Postprandial glycaemic response refers to an elevated blood glucose concentration after a meal. Foods yielding low postprandial glycaemic responses have been suggested to beneficial for the dietary prevention of type 2 diabetes (Livesey et al. 2008). Oat β-glucan can attenuate the glycaemic response (Braaten et al. 1991, 1994, Tappy et al. 1996, Jenkins et al. 2002, ). The increase of intestinal viscosity due to high molecular weight β-glucan is crucial for achieving the positive effect of β-glucan on the peak blood glucose (Wood et al. 1994, 2000, Wood 2007).
Tappy et al. (1996) observed that inclusion of oat β-glucan into breakfast cereals could reduce the postprandial glycaemic response by up to 50 %. At low levels (below 5 %) this appeared to be dose responsive. Levels above 5 % did not show large reductions in the glycaemic response, possibly indicating a saturation point. This may be an important when considering the appropriate levels of β-glucan inclusion in food systems.
Jenkins et al. (2002) found a depression of glycaemic index (GI) by high levels of β-glucan fibre in two functional foods tested in Type 2 diabetic patients. GI is defined as the incremental area under the postprandial blood glucose curve (change in blood glucose level 3 h after a meal) after the consumption of 50 g of (digestible) carbohydrates from a test food, divided by the area under the corresponding curve after a meal containing a similar amount of the reference food, normally white bread or glucose (Wolever et al. 1991).
The reference is given the value 100, and the lower the response, the smaller the GI. The glycaemic indices of the prototype β-glucan enriched cereal (GI = 52) and bar (GI = 43) were significantly lower than the indices of commercial oat bran breakfast cereal (GI = 80) and white bread (GI = 100). Thus, blood glucose levels of diabetic and pre-diabetic individuals can be moderated by using β-glucan rich foods.
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