The digestion of pectin in the human gut and its effect on calcium absorption and large bowel function

Abstract

I . The effect of dietary fibre digestion in the human gut on its ability to alter bowel habit and impair mineral absorption has been investigated using the technique of metabolic balance.2 . Five healthy male students were studied for 9 weeks under controlled dietary conditions and during the last 6 weeks they took 36g pectin/d. Bowel habit, transit through the gut, faecal fibre excretion, calcium balance and faecal composition were measured. 3.During the control period only 15 % of the dietary fibre ingested was excreted in the stools and when pectin was added to the diet there was no increase in fibre excretion. Stool frequency and mean transit time were unchanged by pectin but stool wet weight increased by 33 % and faecal excretion increased (%) for fatty acids 80, nitrogen 47, total dry matter 28 and bile acids 35. Ca balance remained unchanged.4. It may be concluded from these results that dietary fibre is largely metabolized in the human gut and dietary pectin completely so. This could explain its lack of effect on bowel habit and Ca balance. Other changes in the faeces may be related to an increase in bacterial mass.

Effect of psyllium on gastric emptying, hunger feeling and food intake in normal volunteers: a double blind study

“…(3) Another possibility is that psyllium retains alimentary fats into the gastric lumen by modifying motor activity of the gastric muscle (Jenkins et al, 1978). Fat content Inhibition of food intake by psyllium D Rigaud et al is able to modify the effect of dietary ®bre on hunger (Low et al, 1988;Cummings et al, 1979). Unfortunately, we did not study the gastric emptying time of fats, because of the inaccuracy of the methods using labeled fat in mixed meal.…”

“…It has been shown that the increased viscosity of the food obtained with soluble ®bres may further reduce the rate of small intestinal absorption. Indeed an increase in the viscosity of food may have several effects: (a) to slow down the small intestinal transit (Low, 1988;Cherbut et al, 1994); but Cummings et al (1979) did not ®nd any modi®cation of oro-cecal transit time with pectin; (b) to reduce the interaction between food nutrients and digestive enzymes (Flourie  et al, 1984;Cummings et al, 1979; to increase the time for nutrient diffusion, by increasing the thickness of the unstirred water layer (Flourie  et al, 1984;Rydning & Berstad, 1986). This is consistent with the studies which have demonstrated that soluble ®bres could decrease the area under the curve of serum glucose after a duodenal glucose load (Berggren et al, 1993).…”

Physiological aspects of energy metabolism and gastrointestinal effects of carbohydrates

“…For example, studies in rats suggest that guar gum and some pectin preparations induce substantial faecal fat loss, although quantitatively important interactions of a similar kind were not observed in humans (Rumpler et al, 1998). One study in healthy volunteers showed that an increase in dietary fibre intake from 15 to 46 g/day, through addition of pectin to the diet, increased fatty acid excretion from 1.5 to 2.7 g/day (Cummings et al, 1979). Another study reported a smaller increase in fatty acid excretion when dietary fibre intake was increased from 17 to 45 g/day through addition of wheat bran to the diet (Cummings et al, 1976).…”

The Microbial Contribution to Human Faecal Mass

“…It is commonly thought that a major component of human faeces is undigested plant material or fibre, and that when stool output increases on addition of fibre to the diet, the increase is due to water held in the colon by this material. On an average British diet however, only 3-5 g/day of dietary fibre remains in the stool (Cummings et al, 1979) and, on microscopic examination, what remains appears lignified and physically inert and is unlikely to account for the water content of normal faeces.…”