ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Tuesday, February 20, 1996 TAG: 9602200028
SECTION: EXTRA PAGE: 1 EDITION: METRO
COLUMN: Personal Health
SOURCE: JANE BRODY
Having heard countless suggestions that a low-fat diet may reduce their breast cancer risk, women now are told that this advice may be based more on wishful thinking than fact.
Harvard researchers found no evidence among seven studies of more than 335,000 women in four countries that a diet with less than 20 percent of calories from fat reduced a woman's risk of developing breast cancer. Nor was risk related to the types of fats the women ate.
Is this the final word on the subject, and does it mean that diet is not an important factor in breast cancer? Not at all. Several possibilities remain to be explored. One is the relationship between breast-cancer risk and fats consumed in childhood, adolescence and early adulthood. The current studies considered fat intake in mid-adult life.
Another factor to consider is the accuracy of women's dietary reports. People are notoriously poor at remembering what and how much they consume.
A third factor is whether a diet share of less than 20 percent of calories from fat is low enough to be protective, and a fourth concerns the possibility that the kind of fat, not the amount, is the issue.
For example, in animal studies, monounsaturated fats like olive and canola oils do not promote tumor growth the way polyunsaturated fats do. And in Spain and Greece, women with breast cancer were shown to consume less olive oil than did healthy women. But until recently monounsaturated oils were not commonplace in American diets and may not have been well enough represented in the Harvard study to show up as protective.
Finally, and perhaps most important, is the possibility that fat consumption may simply be an indicator of other dietary and life-style factors that play a more direct role in protecting against breast cancer.
The suggestion that dietary fat may influence the risk of breast cancer originally arose from international comparisons. Breast cancer is much less common in Asia and in poor countries that habitually consume a low-fat diet.
Now the equivocal findings about the role of fats is prompting a closer look at other elements in the diets and lives of women that may account for international differences in breast cancer risk.
In a review of breast cancer and diet in the January/February issue of Nutrition Action Health Letter, nutritionist Bonnie Liebman points out that when Asian women move to this country, they and their descendants gradually adopt Western eating habits.
For example, they start eating less soy and more meat. But this too may be a red herring; in two recent studies, Japanese women with breast cancer consumed no less soy than their healthy counterparts.
Another possibility is that in countries with low breast-cancer rates, women mainly subsist on plant-based foods: grains, vegetables, fruits and beans. Evidence is growing that plant foods, especially beans and vegetables, are rich in substances that protect against cancers.
Supporting this possibility is the observation that in countries where women rarely get breast cancer, men rarely develop prostate cancer, which is also influenced by hormones.
Alcohol, too, may be an important factor. Although one drink a day helps to prevent heart disease, the leading killer of American women, it may raise the risk of breast cancer anywhere from 10 percent to 40 percent.
In every country that has a low rate of breast cancer, women traditionally get far more exercise than American women, most of whom have been rendered inactive by motor vehicles and labor-saving devices.
Among Americans, Dr. Leslie Bernstein of the University of Southern California found that premenopausal women who exercised for one to three hours a week had a 30 percent lower risk of developing breast cancer than inactive women, and those who exercised for four or more hours a week had less than half the risk.
Physical activity and a low-fat, plant-based diet are also related to yet another factor associated with breast cancer: body weight and especially distribution of body fat.
Among Americans, being overweight (by American standards) is associated with a slight increase in the risk of breast cancer.
Height may also play a role. Tall women have a breast cancer risk that is 30 percent to 40 percent higher than that for short women. What makes women tall? In part, it is a childhood diet high in protein, which is common among Americans and, until recently at least, rare among the Japanese and other peoples with a low risk of breast cancer.
Another possibly protective factor, at least for premenopausal women, is prolonged breast-feeding - for four to 12 months - which until recently has been rare among ``modern'' American women.
LENGTH: Medium: 85 linesby CNB