Broccoli chemical found to help cells fight cancer Study may find diet that combats disease

March 15, 1992|By Jonathan Bor | Jonathan Bor,Staff Writer

In a discovery that should delight mothers everywhere, a team of Johns Hopkins researchers has isolated a potent chemical found in broccoli and related vegetables that appears to boost the cancer-fighting abilities of human and animal cells.

And the news gets better. Researchers believe that the natural compound may not be particular about the types of cancer it prevents -- possibly guarding against colon and prostate cancers as well as the breast cancers that strike post-menopausal women.

Dr. Paul Talalay, a molecular pharmacologist who directed the research, said the chemical known as sulforaphane boosts the production of an important enzyme that is known to neutralize carcinogens before they trigger tumor growth.

The finding, published in today's Proceedings of the National Academy of Sciences, was based on laboratory observations. Put simply, scientists extracted the chemical from broccoli and then watched what happened when they applied it to cells grown in a dish. In a press briefing Friday, Dr. Talalay cautioned that several years of research on animals and -- ultimately -- humans will be needed before the team can say conclusively that broccoli prevents cancer.

Nor was he ready to advise Americans to eat a particular "dose" of broccoli. But that day may not be too far off, he said.

"In my opinion, when we have a better handle on the chemistry, we will be able to come up with more rational [dietary] guidelines," Dr. Talalay said. "What we're able to say is that we've found in one vegetable a very potent compound that behaves as if it should be an anti-carcinogen."

For about a decade, scientists have suspected that eating the so-called cruciferous vegetables -- a family that includes broccoli, cauliflower, kale, brussels sprouts, collard greens and mustard -- lowers the risk of cancer. The belief is based on epidemiological studies that have found lower cancer rates among vegetable eaters, but no one has ever proved that the foods and not something else deserve the credit.

The next stage will involve mice. In experiments almost under way, the Hopkins team plans to compare cancer rates between two groups of mice: some that have been exposed to a known carcinogen, and others that have been exposed to the same carcinogen as well as the broccoli compound. A lower rate among the latter group would show that the compound really plays a role in preventing cancer.

"Although the story is not yet complete, our prediction is that sulforaphane will block tumor formation in animals and presumably in man," Dr. Talalay said.

President Bush's much-publicized dislike of broccoli has earned it an undeserved reputation as the ugly duckling of vegetables. Broccoli is enjoying unprecedented popularity. The average American is eating nine times more broccoli now than 20 years ago -- an era in which per capita consumption of red meat consumption declined by 16 percent, according to a government survey.

"We may be doing better than we know," Dr. Talalay said. The war against cancer hasn't yet made a dent in overall cancer rates, he said, despite an onslaught of new drugs, surgeries and other treatments for cancer. But shifting dietary habits may produce long-term benefits that have yet to be seen, he said.

The Hopkins research evolved from a growing understanding of how cells fight cancer. Past studies have shown that carcinogenic agents -- such as those found in cigarette smoke -- are harmless substances until they are broken down by chemicals inside the body known as Phase I enzymes.

These enzymes can convert the once-benign chemicals into dangerous compounds that can damage DNA -- the genetic blueprint -- and set off the unrestrained growth of cancer. But other enzymes, known as phase II enzymes, are capable of diverting the cancer-causing molecules before they do their damage.

It is the balance of these two enzymes that determines a cell's ability to resist a carcinogen, Dr. Talalay said. What excites the Hopkins team is the discovery that the broccoli compound appears to tilt the balance toward the helpful enzymes -- a process that could play a big role in preventing cancer.

"It's neat because it works on a step in the carcinogenic process before the damage occurs," he said. "It takes these carcinogens and heads them off at the pass before they have the chance to do any damage."

In their experiments, the research team made a soup made from a strain of Maine broccoli known as Saga. Then, they ran the soup through a device that separated it into component parts. When they subjected the cells to the various compounds, the sulforaphane was the only one to boost the helpful enzymes but not the hurtful ones.

Other cruciferous vegetables contain sulforaphane, but apparently not as much.

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