It's every bit as important, in my opinion, to not eat killer foods, as it is to eat vegetables. That is, a neutral effect alone would be enough to show dramatic health improvements. This is where the pro vitamin arguments went wrong from day one.
Water isn't a miracle elixir that cures cancer. Strip out all high fructose corn syrup and sugar from all American beverages, and the equivalent conclusion would be to suggest that water cures obesity, diabetes and cancer (when in fact the absence of sugar and HFCS is what's doing the trick).
Also, telling me that people took vitamins without showing me their specific day to day diets and exercise routines, is absurdity to put it very mildly. Dietary input and exercise is radically more important than the vitamins in the health outcomes.