Following the Government's Food Pyramid Has Limited Effect on Risk of Major Chronic Disease
For immediate release: October 26, 2000
Boston, MA -- The government's Dietary Guidelines for Americans and its companion educational tool, the food guide pyramid, aim to reduce the risk of major chronic disease in the United States. But in two new studies that analyze disease in men and women whose eating patterns closely match the recommendations, researchers from the Harvard School of Public Health (HSPH) and Brigham and Women’s Hospital (BWH) have found only limited benefit in preventing major chronic diseases, including cardiovascular disease and cancer.
The researchers used the U.S. Department of Agriculture's own scoring system, called the "Healthy Eating Index," to measure the concordance of people's diet with the dietary guidelines. They studied eating patterns and health outcomes in more than 67,000 participants in the Nurses' Health Study (based at BWH) and more than 50,000 male participants in the Health Professionals' Follow-up Study (based at HSPH), across nearly a decade.
After adjustment for smoking and other risk factors, women and men who had the highest score in adhering to the recommended diet had a 3 percent and 11 percent reduction in risk for overall major chronic disease, respectively, compared to those whose diets were least consistent with the food pyramid.
For women who most closely followed the guidelines, there was a 14% reduction in risk of cardiovascular disease, and for men a moderate reduction of 28%. This is good, but better advice could lead to even greater reductions, the researchers say. Further, there was no discernable risk reduction in cancer.
The two studies appear in the November issue of the American Journal of Clinical Nutrition. They constitute the first major effort to evaluate the food guide pyramid in terms of actual chronic disease reduction.
"This does not mean diet is not important in chronic disease; we know it is very important," said Marjorie L. McCullough, lead author of the studies, who performed the analysis while a researcher at HSPH (McCullough is now at the American Cancer Society). "The studies suggest instead that the dietary guidelines need to be improved or made more specific."
For example, said McCullough, the Healthy Eating Index considers white bread and whole wheat bread to be equally healthy. Broccoli and French fries, both in the vegetable category, are given equal weight as healthy foods.
"The food guide pyramid shape conveys the message that all fats are bad and that all carbohydrates are good, despite evidence to the contrary," she continued.
Unsaturated fats such as fish oils are known to combat heart disease. Strict avoidance of all fats and consuming high carbohydrate diets instead appears to be detrimental for heart disease risk, diabetes and possibly other chronic diseases.
The Dietary Guidelines for Americans were recently updated with some improvements, the researchers noted. However, the food guide pyramid, which teaches people how to follow the guidelines, and the Healthy Eating Index, which measures how well diets match the guidelines, remain the same.
"More studies need to be done to evaluate the efficacy of the dietary guidelines," said McCullough, "and to continue the process of improving the recommendations."
For further information, please contact:
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Harvard School of Public Health
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Brigham and Women’s Hospital