The role of dietary carbohydrate in the decreased glucose tolerance of the elderly.

In this study we have attempted to evaluate the role of dietary carbohydrate (CHO) in the decreased glucose tolerance of aging. Eighteen healthy young (mean age, 27 +/- 1 standard error of the mean) (SEM) and 18 old (71 +/- 1 SEM) subjects matched for relative weight and socioeconomic group were studied. Oral glucose tolerance tests were performed while eating ad lib diet and after being given high (85%), medium (45%), and low (20% to 30%) CHO formula diets for at least three days. A three- to seven-day food record was used to determine the major nutrients including CHO and fiber intake in the ad lib diet at home. Our older subjects consumed significantly less total calories and slightly less carbohydrate but there was no difference in dietary fiber, protein, and fat intake. When studies were performed on matched CHO diets, decreased glucose tolerance was present in the older group. However, the mechanism(s) involved may vary with dietary CHO and with age. During the low CHO formula diet and the medium CHO ad lib diet, impaired insulin secretion was prominent in the elderly but was not present in the young. During the high CHO formula diet, insulin response was adequate in both old and young, but decreased glucose tolerance persisted in the older group, suggesting that insulin resistance may be the major contributing factor. We conclude that decreased glucose tolerance in the elderly is modified by CHO intake, but is present even when dietary CHO variability is acutely controlled.(ABSTRACT TRUNCATED AT 250 WORDS)