Features Technical
Technical Talk – August 2009

There have been many discussions and arguments among scientists and regulators regarding the definition of dietary fibre.

Beans and lentils are a great source of fibre.

There have been many discussions and arguments among scientists and regulators regarding the definition of dietary fibre.

Recently, the Codex Alimentarius Commission (CAC) has adopted a new definition of fibre designed to harmonize the use of the term around the globe. The American Association of Cereal Chemists (AACC) provides the following definition, which includes oligosaccharides:

Dietary fibre is the edible part of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine. Dietary fibre includes polysaccharides, oligosaccharides, lignin, and associated plants substances.

Dietary fibres promote beneficial physiological effects including laxation, and/or blood cholesterol attenuation, and/or blood glucose attenuation.

What to include as a dietary fibre varies in the various definitions, particularly in the case of oligosaccharides and the degree of polymerisation (number of monomers). The definition adopted recently by CAC states that the carbohydrate polymers must have 10 or more monomeric units. A footnote included in the provision suggests the “decision on whether to include carbohydrates from three to nine monomeric units should be left to national authorities.”

The AACC definition, however, does not restrict the number of monomeric units to higher than 10.

This article will not extensively discuss the definition of dietary fibre. As formulators of food products we should always use ingredients that are permitted in Canada, and in the case of exports adhere to the regulations of the targeted country. Fibre ingredients that are permitted for food use may not necessarily be recognized as fibre by Health Canada. Therefore, if we are making a fibre claim we should use those that are recognized as such. The fibre ingredients permitted for use in Canada are listed on the CFIA website:  www.inspection.gc.ca.

The food regulations in Canada also state that: The amount of dietary fibre is one of the 13 core nutrients that must be declared in the Nutrition Facts table [item 10 of the table to B.01.401]. The amount of both soluble fibre and insoluble fibre may be separately declared as additional information [item 10 and 11 in the table to B.01.402].

It is well understood that there are two types of fibre. Soluble dietary fibre that will dissolve in water, and insoluble which will not dissolve in water. The total fibre content from most naturally occurring plant sources consists of both types in varying amounts. However, manufactured or processed dietary fibres may exclusively contain one or the other. Soluble and insoluble dietary fibres perform different functions and have different effects on formulation of food products. These different types of fibres also provide different health benefits.

The health benefits for soluble and insoluble fibres are numerous and they are well documented and substantiated with credible scientific research. Some of the health benefits include:

Cardiovascular health:
Soluble fibre has been proven to reduce blood cholesterol levels, thus helping in the reduction of heart disease. In order to reinforce this relationship in the United States, the Food and Drug Administration has approved health claims for beta-glucans from oats and barley as well as fibre from psyllium husks.

Gastrointestinal health:
Insoluble fibre maintains regularity as a bulking agent. Some fibres are also fermented in the colon, providing substantial benefits. Basically they can function as prebiotics, increasing the number of beneficial micro flora in the gut (probiotics) and enhancing the gastrointestinal system and immune system.

Weight management:
Fibre fills you up and breaks down much more slowly (if at all) than other carbohydrates. A study of more than 74,000 nurses in the U.S. showed that women with the highest dietary fibre intake gained an average of 3.5 pounds (1.52 kilograms) less than women with the lowest levels of fibre intake.

Cancer:
Fibre has been associated with preventing specific types of bowel and breast cancer. In one study, it was concluded that individuals with a low average intake of fibre could reduce their risk of colorectal cancer dramatically if they doubled their fibre intake.

Type 2 diabetes:
Individuals with Type 2 diabetes and those with a pre-diabetic position can maintain a healthier blood sugar level with higher fibre consumption, because fibre is slower to breakdown into glucose than other carbohydrates such as starches.

Some natural sources of insoluble fibre include wheat bran, whole grains and some vegetables. High amounts of soluble dietary fibre are found in oats, barley, nuts, seeds, beans, lentils, and some fruits and vegetables.

A plethora of manufactured, extracted or processed fibre ingredients are available in the market. Such include white or light-colour insoluble from oat hulls and various brans. The market demand for high dietary fibre light colour foods led to the development of whole-grain flours and bleached fibres. Such ingredients expand the use of fibre in many food categories.

Many new fibres, especially soluble, are appearing in the market. As we gain further understanding of the benefits of prebiotics and probiotics, the use of such fibres in foods will expand. These new ingredients include inulin and other fructo-oligosaccharides, short chain fructo-oligosaccharides (scFOS) and galacto-oligosaccharides (GOS).

Health Canada recommends that Canadians consume approximately 25 grams of dietary fibre per day; however, it is likely that on average we consume only a fraction of that per day. We need to convince consumers to eat more soluble and insoluble fibre. To achieve this we need to incorporate more fibre into mainstream food products and at the same time maintain the good taste and texture of these foods.

Funding for this report was provided in part by Agriculture and Agri-Food Canada through the Agricultural Adaptation Council’s CanAdvance Program.

Dr. John Michaelides is Guelph Food Technology Institute’s director of research and technology. For more information, or fee-for-service help with product or process development needs, please contact GFTC at 519-821-1246 or  gftc@gftc.ca.