It is believed that different types of antioxidants, when consumed in appropriate amounts, work together to fight free radicals. However, consuming too much or too little of a particular type of antioxidant may inhibit the benefits of other antioxidants. 

At high levels, some antioxidants such as Carotenoids may be dangerous to a person’s health. Some experts believe that high doses of antioxidant supplements may promote oxidation. Others believe that high doses kill too many free radicals, inhibiting the ability of some to attack harmful bacteria or cancer cells. In addition, there is insufficient research to determine what, if any, long-term effects may occur as the result of taking these supplements.