Antioxidants: Cancer Prevention or a Waste of Time? : Health: Two studies dispute the nutrients’ effectiveness. Some say all the findings really reveal is a need for more research.

Not too long ago, as many as 30% of Americans were consuming antioxidant supplements--vitamins E and C and beta carotene--to prevent disease.

But now, Americans may not be so gung-ho.

After a decade of excitement, many antioxidant enthusiasts were crushed this year when two studies found the nutrients useless in protecting against lung cancer and colon cancer.

The two studies also tested the faith of scientists and the vitamin industry.

The studies point up the need for continuing research on antioxidants and “should be viewed as a wake-up call,” said John Cordaro, president of the Council for Responsible Nutrition, a trade group representing vitamin supplement makers and distributors.

“These studies were very surprising, perhaps because we had become accustomed to an almost never-ending onslaught of positive results,” Cordaro told members of the council Monday at its annual meeting in Dana Point.

But adults should continue to take vitamins E and C and beta carotene, even while the research unfolds, conference attendees were told.

“I would not suggest that anyone discontinue taking antioxidants on the basis of any one (study),” said Julie Buring, an antioxidants researcher at Harvard University.

There are still plausible reasons to believe antioxidants work against cancer and heart disease, she said. Scientists propose that antioxidants deactivate free radicals, molecules that cause severe genetic damage to cells and lead to disease.

“(Antioxidants) act like a vacuum cleaner. They go in and get the oxygenated cells that attack DNA,” Buring said.

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The studies that turned the most promising preventive health research of the era into a controversy were published this year in the New England Journal of Medicine.

In April, the Finnish and American researchers announced that a six-year study of 29,000 male smokers in Finland found no evidence that beta carotene supplements could prevent lung cancer.

And, in the most perplexing twist, the study found that the smokers taking beta carotene had an increased risk of stroke and a slightly elevated risk of heart disease.

Then, in July, researchers at Dartmouth Medical School reported that beta carotene and vitamins C and E did nothing to lower the risk of colorectal cancer in 751 people.

The studies were exceptional in that they ran counter to most previous studies. For that reason, many scientists say they remain convinced that antioxidants really do work, said Dr. Kenneth Cooper, the aerobics guru.

“There is so much data out there that show the protective effects of antioxidants. Don’t be led astray by the studies,” Cooper advised the conference participants.

Supportive evidence had been building for more than two decades. For example, one study of 87,000 women during the 1980s showed that those who reported a diet very high in antioxidants from fruits and vegetables had a 46% lower risk of heart disease.

Studies looking at the effects of antioxidants on cancer have not been as conclusive, Buring said, but they too indicate a positive effect.

The problem with most of the previous studies, however, is that they simply compare people’s diets with their health. To be accurate, the study participants have to correctly report what they eat over a period of several years.

Researchers were eager for the results of the Finnish study because it was different. In that study, one group of people were given vitamin E and beta carotene supplements while a comparison group was given a placebo. It is this kind of randomized, controlled study that is considered most scientifically valid, Buring said.

And so the results were especially distressing.

But Buring and others say the study was flawed because the smokers were followed for only six years, too short a time to see the effects of a fairly low dose of beta carotene. Moreover, since the men were heavy smokers, it could be that beta carotene only works to prevent disease and cannot halt lung cancer after it has started.

As for the increased risk of stroke found in the men who took beta carotene, that is much harder to explain, Buring said.

“We cannot exclude that this is just chance,” she said of the finding. “I do not believe the results disprove the benefits of antioxidants. But it suggests that the benefits we’ve seen (in other studies) may have been overestimated.”

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Research on whether antioxidants prevent certain types of cancer have been mixed, which is why the Dartmouth study on colorectal cancer was less upsetting, says Dr. Roberd Bostick, a antioxidants researcher at Wake Forest University.

“The question of whether or not antioxidants have a role in preventing cancer is still a wide-open and very exciting question. The Finnish and Dartmouth studies have not derailed that,” he said.

So, who should take antioxidants? Which ones? In what dosages? No one is eager to answer.

At a recent meeting of cardiologists, two-thirds of the doctors said they took antioxidants but few admitted to recommending them to their patients, Cooper said.

“We’re really not quite sure of the potential for harm from taking antioxidants. For that reason, I think physicians are a little bit scared about recommending them. But there is still enough evidence to convince them to take antioxidants themselves,” Cooper said.

In his new book, “Antioxidant Revolution” (Nelson), Cooper recommends a daily “cocktail” of 400 international units of vitamin E, 1,000 milligrams of vitamin C and 25,000 IU of beta carotene.

But Buring urged patience. The next big randomized, controlled study on antioxidants--the massive, 12-year Physicians’ Health Study--will be completed next year, with results available in 1996, she said.

“If that study comes out positive, I think a lot of people will believe it.”