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updated 12/17/2004 4:18:26 PM ET 2004-12-17T21:18:26

There are many differences between Japanese and American diets that may explain why cancer incidence in Japan is far lower than in the United States. But one difference may be overlooked: The Japanese consume about five times the amount of cruciferous vegetables as Americans do.

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The most common cruciferous vegetables are those from the cabbage family: cabbage, broccoli, Brussels sprouts, Chinese cabbage, cauliflower, kale and watercress. However, even some root veggies, like radishes, parsnips, turnips, rutabaga and kohlrabi, fall in this category. Cruciferous vegetables make a unique contribution to good health. They contain natural substances called glucosinolates that break down in the body to form indoles and other compounds that fight cancer development in several different ways.

Anti-cancer compounds
One way indoles and the other anti-cancer compounds from cruciferous vegetables work is by slowing down the enzymes that activate carcinogenic substances. Another way is by speeding up enzymes that detoxify carcinogens.

In addition, these compounds can increase the self-destruction of cancer cells and stop or slow down the growth of cells developing into cancer. Some studies show that these protective compounds may also change estrogen metabolism, potentially decreasing the risk of hormone-related cancers.

Population studies link an increased consumption of cruciferous vegetables with a lower risk for a variety of cancers. Breast cancer is one of them, although a recent study suggests that premenopausal women may benefit more than older women from eating cruciferous vegetables. The other cancers are colon, lung and ovarian cancers. Although some studies indicate no reduction in prostate cancer risk, other studies show a protective influence during the early stages of prostate cancer development.

Scientists are beginning to understand the variable results from past studies. Recent evidence suggests that the compounds derived from these vegetables may only safeguard individuals who inherit particular forms of enzymes or cell receptors. Other evidence suggests that people who eat diets with high levels of carcinogenic substances from meat cooked at high temperatures or grilled benefit the most.

Avoid over-cooking
Despite the abundance of positive news about the healthfulness of cruciferous vegetables, if memories of over-cooked, slightly bitter side dishes keep you from eating these plant foods regularly, it’s time to learn new preparation methods.

Cook these vegetables only until tender because overcooking produces bitterness. Avoid boiling them in lots of water because this method leaches vitamins. Briefly steaming or stir-frying these vegetables produces much better flavor and texture. Some, like parsnips and Brussels sprouts, are excellent when roasted in the oven.

In the winter months when traditional salad greens become more expensive and less fresh, try switching to salads based on raw broccoli, cabbage, and cauliflower. By countering the assertive taste of these vegetables with equally assertive flavorings, like a drizzle of extra virgin olive oil, you can smooth out their flavor even more.

To find new, easy and healthy recipes for cruciferous vegetables, go to the American Institute for Cancer Research’s Web site, www.aicr.org. It offers a searchable database of healthy, delicious recipes in the “Recipe Corner,” a weekly recipe email you can sign up for, and other recipes you can browse through in the “Press Corner.” You can also visit the Web sites www.aboutproduce.com or www.5aday.com. Each of these also has a searchable database, so you can look for recipes that call for a particular vegetable like broccoli.

Nutrition Notes is provided by the American Institute for Cancer Research in Washington, D.C.

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