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Fibre for all the family

Angie Jefferson
BSc RD
Registered Dietitian

Mention fibre and most people still think in terms of "bran or roughage" and constipation. However, our understanding of fibre and its role in health is developing rapidly, and we now know that fibre plays a key role across a broad range of health issues, including satiety and weight management, cholesterol and heart health, plus reducing the risk of some cancers and type 2 diabetes. However, fibre intakes remain low with eight in 10 adults and children failing to eat enough fibre in the UK.1,2

Getting back to basics: what is dietary fibre?
The traditional definition of fibre as "plant materials resistant to digestion by the enzymes in the human gut, but which may be fermented by microflora in the colon" is set to change with the proposed introduction of a European definition of fibre which takes into account recent technological and scientific developments. This new definition includes plant fibre, but also carbohydrate polymers extracted from plants (eg, inulin) and oligosaccharides generated synthetically, which have proven, beneficial physiological benefits relating to fermentation in the gut. In addition, fibre will no longer be a calorie-free nutrient, but one containing 2 kcal per g as a result of energy released by bacterial fermentation in the lower gut.

Requirements for dietary fibre
Current recommendations for fibre intakes are to consume at least 25 g per day for adults or 15 g for 5-10-year-old children (Guideline Daily Amount (GDA) based on the Association of Official Agricultural Chemists (AOAC) method of analysis). However, intakes shown in Table 1 (measured as non-starch polysaccharides (NSP) therefore relating to the DRV of 18 g per day for adults) remain consistently low.3 Intakes of dietary fibre are, on average, around one quarter less than recommended for good health.

[[Tab 1 Fibre]]

Advice regarding foods rich in dietary fibre during infancy and childhood are vague and based on extrapolation and guesswork from adult figures. UK recommendations state that fibre intakes for children should be proportionally lower than those of adults, based on body size, and among the under-twos, high-fibre foods should not be fed at the expense of energy-rich foods.

Fears that diets high in fibre could cause growth retardation and poor absorption of vitamins and minerals are generally unfounded. In fact, studies suggest that children with higher fibre intakes have higher intakes of vitamins and minerals compared to those consuming lower levels, and that growth rates between eight months and nine years are not affected by fibre intake.4-6 A review has concluded that there is no evidence that fibre affects growth or nutrient status in the developed world, and that with the growing risk of obesity among children, a fibre-rich diet that reduces energy intake may be of great benefit.7 Despite this, advice continues to be given that toddlers' stomachs cannot cope with higher-fibre foods (Eatwell website: www.eatwell.gov.uk). This advice is likely to lead to young children unfamiliar with higher-fibre foods and unwilling to try them as they approach school age.

The UK has one of the lowest recommended intakes of fibre in the world, with other countries recommending up to 38 g per day (based on AOAC).8 Where children's recommendations are published they also tend to be higher than the UK, for example the USA recommendations vary from 19 g at one to three years, to 29 g (females) and 38 g (males) between 14-18 years. What is clear is that much remains to be done to increase fibre intakes in the UK.

Boosting fibre intakes
Foods are "high in fibre" when they contain 6 g or more fibre per 100 g of food and a "source of fibre" when they contain 3 g or more per 100 g. Checking food labels in the supermarket to compare fibre levels is a great start to achieving a higher dietary fibre intake.

Simple changes to dietary habits can have a big impact on fibre intakes. "Stealth health" is the new buzz phrase regarding diet, where a number of small subtle changes are made without compromising the family's enjoyment of the foods they are eating. Many of the swaps shown in Box 1 could be made without the family realising that they are eating a healthier diet. Encourage one swap at every meal and soon the whole family could be reaching their fibre goals.

[[Box 1 Fibre]]

Breakfast provides the ideal time to boost fibre intakes, particularly if a switch to a higher fibre breakfast cereal is made. Many cross-sectional and prospective studies have demonstrated an inverse association between breakfast eating and body weight, especially when ready-to-eat cereals are consumed. In addition, regularly consuming breakfast cereals is associated with higher intakes of micronutrients, dietary fibre and increased calcium from the milk that is generally consumed with cereals.9 

Wholegrain or high fibre?
Whether to recommend wholegrain or high-fibre foods is somewhat controversial, primarily due to the fact that not all wholegrain foods are high in fibre. A recent review carried out by the US Life Sciences Research Office has highlighted the importance of fibre rather than wholegrains.10 This review applied the US legal definition of wholegrains to published research examining the effects of wholegrains in coronary heart disease and diabetes.

Among the studies conforming to the US wholegrain definition little evidence was found to support a role for wholegrains in protecting health. However, when the definition was broadened out to include components of dietary fibre, such as bran, evidence became more conclusive, suggesting that bran fibre is a key driver of the benefits of wholegrains.

Health benefits of increasing fibre for the whole family
Major epidemiological studies have shown a link between higher fibre intakes, lower body mass index (BMI), lower fat mass, smaller waist circumference and reduced weight gain over time among both adults and younger people.11-14 And the converse is true, British children eating an energy-dense, low-fibre, high-fat diet have been found to have higher body fat mass and great odds of excess adiposity during childhood.15 It is suggested that the satiating effects of higher fibre foods may be an important factor here.16 

Fibre is also well established to reduce the risk of chronic heart disease (CHD) and type 2 diabetes among adults, through improved blood lipid profiles and insulin sensitivity, higher antioxidant status and lower body weights. Studies have shown significant reductions in risks of CHD and coronary death with higher intakes of wholegrains and fibre, with bran fibre established as a key driver of these effects.17-21 A low-fat high-fibre diet is also thought to decrease the risk of type 2 diabetes and cardiovascular disease among children.22

Higher intakes of fibre have been associated with lower levels of serum cholesterol among children, which over a lifetime could significantly alter levels of cardiovascular risk.6
Fibre may also protect against the development of breast cancer in women with the UK Women's Cohort Study showing a halving in risk with high fibre intakes.23 Evidence from the US suggests that higher intakes of fibre during adolescence could protect against development of breast cancer in later years.24

[[Box 2 Fibre]] 

Conclusion  
Higher fibre foods tend to be lower in energy density, providing texture and bulk to the diet. As knowledge develops we are beginning to move beyond a simple "eat more fibre" message to more sophisticated targeting of advice to increase intake of different fibre components to manipulate microflora in the gut, prevent weight gain or lower cholesterol levels. However, in general, fibre intakes remain so low in the UK that most people still need to take heed and eat a wider variety of foods with higher fibre content.

Fibre intakes are low for the whole family and so everyone young or old should be encouraged to consume a range of different sources of fibre on a daily basis (fruits, vegetables and cereals). A Cochrane Database Review has found that dietary advice to increase fibre intake can result in an average increase of 6 g per day, which applied to the UK could take fibre intakes from 14 g to 20 g per day - an increase of 30%.25 "Eat more fibre" may seem like an old fashioned message but emerging science continues to highlight the importance of this nutrient sadly lacking in the average UK diet.

References
1. Henderson L, Gregory J. The National Diet and Nutrition Survey: adults aged 19-64 years. London: TSO; 2003.
2. Gregory J, Lowe S. The National Diet and Nutrition Survey: young people aged 4-18 years. London: TSO; 2003.
3. Bates B, Lennox A, Swann G. National Diet and Nutrition Survey Headline results from the Rolling Programme Year 1 (2008/9). London: TSO; 2010.
4. Kranz S, Mitchell DC, Siega-Riz AM et al. Dietary fibre intake by American pre-schoolers is associated with more nutrient dense diets. JADA 2005;105:221-5.
5. Nicklas TA, Myers L, O'Neil C et al. Impact of dietary fat and fiber intake on nutrient intake of adolescents. Pediatrics 2000;105:E21.
6. Ruotinnen S, Langstrom HK, Niinikoski H et al. Dietary fibre does not displace energy but it associated with decreased serum cholesterol concentrations in healthy children. A J Clin Nutr 2010;91:651-61.
7. Edwards CA, Parrett AM. Dietary fibre in infancy and childhood. Proc Nut Soc 2003;62:17-23.
8. Buttriss J, Stokes C. Dietary Fibre and Health: an overview. Nutrition Bulletin 2008;33:186-200.
9. Gibson S. Micronutrient intakes, micronutrient status and lipid profiles among young people consuming different amounts of breakfast cereals: further analysis of the National Diet and Nutrition Survey of Young people aged 4-18 years. Pub Health Nutr 2003;6:815-20.
10. Life Sciences Research Office (LSRO) Wholegrain intake and cardiovascular disease and whole grain intake and diabetes: a review. Bethesda: LSRO; 2008.
11. Koh-Banerjee P, Franz M, Sampson L et al. Changes in whole-grain, bran and cereal fibre consumption in relation to 8-y weight gain among men. AJCN 2004;80:1237-45.
12. Liu S, Willett WC, Manson JE et al. Relation between changes in intakes of dietary fiber and grain products and changes in weight and development of obesity among middle-aged women. AJCN 2003;78:920-7.
13. Ludwig DS, Pereira MA, Kroenke CH et al. Dietary fibre, weight gain, and cardiovascular disease risk factors in young adults. JAMA 1999;282:1539-46.
14. Karnehed N, Tynelius P, Heitmann BL et al. Physical activity, diet and gene-environment interactions in relation to body mass index and waist circumference: the Swedish young male twins study. Publ Health Nutr 2006;7:851-8.
15. Johnson L, Mander AP, Jones LR et al. Energy-dense, low-fiber, high-fat dietary pattern is associated with increased fatness in childhood. Am J Clin Nutr 2008;87:846-54.
16. Slavin J. Whole grains and human health. Nutr Res Reviews 2004;17:99-110.
17. Pereira et al. Dietary fibre and Risk of Coronary Heart Disease. Arch Int Med 2004;164:370-6.
18. Jensen MK, Koh-Banerjee P, Hu FB et al. Intakes of whole grains, bran and germ and the risk of coronary heart disease in men. Am J Clin Nutr 2004;80:1492-9.
19. De Munter JSL, Hu FB, Spiegelman D et al. Whole grain, bran and germ intake and risk of type 2 diabetes: a prospective cohort study and systematic review. PLoS Medicine 2007;4(8):e261:1385-95.
20. Salmeron J, Ascherio A, Rimm EB et al. Dietary fiber, glycaemic load and risk of NIDDM in men. Diabetes Care 1997;20:545-50.
21. Liu S, Manson JE, Stampfer MJ et al. A prospective study of whole grain intake and risk of type 2 diabetes mellitus in US women. Am J Public Health 2000;90:1409-15.
22. Vivian EM. Type 2 diabetes in children and adolescents - the next epidemic? Curr Med Res Opin 2006;22:297-306.
23. Cade et al. Dietary Fibre and risk of breast cancer in the UK Women's Cohort Study. Int J Epid 2007;36:231-8.
24. Su X, Tamimi RM Collins LC et al. Intake of fiber and nuts during adolescence and incidence of proliferative benign breast disease. Cancer Causes Control 2010;21(7):1033-46.
25. Brunner EJ, Rees K, Ward K et al. Dietary advice for reducing cardiovascular risk. Cochrane Database Syst Rev 2007 Oct 17(4):CD002128.

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CPD questions
What is the recommended intake of fibre for UK adults and what is the shortfall in current dietary intakes?

How does dietary fibre affect CHD risk and what are the mechanisms thought to be involved?

How can eating more fibre at breakfast affect an individual's health?

List 5 ways that fibre intakes can easily be increased with little impact on a families enjoyment of food

Do children need the same amount of fibre as adults?