Cereal grains, including oats, are valued primarily as a source of carbohydrates to provide calories for energy needs. In addition to total dietary fibre, in recent years, oats have been recognised as an important source of soluble fibre. Dr Markku Mikola and Uura-Liina Pöyhönen report.
Oats have been part of human diet long before its health promoting properties were known. According to the current knowledge, the most important active oat ingredient for the human body is oat soluble fibre ß-glucan. Inspite of its indisputable healthiness, the consumption of oats is still relatively low. The opportunities to increase oats consumption are, however, getting better as the number of products containing oats is increasing in the market.
Oats have a higher concentration of well-balanced protein than other cereals and therefore have greater potential value to provide protein. In addition, oats contain essential vitamins, minerals, fatty acids and phytochemicals that have been associated with protection from chronic disease.
The components of oats and their effects on human body have been extensively studied for a long period of time. Currently it is thought that the most important health promoting effects of oat ß-glucan are the reduction of blood cholesterol level, balancing blood sugar and improved gut function.
However, since the energy release from oats is fairly slow and the feeling of satiety remains long, oats aid the endurance of physical exercisers and those who are interested in weight maintenance.
High cholesterol is the best known of all the threats to a healthy heart. When excess amounts of cholesterol build up along the walls of the arteries, there is a risk of a complete blockage, leading to a heart attack or stroke. However, at normal levels, cholesterol is not harmful. It poses a problem only when the body is unable to use or eliminate excessive supplies.
The cholesterol reducing effect of oat ß-glucan has been proved in many scientific studies.
According to the present view, the effect is based mainly on the elevation of viscosity in the intestinal tract. Following stages/mechanisms have been proposed: p Oat ß-glucan is partly dissolved in the stomach and small intestine, resulting in an increased viscosity in the small intestine. p Due to the elevated viscosity, an unstirred layer is formed on the absorbing surface of the small intestine retarding the absorption of nutrients, cholesterol and bile acids. p Re-absorption of bile acids is lowered, leading to their increased excretion in the faeces. p To compensate the loss of bile acids, their synthesis in the liver from cholesterol is increased. p The elevated viscosity diminishes contact surfaces of digestive enzymes to nutrients, retarding and diminishing the absorption of nutrients. p This leads to retarded elevation of blood glucose, which in turn diminishes insulin secretion. p The lowered level of insulin diminishes the synthesis of cholesterol in the liver. p The level of deoxycholic acid in the liver is elevated, which also weakens the liver cholesterol synthesis. p The elevated level of deoxycholic acid prevents cholesterol re-absorption.
The ability of oat ß-glucan to increase viscosity of the contents of the alimentary tract prolongs stomach emptying and nutritient absorption in the small intestine. In addition, it balances blood sugar levels by reducing the after-meal elevation in plasma glucose and insulin, and delaying its decline to pre-meal levels or lower. These properties are not beneficial only for active exercisers but also for those who suffer from afternoon sleepiness at work.
Oats balances gut function
Cereal products in general promote the well-being of the intestine. The products containing adequate amounts of oat ß-glucan may aid digestion in many different ways.
Dietary fibre sources, especially insoluble fibres, are regarded as beneficial to enhance colon motility and to alleviate constipation.
Compared with other fibre sources, oat bran has the advantage to contain both soluble and insoluble fibre. The insoluble fibre contributes to the ballast, whereas the soluble fibre acts mainly by increasing the bacterial cell mass in the large bowel. This cell mass has a large volume and a high water holding capacity, improving stool consistency as well.
Bran ingredients
Finn Cereal Ltd develops, processes, and sells ß-glucan rich oat bran ingredients. The minimum ß-glucan content of Natureal Oat Bran is 15 per cent d.s. This is more than threefold to that in conventional oat products (35 per cent d.s.).
By using special milling techniques Finn Cereal separates the part of the oat groat, which has high ß-glucan content without using chemicals or solvents.
The process leaves the essential structure and molecular size of the oat ß-glucan unchanged.
Sources:
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Dr Markku Mikola and Uura-Liina Pöyhönen are with Finn Cereal Ltd, Vantaa, Finland. www.natureal.fi
