Advocates of improved diet and exercise for better cancer prevention are calling for policy changes and physician training to help the public make the kind of lasting improvements that might reduce cancer rates.They hope to bypass the excruciatingly arduous and long path that anti-tobacco advocates had to travel before warnings about the hazards of smoking took hold.
Although the evidence was clear that cigarette smoking caused lung cancer as early as the 1950s, physicians were slow to take up the cause, according to Ernst L. Wynder, M.D., an investigator in the initial tobacco and lung cancer studies. Thirty years passed before political activists began to support legislation to curb tobacco use.
Evidence for the impact of diet and exercise on cancer risk has been building over the years.Although research is still equivocal about the effect of specific nutrients and types of fat, broad recommendations, such as eating more fruits and vegetables and maintaining a Healthy weight, are widely supported. But consensus of opinion among medical experts is not enough to create action unless it is translated into prevention and control measures by government, the media, physicians, and educators, accord to Wynder, founder and president of the American Health Foundation, New York.
Two major reports on cancer prevention released in 1997 - from Harvard University's Center for Cancer Prevention* and the American Institute for Cancer Research -- couple recommendations for individuals with proposals for community level efforts and government policy changes."Lifestyle decisions are up to the individual, but the environment in which the individual is functioning needs to help support that," said Laurence N. Kolonel, M.D.. Ph.D., who participated in development of the AICR guidelines (see News, Nov. 5, 1997). The Harvard report,s authors estimate that 50% of all cancers could be eliminated through a modified diet. increased exercise, decreased alcohol use, and cessation of tobacco use.Two of the policy changes they call for are mandated physical and Health education in all school grades, and use of federal funds to create accessible sites physical activity.
Environmental Support
"By reintroducing physical education into our schools and creating safe and affordable spaces for adults to exercise, we can have a dramatic an(I sustained impact on cancer risk," said Graham A. Colditz, Dr.P.H., director of education at the Harvard Center for Cancer Prevention. In addition, stated Kolonel. who is deputy director of the Cancer Research Center at University of Hawaii, "nutrition should be taught in schools beginning in kindergarten.It should be an essential. like reading and writing.Children should learn about what to eat and what it means, just as they team how to count." Proponents of early education know they are swimming against the tide. For example, the Harvard report notes that enrollment in daily high school physical education classes dropped from 42% in 1991 to 25% in 1995.But proponents thinks this might be the right time to push for school-based interventions.Governors in numerous states, including Illinois, New Jersey and Ohio, have vowed to spend some of their states' budget surpluses on education.
Recent evidence points to a potentially large return if the investment is made.A study released in February from the University of Bristol in England revealed that a childhood diet that provided sufficient nutrients but was lean on calories and high in fruits and vegetables reduced childhood mortality in adulthood.The dietary habits of almost 4,000 youngsters who lived in England in the 1930s were observed for 1 week.The children were their followed into adulthood for cause of death. The children who ate the least were 2.5 times less likely to die from cancer than those who ate the most.
Similarly, the Harvard researchers estimate that with a 30-minute increase in daily physical activity, even among people who already exercise regularly, Americans should see a 15% reduction in the incidence of colon cancer.That would translate to about 1 5,000 fewer cases each year.
Stiff Competition
Research results that show the benefits of good nutrition or exercise aren't enough to change public behavior. "Asking patients to give tip a habit they enjoy today for possible benefit in the future is a tough sell," Wynder acknowledged."Especially without social sup- port.'
Just like tobacco, junk food and processed foods are produced by a huge industry intent on selling its products. According to Advertising Age, the 1996 advertising budget for Coca Cola Classic was $131 million; for McDonald's, it was $599 million.NCI's budget for the 5-A-Day promotion of fruit and vegetable consumption was under $1 million.
Also, restaurants arc serving up more and more of the public's food supply. Meals eaten away from home account for one third of all calories. according to Bonnie Liebman, director of nutrition at Washington, D.C.-based Center for Science in the Public Interest."The kinds of food served away front home are not the ones that are going to reduce risk of disease." And the portions served in U.S. restaurants have grown to sizes that most experts agree are excessive.
Even when people know intellectually what's good for them, that information is hard to act on. The most recent U.S. Department of Agriculture's nationwide food consumption survey revealed the chasm between knowledge and behavior. Although two-thirds of adults think it's very important to choose a diet with plenty of vegetables and fruits, consumption of these foods has increased only slightly since the late 1970s.
Fruit intake is slightly below the minimum two servings recommended in the USDA's Food Guide Pyramid, and vegetable intake is only slightly above the minimum three servings, the survey showed.Vegetable consumption leans more to french fries than dark green and yellow vegetables.
Likewise, 90% of adults believe it's important to maintain a healthy weight, but 40% think they consume too many calories and one-third are overweight (up from one-fourth in 1980).
As was the case with tobacco, Wynder contends, physicians are ill equipped to communicate the diet and exercise messages."Most physicians consider themselves foremost to be healers of disease.They do not regard themselves as political activists and few of them are experts in behavioral medicine," Wynder wrote last year in the American Journal of Epidemiology. He is calling for medical school training in behavioral medicine.
Wynder's grim view of physicians' capacity to do prevention counseling is supported by a recent study on cardiovascular disease counseling published in Morbidity and Mortality Weekly Report.
Data from more than 29,000 general medical and routine gynecologic visits in 1995 showed that physicians offered counseling about physical activity during 19. 1 % of office visits, about diet during 22.8%, and weight reduction during 10.4%. Only 41% of office visits for current smokers included smoking cessation counseling. Cancer prevention interventions are unlikely to be much more common than what this study found for heart disease prevention.
Reluctant Physicians
Almost three-quarters of physicians feel inadequately prepared to provide dietary counseling, according to the MMWR article. And while physically active people often cite a physician's advice as a major motivator in their decision to become active, a 1991 survey of primary care physicians found that only 24% felt they would be able to modify patient behavior.
It's no surprise that dietary counseling is a challenge for physicians and is at- tempted much less often than smoking- cessation counseling.At least with tobacco, the recommended behavior is simple: "Don't smoke." For nutrition, the messages are numerous and complex.With food, "cold turkey" is not an option.
*Copies of the Harvard Report on Cancer Prevention are available by e-mail (hccp@hsph.harvard.edu) or by fax (617-566-7805).
Cori Vanchieri
Material presented on this home page constitutes opinion of the author.
Copyright © 1998 Steven J. Milloy. All rights reserved. Site developed and hosted by WestLake Solutions, Inc.