Fibre is a pretty special nutrient. Although not officially classified as essential, much evidence suggests it to be conditionally essential for health. Although originally believed to provide little more than bulk to the chyme within the gut, within the last few decade the role of fibre in human nutrition has been expanded considerably. In particular, dietary fibre is now thought to regulate metabolism and substrate usage. Further, fibre may be pivotal in modify the health of the intestine to provide a suitable environment for the colonisation of friendly bacteria that can improve health through the manufacture of essential substances. Such bacteria are also also thought to provide health benefits by inhibiting the growth of pathogenic microorganisms. The reason for the wide ranging effects of fibre on human health is the fact that fibre is not a single substance but a complex group of non-digestible carbohydrates with different structures. These structure confer different but often overlapping functions to the fibres with regard human health.
That fibre can actually alter the structure and function of the gut is also evidenced. In this regard animal studies have shown that fibre can alter the cell proliferation in rat mucosa cells in the colon. For example, in one study1, researchers fed rats a diet containing a wheat bran fibre supplement while control rats had an identical diet without the wheat bran supplements. After four weeks there was no difference in the small intestinal DNA, DNA synthesis or mucosal weight. However, those rats fed the wheat bran supplements had a significant increase in their large intestinal mucosal DNA, which increased by 59.1 % in the caecum, by 28.3 % in the proximal colon, and by 35.6 % in the distal colon, when compared to the rats being fed the control diet. When the authors analysed data from rats fed a wheat bran supplement for nine weeks, they found evidence that the wheat bran caused a decrease in cell exfoliation. However, the cell migration rate differed between various sections of the large intestine.
Wheat bran supplements therefore cause an increase on the mucosal weight and DNA synthesis rates of the large intestine. However, this effects is different in different parts of the colon. In particular, the wheat bran supplements may caused a decrease in cell exfoliation in the distal colon, whereas in the proximal colon the fibre may cause an increase in cell proliferation. With regard the latter, this is likely a result of an increase cell hyperplasia. These results therefore support others showing an increase in intestinal weight with fibre supplements. Because the wheat bran produced no growth effects in the small intestine its effects likely relate to its metabolism in the large intestine. This may be caused by the production of short chain volatile fatty acids that can stimulate the growth of intestinal cells, because studies that provide bulk to the diet without the presence of dietary fibre do not experience the same changes in mucosal cell weight. Therefore it is likely that metabolism of the fibre is essential for this effect.
Dr Robert Barrington’s Nutritional Recommendation: fibre is likely a conditionally essential nutrients. Generally, diets devoid of fibre, if they contain starches and sugar, lead to disease. This likely relates to the beneficial glycaemic effects of fibre. However, other effects are clearly present, and in particular some fibre may be able to stimulate the growth of the intestinal mucosa and this may improve gut health.
RdB
