Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: TUESDAY, May 30, 1995 TAG: 9505310005
SECTION: EXTRA PAGE: 1 EDITION: METRO
SOURCE: JANE BRODY
DATELINE: LENGTH: Long
Motivated by reports in the news media, many have changed to a low-fat diet and begun exercising, practices that are generally health-enhancing. But others who avoid alcohol and menopausal hormones in the belief that they are doing the healthful thing may in some cases be putting themselves at a disadvantage.
Despite hundreds of studies, researchers still do not have much definitive information about the causes of breast cancer and what women might do to prevent it.
The most solid evidence involves factors that are either impossible or impractical for many women to do anything about. These include being born into families that have no history of the disease and having babies, preferably before 20 and certainly by 30, and the more babies the better.
Far less certain is the value of various steps that women can readily take. The evidence is at best suggestive and at worst contradictory.
Women worry far more about breast cancer than about any other health threat, and a recent survey showed that this concern prompts most women to greatly overestimate their chances of developing breast cancer within the next 10 years.
Women anxious about breast cancer too often avoid practices that might protect them against far worse threats. Anxiety also prompts many women to overreact to poorly documented reports about things like breast cancer risks from exposure to pesticides or hormones in meat.
Women would do far better to focus on the factors that are within their control. At the very least, making adjustments in diet and exercise habits can do no harm and will almost certainly reduce risks of a threat to women's health that is statistically far greater: heart disease. In any case, though, the wise woman will start by considering her own chances of developing either heart disease or cancer before deciding what to do.
Since it may never be proved in one's lifetime that certain measures like regular exercise reduce the risk of breast cancer or that other practices like taking postmenopausal hormones promote breast cancer, in many cases decisions about preventive practices must be made on the basis of the best available evidence.
Some population studies have suggested that a diet high in fat, and particularly in highly saturated animal fats, can raise the risk of breast cancer. But evidence from the Mediterranean countries, where consumption of olive oil, a mono-unsaturated fat, is high but breast cancer rates are low indicates that dietary fat in general is not a factor.
While it is true that the risk of breast cancer is very low in Japan, where fat intake is well below what it is in this country, and that it rises to American levels when Japanese women immigrate to this country, many factors other than an increase in dietary fat could account for the change.
Probably much more important is the amount of fruits and vegetables in the diet. Several studies point to the protective value of eating lots of fruits and vegetables, which are rich sources of nutrients and plant chemicals that in laboratory studies impede the development of cancer. Soybeans and products made from soybeans and green tea have been singled out as especially rich in substances, called phytoestrogens, that may block the tumor-promoting effects of natural estrogens.
Perhaps the most exciting recent news about preventing breast cancer emerged from a study by Dr. Leslie Bernstein of more than 1,000 California women. She found that moderate but regular physical exercise appeared to reduce the risk of breast cancer in premenopausal women by as much as 60 percent.
While the greatest benefit was associated with four hours a week of an activity like jogging, tennis or swimming laps, women who exercised for only two or three hours a week also had a significantly reduced risk.
This was one of several studies suggesting that exercise, particularly if pursued from adolescence through adulthood, protects against breast cancer. Dr. Bernstein, of the University of Southern California, suggested that exercise might counter breast cancer by occasionally blocking ovulation and therefore reducing the output of cancer-stimulating ovarian hormones. Exercise may also curb the amount of body fat, which is a supplemental source of these hormones.
Alcohol is the focus of a heated dispute. While several studies have pointed to an increase in breast cancer among women who drink any amount of alcohol, when it comes to heart disease, which kills far more women over 55 than breast cancer does, other studies have demonstrated a protective effect of moderate drinking.
The newest study, published recently in The New England Journal of Medicine, showed that among nearly 86,000 nurses overall death rates were lowest among women who had only one to three alcoholic drinks a week. Those who consumed up to two drinks a day also had a lower mortality rate than abstainers, even though this amount of alcohol has been shown to raise estrogen levels (and therefore, presumably, breast cancer risk) in premenopausal women. Women with various risk factors for heart disease, including being over 50, showed the most benefit from a modest intake of alcohol.
Even more controversial than alcohol is the role, if any, that taking estrogens during or after menopause plays in breast cancer. Contradictory studies have left millions of women confused and concerned.
Prevailing evidence strongly indicates that replacement hormones not only reduce symptoms of menopause, but also significantly lower the risk of heart disease and osteoporosis in older women. The amount of estrogen taken is far less than that produced naturally by women before menopause, so the stimulatory effects of replacement therapy on the breast are not nearly as great.
A new study at the University of Buffalo has for the first time indicated that smoking can be carcinogenic to the breast. Dr. Christine Ambrosone and colleagues showed that women who smoke and have a slow-acting version of an enzyme that detoxifies carcinogens in tobacco smoke were up to eight times as likely to develop breast cancer as women who smoked but had a fast-acting version of this enzyme. The risk was highest among women who had started smoking in their teen-age years and in those who smoked more than a pack a day.
Dr. John Gofman, an emeritus professor at the University of California at Berkeley and an expert on the effects of radiation, predicts that breast cancer cases will begin to decline now that physicians are far more circumspect in their use of X-rays. Based on an analysis of the sometimes flagrant past uses of X-rays and the much larger doses delivered by old X-ray equipment, Gofman has calculated that at least two-thirds of current breast cancer cases are the result of radiation exposure received up to 60 years ago.
Particularly hazardous practices were using radiation to shrink enlarged thymus glands, to monitor treatment of tuberculosis and to treat various dermatological conditions, including severe acne. Whole-body fluoroscopic examinations were commonly done to check growth in children. Even mammograms, used to detect breast cancer, formerly involved more than 100 times the maximum dose allowed today, as Gofman noted in his new book, ``Preventing Breast Cancer: The Story of a Major, Proven, Preventable Cause of this Disease,'' published by the Committee for Nuclear Responsibility, Inc.
by CNB