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How to get your gut going: the importance of dietary fibre

Sara FL Kirk
PhD SRD
Senior Research Fellow
Nutrition Epidemiology Group
Nuffield Institute for Health
Leeds
E:s.f.l.kirk@leeds.ac.uk

That fibre is an important dietary component is undisputed. A high intake has long been known to prevent constipation by bulking stool and reducing gastrointestinal transit time.(1) And fibre has other benefits too - it is filling, thereby preventing hunger, essential for those needing to lose weight, and there is increasing evidence that some types can promote the colonisation of the gut by good bacteria.(2) So, with all this evidence, why is it that up to one in five adults are regularly constipated?(3) The answer is that, despite our beliefs to the contrary, we in the UK are still not eating enough fibre. In fact it is estimated that eight out of ten people miss out on sufficient quantities.(4)
 
Fibre is primarily found in wholegrain cereals, pulses, fruits and vegetables. As a society we are moving further towards a "convenience culture", relying on processed foods that are quick and easy to prepare, but which are often higher in fat and lower in fibre than freshly prepared alternatives. High-fibre foods such as pulses, brown rice and wholewheat pasta all take time to prepare. However, there are several notable exceptions. Fruit, vegetables, wholemeal bread and high-fibre breakfast cereals are the ultimate convenience foods - just peel and chop, slap in a filling or pour on the milk and you have a healthy, high-fibre meal or snack in no time.

So how might we encourage people to eat more fibre without the message falling on deaf ears? An interesting study from Australia looked at the effect of promoting increased consumption of wholemeal bread in the elderly on subsequent laxative sales.(5) Three towns were selected for the intervention. One acted as a control, while in the other two a community organisation strategy (COS), involving a campaign to promote bread consumption using the media, local advertising and a reduction in the price of bread, was compared with a patient education strategy (PES) through local doctors to the target patients - people aged over 55 years. The COS used the wonderful slogan "Bread: It's a great way to go", and resulted in a 60% increase in bread sales and a 60% fall in laxative sales!

In another interesting case, a GP in Scotland prescribed herrings to his patients, his rationale being that fish oils help to prevent a range of conditions, most notably coronary heart disease (CHD).(6) Is prescription food the way forward for many lifestyle diseases, such as obesity, heart disease and constipation? Evidence for the effectiveness of laxatives is limited,(7) and without good evidence, can the high cost of laxatives be justified when a simple dietary change may be all that is needed? Increasing fibre should therefore always be the first step in the management of constipation.8 Perhaps high-fibre foods could be prescribed to patients instead of laxatives - a case of "a bowl of high-fibre cereal a day keeps the doctor away (and saves a few pennies in the process!)"?

References

  1. Council on Scientific Affairs. Dietary fiber and health. J Am Med Assoc 1989;262:542-6.
  2. Bengmark S. Immunonutrition: role of biosurfactants, fiber and probiotic bacteria. Nutrition 1998;14(7-8):585-94.
  3. Taylor R. High fibre diets work. BMJ 1990;1063-4.
  4. Gregory J, Foster K, Tyler H, Wiseman M. The diet and nutritional survey of British adults. London: HMSO; 1990.
  5. Eggar G, Wolfenden K, Pares J, Mowbray G. "Bread: It's a great way to go": increasing bread consumption decreases laxative sales in an elderly community. Med J Aust 1991;155:820-1.
  6. Christie B. Doctor puts herring on prescription. BMJ 2000;320:1361.
  7. Tramonte SM, Brand MB, Mulrow CD, Amato MG, O'Keefe ME, Ramirez G. The treatment of chronic constipation in adults: a systematic review. J Gen Int Med 1997;12:15-24.
  8. Bateman DN, Smith JM. A policy for laxatives. BMJ 1988;297:1420-1.

Resources
Food Standards Agency
W:www.foodstandards.gov.uk
British Nutrition Foundation
W:www.nutrition.org.uk
British Dietetic Association
W:www.bda.uk.com