Depression of the glycemic index by high levels of beta-glucan fiber in two functional foods tested in type 2 diabetes.

OBJECTIVES: To determine the extent to which beta-glucan reduces the glycemic index (GI) of oat products and whether high levels of beta-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+/-2 y, body mass index 29+/-2 kg/m(2), HbA1c 7.4+/-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% beta-glucan); and a prototype beta-glucan-enriched breakfast cereal and bar, both high in beta-glucan (8.1 and 6.5 g% beta-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 beta-glucan cereal (mean+/-s.e.m.; 52+/-5) and beta-glucan bar (43+/-4.1) were significantly lower than the commercial oat bran breakfast cereal (86+/-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+/-0.2 units per gram of beta-glucan compared to our estimate of 3.8+/-0.6 for studies reported in the literature.

CONCLUSION: Addition of beta-glucan predictably reduces the GI while maintaining palatability. In a 50 g carbohydrate portion each gram of beta-glucan reduces the GI by 4 units, making it a useful functional food component for reducing postprandial glycemia.

SPONSORSHIP: Nestec, Switzerland.