Dietary Fibre - ILSI Argentina

10 Concise Monograph Series
TABLE 2
Elements of definitions of dietary fibre
• Biological or synthetic origin of the fibre.
• Chemical nature of the substances included.
• Minimum degree of polymerisation of the carbohydrate
polymers.
• Resistance to hydrolysis (digestion) by the enzymes of the
gastrointestinal tract.
• Reference to a method of analysis.
• Reference to fermentability in the colon, including short
chain fatty acid production and associated physiological
effects, such as reduction of toxic stool components,
mineral absorption, prebiotic properties.
• Reference to other measurable physiological properties,
such as laxative or metabolic effects (e.g. reduction in
blood cholesterol or blood glucose or insulin levels).
Adapted from AFSSA, 2002
In 1999, the American Association of Cereal Chemists
proposed a definition that was restricted to plant
sources and did not include physiological aspects. This
was updated in 2001 and has the major advantage of
being simple and straightforward. It does not refer to
the origin of the dietary fibre and encompasses the
various physiological characteristics of different fibres.
It is more precise than earlier definitions that referred
only in very general terms to the physiological
properties of dietary fibre.
The US Institute of Medicine (2001) used a novel approach
in distinguishing between intrinsic, intact components of
plant foods, dietary fibre, and added fibre, summed as total
fibre. This definition was modified later on (2002), as part
of the development of dietary reference intakes. Added
fibre was reclassified as functional fibre, to indicate the
requirement for physiological benefits and functionality
of the isolated non-digestible carbohydrates added to
foods. However, the definition does not include any
precise description of the physiological characteristics of
fibre. It also creates an artificial, analytically impossible
and therefore in practice non-existing distinction between
fibres naturally present in plant cells and those extracted
from plant sources or synthetically produced. The term
functional fibre may also imply that fibres other than
functional fibre are not or at least less functional, which is
not the case. The term functional foods has a similar
drawback.
Most recently, the Agence Française de Sécurité Sanitaire des
Aliments (2002) reviewed existing definitions of dietary
fibre and usefully identified the criteria covered by these
definitions (Table 2). It observed that no definition before
2002 had been sufficiently comprehensive to encompass
all of these criteria and proposed a broader but much
more complex definition, although it is mostly confined
to fibres of plant origin or synthetic fibres, excluding
fibres of animal or microbial origins.
The definition of the Agence Française de Sécurité Sanitaire
des Aliments is one of the most comprehensive definitions
to date. In common with the definition of the American
Association of Cereal Chemists, it encompasses fibres that are
carbohydrate polymers naturally present in plant foods
(but not animal foods), as well as non-carbohydrate
associated materials (for example, lignin, polyphenols
and waxes). In common with the US Institute of Medicine
definitions, the Agence Française de Sécurité Sanitaire des
Aliments also includes processed and synthetic fibres,
because of the important physiological properties of these
materials. It is, however, more specific in including, as an
annex, a positive list of these compounds for labelling
purposes (Table 3). It is stipulated that compounds can be