Impact of food processing on the blood cholesterol-lowering effect of cereal beta-glucan

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About 60% of the population have fasting blood cholesterol concentrations high enough to be a risk factor for coronary heart disease, which is responsible for the deaths of >60,000 people annually in the UK, many of which are potentially preventable with appropriate changes to diet and lifestyle. Water soluble types of dietary fibre (SDF), confer many health benefits; in particular, oat and barley beta-glucan (BG) is effective at reducing blood cholesterol and lipid concentrations and this has been recognised by European Food Safety Authority (EFSA). However, further processing of BG in foods can reduce its efficacy, and so a recommended intake of BG of at least 3 g/day requires large quantities (>100g) of unprocessed cereals such as oats and barley to be consumed daily. Most consumers would find this difficult or unpalatable, so approaches are required to incorporate BG into palatable, commonly consumed foods with demonstrable blood cholesterol and lipid lowering properties.Despite the clear health benefits of BG, its mechanisms of action are still not well understood. It has been suggested that the ability of BG to lower cholesterol is triggered by the interference of this polymer and other types of SDF with various stages of lipid digestion, thus reducing or delaying lipid uptake. This then disturbs the recycling of bile salts (bio-surfactants produced by the liver which aid lipid digestion) from the gut back into the liver. Bile salts are cholesterol derivatives, so increased production of bile salts in the liver could reduce plasma cholesterol concentrations. It is not clear which aspects of lipid digestion are affected by BG, and therefore which molecular properties are crucial for its functionality.The aim of this proposal is to determine the mechanisms of action of SDF and in particular BG on lipid digestion. Various mechanisms have been proposed, and they mostly involve the lipid digestion and transport processes. Therefore in vitro lipid digestion studies will allow us to study in detail all the different stages of lipid digestion including lipase activity and adsorption, bile salt adsorption and transport, and micelle formation and transport. The molecular and biochemical properties of BG and other other types of SDF will be determined using a range of state of the art techniques, including analytical centrifugation, and will allow us to determine which properties are important for functionality. Based on these findings, the effect of processing on BG will be studied to determine exactly why processing attenuates its ability to reduce blood cholesterol and lipids. This knowledge will then allow us to propose strategies by which SDF can be incorporated into palatable, manufactured foods and still retain their ability to reduce blood cholesterol and lipid concentrations.