While consuming antioxidants doesn't seem to do much good, the state of your internal antioxidant systems is very important to health and longevity. "In aerobic organisms, oxygen is essential for efficient energy production but paradoxically, produces chronic toxic stress in cells. Diverse protective systems must exist to enable adaptation to oxidative environments. Oxidative stress (OS) results when production of reactive oxidative species (ROS) exceeds the capacity of cellular antioxidant defenses to remove these toxic species. Epidemiological and clinical studies have linked environmental factors such as diet and lifestyle to cancer, diabetes, atherosclerosis, and neurodegenerative disorders. All of these conditions, as well as the aging process, are associated with OS due to elevation of ROS or insufficient ROS detoxification." You might recall that enhancing or replicating the effect of these internal systems has successfully extended mouse life spans.

Link: http://www.ncbi.nlm.nih.gov/pubmed/18955158