Cancer Prevention: What Works?
Soy, fish oil, and alcohol are still debated, but some things are certain: Stop smoking, lose weight, and exercise.
By Richard Trubo
Reviewed By Michael Smith
Cancer has surpassed heart disease to become the No. 1 cause of death in the U.S. in people under age 85. No wonder more people than ever are turning their attention to cancer prevention strategies that might protect them from becoming a statistic. But the question lingers, which approaches really work? And which may be little more than hype or wishful thinking?
If you're concerned about cancer prevention, one of your challenges is to sort through the research reported in the media and make sense of findings from highly publicized studies that are often contradictory.
"One week, there might be a study that suggests that high coffee intake causes cancer, and the next week, we'll hear about another study concluding that coffee consumption has no relationship to cancer," says Scott Litin, MD, editor-in-chief of the Mayo Clinic Family Health Book and professor of medicine at Mayo Medical School. "News organizations want to report the latest information, but this doesn't always mean it's the most reliable or the best done study. There is a lot of confusion out there, and in many areas, the medical profession doesn't yet know what's going to pan out and what won't."
In some areas of cancer prevention, carefully conducted and controlled studies just haven't been performed yet. "Many claims have been made, but until the research is done, we just don't know which reduce the risk of cancer, which have no effect, and which are harmful," says Cynthia Stein, MD, MPH, of the Harvard Center for Cancer Prevention at Harvard Medical School.
What's Fact? What's Not?
Take high-fat diets. "Ten years ago, cutting down on fat in the diet to lower cancer risk was one of our major recommendations," says Melanie Polk, MMSc, RD, director of nutrition education at the American Institute for Cancer Research in Washington, D.C. "At the time, the evidence indicated that excessive fat in the diet could promote the cancer process."
But, says Polk, the relative importance of fat restriction in cancer prevention is changing as more studies are done. "The research now supports a mostly plant-based diet emphasizing fruits and vegetables as protective of cancer," she says. "The evidence in this area far outweighs the research into fat. So while we still believe that eating a lower-fat diet is one approach to lowering your cancer risk, even more important is to eat a mostly plant-based diet. At least 20% of cancer cases could be avoided by eating at least five servings of fruits and vegetables a day."
In particular, says Stein, there is evidence that by increasing your consumption of fruits and vegetables, you may be able to lower your risk of cancers of the bladder, esophagus, pancreas, lung, and oral cavity.
Therese Bevers, MD, medical director of clinical cancer prevention at the University of Texas M.D. Anderson Cancer Center in Houston, concurs that a healthy diet is important and may reduce the risk of developing cancer. But, she adds, doctors are awaiting more definitive data on the optimal diet for cancer prevention. "Some studies have shown that reducing your dietary fats can lower your risk of breast cancer, but others have shown no such benefit," she says.
Weighing the Evidence
There is plenty of hype in many areas of cancer prevention, even when the scientific evidence isn't persuasive. For example:
Controversial and Unproven
Although you might read about various links between cancer and certain lifestyle choices, many of these claims haven't impressed the serious scientists. Internet emails, for example, have proclaimed that chemicals in underarm antiperspirants are absorbed through the skin and interfere with normal circulation, causing toxins to build up and trigger breast cancer. But according to the American Cancer Society (ACS), there is "no experimental or epidemiological evidence to support this rumor."
One popular urban legend has implicated underwire bras as a cause of breast cancer, claiming that they obstruct lymph circulation, although the ACS insists that there is no credible research that supports this claim. There is probably no need to give up coffee, either -- at least not now. Caffeine may increase symptoms of fibrocystic breast lumps, but there is no proof that this benign breast disease increases the likelihood of breast cancer.
What Makes Sense?
So what should you do for cancer prevention? "At least 50% of cancers in the U.S. could be prevented just based on what we already know about risk factors," says Stein. Here are some recommendations to take seriously:
Originally published May 23, 2003.
Medically updated Jan. 24, 2005.
SOURCES: Therese Bevers, MD, University of Texas M.D. Anderson Cancer Center, Houston. Scott Litin, MD, Mayo Medical School, Rochester, Minn. Melanie Polk, MMSc, RD, American Institute for Cancer Prevention, Washington, D.C. Cynthia Stein, MD, MPH, Harvard Center for Cancer Prevention, Harvard Medical School, Boston.
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