As the nation’s war on cancer continues, with little change in the overall cancer mortality rate, many experts on cancer and public health say more attention should be paid to prevention.was this:
But prevention has proved more difficult than many imagined. It has been devilishly difficult to show conclusively that something simple like eating more fruits and vegetables or exercising regularly helps...
...measures that are often assumed — and marketed — as ways to prevent cancer may not make much difference, researchers say.
For example, public health experts for years recommended eating five servings of fruits and vegetables a day to prevent cancer, but the evidence is conflicting, at best suggestive, and far from definitive.
Low-fat diets were long thought to prevent breast cancer. But a large federal study randomizing women to a low-fat or normal diet and looking for an effect in breast cancer found nothing, said its director, Ross L. Prentice of the Fred Hutchinson Cancer Research Center in Seattle.
Fiber, found in fruits, vegetables and grains, is often thought to prevent colon cancer, even though two large studies found no effect.
“We thought we would show relationships that were strong and true,” said Dr. Tim Byers, professor of epidemiology at the Colorado School of Public Health, “particularly for dietary choices and food and vegetable intake. Now we have settled into thinking they are important but it’s not like saying you can cut your risk in half or three-quarters.” Others wonder whether even such qualified support is misplaced.
There has to be a reason the research disappointed, said Colin B. Begg, chairman of the department of epidemiology and biostatistics at Memorial Sloan-Kettering Cancer Center. Perhaps the crucial time to intervene is early in life.
“That’s one possibility,” Dr. Begg said. “The other is that it’s all sort of nonsense to begin with.”
Many hold out hope for exercise or weight loss. Studies have associated strenuous exercise with less cancer. But that is the same sort of evidence that misled scientists about aspects of diet.
“I think it’s wishful thinking,” said Dr. Susan Love, a breast surgeon and president of the Dr. Susan Love Research Foundation. “We would like things to be more in our control. I think that’s part of it. And in the absence of anything else, what do we tell women about how to prevent breast cancer? We tell them to exercise and eat a good diet.”
As for obesity, researchers differ. Studies that observed large numbers of people often found that fatter people have more cancer. But many of the correlations are weak, and different studies have pointed to different cancers, raising questions about whether some of the effects are real.
Dr. Otis W. Brawley, chief medical officer of the American Cancer Society, said he was convinced. The strongest link, he and others say, is with obesity and breast cancer. But there, Dr. Brawley says, the crucial period may occur early in life — girls who gain weight when they are young, he said, tend to start menstruating earlier, which increases their breast cancer risk because it adds years of exposure to the body’s estrogen. It may be that weight loss in adulthood does not help.
A strong correlative to cancer is a toxic environment, but one hardly ever hears such a possible cause discussed seriously by cancer researchers or in the cancer education programs directed to the public. It is the elephant in the room. Every year that passes increases the amount of toxic materials in our air, water, pharmaceuticals, household goods, building materials, food packaging, and foodstuffs. A recent study found not one sample of fish caught in US streams to be free of mercury. The CDC found that metabolites of plasticizing phthalates, which are finally being phased out here, have already become part of the human body, and studies show that the effects are concentrated especially among the overweight because of adipose storage. Look at breast cancer, where women have been beaten over the head with prescriptions involving fiber, diet, weight, and everything else under the sun, and shamed into guilt about bringing it on themselves. Yet breast fat is some of the most sensitive adipose tissue in the body to environmental toxins, and fatty tissue holds onto chemicals, where they continue to build up over time. If environmental causes are at the bottom of our cancer epidemic, it would make sense that obesity would be an indicator: more fat, more storage capacity for deadly chemicals. Yet no one seems to have made this a centerpiece of any anti-cancer campaign. Why? It's easier to blame individuals for "lifestyle decisions" and invoke "personal responsibility" than it is to really do anything about changing the environment, where a collusion of business interests would certainly push back against any such attempt. Better to just keep doling out the false hope that people can control their own fate, and let them keep dying.UPDATE:In the Great Minds Think Alike Department, the latest issue of Harper's has this.