Oats in the prevention of metabolic syndrome

The overall aim of the project was to generate new knowledge for developing products based on oat, or fractions of oats, with potential to prevent obesity and development of metabolic syndrome. A strategy to combat obesity is to develop products that enhance satiety, for example by inhibiting fat and starch digestion or prolong stomach emptying. Oat grains are rich in fiber, polyphenols and galactolipids that could potentially affect processes in the gastrointestinal tract. The oil content is also higher than for other cereals, and the emulsifying and antioxidant properties of the oil makes it useful for applications in processed foods and pharmaceuticals, e.g. for protection of marine oil rich in omega-3s. Results of the project show that galactolipids in oat oil inhibit fat digestion. However, more research is needed to establish whether this will increase satiety. It is also shown that components in oat oil protect marine oil against oxidation and the formation of harmful genotoxic aldehydes during digestion. Results from field experiments show that there are small, but significant, variations in the nutritional profile of Nordic oat varieties. The content of beta-glucan is generally high, and Belinda is among the varieties with the highest content. Hot and dry climate can give slightly higher contents of beta-glucan. The nutritional quality of oats is largely affected by processing conditions. Both cooking, soaking, fermentation, extrusion, high pressure homogenization (HPH) and high pressure processing (HPP) increase the release of phenolic acids, known to possess antioxidant properties. When using a static in vitro digestion model to study the digestive process, it appears that certain phenolic acids found in oats may affect the activity of the digestive enzyme maltase, and hence potentially give a slower rise in blood sugar. Furthermore, it is shown that the availability of fiber during digestion is higher in oat porridge made of flour compared to flakes. This makes oat flour porridge more viscous during digestion, which probably contributes to higher satiety. A randomized crossover design study with healthy volunteers ingesting oat porridges enriched in beta-glucan, phenolic acids or galactolipids (oat oil emulsion), respectively, confirms that beta-glucan is the main ingredient that increase satiety, giving the highest levels of satiety hormone (PYY) in blood. A MRI (magnetic resonance imaging) study at the Institute of Food Research (Norwich, UK), where healthy subjects ingested oat porridges with identical nutrient content, but different texture (flour vs flakes), shows that the texture influences stomach emptying, as well as blood levels of glucose, insulin and satiety hormones. In conclusion, the project has built a solid basis for further research on the underlying mechanisms of satiety, and health beneficial components in cereals.

The project will contribute to value creation in the food chain by exploring the potential of utilizing oat and oat fractions in the prevention of obesity and metabolic syndrome. Oat is an annual crop well adapted for the Norwegian climate. It is primaril y used for animal feed, but the interest for use in human nutrition is growing as more knowledge about health promoting components is achieved. Oat grains are rich in fibre and fenolic acids, and the oil content is higher than in other cereals. The oil co ntains components with emulsifying and antioxidant capacity, making it useful for applications in processed foods and pharmaceuticals, e.g. for encapsulation of marine oils high in omega- fatty acids. Strategies to combat obesity include developing foods that increase satiety and improve weight control. Novels ways to control satiety include food ingredients that are able to delay fat digestion and/or affect rates of gastric emptying. The project will investigate the ability of polar lipids in oat (galact olipids) to coat fat droplets in emulsions making them resistant to lipid digestion, as well as study lipase inhibitory effects of oat polyphenols and soluble fibre. In vitro models will be used to study the digestive process and potential effects of dige sted fractions on blood pressure related enzyme. Results will contribute to hypotheses that will be tested out in vivo in a postprandial study with healthy volunteers, comparing physiological measurements with consumer perception and satiety. The project will identify the most relevant oat varieties and evaluate the potential of existing and new processing techniques to design oat products with increased nutrient bio-accessibility and improved health properties.