…at Nobel Intent, the science-oriented journal/blog at Ars Technica:

Although this is contrary to common sense, the authors suggest a reason for this finding. Although antioxidant production is associated with a number of diseases, many physiologic processes also involve free radical generation. They propose that “eliminating free radicals from our organism, we interfere with some essential defensive mechanisms like apoptosis, phagocytosis, and detoxification.” As ever, the best advice would seem to be to make sure you get those five portions of fresh fruit and vegetables a day, and lay off the pills.