I have thought about this problem for a long time now. Does the oxidative damage occur first causing aging or does aging lead a reduction in the cell's ability to combat oxidative stress?
A lab at the University of Michigan has done some great work on this, but the still have not quite answered the question.
My opinion for a long time follows the article. I don't think that antioxidants from foods prevent DNA damage. I think that fruits and vegetables actually have compounds that are potentially carcinogens, and your body's oxidative stress response is upregulated by these. Yeast cells that are challenged with a low does of an oxidant are better able to handle a higher dose of oxidant than cells that were not. It's akin to whatever doesn't kill you makes you stronger.
Bruce Ames who invented the ames test to determine the mutagenic potential of compounds has published articles about how natural carcinogens are just as common as synthetic ones. Plants produce many of their own pesticides which have been shown to be carcinogens. I would highly recommend reading about this for any of you are into organic food choices.
So, fruits and vegetables help us live longer, but possibly by exactly the opposite reason that everyone believes.