Grocery Bag Therapy

Scientists get a better idea of how nutrition can help prevent cancer

You've heard it over and over again: To ward off cancer, eat more broccoli and tomatoes, drink more tea and red wine. Now, new research is helping us to better understand why you should do those things.

Over the past decade, scientists have studied people with cancer and compared their diets with those of similar folks who don't have the disease. The conclusion? Those who eat more vegetables, fruits, and other wholesome foods usually have lower cancer rates.

But simply showing that people who eat a particular diet get less cancer doesn't prove these foods are actually protective. What if those people are simply healthier to begin with? So scientists are going beyond simple observations to probe the cellular and biochemical details of the effects of individual chemicals in foods. And they're beginning to paint a compelling picture of the mechanisms by which foods can, in fact, protect against cancer. Helping in this effort is the National Cancer Institute, which is sponsoring some 60 clinical trials that test the cancer-preventive effects of chemicals in everything from grapes to garlic. It's also funding studies that probe the molecular targets of substances found in food.

The basic idea is that individual nutrients act like drugs in the body, hitting targets in cells that affect cancer development. For instance, toxicologist Tom Kensler at Johns Hopkins University has shown that substances called isothiocyanates, found in cruciferous vegetables such as broccoli, cause cells to boost production of enzymes capable of breaking down carcinogens before they do harm. Dr. Andrew Dannenberg of New York-Presbyterian Hospital has learned that the omega-3 fatty acids in fish oil "have spectacularly interesting molecular effects," controlling genes involved in cancer. Dannenberg says typically many years elapse before an initial malfunction in cells turns into a tumor. Research like his is designed to find substances that could be eaten or taken to keep tumors from starting.

Nutrients in other foods also seem to act like anticancer drugs. Resveratrol, found in grapes and red wine, kills cancer in the test tube and reduces the number of tumors in animals. Another intriguing substance is lycopene, found in tomatoes. Cooking the tomatoes--think tomato sauce--affects the lycopene in a way that makes it easier for the body to absorb. In test tubes, lycopene is able to slow the kind of cell growth that leads to cancer.

Researchers believe scores of such protective substances exist, with many still to be discovered. Eventually, it may be possible to concoct a dietary supplement packed with the right amounts to minimize your cancer risk.

Until then, however, the best advice is still the old-fashioned kind: Eat lots of fruits, veggies, and whole grains, drink moderate amounts of red wine or grape juice, don't stint on the garlic, and stay trim and fit. "Some 30% to 40% of cancers could be avoided with diet, physical activity, and weight loss," says Dr. George A. Bray, professor of medicine at Louisiana State University Medical Center. You might also want to be careful about barbecuing meat, poultry, and fish at high temperatures. High-heat promotes chemical reactions that form carcinogens, as does the fat that drips on coals. One fix: Turn meat more frequently or slather on sauce to keep temperatures down.

A healthy diet is no guarantee that you'll be cancer-free. But it'll lessen your chances of getting a diagnosis you will dread.

By John Carey

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