Objective: To study the possibility of improving blood lipids, glucose tolerance and insulin sensitivity in women with impaired glucose tolerance and a history of gestational diabetes by merely changing the glycaemic index (GI) and dietary fibre (DF) content of their bread.
Design: Randomized crossover study where test subjects were given either low GI/high DF or high GI/low DF bread products during two consecutive 3-week periods, separated by a 3-week washout period. An intravenous glucose tolerance test followed by a euglycaemic-hyperinsulinaemic clamp was performed on days 1 and 21 in both the high- and low-GI periods, to assess insulin secretion and insulin sensitivity. Blood samples were also collected on days 1 and 21 for analysis of fasting levels of glucose, insulin, HDL-cholesterol and triacylglycerols (TG).
Setting: Lund University, Sweden.
Subjects: Seven women with impaired glucose tolerance.
Results: The study shows that a modest dietary modification, confined to a lowering of the GI character and increasing cereal DF of the bread products, improved insulin economy as judged from the fact that all women lowered their insulin responses to the intravenous glucose challenge on average by 35% (0-60 min), in the absence of effect on glycaemia. No changes were found in fasting levels of glucose, insulin, HDL-cholesterol or TG.
Conclusion: It is concluded that a combination of low GI and a high content of cereal DF has a beneficial effect on insulin economy in women at risk of developing type II diabetes. This is in accordance with epidemiological data, suggesting that a low dietary GI and/or increased intake of whole grain prevent against development of type II diabetes.
Sponsorship: Supported by grants from Cerealia Research Foundation.