"My conclusion was that cancer is best prevented by removing negatives from life, not necessarily adding positives."

I'm also skeptical that adding foods/vitamins/supplements will prevent cancer.

However, there is one area that adding things seems to be very beneficial, and that is adding things that promote regular bowel movements.

There have been studies of heavy coffee drinkers and their reduced risks of colon cancer. Everyone is looking for some mysterious phenol or antioxidant from the coffee as a magic elixir, but I think it should be obvious that coffee as a laxative is the agent here.

There's also the age-old rule of thumb: an apple a day keeps the doctor away. It's not the apple, it's the fiber.