High-fiber anything. Fiber's ability to keep things moving appears to have a protective effect not only on the colon (no surprise) but also on the breasts. Researchers in Sweden followed more than 61,000 women and discovered that those who consumed more than 4.5 servings of whole grains daily had a 35 percent lower risk for colon cancer. Because fiber speeds the passage of stool through the colon, cells have less exposure to potentially carcinogenic waste. Roughage may also sop up excess estrogen and insulin, two hormones linked to breast cancer.