Diet alone of little benefit in preventing ills
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Postmenopausal women see little change in their risk of breast cancer, colorectal cancer, cardiovascular disease or stroke, after changing their diet to reduce fat content and increase fruit, vegetable, and grain intake, researchers report.
That news comes from three articles in this week’s Journal of the American Medical Association8.
“It would be easy to misinterpret the results of this study, and it is important that we get it right,” Dr. Robert H. Eckel, president of the American Heart Association, said in a press statement. “Reducing the risk of cardiovascular disease is about following an integrated lifestyle program, rather than concentrating solely on dietary composition.”
The JAMA report is based on the results of the Women’s Health Initiative Dietary Modification Trial, involving almost 49,000 women who joined the study between 1993 and 1998 at 40 U.S. clinical centers. The participants were assigned to dietary intervention or a comparison group.
Women in the intervention group were instructed to reduce their intake of total fat to 20 percent of their energy intake and to increase their consumption of vegetables and fruits to at least five servings daily, and grains to at least six servings daily. This group also participated in behavioral modification sessions.
After six years, the woman had not fully met the dietary goals, although they did somewhat better than the comparison group.
Dr. Barbara V. Howard, from MedStar Research Institute in Hyattsville, Maryland, and colleagues found that, after an average follow-up of 8 years, there was little effect of the dietary intervention on rates of coronary heart disease, stroke, or cardiovascular disease (CVD).
“To achieve a significant public health impact on CVD events, a greater magnitude of change in multiple macronutrients and micronutrients and other behaviors that influence CVD risk factors may be necessary,” Dr. Howard’s group writes.
Meanwhile, Dr. Ross L. Prentice, from Fred Hutchinson Cancer Research Center in Seattle, and his associates followed the women for risk of breast cancer. Again, diet modification did not alter the risk significantly.
And a team led by Dr. Shirley A. A. Beresford at the University of Washington in Seattle also found that the intervention had no significant effect on the occurrence of colorectal cancer incidence
In a related editorial, Dr. Cheryl A. M. Anderson and Lawrence J. Appel from Johns Hopkins University in Baltimore remark that the study did not look at dietary measures that might have had a greater impact in reducing cardiovascular disease, such as reducing salt and saturated fats and increasing potassium and polyunsaturated fats.
Also, they point out, even though most of the participants were overweight, the trial did not focus on lifestyle interventions that could have had an influence, including weight loss, physical activity, and avoiding tobacco exposure.
SOURCE: Journal of the American Medical Association, for February 8, 2006.
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