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oats for HEALTH: A research summary for health professionals edited by Elisabeth Weichselbaum PhD, MSc, NZ Registered Nutritionist 2014 authors Dr Elisabeth Weichselbaum Dr Michelle Broom OATS WITH MILK Page 8 Grains & Legumes Nutrition Council, Australia PhD, MSc, NZ Registered Nutritionist APD, Nutrition Program Manager Dr Peter Clifton Professor of Nutrition University of South Australia, Adelaide, South Australia UNPACKING THE OAT GRAIN Page 12 OATS CONSUMPTION & GLUCOSE CONTROL Page 25 Dr Alastair Ross Prof. Mohsen Meydani Dr Kristina Andersson Dr Luud JWJ Gilissen Assistant Professor in Food & Nutritional Science Director, Vascular Biology Laboratory Professor of Nutrition, Senior Scientist PhD Researcher Coordinator Allergy Research JM USDA-Human Nutr. Res. Ctr. on Aging, Tufts University, Boston Dept. Experimental Medical Science, Lund University, Sweden ANTI-INFLAMMATORY PROPERTIES OF OATS Page 22 OATS & VASCULAR HEALTH Page 35 Chalmers University of Technology, Gothenburg, Sweden OATS & CHOLESTEROL LOWERING Page 30 Dr Per Hellstrand MD, PhD, Professor Dr Ingrid M van der Meer Group Leader Applied Genomics & Proteomics Diana M Londono PhD Student Dr Marinus JM Smulders Business Unit Manager Plant Breeding Plant Research International – Wageningen UR, The Netherlands OATS & ALLERGY/ INTOLERANCE Page 18 2 oats for health 3 contents KEY TAKE OUTS........................................................................................................... 6 KEY NUTRITION FACTS............................................................................................... 7 OATS WITH MILK......................................................................................................... 8 A HEALTHY BREAKFAST.............................................................................................. 8 DIFFERENT TYPES OF OATS........................................................................................11 UNPACKING THE OAT GRAIN................................................................................... 12 OATS: A UNIQUE PACKAGE OF NUTRIENTS............................................................ 14 OATS & ALLERGY/INTOLERANCE............................................................................. 18 ANTI-INFLAMMATORY PROPERTIES OF OATS........................................................ 22 OATS CONSUMPTION & GLUCOSE CONTROL...................................................... 25 OATS & CHOLESTEROL LOWERING......................................................................... 30 OATS & VASCULAR HEALTH..................................................................................... 35 REFERENCES.............................................................................................................. 38 4 oats for health 5 KEY TAKE OUTS OATS ARE: LOW IN SODIUM Oats are one of the few breakfast cereal options with no added salt and are therefore low in sodium HELP REDUCE BLOOD PRESSURE Oats may help reduce blood pressure in humans, and there have been indications of a greater effect in obese than in lean persons UNIQUE ANTIOXIDANTS Oats are the only grain to provide an antioxidant-like substance known as avenanthramides HELP REDUCE HEART DISEASE RISK Avenanthramides have antioxidant, anti-inflammatory and antihistamine properties and may reduce the risk of heart disease and several other diseases associated with inflammation RICH IN -GLUCAN Oats are unique in that they are one of the richest sources of -glucan soluble fibres (together with barley, rye and fungus) HELP LOWER BLOOD CHOLESTEROL -glucan in oats is proven to help lower blood cholesterol levels and, as a viscous fibre, lowers the glycaemic response to a food SOURCE OF WHOLE GRAINS, VITAMINS & MINERALS Typically eaten as whole grains, oats provide dietary fibre, a range of essential vitamins and minerals, and over 26 bioactive substances (Themselves) ARE GLUTEN-FREE Oats themselves are gluten-free, but as they are a between season crop and may become contaminated with wheat either in the field or across the supply-chain, they cannot be labelled as such in Australia or NZ. A small number of Coeliac sufferers may also react to a type of protein naturally found in oats (avenins), but for most Coeliac sufferers, uncontaminated oats (where available) are safe to eat. key nutrition facts on oats: Oats have the capacity to help maintain endothelial function Oats are typically eaten as the whole grain, providing the whole package of fibre, nutrients and other bioactive compounds. Fibre Oats provide fibres that are important for gut regularity, and fibre that helps manage cholesterol levels. High in β- glucan -glucan is a type of fibre that helps with glycaemic control and lower blood cholesterol levels. Source of thiamin, iron, magnesium & phosphorous Vitamins and minerals provided by oats are important for good health. Combining oats with milk provides a whole package of essential nutrients. 6 Whole grains A natural source of energy Oats provide energy in the form of starchy carbohydrates. These provide fuel for the brain (glucose), helping with mental performance throughout the morning. HELP MAINTAIN ENDOTHELIAL FUNCTION Low in sodium Oats are naturally low in sodium oats for health 7 Oats with milk A nutritious start to the day! Dr Elisabeth Weichselbaum, Independent Nutrition Scientist and Consultant Not only does breakfast provide us with the energy we need, eating breakfast has also been associated with improved cognitive performance throughout the morning (Hoyland et al. 2009), a lower likelihood of being obese (Szajewska & Ruszczynski 2010), and with better nutrient intakes (Grieger & Cobiac 2012; Fayet-Moore et al. 2012; Gibson & Gunn 2011; Williams 2007) compared with breakfast skipping. Because it is such an important meal of the day, it is best to choose a breakfast that provides a good balance of important nutrients, without providing too much sodium, fat or sugar. Having oats with milk or yoghurt is a great option for breakfast. Adding a handful of chopped fruits ensures you are getting several major Core Food Groups in one meal. Australian Guide to Healthy Eating Australian Guide to Healthy Eating A healthy breakfast provides.... Enjoy a wide variety of nutritious foods from these five food groups every day. Drink plenty of water. Enjoy a wide variety of nutritious foods from these five food groups every day. Grain (cereal) foods, Drink plenty of water. mostly wholegrain and/or high cereal fibre varieties Oats provide starchy carbohydrates, which provide the fuel not only for muscles and organs, but provide the sole fuel (glucose) for the brain. Vegetables and legumes/beans Muesli Grain (cereal) foods, Polenta mostly wholegrain and/or high cereal fibreQuinoa varieties Muesli Polenta Fettuccine Penne As oats are eaten as a whole grain, they provide good amounts of dietary fibre. One type of fibre that is present in good amounts in oats (and barley), but not in some other cereals, is -glucan, a soluble fibre that helps lower the glycaemic response and reduce blood cholesterol levels. 4. A drink for hydration Red kidney beans Quinoa Fettuccine Penne Wheat flakes Red lentils Red kidney Chickpeas beans Wheat flakes Red lentils Chickpeas Red kidney beans 3. A serve of fruit or vegetable Lentils Mixed nuts Chickpeas Red kidney beans Lentils Mixed nuts Chickpeas Fruit OATS thiamine iron magnesium fibre Lean meats and poultry, fish, eggs, tofu, nuts and seeds and legumes/beans MILK Lean meats and poultry, fish, eggs, tofu, nuts and seeds and legumes/beans Use small amounts calcium riboflavin Use small amounts vitamin B12 Fruit Milk, yoghurt, cheese and/or alternatives, mostly reduced fat Only sometimes and in small amounts Milk, yoghurt, cheese and/or 2. Dairy for protein A bowl of oats and milk is a good source of protein, is high in whole grains and fibre, rich in β -glucan (proven to help lower cholesterol), is a low GL meal and low in sodium – overall, a healthy start to the day! OATS FOR BETTER HEALTH As well as providing valuable nutrients, oats have been suggested to benefit health in other ways. These benefits will be discussed in more detail in this brochure – written by various experts working and researching in the respective areas. The different sections discuss what components of oats provide benefits, and how they do so. FIGURE 1: Contribution of 40g oats with 125mL reduced fat milk to an adult’s daily nutrient requirements %of Recommended Daily Intake THIAMINE 4 RIBOFLAVIN 14 NIACIN 1 4 FOLATE 3 4 VITAMIN B6 3 2 VITAMIN B12 38 CALCIUM 19 ZINC 22% 18 18% 4 5% 7% 5% 38% 2 10% 3 7 IODINE 12 12% IRON 13 13% MAGNESIUM 5 PHOSPHORUS 13 FIBRE 13 PROTEIN 9 21% 21% 16 29% 16 13% 9 18% alternatives, mostly reduced fat Only sometimes and in small amounts Source: Australian Government (www.eatforhealth.gov.au) 8 Oats with milk is not only a delicious breakfast option, but also provides a whole package of important nutrients, making it a nutritious start to the day (see section ‘Unpacking the oat grain’). Oats with milk are also a low sodium breakfast with less than 0.1g. This is because rolled oats have no added salt, unlike bread and various types of other breakfast cereals on the market. Oats also provide more protein than other cereal grains – as well as being important for growth and tissue repair, protein helps increase satiety. A 40g portion of rolled oats together with 125mL (½ cup) milk provide almost 20% of the daily protein requirements. Vegetables and legumes/beans 1. Cereals for fibre & whole grain Combining oats with milk makes a breakfast combo packed with nutrients Reduced Fat Milk (1%) Oats, rolled, 40g The clear conclusion is still that oats can help lower cholesterol and should be an important component of heart healthy diets. oats for health 9 Oat Groats The whole oat as it is harvested from the grain but “de-hulled” so that the inedible husk has been removed and the oat has been cleaned, making it safe to eat. These oats can take up to an hour to cook. Steel Cut Oats/Oat Kibble/ Irish Oatmeal Oat groats cut into 2-3 pieces with a steel blade (before being rolled). Cutting the oat exposes more surface area which can be penetrated by water during cooking, making it quicker to prepare than an oat groat (around 30 minutes). Different types of oats Scottish Oats The Scots traditionally stone ground their groats and then rolled them rather than rolling out steel cut oats. The result are rolled oats that naturally vary in size and can help deliver a creamy textured oatmeal. Muesli Oats Muesli oats are rolled to a greater thickness than other rolled porridge-type oats. As with other rolled oats, the oats are often kilned to give them a “nutty” taste and help prevent rancidity and then steamed and rolled to the desired thickness. Traditional/Rolled Oats/Oatmeal As with muesli oats, these are steel cut oats which are then kilned, steamed and rolled to a specific thickness. They generally take around 2-5 minutes to prepare. Quick Oats Quick oats are the same as other rolled oats, taking the steel cut oat groats and then kilning, steaming and rolling the oat. They are simply rolled thinner to allow the oat to cook more quickly; around 90 seconds to prepare in the microwave. 10 oats for health 11 UNPACKING THE OAT GRAIN Michelle Broom, APD, Nutrition Program Manager, Grains & Legumes Nutrition Council It is believed oats have been grown as a food crop since 1000BC (Kent & Evers 1994). Today, oats are the fourth largest grain crop in Australia with more than 1 million tonnes grown every year (Primary Industries Standing Committee 2011). Oats are predominantly grown in the moist, temperate regions of the southern states of Australia with significant winter rainfall. Australia is a major producer of oats globally, as the fourth largest producer of oats (see Figure 2). Oats are more frost and waterlog resistant than wheat and barley (AEGIC 2012). However, like all other grains, drought can affect yield. Although drought affects groat size, drought or excess rain do not have a significant impact on the nutritional qualities of oats. In Australia, oats are usually planted in May and harvested in November. The hot, dry weather in November enhances the storage capacity of the oats (AEGIC 2012). Most oats grown in Australia are used as stock feed, with only 40% grown as higher quality milling oats used to feed humans and racehorses (Index Mundi 2013 and Australian Bureau of Statistics 2012). FIGURE 2: Main producers of oats worldwide EU (27 countries) 8.44 Russian Federation Approximately 20% of Australia’s milling oats are exported, primarily to Mexico, China and Japan (AEGIC 2012). 5 Canada 3.25 Australia FIGURE 3: Areas of oat production. 1.2 0.96 United States Chile 0.6 China 0.58 Belarus 0.45 Ukraine 0.45 Argentina Source: AEGIC 2012 0.4 0 1 2 3 4 5 6 7 8 9 OAT PRODUCTION (MILLION TONNES PER YEAR) Source: Index Mundi, 2013 INCREASING PRODUCTION 12 oats for health 13 Oats: a unique package of nutrients Oats are a cereal grain which means they are the seed of the grass family of plants belonging to the botanical family Poaceae, or Germinae. Unlike wheat and rye, oats grow with a husk covering the seed. This husk is not digestible by humans so must be removed from oats before they can be used as food. The husk is removed and then the remaining seed, called the oat ‘groat’, is dried in a kiln so the grain can be stored without spoiling. This kiln drying gives oats their characteristic ‘nutty’ flavour. Oat husks are sometimes added back into porridge oats as an additional source of fibre or may be re-used as a source of fibre in animal feeds. The oat groats are then steamed to stop the enzymes from breaking down the naturally occurring fats and reduce rancidity. The steamed oats are rolled to form the traditional rolled oats available in the supermarket. To make quick cooking oats, or instant oats, the oat groat is cut before being rolled. The smaller pieces of oat cook more rapidly but still contain all the nutrients of the whole grain. Traditional and instant oats are whole grain. They contain all the parts of the original ‘groat’ including the germ (the embryo of the new plant), the endosperm which supplies energy and nutrients for the growing seed and the outer protective fibre-rich bran layer (Figure 4). Like in other whole grains, the bran and germ of oats are rich in fibre, vitamins and minerals and phytonutrients (Fardet 2010). FIGURE 4: Whole grain structure showing location of key nutrients Bran The outer layer of the grain which includes the aleurone layer • Fibre • Protein • B Vitamins • Trace Minerals • Phytochemicals • Enzymes Endosperm Provides nourishment to the germ •Carbohydrate • Protein • Some B Vitamins •Oil Germ Husk (or hull) Embryo from which the seedling develops T he outer protective shell of the grain • B Vitamins • Vitamin E • Trace Minerals • Phytochemicals • Antioxidants • Unsaturated fats Whole grains such as oats contain dietary fibre, a range of essential nutrients and over 26 bioactive substances such as phenolic compounds and plant sterols (Fardet 2010). It is the whole package of fibre, nutrients and bioactives acting synergistically that are thought to help protect against chronic diseases like heart disease, diabetes and cancer (Fardet 2010). At only 58% carbohydrate, oats are lower in carbohydrate than other grains. A 40g serve of raw oats contains 23g of carbohydrate (Grains & Legumes Nutrition Council 2013). Oats tend to have a slightly higher protein content than most other cereals at approximately 12% and a higher fat content (mainly poly- and monounsaturated) (Grains & Legumes Nutrition Council 2013). It is worth noting that Food Standards Code for Australia and New Zealand (Standard 1.2.8) specifically prohibits the use of gluten free claims on oat products due to the likelihood of cross-contamination with wheat, barley or rye (Food Standards Australia New Zealand 2013). However, efforts to produce uncontaminated oats have led to more and more uncontaminated products being available on the market internationally (see section ‘Oats and allergy/ intolerance’ for more details). 14 oats for health 15 Oats: a unique package of nutrients continued... Like other whole grains, the bran layer of oats is rich in vitamins and minerals. It contains a range of nutrients essential for maintaining health including B-group vitamins, and minerals such as iron, zinc, magnesium and phosphorus (Table 1). TABLE 1: Nutrient content of rolled oats per 40g serve Amount per 40g of oats % Daily Intake* (per serving) Energy 631kJ 7% Carbohydrate 23.2g 7% Protein 4.4g 9% Fat 3.5g 5% Saturated 0.7g 3% Polyunsaturated fat 1.2g n/a Monounsaturated fat 1.4g n/a Fibre 3.8g 13% Insoluble Fibre** 1.9g n/a Soluble Fibre** 1.9g n/a ß-glucan** 1.4g n/a Thiamin (Vitamin B1) 0.2mg 18% Riboflavin (Vitamin B2) 0.06mg 4% Niacin 0.4mg 4% Folate 7.2µg 4% Vitamin E 0.1mg 1% Nutrient Permitted nutrition content claim** Oats also contain both insoluble and soluble fibre (see Table 2). They have lower levels of insoluble fibre than other grains such as wheat and rye, but more than other grains such as rice, millet and corn. However oats are higher in soluble fibre than most other grains, most notably -glucan which is proven to help lower blood cholesterol levels and glycaemic response. Oats are one of the richest cereal sources of -glucan containing 3.4g per 100g or around 1.4g per 40g serve. The ability of whole grains such as oats to increase the total antioxidant capacity in the plasma is thought to be predominantly due to phenolic compounds, such as ferrulic and caffeic acids. Up to 30% of the total phenolic content of oats is as ‘free phenolics’, which are not bound to fibre or other compounds. Oats contain up to ten-fold higher levels of free phenolics than other grains and so have greater potential to increase antioxidant potential and reduce oxidative stress than other types of grain (Belobrajdic & Bird 2013). A serve of goodness.... a 40g serve of rolled oats contains: Content of free phenolic acids in different types of cereal Source Note: good source of fibre under previous and transitional regulations 629kJ (150 calories) Source: Belobrajdic & Bird 2013 23g carbohydrate Barley 5-23µg/g Wheat 5-39µg/g 4.4g protein Oat Rye 3g saturated fat 5-110µg/g 10-35µg/g 4g fibre Source TABLE 2: Dietary fibre content of different types of cereal per 100g Iron 1.5g 13% Zinc 0.8mg 7% Magnesium 52mg 16% Source Phosphorus 164mg 16% Source Potassium 125mg n/a Calcium 18mg 2% Sodium 2.8mg 0% Source Oats Whole wheat Brown rice Pearled barley 9.5 11.3 3.2 11.7 Insoluble fibre (g) 6 10.6 1.6 5.2 Soluble fibre (g) 5 1.6 <0.1 5.4 3.4 0.7 0.1 4.4 Nutrient Low salt or sodium Total dietary fibre (g) ß-glucan (g) Source: Food Standards Australia and New Zealand 2010; http://www.foodstandards.gov.au/science/monitoringnutrients/nutrientables/Pages/default.aspx * %Daily intake and permitted nutrition claims are based on Standards 1.1.1, 1.2.7, and 1.2.8 of the Food Standards Australia New Zealand. **Grains & Legumes Nutrition Council (2013; unpublished). Single sample analysis. Information is true and accurate at time of publication and supplied for educational purposes only. Grains & Legumes Nutrition Council takes no responsibility for any other use of this data. 16 Oats have a higher fat content than other grains as predominantly polyunsaturated and monounsaturated fats present not only in the oat germ but especially in the endosperm. Of the total fat content of oats, 43% is oleic acid and 35% in linoleic acid (Kent & Evers 1994). The bran and germ of oats also contain phytochemicals including tocopherols, tocotrienols, phenolic compounds and plant sterols, thought to have a beneficial effect on health. More recent research indicates oats contain avenanthramides, a unique bioactive substance that has been shown to help protect blood vessels from the damaging effects of LDL-cholesterol (Meydani 2009; see section ‘Anti-inflammatory properties of oats’ Page 20). Source: Food Standards Australia and New Zealand 2010 and courtesy of Grains & Legumes Nutrition Council, various sources. http://www.foodstandards.gov.au/science/monitoringnutrients/nutrientables/Pages/default.aspx oats for health 17 Oats & ALLERGY/INTOLERANCE Dr Luud JWJ Gilissen, Dr Ingrid M van der Meer, Diana M Londono, Dr Marinus JM Smulders Plant Research International – Wageningen UR, The Netherlands food allergy & intolerance definitions Allergy •An excessive reaction of the immune system to a normally harmless compound, usually a protein (which becomes an ‘allergen’) •Allergies are immunoglogulin E (IgE)-mediated, and are immediate and often severe •Allergic reactions can occur in any body surface including skin, lungs and intestine in contact with the environment Intolerance •Detrimental physiological or (auto-)immune reaction •Often delayed or chronic reaction •Gluten intolerance (coeliac disease) is an auto-immune disease leading to a wide spectrum of symptoms (e.g. chronic bowel complaints, growth retardation, chronic fatigue) 18 Proteins with little potential to trigger intolerances Oats – a cereal suitable for most coeliac sufferers Oats, as other cereals (rice, wheat, barley, rye, maize, sorghum and various species of millet), contain various types of proteins, including water-soluble albumins, saline-soluble globulins, ethanol-soluble prolamins, and ethanol- plus reducing agent-soluble glutenins. The absolute and relative amounts of these protein types vary considerably among cereals. Coeliac disease (CD) is a common food intolerance to gluten proteins of wheat, barley and rye, with a prevalence of 0.5-2% among the Western population. Most patients with CD can consume oats without detrimental inflammation of the small intestine. For example, wheat grains contain mostly (80% of the total protein content) prolamins and glutenins, which are highly diverse in composition, poorly degradable by humans, and remain immunogenic in the intestine (i.e. they can still trigger allergic and intolerance reactions). In contrast, oat grains contain mostly (80% of the protein fraction) easilydegradable globulins. The prolamin plus glutenin content (glutenin makes up a very minor portion) of oats is generally below 10% (Webster & Wood 2011) and the molecular variation among and immunogenicity of these proteins is limited, which means they are unlikely to trigger intolerances (Londono et al., 2013). The prolamins in oat are called ‘avenins’. Allergies to oats are rare Although allergy to cereals is rare, representative proteins of all the above-mentioned solubility groups are known as potential food allergens in several cereal species. In patients with food allergy-related atopic dermatitis, strong IgE cross-reactivity of several proteins of different molecular weight was seen between wheat, barley and rye, reflecting their close taxonomic relationship (Varjonen et al., 1994). This means that a person who is allergic to proteins present in wheat may also experience allergic reactions to similar proteins present in barley or rye. In terms of cereal food allergy, the most commonly mentioned crops triggering reactions are wheat, maize and rice. In contrast, oat food allergy is only known as an exceptional, delayed-type, cell-mediated allergy, limited to infancy and usually resolving later in life (Sicherer & Sampson 2010). The majority of adults and children with CD appear to tolerate moderate amounts (20 g/day for children to 70 g/day for adults) of pure oats (Pulido et al. 2009). The biggest problem with oats for CD patients is the fact that commercial oat products can become contaminated with wheat (Gelinas et al. 2008). Contamination can already occur in the field when wheat, barley or rye plants grow among oat plants and are not removed systematically, but contamination can also occur later in the food production chain, during harvest, transport, storage and further processing. The level of contamination is almost always sufficient to cause symptoms in CD sufferers. Consequently, a guaranteed gluten-free oat production chain is an essential requirement for the production of oat suitable for the gluten-free market. Uncontaminated gluten-free oat products are also available on the Australian market but under the Food Standards code (Standard 1.2.8) in Australia and NZ, oats are prohibited from claiming to be gluten free due to the presence of small amounts of prolamins (i.c. avenins). However, such prolamin type of proteins are also present in known-as-safe grains like maize (zeins)and rice (orizalin) (Gilissen et al. 2008). Most CD sufferers are sensitive to gluten proteins, and only few cases of oat avenin-sensitive CD patients have been described. The response in these rare cases has been attributed to two specific avenin-derived peptides that are different from all known T-cell epitopes (immunogenic protein fragments) of wheat, barley and rye (Vader et al. 2003; Arentz-Hansen et al. 2004). Although only a very small number of oat-sensitive CD patients exist that react to these epitopes, they attained much attention and caused reluctance in oat consumption by coeliac sufferers. Recently, further in vitro study results raised questions whether toxicity in oats may have been overlooked, which would have implications on whether promotion of oat consumption by CD patients is justified. To shed light on this issue, Londono et al. (2013) analysed the presence of known epitopes from wheat, barley and rye in avenins. This analysis confirmed that none of the epitopes from gluten of wheat, barley and rye are present in oat avenins and suggests that reactions in such patients are attributed, most likely, to a rare reaction to the specific oat avenins. These data give an additional support to the general safety of oats for CD patients. Recently, Kaukinen et al. (2013) further confirmed the safety of oats for CD sufferers from a long-term consumption study involving over 100 coeliac volunteers. Oat consumption of 20g (range 1-100g) per day for eight years resulted in significantly better mucosal morphology when oats were consumed in higher amounts over a longer period, as compared to the controls that used a gluten-free diet without oat during this period, which is suggested to be the positive effect of oat fibre intake. These data also confirmed earlier studies that long-term ingestion of oats is safe. (Kaukinen et al, 2013). In summary, oats lack all coeliac diseaseinducing gluten fragments of wheat, rye and barley. The real positive effects of oat consumption by coeliac sufferers by far outweigh the minor potential hazards. oats for health 19 Oats & ALLERGY/INTOLERANCE continued... Why are oats not permitted to be considered gluten free in Australia and NZ but may be recommended for CD patients in Europe and the USA? Because of the general safety of oats, EU regulation allows oats in foodstuffs for people with CD when it is produced, prepared and processed in a way to avoid contamination by wheat, rye and barley and the gluten content of these products is below 20 ppm (EC 41/2009). Efforts have been made in several Nordic countries (Sweden, Finland) where they guarantee a gluten-free supply chain for oats and consequently, over 70% of CD patients eat oats regularly as a healthy component of their gluten-free diet (Salovaara et al., 2010). This was also recently established in The Netherlands with support of the Dutch Celiac Patient Association. Since August 2013, the USA. allows oats to be sold as gluten-free provided any contamination with gluten from wheat, barley and rye is below 20 ppm. In Australia and NZ, however, oats are prohibited from claiming to be gluten free. The Food Standards Code only permits the use of gluten free claims on products with “no detectable gluten and products that do not contain oats or their products; or cereals containing gluten that have been malted, or their products”. As modern testing now allows us to detect levels of gluten to very low levels, this means that products with >20ppm (from contaminating gluten sources) are also prevented from carrying gluten free claims even though the risk to CD patients may be very low (note that current test methods approved by Codex Alimentarius cannot reliably test for the presence of inherent gluten, only the presence of contaminating gluten in oats). What do Coeliac Associations recommend? Coeliac Australia and Coeliac New Zealand currently recommend that coeliac patients should avoid even uncontaminated oats because of some coeliac sufferers reacting to oat avenins (Coeliac Research Fund 2008). Coeliac associations from other countries (e.g. Canada, UK, USA, Finland, The Netherlands), however, suggest that for most coeliac sufferers it is okay to include uncontaminated oats in the diet. It has been suggested that the decision about whether or not to include oats should be made on an individual basis (i.e. this should be tested) rather than excluding oats form the diet of all coeliac patients, recognising that the availability of oats would improve food choices for those on a gluten-free diet (Canadian Coeliac Association 2013; Coeliac UK 2013). 20 oats for health 21 Anti-inflammatory properties of oats Prof. Mohsen Meydani, JM USDA-Human Nutrition Research Center on Aging, Tufts University, Boston Epidemiological evidence suggests that a high intake of whole grain foods including wheat, rice, barley, maize and oats is associated with reduced risk of coronary heart disease (CHD) and diabetes. The high fibre content of whole grains, and more specifically the high content of beta-glucans, is believed to be the major contributing factor to their beneficial health effects. A comprehensive review of literature by Kelly et al. (2007) provides evidence that the beneficial effect of consuming whole grains on CHD in clinical intervention trials is mainly limited to whole grain oats. Avenanthramides – bioactive compounds unique to oats In addition to their cholesterol lowering effect (see section ‘Oats and cholesterol lowering’), oats have been shown to improve endothelial function and to reduce blood pressure (Saltzman et al. 2001) potentially through modulation of vascular endothelium production of nitric oxide (NO) (Katz et al. 2001; see section ‘Oats and vascular health’). Oats, in addition to containing soluble fibres ( -glucan), are a good source of several antioxidants including vitamin E, phytic acid, phenolics, and avenanthramides, unique soluble bioactive compounds not present in any other cereal grains (Collins et al. 1989). Avenanthramides from oats exhibit potent antioxidant activity in vitro and in vivo (Dimberg et al. 1992; Peterson et al. 2002; Bratt et al. 2003; Chen et al. 2005; Ren et al. 2011). Combined with vitamin C, they synergistically inhibited LDL -cholesterol oxidation in vitro, a major factor involved in the formation of atherosclerotic lesions. More than 20 different forms of avenanthramides are present in oat extract. The three major forms are A, B, and C (see Figure 5, Peterson et al. 2002), and avenanthramide-C often makes up about one-third of the total concentration of avenanthramides in oat grain. While the bioavailability of avenanthramides has been shown in animals and in humans (Chen et al. 2007; Chen et al. 2004), its metabolism and tissue distribution in the human body is currently unknown. 22 Antioxidant, antihistamine and antiinflammatory properties of avenanthramides In vivo and in vitro studies have shown that avenanthramides possess antihistamine and anti-inflammatory properties (Chen et al. 2007). For centuries, oatmeal has been topically used as a remedy to treat skin irritation from poison ivy, sunburn, eczema, and psoriasis. Oat colloidal extract (very finely ground oats suspended in water) containing avenanthramides has also proved to have antihistamine and anti-irritation activity (Kurtz & Wallo 2007). Avenanthramides and dihydro-avenanthramides, a synthetic derivative, reduce histamine release from mast cells and consequently reduce associated skin disorders like itching, redness, and wheals, resulting in lower use of corticosteroids (Heuschkel et al. 2008; Cerio et al. 2010). In addition to their antioxidant and antihistamine activities, oat avenanthramides also possess anti-inflammatory properties. While the anti-itching property of oats and oatmeal has been recognised for many years, recent reports provided molecular evidence for the mechanism by which oats may exert their soothing effect on irritated skin. Avenanthramides can modulate cellular signalling pathways that govern cellular responses during inflammation. In a cell culture system using human aortic endothelial cells, the potential health benefit effect of avenanthramides was found to be mediated by molecular processes that are known to play an important role in the inflammation of arteries and the development of atherosclerosis (Liu et al. 2004). Vascular benefits of avenanthramides When the levels of fat and cholesterol increase in circulation, certain locations in blood vessels become susceptible to inflammation, which attracts and attaches circulating immune cells to the site of inflammation. This eventually leads to formation of atherosclerotic lesions in the arteries. For this process to occur, several inflammatory mediators [such as IL-1, IL-6, IL-8 and monocyte chemotactic protein (MCP)-1] and adhesion molecules [including intracellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and E-selectin] need to be expressed. Avenanthramides enriched extracts of oats have been shown to inhibit expression of these molecules in the endothelial cells in culture and other tissues by suppressing NF- KB, an important transcription factor in inflammation (Collins 1993; Collins & Cybulsky 2001; Collins et al. 1995). In addition, oatmeal extract containing avenanthramides suppresses production of prostaglandin E2, which is another mediator in inflammation (Alexandrescu et al. 2007; Sur et al. 2008). We also examined the antiproliferative effect of avenanthramides on several cancer cell lines and found that they are effective in inhibiting proliferation of colonic cancer cell lines, but not prostate or breast cancer cells (Guo et al. 2010). Taken altogether, whole oats, oat bran, oatmeal and colloidal of oats, as well as avenanthramides enriched extracts of oats (currently not available in Australia or New Zealand, but in other countries including Canada) have the potential to provide a broad range of health benefits through antioxidant, anti-inflammatory and antihistamine activities, which complement the already established cholesterol lowering properties of oats. Thus, regular inclusion of foods containing oats and oat products in the daily diet may reduce the risk of CHD and several diseases associated with inflammation. In addition to their anti-inflammatory properties, oat avenanthramides have been shown to suppress proliferation of vascular smooth muscle cells, a process that is known to be a major contributing factor in the development of atherosclerosis. This effect of avenanthramides is mediated through suppression of phosphorylation of retinoblastoma protein (pRb) in the cell cycle (Nie et al. 2006a+b). FIGURE 5: Chemical structure of major Avenanthramides (see Peterserson et al. 2002) HO O R N H H O O Avenanthramide - a R=H Avenanthramide - b R=OCH3 Avenanthramide - c R=OH O H oats for health 23 oat consumption & glucose control Dr Peter Clifton, Professor of Nutrition, University of South Australia Soluble dietary fibre in carbohydrate-rich foods influences the glycaemic response after a meal. In particular, β- glucans present in oats (and also barley) have been widely studied for their health benefits including their ability to reduce post-prandial glucose levels (Tosh 2013). Oat -glucans, in their native state, are very high molecular-weight (MW) polysaccharides that exhibit high viscosities at low concentrations (Ren et al. 2003). The degree of glycemic lowering is related to the MW of the oats (Tosh et al. 2008) as well as the total dose. Consumption of -glucan increases the viscosity of the meal bolus in the stomach (Marciani et al. 2001), which reduces mixing of the food with digestive enzymes and delays gastric emptying (Tosh 2013). Increased viscosity also slows the absorption of glucose (Braaten et al. 1991, Panahi et al. 2007), further contributing to reduced post-prandial glucose levels. -glucan is also easily fermented by the gut microbiota, producing short-chain fatty acids including actetate, propionate and butyrate, which may affect the post-prandial glucose at subsequent meals (Tosh 2013). BETA-GLUCANS ARE PROVEN TO LOWER GLYCAEMIC RESPONSE The positive effect of β -glucan has been confirmed in the scientific opinion of the European Food Safety Authority (EFSA), which advises the European Commission on matters relating to health claims. EFSA recognised that a cause and effect relationship between oat and barley -glucans and a reduction of post-prandial glycaemic response has been established. However, EFSA suggests that in order to obtain the claimed effect, 4 g of β -glucans from oat or barley for each 30 g of available carbohydrates should be consumed per meal (EFSA 2011), a level that is likely to be difficult to achieve (Tosh 2013). Health claims relating to -glucans and blood glucose regulation have yet to be evaluated in Australia and New Zealand, however, the list of health claims is continuously updated. Tosh (2013) reviewed all the available randomised, double-blind, placebo-controlled clinical trials on oat and barley -glucan and post-prandial blood glucose response. The studies using oat-based products are shown in Table 3 (see over). The effect of -glucans on the area under the post-prandial blood-glucose curve (AUC), which is a measure used when determining the glycaemic index (GI) of a food, as well as the peak blood-glucose rise, another useful measure of post-prandial blood-glucose response, were investigated. The study findings are shown on the next page. 24 oats for health 25 Oat CONSUMPTION & GLUCOSE CONTROL continued... STUDY FINDINGS Altogether, 24 studies tested 55 separate oat products: 69% of the oat treatments showed a reduction in the AUC and/or GI 72% 71% showed a reduction in peak blood-glucose rise Insulin was not elevated in any studies, and of the studies that used ≥4g -glucan from oats and barley 72% showed a lowering of the insulin response The findings indicate that the amount of -glucan consumed, rather than the ratio of -glucan to available carbohydrate, is important for blood glucose regulation, suggesting that the EFSA claim may be too restrictive. Overall, Tosh proposed that a dose of 4g -glucan in processed products predict a physiologically relevant decrease equivalent to 15 GI units and people would achieve this intake by consuming several different oat products throughout the day. There was a correlation between the increase in viscosity achieved by the oat product and glucose lowering (Tosh 2013). Lower amounts of unprocessed high MW oat -glucan (1.8-2.1g) are needed to achieve a similar effect to 4g of processed, lower MW beta-glucan. These levels of high MW beta-glucan would typically be found in a large portion of low processed oat products such as oat tempe and oat bread made with coarse boiled oats. Breaking down the oat -glucan to smaller fragments reduces the effectiveness of -glucan (Tosh et al. 2008). Food-processing methods that reduce the molecular weight and solubility of oat -glucan reduces its ability to lower blood glucose (Wolever et al. 2010). This has also been found in the recent review by Tosh (2013), where the average reduction of AUC was more pronounced with intact boiled grains compared to processed products (including porridge). Nevertheless, both processed and unprocessed oat-based products led to significant reductions in blood glucose levels (Tosh 2013). There is also evidence that suggests that type 2 diabetics benefit just as much as non diabetics from the consumption of oat products (Kabir et al. 2002, Jenkins et al. 2002, Tappy et al. 1996). In conclusion, there is convincing evidence that oat β -glucan lowers postprandial glucose response, which is considered to be beneficial for all people at all stages of life. It may be particularly useful in those with risk factors for type 2 diabetes in preventing progression to type 2 diabetes, as glycemic load is a predictor of disease progression. /4 3 of the oat and barley products that contained ≥4g -glucan showed significant reductions in post-prandial glucose despite the available carbohydrate dose being clearly above the 30g dose suggested by EFSA (51g on average). 26 oats for health 27 TABLE 3: Studies investigating the effect of oat products on blood glucose response (adapted from Tosh 2013) Food format Subjects n Betaglucan dose (g) AC dose (g) Change in AUC (mmol ·min/l) Significant Change in GI values Peak Change sig. First author and source Oat bran muffins Food format Subjects n ß-G dose (g) AC dose (g) Change in AUC (mmol ·min/l) sig Change in GI values Peak Change sig. First author and source Oat bran drink 18 0.3 a 72b 3 No No Behall, Diabetes Care 2006; 29:976-81 10 2 50 −26.9 n/a −16.3 Yes Mäkeläinen, Eur J Clin Nutr 2007; 61:779-85 18 0.9 a 72b 5 No No Behall, Diabetes Care 2006; 29:976-81 10 4 50 −68.8 n/a −41.7 Yes Mäkeläinen, Eur J Clin Nutr 2007; 61:779-85 18 3.7 a 72b −26 No Yes Behall, Diabetes Care 2006; 29:976-81 10 6 50 −60.6 n/a −36.7 Yes Mäkeläinen, Eur J Clin Nutr 2007; 61:779-85 11 12 50 −73 Yes Yes Lan-Pidhainy, Cereal Chem 2007; 84:512-7 10 4 50 −58.9 n/a −35.7 Yes Mäkeläinen, Eur J Clin Nutr 2007; 61:779-85 Yes Lan-Pidhainy, Cereal Chem 2007; 84:512-7 18 5 75 −40 No −40 Ulmius, Genes Nutr 2011; 6:429-39 9 3.3 a 50 −40.4 No −15 Nilsson, Am J Clin Nutr 2008; 87:645-54 19 3 50 −80.0 Yes −40 Yes Granfeldt, Eur J Clin Nutr 1995; 49:189-99 −18.3 Yes De Angelis, Br J Nutr 2007; 98:1196-205 Yes Juntunen, Am J Clin Nutr 2002; 75:254-62 Yes Liljeberg, Eur J Clin Nutr 1992; 46:561-75 No Regand, J Agric Food Chem 2009; 57:8831-38 previously frozen 11 8 50 −79 Yes medium MW 10 4 50 −26 No Thosh, Cereal Chem 2008; 85:211-7 medium MW 10 4 50 −44 Yes Thosh, Cereal Chem 2008; 85:211-7 medium MW 10 8 50 −49 Yes Thosh, Cereal Chem 2008; 85:211-7 medium MW 10 8 50 −74 Yes Thosh, Cereal Chem 2008; 85:211-7 Breads high MW 10 4 50 −50 Yes Thosh, Cereal Chem 2008; 85:211-7 3.9 50 −35 Yes 10 8 50 −76 Yes Thosh, Cereal Chem 2008; 85:211-7 Sourdough bread with oat fibre 15 high MW previously frozen 11 8 50 −66 Yes Yes Lan-Pidhainy, Cereal Chem 2007; 84:512-7 10 5.4 50 −48 Yes previously frozen 11 8 50 −48 Yes Yes Lan-Pidhainy, Cereal Chem 2007; 84:512-7 Rye bread with oat ß-glucan concentrate previously frozen 11 12 50 −68 Yes Yes Lan-Pidhainy, Cereal Chem 2007; 84:512-7 Bread with coarse boiled oats 10 2.1 a 50 −15.6 Yes previously frozen 11 12 50 −63 Yes Yes Lan-Pidhainy, Cereal Chem 2007; 84:512-7 Oat crisp bread (medium MW) 12 4 64 −11 No Oat bran cereal Boiled oat kernels medium MW 12 8.3 31 −46 Yes −46 Yes Brummer, Cereal Chem 2012; 89:255-61 Pasta medium MW 12 8.7 31 −64 Yes −44 Yes Brummer, Cereal Chem 2012; 89:255-61 Oat bran fettuccini 10 5.2 54.2 −4.5 Yes medium MW 12 8.4 31 -65 Yes -27 Yes Brummer, Cereal Chem 2012; 89:255-61 high MW 12 8.6 31 −56 Yes −56 Yes Brummer, Cereal Chem 2012; 89:255-61 Oat pasta (medium MW) 12 4 42 −7 No 9 3.3 a 50 −23.6 No −11 No Granfeldt, Eur J Clin Nutr 1995; 49:189-99 11 6 75 −39 Yes 19 3 50 −16.7 No No Granfeldt, Am J Clin Nutr 1994; 59:1075-82 Glucose drink with oat extract 13 4a 50 −29.3 Yes Yes Granfeldt, Am J Clin Nutr 1994; 59:1075-82 Oat tempe 13 1.8 25 −79 Yes 12 4 32.7 −15.5 Yes Yes Hlebowicz, J Am Coll Nutr 2008; 27:470-5 Pudding with oat flour 10 3.23 a 50 −35 Pudding with oatmeal 10 73.7b 50 Oat ß-glucan isolate gel 10 −62 Oat bran 20 Oat extract −6.7 Holm, Eur J Clin Nutr 1992; 46:629-40 No Regand, J Agric Food Chem 2009; 57:8831-38 Other Oat bran muesli Oat granola medium MW 12 6.2 38 −28 Yes Yes Regand, Food Chem 2011; 129:297-304 medium MW 12 6.3 60 0 No No Regand, Food Chem 2011; 129:297-304 high MW 12 4 44 −29 No Yes Regand, J Agric Food Chem 2009; 57:8831-38 high MW 12 6.2 38 −35 Yes Yes Regand, Food Chem 2011; 129:297-304 high MW 12 6.3 60 −33 Yes Yes Regand, Food Chem 2011; 129:297-304 9 3.3 a 50 −11.5 No −7 No Granfeldt, Eur J Clin Nutr 1995; 49:189-99 9 2.1 a 35.5 −7.1 No 5.8 No Liljeberg, J Nutr 1996; 126:458-66 12 4 50 −29.4 Yes −24 Panahi, J Am Coll Nutr 2007; 26:639-44 −37 Yes Alminger, Eur J Clin Nutr 2008; 47:294-300 Yes Yes Behall, J Am Coll Nutr 2005; 24:182-8 −35 Yes Yes Behall, J Am Coll Nutr 2005; 24:182-8 Yes −35 Yes Yes Braaten, Am J Clin Nutr 1991; 53:1425-30 3.23 a 50 −35 Yes No Hallfrisch, Cereal Chem 2003; 80:80-3 20 73.7b 50 −35 Yes No Hallfrisch, Cereal Chem 2003; 80:80-3 Wholemeal oatflakes 12 −49 Yes −35 Yes No Hlebowicz, Nutr J 2007; 6:22 Cream of wheat+oat ß-glucan isolate 9 11.3 50 −35 Yes −48 Oat porridge high MW 12 4 43 −37 No oat bran porridge 9 8.8 60 −54 Yes Hätönen, Am J Clin Nutr 2006; 84:1055-61 Yes −38 Regand, J Agric Food Chem 2009; 57:8831-38 Wood, J Agric Food Chem 1990; 38:753-57 −40 Wood, J Agric Food Chem 1990; 38:753-57 Abbreviations: AC, available carbohydrate; beta- G, -glucan; MW, molecular weight; n/a, not available, AUC, area under the curve; significant, statistically significant; GI, glycemic index; a Soluble fibre measured; b 1g AC/kg body weight, average given. c 1 h AUC data reported. 28 oats for health 29 OATS & CHOLESTEROL LOWERING TABLE 4: Permitted health claims relating to β -glucan/oats -glucan and cholesterol lowering Dr Alastair Ross, Chalmers University of Technology, Gothenburg, Sweden Region High circulating LDL cholesterol is one of the most common markers of cardiovascular disease risk used in clinical practice, and people with high LDL cholesterol are often given drugs and/or advised to adapt their diet to eat more foods that can lower cholesterol. As no drugs are without side effects, the latter option can be especially attractive in cases of people with a family history of cardiovascular disease or mildly elevated LDL cholesterol, who wish to take proactive preventative measures. Beta-glucans in oats help lower cholesterol levels Oats are one of the few foods that are proven to lower blood cholesterol levels, and where there is a sound understanding of how this happens. Oats, like barley, contain high amounts of a soluble fibre called -glucan (see Table 2). -glucan is not digested, but forms a gel inside the intestines, which both inhibits the absorption of dietary cholesterol and binds bile acids that are secreted to solubilise the fats that we eat. Bile acids are synthesised from cholesterol in the liver, so losing bile acids through their binding to -glucan, leads to more liver cholesterol being used for synthesising new bile acids. This double action of preventing cholesterol absorption and increasing internal cholesterol turnover has the concrete action of reducing the amount of cholesterol transported throughout the body (i.e. LDL-cholesterol). These mechanisms have been demonstrated in many studies in humans (Agot et al. 1995; Ellegård & Andersson, 2007). European Union -glucans contribute to the maintenance of normal blood cholesterol levels The effect of oats on cholesterol appears to be dose dependent – that is, the more oats (and -glucan) is eaten, the greater the cholesterol lowering effect is (this is provided everything else is equal, e.g. viscosity) (Wolever et al. 2010), with a maximum effect around 3-4 g beta-glucan per day (Tiwari & Cummings 2011). The overall effect of 3 g/day of oat -glucan is a 0.23 mmol/L reduction in total cholesterol and 0.21 mmol/L reduction in LDL, based on studies including a total of 1080 subjects. This 5 % decrease in LDL-cholesterol is considered to be clinically significant. No reduction of HDL cholesterol was reported from these studies (EFSA 2010). Unsurprisingly, most studies show that reduction of total and LDL cholesterol is greater in those people starting with higher cholesterol. These amounts of -glucan translate to about 60g of oats per day, and an effect on cholesterol would be expected after 1-2 months. Australia & New Zealand USA Condition The claim may be used only for food which contains at least 1g of -glucans from oats, oat bran, barley, barley bran, or from mixtures of these sources per quantified portion. In order to bear the claim information shall be given to the consumer that the beneficial effect is obtained with a daily intake of 3g of -glucans from oats, oat bran, barley, barley bran, or from mixtures of these beta-glucans. Oat -glucan has been shown to lower/reduce blood cholesterol. High cholesterol is a risk factor in the development of coronary heart disease The more oats, the greater the effect Information shall be given to the consumer that the beneficial effect is obtained with a daily intake of 3g of oat -glucan. The claim can be used for foods which provide at least 1g of oat -glucans per quantified portion. -glucan reduces dietary and biliary cholesterol absorption (general level claim) The food must contain one or more of the following oat or barley foods: oat bran; whole grain oats; or whole grain barley. -glucanβ reduced blood cholesterol (high level claim) In addition, the following dietary context statements are required: diet containing 3g -glucan; diet low in saturated fatty acids. The food must contain at least 1g per serving of -glucan from the foods listed. In order to carry a health claim, a food must also meet the nutrient profiling scoring criteria set out in the standard. Soluble fibre from foods such as [name of soluble fibre source], as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. The food product must include one or more of the following whole oat or barley foods: 1) oat bran, 2) rolled oats, 3) whole oat flour, 4) whole grain barley or dry milled barley, and the whole oat or barley foods must contain at least 0.75g of soluble fibre per RACC of the food product; or Oatrim that contains at least 0.75g of beta-glucan soluble per RACC of the food product. Eligible sources of soluble fibre: -glucan from oats and barley. Canada Several countries allow health claims for the effect of oats (or oat -glucan) on cholesterol lowering – including the European Union, which has the most stringent food health claim requirements worldwide (see Table 4). Eating oats uncooked (e.g. as muesli) or as porridge has no negative/deleterious effect on their cholesterol lowering properties, though processing methods that involve fermentation (e.g. bread baking) will break down the -glucan (Åman et al. 2004). Oat -glucan can be isolated and purified, and added as an ingredient to food, and provided it has not been fermented, still has the cholesterol lowering properties (Wolever et al. 2010). Purified -glucan tends to be expensive however. Claim [Name and serving size of food] provides X % of the daily amount [3g] of the fibres shown to help reduce/lower cholesterol. Eligible sources of -glucan are oat bran, rolled oats (also known as oatmeal), and whole oat flour. Contain at least 0.75g -glucan per serving. Also has to meet other nutrient standards relating to sodium, vitamins/minerals, cholesterol, alcohol and saturated fatty acids. Sources: European Commission 2013; Food Standards Australia New Zealand 2013; US Food and Drug Administration 2009; Health Canada 2010 For more information For more information on oats and cholesterol lowering, including detailed information on key studies, see brochure on Oats for cholesterol lowering: A research summary for health professionals by Dr Peter Williams. 30 oats for health 31 Oats & cholesterol lowering continued... FIGURE 6: Oats reduce cardiovascular risk by interfering with cholesterol absorption, and other mechanisms may also play a role. Oats help control cholesterol levels in more than one way 3g/day or more of β -glucans from oats will prevent absorption of dietary cholesterol and bind bile acids, causing increased excretion of both in the faeces. The main mechanism whereby oats lower cholesterol is undoubtedly via the -glucan content, though other mechanisms may also play a role. Fat metabolism is highly linked to glucose metabolism and insulin sensitivity, and -glucan also has an effect on dampening the blood glucose response after a meal (EFSA 2011). Total body fat and fat distribution are also key risk factors for cardiovascular diseases, and one study found that eating 80 g of oat-based breakfast cereal a day for 12 weeks led to reduced waist circumference (1.4 cm after 12 weeks) along with a 4.4% decrease in LDL cholesterol, compared to an iso-energetic placebo control (Maki et al. 2010). Weight reduction remains one of the best ways of reducing blood cholesterol and cardiovascular disease risk, though more studies would be needed to confirm that oats have additional benefits on weight reduction or loss of body fat over and above energy/calorie restriction. Whole grain-rich diets that include oats, as well as other whole grains such as wheat and rice, have also been demonstrated to lower LDL cholesterol (Ross et al. 2011) and blood pressure (Tighe et al. 2010), an additional risk factor for cardiovascular disease. Cholesterol from the diet or made in the liver is used to make bile acids. While there is a lot of focus on the -glucan content of oats as the mediator of health benefits, there are likely other oat factors that contribute to their health benefits, including the grain structure and phytochemicals. At the moment, nutrition science is at the beginning of grasping the importance of the gut microbiota in maintaining health, and recent evidence has pointed to the gut microbiota being a key factor in whether diet leads to cardiovascular disease or not (Zhang et al. 2011). The dietary fibre from oats is readily fermentable by the bacteria in the large intestine (colon), with the short chain fatty acids (SCFAs) acetate, propionate and butyrate being major by-products. These SCFAs have been suggested to influence lipid metabolism in both the intestine and liver (Wong et al. 2006; Marcil et al. 2003). Improving gut integrity is another possible area where oats may have a protective role against metabolic diseases (Keshavarzian et al. 2001; Ross et al. 2013), though again human studies are required to confirm this hypothesis. Overall evidence that eating a significant amount of oats and β -glucan from oats each day lowers blood cholesterol is strong. Alongside the general recommendation to choose whole grains over refined grains (NHMRC, 2013), regular consumption of oats is a scientifically supported way of reducing risk for cardiovascular disease. Bile acids are secreted into the small intestine to solubilise dietary fat. -glucans in the colon are fermented to short chain fatty acids, which may decrease cholesterol synthesis in the liver. Bile acids are bound to -glucans and excreted. 32 oats for health 33 OATS & VASCULAR HEALTH Dr Kristina Andersson, Dr Per Hellstrand, Dept. Experimental Medical Science, Lund University, Sweden Most focus regarding vascular effects of oats has been on its cholesterol-lowering properties, mainly ascribed to the soluble fibres in oats, -glucans (see section ‘Oats and cholesterol lowering’). There might however be other components in oats that can influence atherosclerosis development, the underlying cause of cardiovascular diseases such as myocardial infarction and stroke. Atherosclerosis is a complex inflammatory process in the vascular wall, engaging in particular the endothelial cells lining the inner surface of the vessel wall and the smooth muscle cells forming its muscular coat. This process is multifactorial, involving oxidative stress and endothelial dysfunction as well as immune cells, pro-inflammatory molecules, triglycerides and circulating cholesterol carried by low density lipoprotein (LDL) particles (see Figure 7). Various dietary components in oats have the potential to exert anti-oxidative or anti-inflammatory effects and to beneficially affect endothelial function. The antioxidative properties of oats The contents of proteins and lipids in oats are relatively high compared with other cereals (Drzikova et al. 2005, Ryan et al. 2007, Zhou et al. 1999). Various anti-oxidative components, such as vitamin E (tocopherols and tocotrienols), phenolic compounds (e.g. the oat-specific avenanthramides), phytic acids, sterols and flavonoids protect the oat grain lipids from oxidation (Peterson 2001). The free-radical scavenging properties might also be beneficial for the human body when oats and other antioxidant-rich foods such as fruits and vegetables are consumed (Ryan et al. 2007, Zadernowski et al. 1999). In the formation of an atherosclerotic lesion, it is mainly the oxidized form of LDL (oxLDL) that is engulfed by macrophages in the blood vessel wall (Libby et al. 2011). Dietary antioxidants therefore offer the potential of limiting the atherosclerosis process. 34 Extracts from oats, as well as isolated oat phenolics, reduce oxidation of LDL particles in vitro (Chen et al. 2007, Gray et al. 2002, Handelman et al. 1999). However, when similar extracts were given to either hamsters or humans, and LDL particles isolated from the subjects were oxidised in vitro, no protective effect of the ingested extracts could be detected (Chen et al. 2007, Chen et al. 2004). In accordance with this, ingestion of whole oats in a human study did not lead to reduced levels of biomarkers for oxidative stress (oxLDL, malondialdehyde) (Maki et al. 2007). On the other hand, there are in vivo reports showing that intake of avenanthramides and avenanthramide-rich extracts can stimulate the body’s own oxygen scavenging system in both man, mice and rats, with increased levels and activity of endogenous enzymes such as superoxide dismutase (SOD), reduced glutathione (GSH), and glutathione peroxidase (GPx) – all protecting the organism from oxidative damage (Chen et al. 2007, Ji et al. 2003, Liu et al. 2011, Ren et al. 2011; see section ‘Anti-inflammatory properties of oats’ for more details). Further studies are needed to clarify if higher levels of bioactive components with anti-oxidative properties than the levels present in whole oats are needed to produce measurable effects. It is also possible that whereas some biological anti-oxidative systems are affected in vivo, others are not. oats for health 35 Oats & VASCULAR HEALTH continued... FIGURE 7: The initial steps in atherosclerosis in a simplified cartoon modified from Andersson & Hellstrand 2012. Vascular alterations involved in the progress of atherosclerosis are marked out, as well as the potential steps at which oats can interfere with the atherosclerosis process (indicated by a yellow box). LDL, low density lipoprotein; oxLDL, oxidized LDL, eNOS, endothelial nitric oxide synthase; NO, nitric oxide. Inflammation In vitro experiments show that oat-specific polyphenols avenanthramides reduce endothelial cell production of pro-inflammatory cytokines Adhesion of monocytes & macrophages Vascular Lumen Both cell culture experiments with avenanthramides, and experiments with mice fed oat bran show a reduced expression of adhesion molecules on the endothelial cell surface. Inflammation Increased LDL Endothelial dysfunction LDL Monocyte NO Increased LDL The LDL cholesterol-lowering properties of oats are well documented from both human and animal studies. ENOS Endothelial cells Adhesion of monocytes and macrophages Reactive oxygen species Oxidative stress As mentioned in the section of “Anti-inflammatory properties of oats”, cell culture experiments have revealed that avenanthramides reduce the expression of adhesion molecules like VCAM-1, ICAM-1 and E-selectin on endothelial cell surfaces, all important for recruiting macrophages to the vascular wall in the atherosclerosis process. Moreover, anti-inflammatory effects of oats have been demonstrated in animal studies in vivo. Mice fed oat bran had reduced levels of the adhesion molecule VCAM-1 both in the aortic wall and in plasma, as well as reduced plasma levels of fibrinogen, a common inflammatory marker related to cardiovascular risk (Andersson et al. 2010). Few human studies have addressed the effects of oats on systemic inflammation. Intake of oat products enriched in -glucans did not reduce plasma levels of inflammatory markers such as C-reactive protein (CRP), IL-6, IL-8 or TNF-α (Queenan et al. 2007, Theuwissen et al. 2009). Also, in type 2 diabetic patients, an oat-enriched diet did not change the inflammatory status (McGeoch et al. 2013). Despite promising results from cell culture and animal experiments, more human studies are needed to allow final conclusions regarding the anti-inflammatory effects of oats. 36 Blood pressure & maintenance of endothelial function Several human intervention studies have shown that intake of oats can reduce blood pressure (He et al. 2004, Keenan et al. 2002, Maki et al. 2007, Saltzman et al. 2001), and there have been indications of a greater effect in obese than in lean persons (Maki et al. 2007). Furthermore, in a study on hypertensive patients the use of antihypertensive drugs could be reduced in 73% of the patients after oat cereal consumption, as compared to 42% in a control cereal group (Pins et al. 2002). It has been suggested that the reduced blood pressure after oat intake results from reduced postprandial glucose and insulin levels (Katz et al. 2001, Maki et al. 2007). In addition, some in vitro studies suggest that specific oat components can directly influence the endothelial cells and thereby contribute to lowering blood pressure by improving endothelial function. In human endothelial cells avenanthramides increased the expression of endothelial nitric oxide synthase (eNOS), which generates the vasodilating agent nitric oxide (NO), a key mediator of multiple effects protecting against vascular complications (Nie et al. 2006a). An increased expression of eNOS was also found in the aortas of mice fed oat bran (Andersson et al. 2010), further supporting the notion that consumption of oats may help to maintain endothelial function by increasing the production of NO. In humans, endothelial dysfunction (impaired flow-induced arterial dilatation) provoked by a high-fat meal could be prevented by concomitant oat intake (Katz et al. 2001). LDL oxidation Both human and animal studies report that avenanthramide-rich extracts can stimulate the body’s own oxygen scavenging system, thereby reducing the level of oxidative stress. LDL oxidation Oat extracts and isolated oat phenolics reduce oxidation of LDL in vitro, but this has not been confromed in vivo. Macrophage foam cell formation Endothelial dysfunction Both in vitro and in vivo studies support that oats and/or specific oat components prevent endothelial dysfunction. Media Although there is compelling evidence for an antioxidative effect of isolated oat components, the evidence of activity after consumption of oats or oat products is still somewhat conflicting and more research in this area is warranted. Intima oxLDL Oxidative stress Vascular Smooth Muscle cells Oats & prevention of cardiovascular disease an area to be explored further No epidemiological studies have so far directly addressed the association between oats consumption and cardiovascular disease (CVD). To date, evidence of a possible role of oats in CVD mainly comes from experimental and short-term human studies, the latter primarily focusing on biomarkers such as cholesterol levels. Therefore, no strong conclusions on the role of oats in association with CVD can be drawn as yet, but evidence suggests that there may be a benefit of including oats in the diet. Oats may also help simply by displacing other breakfast foods that may be higher in sodium, saturated fat or total kilojoules. A handful of experimental animal studies have shown that oat consumption reduces the incidence of atherosclerotic lesions in blood vessels (Andersson et al. 2010, Delaney et al. 2003, Eussen et al. 2011, Wilson et al. 2002). In these studies it is difficult to discriminate whether the anti-atherogenic effects originate solely from the reduction of plasma cholesterol or if there are also direct effects of specific oat components that contribute to the beneficial effect. More studies with isolated oat components or fractions of whole oats are warranted. From a public health perspective, the ability of oats to reduce plasma (LDL) cholesterol and to reduce glycaemic response, in combination with its capacity to maintain endothelial function, and its possible anti-oxidative and anti-inflammatory actions, makes oat consumption a promising approach for the prevention of cardiovascular disease. oats for health 37 REFERENCES AEGIC (Australian Export Grains Innovation Centre) (2012). 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