Low-fat diets don't halt cancer, stroke
Christine Dell'Amore, UPI Consumer Health Correspondent
WASHINGTON (UPI) -- A major eight-year research effort has found women
who eat a low-fat diet do not cut their chances of getting certain
cancers and cardiovascular disease, but researchers stress there are
still positives in the results.
In three papers released this month in the Journal of the American Medical Association, researchers around the country evaluated post-menopausal women who followed a low-fat diet.
"This is a novel study, and although the results seem disappointing to some, we see points of encouragement," said Ross Prentice, lead author of the study on breast cancer and a biostatistician at the Fred Hutchinson Cancer Research Center in Seattle.
Early research had suggested fat was a main determinant in cancer development, and so scientists set out to determine if there was a single healthy diet that could reduce breast cancer, colon cancer, coronary heart disease and stroke in women. However, the results of the study, which lasted from 1993 to 1998, showed no statistically significant drops in the diseases.
The research is part of the Women's Health Initiative, a National Institutes of Health program to examine the chronic diseases of women as they age.
Prentice and colleagues organized a trial of nearly 50,000 diverse women, aged 50 to 79, who self-reported their diet intake. Women were randomly assigned to either an intervention group of 19,541 people who ate low-fat meals or a comparison group of 29,294 who did not follow dietary restrictions.
The women followed a total-fat-reduction diet designed to slash fat intake to 20 percent of calories ingested, as well as increase fruits and vegetables to five servings and grains to at least six servings a day.
Over the eight-year period, 655 women following a low-fat diet and 1,072 in the comparison group developed breast cancer. Although this 9-percent difference is statistically insignificant, Prentice said, "there are several reasons to think this modest reduction may be real."
For instance, women who switched from a high-fat diet to a low-fat diet at the study's onset lowered their risk of breast cancer between 15 percent and 20 percent.
If the study had decreased the intake of a particular kind of "bad fat," such as trans or saturated fats, the women may have lowered their risk for heart disease, Prentice added.
Likewise, an analysis of colon-cancer rates, led by Shirley Beresford, revealed women in the low-fat group had a decrease in colorectal polyps, which can lead to colon cancer.
Overall, the researchers aimed for the women to achieve a 12 percent to 15 percent reduction in total fat; however, the women only lowered their intake 8 percent to 12 percent. "In retrospect, we're not surprised at that," said Barbara Howard, lead author on the cardiovascular disease portion of the research and the president of Medstar Institute, a Washington-based medical research non-profit. "It's difficult to get huge numbers of diverse people to change their eating habits," she added.
In the cardiovascular analysis, dietary intervention did not control incidence of stroke or cardiovascular disease and had no effect on triglyceride levels. However, women on the low-fat diet experienced small but significant decreases in weight, waist circumference and blood pressure.
"It gives promising validation of a dietary pattern that lowers fat and raises carbohydrates. None of the bad things happened that people accuse carbohydrates of doing," Howard said.
Overall, the biggest nutrition problem today is obesity, and this diet, coupled with an effort to cut calories, could be ideal for long-term weight management, Howard said.
The research will not adjust existing dietary guidelines, particularly those of the American Cancer Society, said Michael Thun, who heads epidemiological research for the organization.
Nonetheless, "this is unlikely to end the debate (on diet) completely," Thun said.
As for the public, which tends to either ignore studies or embrace them wholeheartedly, Thun warns them not to misinterpret the findings.
"This does not mean it's a good thing to go out and eat as much fat as you want," he said.
Thun recommended older women maintain a healthy body weight, exercise vigorously up to six days a week, avoid alcohol and get screened early for cancer.
Prentice and Howard plan to continue monitoring the women in the study for five years, hoping to trace further trends in cancer and cardiovascular disease.
"The long-term legacy will be one of encouraging this research area," Prentice said. "We need to find that intervention that will make a big difference."
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E-mail: consumerhealth@upi.com
Copyright 2006 by United Press International
This news arrived on: 02/07/2006
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