Perhaps the best example of the ability of differences in glycaemic index of CHO-enriched diets to modify glycaemic control and lipoprotein metabolism in patients with Type 2 diabetes is the report by Jarvi and colleagues (38). These investigators compared the metabolic effects of two diets, each containing 55% of total calories as CHO, in 20 patients, consuming each of the test diets for 24 days. The glycaemic indices were calculated to vary from 57 to 83 as compared to white wheat bread. The two test diets were compared to each other, as well as to baseline values obtained on an uncontrolled diet. Of considerable interest was the observation that fasting plasma glucose, TG, and LDL cholesterol concentrations fell on both diets, supporting the general belief that essentially any prescribed diet is better than no diet plan. On the other hand, the degree of improvement in all of these variables was the same, irrespective of the difference in glycaemic index of the diet. Furthermore, the improvements in day-long plasma glucose and insulin concentration appeared to be of somewhat lesser magnitude than in the study in which the CHO intake was reduced, and unsaturated fat intake increased (20). Brand and associates (39) conducted a somewhat similar study in 16 patients with Type 2 diabetes, comparing the metabolic effects of two diets, differing in their glycaemic index from 77 to 91. However, both of the diets were relatively low in CHO (*45%). The fasting plasma glucose concentrations were similar after the high glycaemic index and low glycaemic index diets, as were the fasting concentrations of plasma insulin, TG, LDL cholesterol and HDL cholesterol. However, the total integrated postprandial plasma glucose response following the low glycaemic index breakfast and lunch was lower by 14% as compared to the high glycaemic meals.
Two other papers are often cited as showing the benefits of differences in the glycaemic index of CHO-rich foods: in one of these (40), only six patients with Type 2 diabetes were studied, and their data were not presented separately; while in the other paper the patients were only followed for two weeks (41).
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