Soluble fibre has been shown to have beneficial properties on the lipid profiles of hyperlipidaemic individuals. Soluble fibre is particularly effective at lowering total cholesterol and low density lipoprotein (LDL) cholesterol, when compared to control diets or diets with equal amounts of insoluble fibre. Soluble fibre forms a gelatinous mass with liquid that may slow digestion and absorption of carbohydrates and thus lower insulin levels. However, soluble fibre appears to have little effect on high density cholesterol, and this suggests that the mechanism of action of the fibre is on production of lipids in the liver. Soluble fibre acts as a substrate for colonic bacteria that synthesise short chain fatty acids, particularly acetate and propionate, that have been shown to reduce cholesterol synthesis in the liver. Interestingly, soluble fibre has also been shown to lower cholesterol levels in a healthy people.
For example, researchers1 fed 29 healthy volunteers 50g of oat based cereal at breakfast while another group of 30 subjects were fed a normal non-oat containing cereal. Subjects were requested to make no lifestyle changes other that ingesting the cereal for breakfast. They followed this regime for 4 weeks before crossing over to the other protocol. Following ingestion of the oat based cereal small but significant reductions in total cholesterol (2.23%) and LDL cholesterol (4.55%) were reported. When the analysis was repeated with subject who had a cholesterol level above 6mmol/L the reductions in total and LDL cholesterol increased to 2.69 and 5.87%, respectively. This suggests that the lipid lowering effects of soluble fibre are greater in those subjects with higher initial levels. This supports previous findings that found no effect of oat cereal on subjects with a mean cholesterol concentration of 4.8mmol/L.
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