Manipulation of gut hormone response to food by soluble fiber and alpha-glucosidase inhibition.

Preliminary data indicated that viscous fiber (guar) and alpha-glycosidase inhibition (acarbose) used in combination to slow carbohydrate absorption have an apparently additive effect in reducing the postprandial glycemic response. The full endocrine data reported here also demonstrate that reductions in insulin and gastric inhibitory polypeptide are most significant when guar and acarbose are used in combination. The results are divergent for enteroglucagon when guar and acarbose were given singly. Raised enterglucagon levels seen after acarbose are in keeping with inhibition of proximal absorption resulting in more distal absorption of carbohydrate. However, with viscous fiber, the enteroglucagon response was reduced, and this reduction was maintained even after addition of acarbose. The results demonstrate that the gut endocrine response can be manipulated by pharmacological interventions which alter the pattern of carbohydrate absorption.

Diabetic diets: high carbohydrate combined with high fiber.

The ideal level of carbohydrate intake for diabetics placed on high-fiber diets is unknown. Nineteen diabetics, therefore, took part in a total of twenty-four 5-day studies of fiber supplementation (guar) with carbohydrate intakes ranging from 22 to 61% of total calories. Where carbohydrate formed more than 40% of the calorie intake, there was a mean 64% reduction in glycosuria over the last 2 days on guar (P < 0.001, 14 studies, 11 patients). No significant reduction in glycosuria was seen in the 10 studies on lower carbohydrate intakes. This suggests that dietary fiber supplements in diabetes should be given against a background of higher rather than lower carbohydrate intake.

Improved glucose tolerance four hours after taking guar with glucose.

To gain some insights about the possible cumulative metabolic effect after a high-fibre meal, 6 subjects took two 80 g oral glucose loads, 4 h apart. Addition of 22.3 g guar to the first load decreased the rise in blood glucose and insulin after the second (guar-free) load by 50% (p less than 0.002) and 31% (p less than 0.02) respectively. This corresponded with decreased 3-hydroxybutyrate levels at the start of the glucose tolerance test after guar (by 20%, p less than 0.02). When no guar was added to the first glucose load, both 3-hydroxybutyrate and non-esterified fatty acids tended to rise before the second test. No significant effect was seen in the responses of the gut hormones, gastric inhibitory peptide and enteroglucagon. Spreading the intake of the first 80 g of glucose over the initial 4 h (2 subjects) similarly flattened the glycaemic but increased the insulin response. The effect of guar on carbohydrate and fat metabolism, therefore, lasts at least 4 h and may result in improved carbohydrate tolerance to subsequent guar-free meals.

Combined use of guar and acarbose in reduction of postprandial glycaemia.

Symptoms associated with carbohydrate malabsorption limit the usefulness to diabetics of a powerful glycoside-hydrolase inhibitor (acarbose) which reduces postprandial glycaemia. Addition of a low dose (50 mg) of a acarbose together with 14.5 g guar gum to a breakfast test meal taken by 8 healthy volunteers reduced the mean peak rise in blood-glucose at 30 min by 70%. Areas under the insulin and gastrointestinal-polypeptide response curves were also greatly reduced. No evidence of carbohydrate malabsorption, as assessed by measurement of breath hydrogen, was found during any of the test periods. When acarbose was taken alone, 3 of the 8 subjects had troublesome symptoms and the 30 min rise in blood-glucose was reduced by only 28%. Thus, combination of these two agents effectively reduces the rate of carbohydrate absorption without increasing side-effects and may make combined acarbose and guar acceptable in the management of some diabetics.

Guar gum and reduction of post-prandial glycaemia: effect of incorporation into solid food, liquid food, and both.

1. The influence of the dose and the form in which guar gum was given on the degree of "flattening" of blood glucose curves was studied in five subjects using meals of bread and soup containing 5 or 10 g guar gum. 2. When 5 g guar gum was added to bread the peak increase of blood glucose was reduced by 41% (P less than 0.002), with 5 g guar in soup, the reduction was 54% (P less than 0.001) while a reduction of 68% (P less than 0.001) was seen with 10 g guar gum (5 g in bread and 5 g in soup). The corresponding reduction in insulin peak increases were 37% (P less than 0.002), 50% (P less than 0.001) and 65% (P less than 0.001) respectively. 3. The difference between the two 5 g doses was significant with respect to the reduction of the peak increases in blood glucose and serum insulin; however the difference between the 5 g dose in bread and the 10 g dose was significantly different (P less than 0.02 for glucose, P less than 0.01 for insulin). 4. The results indicate that as little as 5 g guar gum may reduce the glycaemia following a 45 g carbohydrate meal, but perhaps due to earlier and more complete mixing, guar gum is most effective when added to the liquid phase of the meal.

Guar crispbread in the diabetic diet.

Nine diabetic patients who were receiving various treatments supplemented their normal home diets (two patients) or metabolic ward diets (seven patients) with guar crispbread for five days. Their mean urinary glucose excretion fell significantly by 38% during the last two days. A significant fall in fasting blood glucose concentration of 1.1 +/- 0.4 mmol/1 (19.8 +/- 7.2 mg/100 ml) was seen only in those who took guar after the control period. Over eight weeks' treatment insulin dosage was reduced by 21% in five patients, and home testing showed that glycosuria was reduced by 68% in six patients. Guar crispbread is likely to be a useful adjunct to diabetic treatment irrespective of the type of treatment or insulin dosage used.