Feature Article

Eat Your Broccoli!

An interesting article was just published in the European Journal of Clinical Nutrition. In a survey of 123 Finnish women with breast cancer, Dr. Hanna Lagstrom of the University of Turku found that only 9 percent believed that an unhealthy diet had contributed to their disease. Yet nearly a third of them (32 percent) significantly changed their dietary habits after their diagnosis.

Many of the women reduced their intake of animal fat, sugar and red meat, while eating more fruits, vegetables and dietary supplements. This was especially true for younger women. Lagstrom suggested that such dietary changes represented a way for women to exert some influence over their own well-being.

However, less than 20 percent of the women in the study received nutritional advice from a doctor or nurse, and only 11 percent were advised by dieticians. One-third of the women relied solely on the mass media for nutritional information.

Betting on Broccoli

There is an extraordinary body of research showing that a balanced diet with plenty of fruits and vegetables can minimize the risk of many diseases, including cancer. However, a new report takes these findings a step further by focusing on just one of these risk reducers—broccoli.

Dr. Chibo Hong of the University of California at Berkeley and colleagues specifically studied the effects of broccoli on human breast cancer cells. According to their findings, compounds in broccoli known as indoles are digested and broken down by the stomach into a compound called diindolylmethane or DIM.

In a presentation at the recent meeting of the American Society for Cell Biology in San Francisco, Hong noted that DIM suppresses human breast cancer cell growth by preventing cancerous cells from dividing and multiplying. In addition, beyond preventing the actual spread of the disease, DIM also promotes the death of existing tumor cells by altering levels of certain proteins that keep tumor cells alive.

And which specific part of the broccoli plant confers the greatest benefit? Interestingly enough, researchers at Johns Hopkins University in Baltimore asked just such a question a few years ago.

A team led by Dr. Paul Talalay cultivated three-day-old broccoli sprouts and compared their cancer-preventive benefits with more mature broccoli and similar crucifers.

As reported in the journal Proceedings of the National Academy of Sciences, they placed one group of laboratory rats on a five-day diet of freeze-dried broccoli sprouts and kept another group on their regular diet. All of the rats were then exposed to the carcinogen dimethylbenzanthracene.

Compared with the control rats, those that ate the broccoli-sprout diet had a lower risk of developing tumors, or they developed smaller tumors that grew more slowly. Subsequent analysis showed that the broccoli sprouts contained 20 to 50 times the amount of the phytochemical glucoraphanin than mature broccoli. Glucoraphanin neutralizes cancer-causing chemicals before they can damage a cell’s DNA.

Broccoli sprouts have another advantage over mature broccoli, they found. While the glucoraphanin levels of 22 varieties of fresh and frozen mature broccoli varied significantly, without an apparent link to growing conditions, the glucoraphanin levels remained consistent for all of the broccoli sprouts sampled.

Their findings suggested that the point in the broccoli life cycle when phytochemicals are most potent is in the sprout stage, although additional studies were called for to further compare the cancer-fighting capabilities of broccoli sprouts with mature broccoli.

Fruits vs. Vegetables

While a diet rich in fruits and vegetables is clearly essential for a healthy lifestyle, which of these food groups is actually better as a cancer-preventive? According to one group of Italian researchers—vegetables.

Dr. Silvia Franceschi of the Centro di Riferimento Oncologico in Aviano and colleagues compared the diets of 4,522 patients with breast, colon or rectal cancer with 5,155 healthy control participants. Writing in the journal Epidemiology, they noted that those who consumed the highest amount of raw vegetables—about 12 servings per week—had a 15 percent reduction in breast cancer risk, a 26 percent risk reduction for colon cancer, and a 16 percent risk reduction for rectal cancer when compared with those who consumed only 4 servings of raw vegetables per week.

(The researchers acknowledged that many Italians consume their raw vegetables with vegetable oil, which may be responsible for some of the protective benefits that they found.)

Raw carrots seemed to offer the greatest amount of protection against all three types of cancer. When compared to participants who consumed a half serving of raw carrots each week, those who ate four servings of raw carrots a week were 20 percent less likely to develop breast cancer and 30 percent less likely to develop colon or rectal cancer.

The researchers found that peas, bean, onions, spinach, zucchini, eggplant and peppers offered protection against colon and rectal cancer, but not breast cancer.

Among the different types of fruit, only apples, pears and kiwis were associated with risk reductions of at least 5 percent for all three cancer types, the study showed.

Eat a Balanced Diet

The sampling of studies mentioned above is obviously not indicative of the wealth of research that has confirmed the importance of a well-balanced diet containing a variety of fruits and vegetables. As Colleen Doyle of The American Cancer Society pointed out in response to the Italian study, "Our best recommendation is to consume a wide variety of fruits and vegetables, and eat them at least five times a day. Carrots are great, but so is broccoli and so are tomatoes."

SOURCES:

European Journal of Clinical Nutrition, December 2000; 54:844-848
Annual Meeting of the American Society for Cell Biology, December 11, 2000, San Francisco, CA
Proceeding of the National Academy of Sciences, 1997; 94:10367-10372
Epidemiology, 1998; 9:338-341

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