EFFECTS OF DIETARY FIBRE ON THE APPARENT DIGESTIBILITY OF MAJOR FOOD COMPONENTS AND ON BLOOD LIPIDS IN MEN

Abstract

Summary Measurements were made on 14 mule subjects to determine effects of dietary fibre on the apparent digestibility of dietary components and on blood lipids. For 23 days all subjects were on a low fibre regimen, followed by 24 days when 12 subjects were on a high fibre regimen. Additional fibre was largely in the form of wheat bran (12 g/day). Faecal dry matter determined over 4 days increased from 116 g to 200 g when subjects were on the high fibre diet. There was a significant decrease in apparent digestibility of dry matter, energy, protein and minerals, but not of fat. when subjects changed to the high fibre regimen. Plasma cholesterol had increased significantly by the end of the low fibre regimen but had declined significantly by the end of the high fibre regimen. There was a significant fall in plasma triglycerides at the end of the low fibre regimen, and this level was maintained until the end of the experiment. During the course of digestion 80% and 55% of the neutral detergent fibre in the diet disappeared from the low and high fibre diet, respectively. Hemicellulose was completely digested on the low fibre regimen; this was attributed largely to increased transit time of digesta. Calcium and iron digestibilities were not significantly different on either regimen, although there was much variation among individuals, particularly in iron digestibility. The two control subjects that remained on the low fibre regimen throughout showed no change in digestibility of the majority of dietary components, but variation in blood lipid and faecal iron concentrations were such that no conclusion could be drawn from these data.