The exclusion/inclusion of carbohydrates with degrees of polymerization (DP) in the range of 3 to 9

Debate about the exclusion or inclusion of carbohydrates with DPs in the range of 3 to 9 was focused on two major areas: (1) the lack of scientific support for differences in physiological effects between those oligomers with DP 3–9 and those with a higher DP and the absence of readily applicable methods that could clearly distinguish between them; and (2) the fact that the coexistence of regulations allowing two different standards for the same definition would undermine the validity of the definition.

All those who spoke regarding the physiological aspects argued that there was no basis for distinguishing between carbohydrates with a DP ≥10 and those with DP ≤9 because there were carbohydrates both above and below this cutoff point that exhibited one or more beneficial physiological effect(s) generally associated with fiber. The view was expressed that carbohydrates exhibiting beneficial physiological effects are distributed along a continuous spectrum of chain lengths with no clear differentiation at any particular DP.

Similarly, all those who spoke about methodological aspects were of the view that a universal cutoff point at a DP of 10 and above did not reflect methodological capability. Among those who spoke, there was a view that historically the cutoff point of DP ≥10¹ had gained currency in the mistaken belief that it was consistently applicable to all carbohydrates in the frame for consideration as dietary fibers through precipitation in alcohol. In practice, this is not the case and methodology provides no reliable basis for imposing a distinction between carbohydrates with or without fiber-like properties on the basis of chain length alone.

In addition, many contributors to the debate were of the view that to provide a discretionary approach at the national level to excluding or including carbohydrate fractions within the scope of the definition was undesirable. For nutrition research and assessment, the absence of a common definition creates difficulties for the comparison of fiber intakes across different geographic regions and in the interpretation of studies assessing possible beneficial physiological effects where datasets are drawn from different regions. For consumers and food manufacturers, the application of different interpretations of what constitutes dietary fiber can result in a confusing nutrition messages for consumers, demand differences in food labeling of the same food marketed in different countries, and create difficulties for food manufacturers seeking to formulate products for a global market.

Nevertheless, if there had been a necessity for compromise in order to achieve agreement on a definition, then it would have been preferable to default to a position that included carbohydrates with DPs in the range of 3 to 9 within the body of the definition, with discretion included in the footnote for those who disagreed, rather than in the opposite manner as is currently in the Codex definition. If structured in this way, the default form of the definition would have been fully inclusive, more aligned with other existing definitions, and would have more accurately reflected the majority of opinion in the scientific community.

In summary, there was a strong consensus among contributors that there is no sound scientific basis for a cutoff point at a DP ≥10. The difficulty of achieving a reconsideration of this issue within the Codex Alimentarius was acknowledged. It was suggested that the reaffirmation of the existing scientific agreement on the issue would provide better, practical support to national authorities in their implementation.

Agreement on a list of beneficial physiological effects

Initiating the discussion of beneficial physiological effects, Joanne Lupton drew attention to the three categories of dietary fiber differentiated within the Codex definition by their source: those occurring naturally in food as consumed; those obtained from food raw material by physical, enzymatic, or chemical means; and those that are synthetic in origin. Of the three categories, the definition requires that the latter two must be shown to have a physiological benefit to health, while for those occurring naturally in food as consumed, no such beneficial effect is required to be demonstrated. At the same time, the definition provides no description of what constitutes a beneficial physiological effect so, to the extent that this remains open to interpretation, it provides no clear indication of the qualifying features of fibers falling within the last two categories.

There is a diverse list of beneficial effects in common use in academia and by institutes, agencies, and authorities worldwide. Until the 2008 session of the Codex Committee on Nutrition and Foods for Special Dietary Uses (CCNFSDU) where the current definition was recommended for adoption, the Codex definition of dietary fiber itself had been presented in conjunction with an illustrative list of relevant beneficial physiological effects and had met with a clear majority of support among participating governments and observer organizations (2). The list was removed during the 2008 CCNFSDU session to simplify the definition (3), but the list's removal potentially leads to risks of higher levels of confusion as beneficial physiological effects are now open for different interpretations at the national level.

Dr. Lupton suggested that progress might be made by attempting to characterize effects in relation to three levels of agreement on the certainty of their validation:

1. Well-established beneficial effects

2. Probable beneficial effects

3. Possible beneficial effects

In this way, an agreed core list of beneficial effects could be drawn up to provide a working basis for the definition but, at the same time, the list could remain open to additions as emerging science provided sufficient validation.

During a discussion, the following physiological effects received support:

1. Reduced blood total and/or LDL cholesterol levels

2. Attenuation of postprandial glycemia/insulinemia

3. Reduced blood pressure

4. Increased fecal bulk/laxation

5. Decreased transit time

6. Increased colonic fermentation/short chain fatty acid production

7. Positive modulation of colonic microflora

8. Weight loss/reduction in adiposity

9. Increased satiety

Support was not unequivocal in every case. The occurrence of most of the effects was considered to be well established for fibers in general but the health impact of some effects was the subject of discussion. While in a few cases (reduced blood total cholesterol, reduced blood pressure) there were considered to be clear associations between the endpoints measured and the reduction of disease risk, in other cases (increased colonic fermentability, attenuation of postprandial glycemia/insulinemia, increased satiety) the relevance of the endpoint measured was considered by some to be indeterminate. It was also noted that there is an ongoing discussion about relevant methods and the interpretation of the magnitude of effect from the perspective of a contribution to health. Furthermore, it was pointed out that an agreement of the substantiation of the beneficial nature of any proposed effects is a case-by-case process.

The view was expressed that in considering beneficial effects in the context of a definition for dietary fiber and resultant nutrient content claims, it is important to keep in mind the consumption of fibers of all types. The total fiber content of the diet contributes several different effects simultaneously and the overall benefit, however achieved mechanistically, derives primarily from the fact that fiber is not digested in the small intestine and passes to the colon intact. The beneficial outcomes of individual fiber types in individual foods should be seen in terms of their contribution to the overall benefit achieved through their contribution to total dietary fiber intake as reflected in nutrient content claims. This is in contrast to health claims made in relation to individual components where the claim is product specific and requires substantiation on a case-by-case basis in relation to the individual food ingredient.

The distinction between these two circumstances is reflected in the nature of the claims made. In the case of fiber content claims, the primary consideration of beneficial effect is in relation to the total fiber content of the diet and the value to consumers of an awareness of the importance of maintaining an adequate intake of dietary fiber from a variety of sources. In the case of health claims, the consideration is entirely product-specific with the objective of making an on-pack claim, in a language understood by consumers for products containing the effective amount of the specific component.

Overall, there was enthusiasm for agreeing on a core list of beneficial physiological effects.

J.H. had primary responsibility for final content; V.B, M.C., and J.J. chaired the scientific session discussion and provided substantive input into the paper content; A.M. and S.A.S.C. contributed substantially to writing and editing. All authors read and approved the final manuscript. The authors would like to particularly thank Dr. Jon deVries, Dr. Gunhild Kozianowski, Dr. Lisa Sanders, and Ms. Marie Latulippe for their contributions to this paper.