Scientists, mothers agree: Vegetables are good for you

April 14, 1993|By New York Times News Service

Lurking in the soul of every red-blooded American who fondly recalls when carnivorousness was a virtue, and supper wasn't supper without a centerpiece of pork chops or prime rib, lies the frail hope that the recent emphasis on fruits, grains and vegetables, vegetables, vegetables will somehow turn out to be a terrible mistake.

The time has come to relinquish that hope and give it a proper burial.

The truth is that the more researchers understand about the ingredients found in fruits, vegetables, beans and herbs, the more impressed they are with the power of those compounds to retard the bodily breakdown that results in cancer and other chronic diseases. Nutritionists and epidemiologists have long observed that people who eat a plant-rich diet suffer lower rates of cancer than do meat loyalists, and now scientists are beginning to figure out why.

Beyond the well-known benefits of vitamins and fiber, plant foods are plush with chemicals that have no nutritional value and are not necessary for immediate survival yet may impede cancer at a number of stages in its slow, savage evolution.

Most of the experiments performed so far have been done on animals or isolated cells, and no specific ingredient from fruits or vegetables has been proved in long-term human trials to prevent or retard cancer. But biologists are encouraged that many laboratory results are in harmony with the empirical studies of long-lived populations.

And just when researchers thought they had a reasonable grasp of the basic anti-cancer compounds that might be found in a healthy diet, they discover a novel pathway through which ingredients in plants may help foil disease.

In the current issue of the Proceedings of the National Academy of Sciences, scientists from Children's University Hospital in Heidelberg, Germany, report that they have isolated a compound called genistein from the urine of people who eat a traditional Japanese diet, heavy on soybeans and vegetables. Through test-tube experiments with a synthetic version of the chemical, Dr. Lothar Schweigerer and his colleagues have discovered that genistein blocks a process called angiogenesis -- the growth of new blood vessels.

That talent could have significant implications for preventing and treating many types of solid tumors, including malignancies of the breast, prostate and brain. Scientists had previously determined that if a tumor was to expand beyond pinpoint size, it first must foster the growth of new capillaries around it. Through these tiny blood vessels, the malignancy then receives the oxygen and nourishment it needs to keep swelling, eventually invading the blood and lymph system and seeding fatal colonies elsewhere in the body.

By inhibiting capillary growth, genistein may keep nascent tumors from growing beyond harmless dimensions.

Genistein is found in high concentrations in soybeans and to a lesser degree in cruciferous vegetables like cabbage. In those who eat a traditional Japanese diet, the scientists found, the urine level of the compound is at least 30 times that of Westerners.

Dr. Schweigerer also speculated that such a diet could explain why, when Japanese men leave their country for several years to work in the United States or Europe, their rate of invasive prostate cancer rises sharply. If genistein proves its mettle through testing in animals, the compound may be useful not only as a dietary measure to prevent cancer but in a concentrated form to treat tumors already in progress.

"This is a fascinating report," said Dr. Judah Folkmann of Harvard Medical School, who has worked out many of the details of how tumors develop a blood supply as they grow. "It's a novel finding. Nobody has ever suggested before that you could find in the urine certain dietary factors that inhibit the proliferation of blood vessels, and I think this work will get wide attention."

Dr. Folkmann and others view blocking angiogenesis as an ideal sort of therapy, one that would attack the malignancy while leaving normal tissue intact. Four such blockers are now being tested, but genistein would be the first compound isolated from food to be added to the list.

Encouraged as they are by the findings of anti-carcinogens in food, researchers admit that the field of food analysis is in its infancy. Food is chemically daunting, with every stalk of broccoli and slice of melon composed of hundreds or thousands of individual yet interacting chemicals. Some plant products may harbor chemicals that promote cancer along with compounds that inhibit the disease, and it can be difficult to sort out which class of chemicals predominates in a given food.

Beyond its inherent difficulties, nutrition has been viewed as an areaprone to faddishness and charlatanism, another reason traditional researchers have tended to avoid it.

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