Objectives: To determine the extent to which b-glucan reduces the glycemic index (GI) of oat products and whether high levels of b-glucan impair palatability. Design: The study design was an open-label, randomized cross-over study with six treatment segments. Setting: Free-living outpatients. Subjects: Sixteen volunteers with type 2 diabetes (10 men, six women, 61 AE 2 y, body mass index 29 AE 2 kg=m 2 , HbA1c 7.4 AE 0.4%) were recruited from the St Michael's Hospital diabetes clinic. Interventions: Volunteers were given, in random order, 50 g available carbohydrate portions of: white bread; a commercial oat bran breakfast cereal (4.4 g% b-glucan); and a prototype b-glucan-enriched breakfast cereal and bar, both high in b-glucan (8.1 and 6.5 g% b-glucan, respectively) and sweetened with fructose. Capillary blood samples were taken fasting and then 30, 60, 90, 120, 150 and 180 min after the start of the meal. Palatability was recorded using two different methods. Results: The glycemic indices of the prototype b-glucan cereal (mean AE s.e.m.; 52 AE 5) and b-glucan bar (43 AE 4.1) were significantly lower than the commercial oat bran breakfast cereal (86 AE 6) and white bread (100; P < 0.05). All foods were highly palatable and not significantly different. It was found that the GI of the test foods used in this study decreased by 4.0 AE 0.2 units per gram of b-glucan compared to our estimate of 3.8 AE 0.6 for studies reported in the literature. Conclusion: Addition of b-glucan predictably reduces the GI while maintaining palatability. In a 50 g carbohydrate portion each gram of b-glucan reduces the GI by 4 units, making it a useful functional food component for reducing postprandial glycemia.

Recent recommendations for the dietary management of diabetes mellitus state that diet needs to be individualized so that there is improved glucose and lipid control in the patient. In a majority of individuals with diabetes, this is best done with a diet that is low in fat and high in carbohydrate, particularly that of cereal origin. However, symptoms of hyper- and hypoglycemia must be averted. Most cereal products, however, tend to have a high glycemic index Cereals such as Prowashonupana barley or fractions of oat bran are particularly high in the soluble fiber beta-glucan, which when taken with a meal increases the viscosity of the meal bolus once it has reached the small intestine, where the absorption of nutrients occurs. This high viscosity delays absorption. A 50% reduction in glycemic peak can be achieved with a concentration of 10% beta-glucan in a cereal food. A significant lowering of plasma LDL cholesterol concentrations can also be anticipated with the daily consumption of > or = 3 g of beta-glucan. Diabetic individuals can benefit from diets that are high in beta-glucan, which, as a component of oats and barley, can be incorporated into breakfast cereals and other products.

The potential physiological benefits of the resistant starches studied appear to relate to colonic health in terms of effects on fecal bulk and SCFA metabolism.

The factors responsible for the slow digestibility of starch in leguminous seeds have been studied by examining microscopically the cooked seeds after various treatments and by measuring starch digestion in vitro. Starch in leguminous seeds is entrapped in parenchyma cells and swells only partially during cooking. The alpha-amylase cannot easily penetrate within the gelatinized starch granules due to steric hindrance and the physical nature of the leguminous starch. Disruption of the cells, especially before cooking increases the susceptibility of starch to alpha-amylase digestion.

The 50% decrease in glycemic response that was observed after the ingestion of 35 g carbohydrate is estimated to occur with approximately 5 g beta-glucan. This dose of beta-glucan can easily be attained without the loss of taste by incorporating oat bran concentrate in products.