Antioxidants are substances that help our bodies to destroy or quench harmful free radicals that are produced quite naturally in the human body and which, if allowed to proceed unchecked, can harm tissues and organs. Many useful antioxidants are nutrients that we obtain from our food. Increasingly the effectiveness of each antioxidant is being measured in Oxygen Radical Absorbance Capacity (ORAC) units for comparison, which have become an accepted industry standard.