Soluble fibre has been shown to be beneficial to the health even when consumed in quantities as low as 20g/d. In particular, soluble fibre can lower total cholesterol and low density lipoprotein (LDL) cholesterol levels in plasma. It is not exactly clear why soluble fibre shows beneficial effects on blood lipids compared with insoluble fibre, but it may relate to increased gut transit time which may decrease carbohydrate absorption and stabilise blood glucose levels. Alternatively, fermentation of soluble fibre in the colon produces short chain fatty acids and these may inhibit hepatic cholesterol synthesis. Guar gum is a galactomannan soluble fibre composed of the sugars mannose and galactose which is extracted from the guar bean. Research suggests that guar gum has beneficial effects on blood sugar control when given to type 2 diabetics in long term studies.
For example1, researchers have investigated the effects of 15g of guar gum of the glycaemic control of 15 subjects with type 2 diabetes in a 48 week study. The subjects were a mixture of male and female, and had an average age of 60, with a body mass index of 28.6kg/m2. Before being administered the gum, a placebo was used for 8 weeks in order to establish baseline parameters, and the placebo was also administered for 8 weeks at the end of the 48 week treatment. The results showed that guar gum improved long term glycaemic control and postprandial glucose tolerance and reduced the total and LDL cholesterol concentrations of plasma compared to baseline levels. The subjects lost weight while taking the guar gum and this loss was statistically significant. Glycosylated haemoglobin was reduced with the guar gum treatment and remained low throughout the second placebo period.
Interestingly, in response to a test meal guar gum treatment increased the production of C-peptide, a protein secreted along with insulin and involved in its synthesis. However, the insulin response to the same test meal did not change. Because C-peptide is a more accurate marker of insulin synthesis than peripheral insulin concentrations, this data confirms that insulin secretion is enhanced by guar gum, and this may explain the beneficial effects on glycaemic control. Guar gum may increase insulin secretion by increasing intestinal transit time and thereby increasing the time the pancreas is exposed to insulin secretogogues. Analysis of the data revealed that the reduction in body weight was not the cause of the reduced plasma glucose. Guar gum therefore appears to be an effective long-term strategy to improve diabetic parameters in those with type 2 diabetes.
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