vidence suggests that high intakes of dietary fibre improves health. The exact reason for this is unclear, but researchers have reported that fibre has a number of physiological effects beyond its classic role of providing bulk to chyme passing through the gut. For example, fibre can undergo microbial fermentation in the colon to form short-chain fatty acids, and these are subsequently absorbed and may inhibit the synthesis of cholesterol. Fibre has also been shown to inhibit a number of dietary components including protein, fat and some minerals. Studies have shown that the composition of the diet is able to alter the enzyme secretions of the gut, with high protein and high carbohydrate diets increasing the secretion of trypsin and amylase from the pancreas, respectively. Fibre too may alter the exocrine function of the pancreas, and this may explain some of the physiological effects seen with high fibre diets.
For example, researchers1 have investigated the effects of an increased fibre intake on exocrine secretions from the pancreas in healthy male subjects. The subjects consumed 20 grams of fibre per day for 4 weeks, and of this 97 % was insoluble fibre and 3 % was soluble fibre. The insoluble fibre was composed mainly of corn flour (25 %) and wheat bran (5 %) and the soluble fibre was mainly pectin. Duodenal perfusion was used to assess the content of the pancreatic juice secreted in response to ingested fibre containing food. The fibre supplementation resulted in an increase in the concentration and flow rate of pancreatic lipase in both the resting and postprandial states, with the increase being statistically significant at 120 min postprandially. However, there were no changes to the pH or increases in the secretion of other enzymes as a result of dietary fibre supplementation.
These results suggest that dietary fat digestion might be altered by increasing intakes of dietary fibre. Rat studies have also shown that dietary fibre can increase pancreatic lipase secretion. The reason for this and the consequences of it are not well understood. However, dietary fibre may stimulate and modify the release of gastrointestinal hormones, which then subsequently affect the release of enzymes. This may occur through short-term fibre induced inhibition of the absorption of fat. The increased fatty acids remaining in the lumen of the gut may then lead to upregulation of dietary lipase secretion from the pancreas. The increased pancreatic lipase secretion may therefore be a compensatory mechanisms and this may normalise fat absorption following an initial decline. However, lipase is usually secreted in far greater amounts than is required for fat digestion and so the implications of these data are not clear.
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