Incidentally, another bit of "conventional wisdom" that's been overturned, along the lines of the butter/margarine reversal: according to controlled studies, large doses of antioxidants reduces life expectancy. And by "antioxidants" I mostly mean vitamin E:

This does make you wonder just what on earth people were thinking when they thought extremely large doses of something fat soluble was a good idea. Crazy. I am somewhat wary of saying 'large doses of antioxidants reduces life expectancy'... that seems to be completely the wrong inference to make. Melatonin is a far stronger anti-oxidant than vitamin E but ridiculously high doses of melatonin don't cause the same problem. (By ridiculously high I refer to levels of antioxidising power that would require easily fatal levels of vitamin E to achieve.) Why don't they try the generalisation "large doses of fat soluble vitamins"? That's far more credible.