Natural antioxidants are molecules that prevent damage against free radicals in the body. Free radicals cause damage to our immune cells when produced in excessive quantities during the inflammatory process (part of the immune response). It is necessary for our bodies to eliminate them to avoid this damage and help our bodies in the fight against infections caused by bacteria,viruses, and parasites. We can help our body in the fight against excessive damage from free radicals by eating certain antioxidant rich foods. Examples of these foods are; blueberries, cranberries, blackberries, strawberries, beans, artichoke hearts, and spinach. There are many others. Including a mixture of these fruits and vegetables in your diet, along with others, can help improve overall health and defense against free radicals in the body.

http://www.ncbi.nlm.nih.gov/pubmed/21506934