Abstract
Commercially available wholegrain foods range from highly processed products that use finely milled cereals to minimally processed products that use intact cereals. The impact of the different types of wholegrain foods on the postprandial glycaemia of individuals with diabetes could be of clinical importance. We examined the glycaemic response to wheat-based cereals differing in particle size with and without starch gelatinisation.
We conducted a study to test the postprandial glycaemic response over three hours to repeated glucose standards and four different cereals in 18 participants with type 2 diabetes (age, mean(SD), 63(10) years, BMI 33(8) kg/m2, HbA1c 57(12) mmol/mol). The test cereals and the glucose standards contained 50g available carbohydrate. The test cereals were matched for energy and macronutrient content and included cereals of different particle size (finely milled versus intact) with or without starch gelatinisation (gelatinised versus ungelatinised). The primary outcome was postprandial incremental area under the blood glucose curve (iAUC).
The mean iAUC was lowest for ungelatinised intact cereal (mean(SD), 94(86) mmol.min/L). Compared with the ungelatinised intact cereal, the mean iAUC was 180.4 mmol.min/L (95% CI: -287.3:-73.4, p<0.001) higher for the ungelatinised finely milled cereal, 275.2 mmol.min /L (95% CI: 155:395.4, p<0.001) higher for the gelatinised intact cereal, and 441.3 mmol.min /L (95% CI: 275.2:607.4, p<0.001) higher for the gelatinised finely milled cereal. However, the difference between gelatinised intact and gelatinised finely milled cereals didn’t reach significance.
Both starch gelatinisation and the particle size of wholegrain cereals appear to be determinants of postprandial blood glucose in individuals with type 2 diabetes. The advice to consume cold intact wholegrain cereals rather than hot cereals that have been finely milled may provide clinical benefits to patients with diabetes.