From apples to zucchini, plant foods provide phytochemicals which all have different protective effects against cancer. Red peppers and strawberries, for example, are rich in vitamin C, an antioxidant that blocks the formation of harmful free radicals that corrode cells, which leads to cancer. Postmenopausal women with a high intake of vitamin C may reduce risk of cancer by 16 percent, one early study suggests. Citrus bioflavonoids, found in the peel of oranges and tangerines, and reserterol in grape peels may also protect against breast cancer.
"Population studies show that people who consumed flavonoids over their entire lives have lower incidences of breast cancer," says Patricia Murphy, Ph.D., professor in food science and human nutrition research at Iowa State University. Flavonoids may have weakly estrogenic effects, meaning they attach to estrogen receptors throughout the body, thus blocking the attachment of one's own estrogens. The most widely studied flavonoid is soy. The soybean's isoflavones (most notably genistein) has been shown in lab studies to inhibit the growth of breast tumors.
While five daily servings of fruits and vegetables is the minimum for good health, doubling that amount may be more protective against breast cancer, according to a pilot study at the AMC Cancer Research Center in Lakewood, Colorado sponsored by the American Institute for Cancer Research (ACIR) in Washington. Blood samples taken from 28 women at high risk for breast cancer who ate 10 or more servings of vegetables and fruits daily for two weeks showed reduced damage to the DNA by nearly more than 20 percent in just two weeks. "The key is quantity, variety and eating the whole — not processed — food," says Melanie Polk, R.D., AICR's director of nutrition education. Strawberry jam on your toast doesn't count. But juices and frozen foods do.