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

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.

The effect of beta-glucan (BG), a water-soluble form of fibre, in lowering LDL cholesterol concentrations has been demonstrated by many research groups. This beneficial impact has been accepted as a valid health claim for BG, in non-processed or minimally processed forms of oats and barley, by EFSA. The mechanism(s) of action of BG are strongly linked to its capacity to generate high viscosity in the gastrointestinal tract and a subsequent decrease in bile reabsorption through decreases in rates of digestion, inhibition of lipolysis and/or transport of mixed micelles. The BG may also directly interact with lipase, bile salts and the mucus layer, leading to decreased bile recycling. However, the precise mechanisms are still not fully understood. Moreover, the cholesterol-lowering activity of BG varies significantly depending on food type, processing and storage conditions, mainly due to depolymerisation and poor solubility of BG.

The main aims of this project therefore are to understand (a) the mechanism(s) by which BG lowers blood cholesterol and (b) how the processing of BG-containing foods attenuates this capacity of the polymer. A multidisciplinary approach involving a range of in vitro methods, biochemical (e.g. in vitro digestion, enzyme kinetics) and biophysical (e.g. rheology, fluorescence microscopy), will be used. Samples of purified BG and BG-containing cereals and real foods (porridge & biscuits) will be characterised (e.g. molecular weight, polymer dissolution), before and after food processing, and their behaviour during in vitro digestion and their interactions with BS and lipase(s), will be studied. These samples will be subjected to a range of sophisticated in vitro digestion models allowing viscosity and interactions to be determined during breakdown and transport. This work will provide new information on how BG can be processed and added to food matrices in a way that maintains optimal health effects.

The proposed project will benefit relevant stakeholders outside the academic communities, including the commercial sector, public sector bodies and the general public. It addresses one of the UK's major diet-related health challenges, cardiovascular disease (CVD). The project objective is also relevant to the BBSRC strategy priorities as it will "improve our understanding of the links between diet and health" by "optimisation of product formulation through new uses of existing ingredients, novel ingredients and novel formulations of ingredients." It therefore has huge potential long-term impact on a wide range of stakeholders from consumers to policy makers.

The number of individuals diagnosed with CVD in the UK has remained roughly static over the last 15-20 years at 5% of the adult population with 35% of cases being over the age of 55. Raised blood cholesterol is an important risk factor for CVD. Each year more than 150,000 deaths are caused by CVD in the UK. Associated with this alarming death rate, the annual financial cost exceeds £30bn, with cholesterol-lowering drugs alone costing the NHS approximately £500 million. Dietary interventions appear to be more appealing solutions, especially since this approach may simultaneously have positive effects on other diet-related conditions such as obesity and type II diabetes.

Our work will be particularly useful to the food industry and may lead to innovative applications in the future, such as the development of 'functional ingredients and foods' that have the capacity to consistently reduce blood cholesterol concentrations. The design of foods made from oats or barley beta-glucan would benefit public health. The main beneficiaries will be the DRINC members, especially those that are involved in the processing of oats and barley.

Individual consumers will have new knowledge regarding the health benefits of certain fibre-containing foods, together with a wider choice of manufactured foods with specific, proven health benefits. However, care has to be taken with the health communication aspects, since the consumption of these foods may only be effective as part of a healthy balanced diet. The foods ought to have comparable consumer acceptability, making it more convenient for consumers to adopt healthier dietary options. The long-term health benefits of reducing obesity and the risks associated with diabetes will benefit the lifelong health and well-being of individuals and improve their quality of life into old age.
The research should also help policy-makers in formulating new dietary advice and guidelines from new data on plant foods (oats and barley). The applicants regularly give talks at schools and media interviews about their research.

The applicants at the three academic centres will have regular meetings to discuss research findings. The consortium of food companies in DRINC will be offered first-market access to intellectual property if the results of the research lead to industrial applications. All the academic centres at KCL, IFR and Nottingham have mechanisms in place for exploring industrial applications from the research work. The applicants, research staff and PhD student will all play some role in undertaking impact activities. Many of the applicants have relevant experience for achieving successful knowledge exchange and impact with the beneficiaries. The applicants have also a long history of Knowledge Exchange and Commercialisation activities, particularly with the food industry, including industrial grants, patents, exploitation activities and dissemination events.