Defining dietary fibre
In the EU, regulation 1169/2011 ( ) on the provision of food information to consumers, defines fibre as 'carbohydrate polymers with three or more monomeric units, which are neither digested nor absorbed in the human small intestine and belong to the following categories:
-edible carbohydrate polymers naturally occurring in the food as consumed,
-edible carbohydrate polymers which have been obtained from food raw material by physical, enzymatic or chemical means and which have a beneficial physiological effect demonstrated by generally accepted scientific evidence,
-edible synthetic carbohydrate polymers which have a beneficial physiological effect demonstrated by generally accepted scientific evidence'.
Similar to the EU, the United States (US) Food and Drug Administration (FDA) definition ( (pdf)) refers to 'non-digestible soluble and insoluble carbohydrates (with 3 or more monomeric units), and lignin that are intrinsic and intact in plants; isolated or synthetic non-digestible carbohydrates (with 3 or more monomeric units) determined by FDA to have physiological effects that are beneficial to human health'.
The EU and US definitions differ from the Codex Alimentarius definition ( (pdf)) on the number of monomers that constitute the carbohydrate polymer; while the EU and US includes three or more monomeric units, the Codex definition specifies ten or more, leaving national authorities to decide whether to include as fibre also carbohydrates with 3-9 monomers.
Dietary fibre is often referred to as non-starch polysaccharides (NSP) fibre or as AOAC fibre. NSP fibre only includes polysaccharides of the plant cell wall components characteristic of plant foods, such as wholegrain cereals, fruits and vegetables ( , , pdf). AOAC fibre comprises of the total amount of non-digestible polysaccharides, and includes e.g. lignin and resistant starches, measured with a set of methods developed by the Association of Analytical Chemists (AOAC) ( ). In effect, AOAC fibre includes NSP fibre but in addition it also includes non-digestible carbohydrates (naturally present and isolated from foods and/or synthesized) that can be added as ingredients to foods. In general, figures for AOAC fibre are higher than NSP fibre. As such, the reported fibre content in foods can vary depending on the definition and/or the method used to quantify it.
As an example, both the Food and Agriculture Organization (FAO) of the United Nations and the World Health Organization (WHO) refer to NSP fibre as dietary fibre and express their intake recommendations accordingly. On the other hand, the European Food Safety Authority (EFSA) uses AOAC fibre as a basis for intake recommendations ( ).
Finally, and albeit outdated, a terminology often encountered in the literature is the classification of dietary fibre into soluble and insoluble. This distinction was made on the basis of the different physiological effects of the two types of fibre. However, over the years a good amount of scientific research has shown that solubility is not necessarily a determinant of physiological effect. Therefore FAO/WHO in 1998 proposed to no longer use this classification ( ).
Labelling of fibre in the EU
EU Regulation No. 1169/2011 ( ) allows for voluntary fibre content declaration on the nutrition label, following the rules discussed previously. As reported above, the definition of dietary fibre that can be declared in the EU on the label also includes carbohydrates which are not naturally occurring in a food, if however the latter have a beneficial physiological effect demonstrated by generally accepted scientific evidence and, for those carbohydrates that fit these criteria, largely relies on measurement methods proposed by the AOAC. An accompanying guidance document for competent authorities specifies sets of analytic methods for the determination of fibre content to be declared on the label ( , pdf). In addition, the guidance document specifies that Member States are responsible to ensure conformity with the fibre definition as a whole and 'in particular concerning components not naturally occurring in the food as consumed'.
Food energy content is among the mandatory information that must be reported in the nutrition declaration section on labels. Fibre - similarly to carbohydrates, fats, and proteins - is a source of metabolic energy for the human body providing on average 8 kJ (2kcal) per gram ( ). This amount of energy needs to be accounted for when calculating total energy content of foods.
- Source of fibre: 'A claim that a food is a source of fibre, and any claim likely to have the same meaning for the consumer, can only be made where the product contains at least 3 g of fibre per 100 g or at least 1.5 g of fibre per 100 kcal'
- High in fibre: 'A claim that a food is high in fibre, and any claim likely to have the same meaning for the consumer, can only be made where the product contains at least 6 g of fibre per 100 g or at least 3 g of fibre per 100 kcal'
Approved nutrition and health claims (mainly relating to gastrointestinal health) for food products containing dietary fibre can be found at the relevant EU Register ( ).
Fibre intake: effects on health
According to major food and health related organisations, and as described in Table 1, the health benefits associated with dietary fibre are manifold, e.g. on gastrointestinal health and risk reduction of non-communicable diseases such as cardiovascular diseases, diabetes type 2, colorectal cancer as well as reduced risk of weight gain. Main dietary sources of fibre include whole grain cereals, pulses, fruit, vegetables and potatoes ( ).
Assessing the specific or unique role of dietary fibre in reducing the risk of NCDs and on other health outcomes is complicated by the existence of other nutrients in fibre-rich diets that may also exert a protective role as well as other confounding factors. For example, fibre is found in many foods that also have lower energy density (e.g. most fruits and vegetables), low glycaemic index (e.g. pulses, vegetables, whole grain cereals, some fruits,) and that are sources of a wide variety of micronutrients and bioactive compounds (pulses, fruit, vegetables, whole grain cereals, seeds, nuts).
Recommended intake of fibre
In adults, the recommended amounts of dietary fibre for promotion of adequate laxation and for prevention of NCDs such as diabetes type 2, colorectal cancer, CVD or of overweight and obesity range from 25 to 38 grams/day (Table 2). In children, recommended amounts vary according to the energy requirements of different age groups.
Recommended intake values are expressed in the majority of the cases as adequate intakes (AI) of AOAC fibre unless differently stated; some public health organisations also recommend fibre intakes on per energy requirements basis (grams fibre per MJ or grams per 1000kcal).
The majority of food and health-related organisations encourage meeting the recommendations through a diet rich in vegetables, fruit and whole grain cereals.
Fibre intake across European countries
In the EU, whole grain cereals, pulses, fruit, vegetables and potatoes are the main sources of dietary fibre. According to data from national reports collected in the 2009 European Nutrition and Health (ENH) report ( ), daily dietary fibre intakes vary broadly across different European countries and within populations groups. More recent data from food and nutrition surveys (Table 3) confirm the EHN 2009 data.
Despite the different methodologies used for the assessment of food consumption in the surveys and lack of comparable data between countries, it appears reasonable to conclude that many EU citizens do not meet recommended intakes of dietary fibre.
Disease burden related to low intake of fibre
Fibre is not an indispensable component in human diets; however as detailed in Table 2, poor fibre intake is a risk factor for ill health. The most recent Global Burden of Disease study (GBD) ( ) estimated that in the EU, in 2017 diets low in fibre account for approximately 97,000 deaths and more than 1440000 Disability Adjusted Life Years (DALYs), mainly caused by ischaemic heart disease (approx. 75,000 deaths and 1,077,000 DALYs) and colon and rectum cancer (22,000 deaths and 366,000 DALYs) ( ). Values for individual EU Member States in 2017 can be seen in the map below. In the GBD study, exposure to diet low in fibre is defined as average daily consumption of less than 23.5 grams per day of than fibre from all sources including fruits, vegetables, grains, legumes and pulses.
Implemented policies addressing fibre intake
A number of policies have the aim of improving diets and nutrition in the population and among these, some include explicit indications on how to achieve recommended fibre intakes. Table 4 lists some implemented policies across the globe that address fibre intake and include explicit indications to meet the recommended intakes. Policies targeted at increasing fruit and vegetables (refer to Fruit and Vegetables in this series) and whole grain foods (refer to Whole Grain in this series) consumption can also increase dietary fibre intake.
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