Most people get a meager 12 grams of fiber a day. Our studies showed that doubling that amount could reduce breast cancer," says Dr. Cohen. The reason? A diet chock full of whole grains, fruits and vegetables supplies both soluble and insoluble fiber (the type that doesn't dissolve in the body) which binds to estrogen and escorts it out of the body. Fiber may also enhance bacteria that metabolize estrogen. Wheat bran also contains phytic acid and lignans shown to block the growth of mammary cancer in the lab studies. A bowl of cereal will provide one quarter of your quota.