Getting Rich on Fibre

The food industry has to innovate to develop a wider range of fibre-rich foods, says J Lunn and J L Butriss, Nutrition Scientists, the British Nutrition Foundation.

The term fibre has considerable resonance with consumers and frequently appears on food packages to denote healthy carbohydrates. However, studies have shown that consumers are not meeting recommended daily intakes of fibre, highlighting the need for innovation by industry to create products that may bridge this gap.

The report Carbohydrates and Dietary Fibre by J Lunn and J L Buttriss of the British Nutrition Foundation states: “Through innovation by the food industry, one option is to develop a wider range of foods that include non-digestible carbohydrates as ingredients.”

Big FiveDietary fibre has been reported to have many health benefits, but the ‘big five’ with the most science to back them up, are: improvements in gastrointestinal health; improvements in glucose tolerance and insulin response; reduction of hyperlipidaemia, hypertension and other coronary heart disease (CHD) risk factors; reduction in the risk of developing some cancers; and increased satiety and hence some degree of weight management.

As our understanding of fibre has improved it was becoming clear that a better definition was required. The authors define dietary fibre as: “A primary characteristic is resistance to digestion and absorption in the small intestine and fermentation in the large intestine; and demonstrate that fibre has physiological properties.”

The authors also comment that there is “a convincing argument for including slowly fermented components, such as resistant starches, that are well tolerated in the digestive system and can bring about improvements in 
gut function.”

Such a definition, they state, would ensure that components, such as resistant starches and oligosaccharides, are considered to contribute to the total dietary fibre in the diet.

Such statements are in-line with proposals from Codex. Although a definition currently exists within the framework of Codex guidelines, the matter was thrown open in 2005 when a FAO representative informed the committee that a FAO/WHO expert working group was reviewing evidence on the physiology of carbohydrates and relevant definitions.

If a new definition is adopted and comes to bear on nutritional claims, ‘fibre-like’ ingredients in supplements, resistant starch and oligosaccharides could be assessed on their own individual merits and not bundled together under the broad umbrella of ‘fibres’. Health BenefitsThe health benefits of including sufficient dietary fibre in the diet have been well described and have formed the basis of dietary recommendations around the world.

However, dietary fibre is a complex dietary entity, consisting of many non-digestible components of food. Debate surrounding the definition and measurement of dietary fibre has resulted in inconsistencies in labelling, description and recommendations set across the world. In the UK, dietary recommen-dations are made using the fraction of non-digestible material described as non-starch polysaccharide that is measured by the Englyst method.

However, the Association of Official Analytical Chemists (AOAC) methods, used widely by the food industry, capture a much greater range of non-digestible material, that some suggest should be included in any definition of dietary fibre. An attempt to resolve such discrepancies, possibly by taking an approach that considers the health effects of fractions not captured in the Englyst method, is probably overdue.

Additionally, it is clear that the effects of these various non-digestible components of dietary fibre are not interchangeable, and it is important that fibre comes from a range of sources to ensure maximum health benefits from the fibre in the diet.

Traditional ‘insoluble’ fibres are required to add bulk as well as rapidly fermentable, viscous fibres to bring about cholesterol lowering. There is also a convincing argument for including slowly fermented components, such as resistant starches, that are well tolerated in the digestive system and can bring about improvements in 
gut function.

Currently there is insufficient data from well designed human intervention trials to make specific recommendations on the amounts of these fibre components in the diet, but it may be useful for health professionals to talk in terms of the different food sources of these types of fibre, as well as total fibre amounts.

Dietary Fibre: Source of Goodness
Fibre is found in plant foods and exists in two main forms. Insoluble fibre is the tough, fibrous parts of the plant. Foods rich in insoluble fibre include whole grain foods, such as whole grain and bran cereals, wholemeal bread and pasta, brown rice and a small amount in fruits and vegetables.

Soluble fibre is found mostly in vegetables, especially pulses and legumes, and in many fruits. Oats are also a source of soluble fibre. The majority of the fibre in our diet is insoluble fibre. Insoluble fibre is not absorbed and reaches the large gut intact where it has many health benefits. It can help prevent constipation and may reduce the risk of bowel cancer. Soluble fibre reduces blood cholesterol levels and helps to slow the absorption of nutrients.

Dietary fibre may help weight control. A large study of almost 3,000 young adults in the US showed that over 10 years the group eating the most dietary fibre gained less weight than the group with the lowest intake of dietary fibre. Studies suggest that diets that include plenty of fibre, especially insoluble fibre, may be associated with increased weight loss.

High fibre foods may help reduce appetite. This may be related to the bulky nature of these foods, their effects on blood glucose and insulin levels due to delayed gastric emptying or effects on gut hormones that regulate appetite.

Updated on 2 Aug 2007, Asia Pacific Food Industry