Higher intakes of both soluble and insoluble fibre are know to lower the risk of developing a number of diseases such as cardiovascular disease, diabetes and cancer. The effects of fibre in the diet appear to be multi-factorial, possibly because there are a number of different types of fibre that may have different but overlapping mechanisms of action. Generally fibres can be split into soluble and insoluble groups, but within these broad categories are a number of sub groupings including cellulose, pectin, lignin, oligosaccharides, resistant starches, hydrocolloids and alcohol sugars. Of particular interest to researchers in the ability of the soluble fibres to reduce the glycaemic response to carbohydrate foods. Control of glycaemic response is important because evidence is growing that is helps maintain lower fasting blood glucose levels, reduces glycated haemoglobin and improves insulin sensitivity in both diabetic and non-diabetic subjects.
In a meta-analysis1 of previous studies, researchers analysed data to investigate the effects of soluble fibre on the attenuation of blood glucose response to foods. The data they selected came from 37 placebo controlled studies that involved the addition of soluble fibre to carbohydrate foods, in both liquid and solid forms. The results of the meta-analysis showed that the attenuation of glycaemic response was significant for soluble fibre in both solid food and in liquids. Soluble fibre (6g) added to starchy solid food reduced glycaemic response by around 10%. However, the attenuation of glycaemic response when the same fibre was added to liquid carbohydrate was around 20%. Addition of fibre to carbohydrate foods reduces the glycaemic response because the transit time through the digestive tract increases. High intakes of refined carbohydrates missing soluble fibres will produce high glycaemic responses and may increase the risk of developing disease.
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