by the smog, toxic products and waste products of cellular metabolism. These free radicals affect premature aging, degenerative diseases, cancer, arthritis, cataracts, arteriosclerosis, etc. 
Vegetables are high in vitamins A, C, E and the minerals selenium and zinc, have powerful antioxidants to help neutralize the action of these harmful free radicals.