Since 1980, the Dietary Guidelines for Americans has provided advice for Americans about food choices that may promote health and prevent a variety of chronic diseases. The Guidelines are reviewed and updated every 5 years to reflect current nutritional research. In an article published in the American Journal of Clinical Nutrition, Harnack et al. evaluated data from the Iowa Women's Health Study regarding nutrition-related behaviors in a large group of postmenopausal women. They found that better compliance with the Dietary Guidelines resulted in an overall reduced risk for cancer, although measures of physical activity and weight status may have influenced this outcome.
The female study population were rural residents of Iowa and were 99% white. A total of 34,708 postmenopausal women completed a series of questionnaires on diet and lifestyle factors and were followed for cancer incidence and mortality. During a 13-year period, 5038 cancers were diagnosed in the group. Each woman was assigned an index score based on compliance with dietary recommendations contained in the Dietary Guidelines, as well as nondietary recommendations relating to lifestyle. The women were divided into 5 quintiles according to their index scores; for instance, those in quintile 5 tended to be more physically active, eat more whole grains and less fat, eat more fruits and vegetables, and to be non-smokers. Compared to the lowest quintile of compliance, overall cancer incidence for the 2nd lowest quintile was reduced by a non-significant 5%, by a significant 12% for quintiles 3 and 4, and by 15% for quintile 5. The decline in risk was quite dramatic for some forms of cancer: women in quintile 4 had less than half the risk of uterine cancer of those in the lowest quintile. Risk reduction for breast and colon cancer declined an average of 25% from quintile 1 to quintile 4. The reduction in cancer risk was associated not just with healthy eating, but also with regular exercise and avoidance of overweight and obesity.
In an accompanying editorial, McCullough and Stampfer point out that the relative risk reductions should be interpreted cautiously. When guidelines relating to weight and physical activity were removed from the analysis, the apparent benefits of adherence to the Guidelines were much more modest. In preventing cancer, lifestyle modifications that include smoking cessation and avoidance of overweight may be just as important as observing a dietary pattern that is low in red meats and high in a variety of vegetables, fruits, and whole grains.
Harnack, Lisa et al. An evaluation of the Dietary Guidelines for Americans in relation to cancer incidence. Am J Clin Nutr 2002;76:889-96.
McCullough, Marjorie and Meir J Stampfer. The Dietary Guidelines for Americans and cancer risk in women: still a long way to go. Am J. Clin Nutr 2002;76:701-2.
This media release is provided by The American Society for Clinical Nutrition to provide current information on nutrition-related research. This information should not be construed as medical advice. If you have a medical concern, consult your doctor. To see the complete text of this article, please go to: http://www.faseb.org/ajcn/October2002/13470.Harnack.pdf
For more information, please contact:
harnack@epi.umn.edu or marji.mccullough@cancer.org
Journal
American Journal of Clinical Nutrition