Fibre should really be a conditionally essential nutrient. When carbohydrates are present in the diet, fibre is essential to prevent detrimental glycaemic effects that can cause metabolic deterioration and weight gain. Fibre is also required for gut health and an absence of fibre can lead to deteriorations in gut function because the fibre acts as a food for bacterial populations in the colon which interact with enterocytes and this provides a favourable health outcome. Refined carbohydrates, devoid of their natural fibre can cause disease and this is increasingly being observed in the nutritional literature from well designed clinical and epidemiological studies. The association between low fibre diets and the development of Western diseases is well established, and increases in the prevalence of such diseases are traceable to concomitant decreases in the intake of fibre rich foods, particularly cereals, within the populations. The increases in diseases such as diverticular disease have been studied as populations Westernise.
For example, in one study1, the dietary changes to the fibre intake of Japanese populations were investigated by researchers. A sharp decline in the amount of dietary fibre in the diets of those living in the United States of America was observed between the 1930s and the 1950s and this coincided with an increase in the prevalence of diverticular disease. The authors set out to investigate if similar patterns were present as the Japanese population Westernised throughout the twentieth century. Consumption tables for the crude fibre intake amongst japanese populations showed that fibre intake had declined in two phases. The first decline was apparent during the end of the 19th century and lasted until the war. Between the war and the 1950s, fibre intake amongst the Japanese increased as it became common to supplement rice with other cereals. A second phase of fibre decline due to a reduction in cereal consumption was apparent from the 1950s and this coincided with the period of economic growth.
The large increase in the rates of diverticular disease in the US between the 1930s and 1950s is similar to that seen in the data from the Japanese populations in the two phases of reduced fibre intake. However, the largest increase in the rates of diverticular disease are not seen amongst Japanese population until the 1970s, suggesting that as fibre content declines, a threshold is reached, beyond which gut disease becomes apparent. The exact amount of fibre required to prevent diverticular disease is difficult to quality, however, similar patterns have been reported in other Western countries such as Great Britain. In addition it is interesting that differences exist in the location of diverticular disease amongst US and Japanese populations. In the US, diverticular disease is more common on the descending or left side of the colon, while in Japanese populations the diverticular disease is more common on the ascending or right side of the colon. This may suggest that genetic factors also play a role in its development.
Dr Robert Barrington’s Nutritional Comment: Fibre is a large group of diverse non-digestible carbohydrate molecules. The role of dietary fibres in human health has been massively underestimated. Fibre should be considered a conditionally essential nutrient because it is required for correct glycaemic control during intakes of dietary starch. However, its role is not limited to that of a glycaemic modulator because it plays an equally important role in the maintenance of gut health. A high quality diet based on unrefined plant foods is the best way to ensure an adequate intake of fibre.
RdB
