With the recent revision of the Food Guide Pyramid, the Dietary Guidelines for Americans have for the first time provided the public with a quantitative recommendation for whole-grain intake. In a study published in the January issue of American Journal of Clinical Nutrition, researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University (HNRCA) found that consuming a diet rich in whole-grain foods may lower an elderly person's risk for cardiovascular disease and reduce the onset of metabolic syndrome. Metabolic syndrome, which is a collection of risk factors, puts people at an increased risk of cardiovascular disease and type 2 diabetes.
The study, a collaborative effort that included Paul Jacques, DSc, director of the Nutritional Epidemiology Program at the HNRCA, Nicola McKeown, PhD, scientist in the same program, and others, examined the relationship between whole-grain intake and cardiovascular disease risk factors, metabolic syndrome, and the incidence of death due to cardiovascular disease in the elderly.
"Previous studies have found a link between whole-grain intake and reduced risk of metabolic syndrome in middle-aged populations. What's unique about our study," says McKeown, "is that we went back to data that was collected 20 years ago, using diet records that captured food intake, and found that whole-grain foods had a subsequent benefit in the elderly." The ability of researchers to differentiate whole grains from refined grains more accurately through the use of diet records is a major advantage when assessing dietary intake. "In past studies," states McKeown, "fixed food categories have made it difficult to accurately separate whole and refined grains for some food items -- such as breads."
According to Jacques, who is also a professor at the Friedman School of Nutrition Science and Policy at Tufts, "consuming a high whole-grain diet is likely to have positive metabolic effects in elderly individuals, who are prone to greater insulin resistance and impaired glucose tolerance."
McKeown and Jacques found that, indeed, as whole-grain intake increased, fasting blood sugar levels were lower in these subjects. Refined grain intake, on the other hand, was associated with higher fasting blood sugar levels. Elevated fasting blood sugar levels can indicate impaired glucose tolerance and the presence of diabetes. In addition, people who consumed high amounts of refined grains had twice the risk of having metabolic syndrome than those people who consumed the fewest servings of refined grains.
"It is important to note," cautions McKeown, "that the subjects in the study were not a representative sample of the elderly, so we do not know the implications of applying these results to other populations. Based on the research, whole-grain intake is one modifiable dietary risk factor that may lead to substantial health benefits at the population level, even among an older population. Older adults should be encouraged to increase their daily intake of whole grain foods to three or more servings a day by substituting whole grains for refined grains."
Sahyoun NR , Jacques PF, Zhang XL, Juan W, McKeown NM. American Journal of Clinical Nutrition. 2006 (January); 83: 124-131. "Whole-grain intake is inversely associated with the metabolic syndrome and mortality in older adults."
If you are interested in hearing more about any of the studies or speaking with a member of the faculty of the Friedman School of Nutrition Science and Policy or another Tufts health sciences researcher, please contact Peggy Hayes by calling 617-636-3707 or Siobhan Gallagher by calling 617-636-6586.
The Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy at Tufts University is the only independent school of nutrition in the United States. The school's eight centers, which focus on questions relating to famine, hunger, poverty, and communications, are renowned for the application of scientific research to national and international policy. For two decades, the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University has studied the relationship between good nutrition and good health in aging populations. Tufts research scientists work with federal agencies to establish the USDA Dietary Guidelines, the Dietary Reference Intakes, and other significant public policies.
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