Faecal weight

A detailed review of the many possible effects of fibre is inappropriate here. Several comprehensive reviews and series of papers covering most of these topics have appeared in the last few years and should be consulted for more information It is worthwhile, however, to take a detailed look at one aspect of dietary fibre, namely its effect on faecal weight, as this illustrates several important general principles relating to its metabolism as a whole. 

Were it not for the fact that fibre in the diet increases faecal weight, people s attention might never have been drawn to this relatively minor component of the diet. It has been known since ancient times that when wholewheat products were consumed, then a predictable increase in stool output occurred. Many investigators have now shown that fibre, especially wheat fibre, will increase faecal weight. In fact the majority of studies have concentrated on the effect of bran or other forms of wheat fibre, probably because it is a readily available concentrated form of fibre, to the exclusion of other types. Figure 2 shows a typical example of such a study Seven healthy male student... 

Fig. 2. Mean daily faecal weight of seven healthy young adults during three-week periods on low fibre (17g/day) controlled metabolic diet and then with an addition of 28 g dietary fibre from wheat. From Cummings, J. H. Dietary fibre and large bowel cancer. In Proceedings of a Symposium on Dietary Fibre, Leeds, 1976. Reckitt Colman Ltd, 1978 (with permission).

Several observations about the effect of dietary fibre on faecal weight can be made from this figure. First, all the subjects except one showed an increase in faecal weight. Secondly the nett effect of each... 

Fig. 3. Mean daily faecal weight during third week of controlled dietary studies in healthy young men eating a standard diet (22 g dietary fibre/day with the addition of 20 g dietary fibre from various fruit and vegetable sources). Mean values for groups are given below each figure. Open circles = control diet. Closed circles = added fibre. From Cummings et al. 1979. Lancet i, 5-8 . (With permission).

Two main hypotheses have been advanced to explain the faecal bulking properties of fibre. The water-holding idea, mentioned above, is probably the most widely held view. In addition, it was suggested by Williams and Olmsted in 1936 that the way in which fibre increased faecal weight was through an effect of its metabolites, the short-chain fatty acids (acetic, propionic and butyric). They noted that dietary fibre was broken down in the gut and that the increased faecal weight was associated with an increased faecal excretion of short-chain fatty acids. 

Antigen Molecular weight (kDa) Identity Sheep breed Faecal egg output Worms References... 

The first observation in this field was made by Heaton et al In normal-weight women with gallstones but no other obvious risk factors, the Bristol investigators found that, compared with age- and sex-matched controls, the gallstone carriers had almost a 20-h longer whole gut transit time. Despite this, their mean faecal wet weight was only half that of the controls. Put another way, the women with gallstones had slow transit constipation. 

As would be expected, the smaller the feed particle size, the greater the surface area per given weight is available for bonding to the ytterbium ions, hence the greater the concentration of marker. The greatest concentration of ytterbium in faecal DM occurred after approximately 24 h, with the concentration approximately zero after 75 h the mean retention time was 26.07 h. The maximum ranges for the concentration of ytterbium in the faecal DM after approximately 24 h was approximately as follows ... 

Table 5.4.2 Comparison of BA contents (dry weight, mg/g) in faecal matter of healthy subjects (reprinted from [16])...

Ito M, Deguchi Y, Miyamori A, et al. Effects of administration of galactooligosaccharides on the human faecal microflora, stool weight and abdominal sensation. Microb Ecol Health Dis. 1990 3 285-292. 

Faecal tagging is performed with a 40% weight/ volume barium suspension (Tagitol V , E-Z-EM). The patients only have to drink a total of 60 ml 20 ml at breakfast, lunch and dinner respectively. The patients are instructed to drink the barium at once after the meal. 

Chitosan also has hypocholesterolemic effects and acts as an adjuvant to weight loss in rat studies [31,32]. Studies have reported that chitosan reduced the concentration of plasma cholesterol in animals [33,34] and type If diabetes patients in combination with hypercholesterolemia [33]. This property is being attributed to the positive charge of the molecule that binds to fatty acids (released from consumed fat) and bile salt components, which results in disrupted lipid absorption in the gut [5]. Also, chitosan is dissolved in the stomach, emulsifying the fat and forming a gel in the intestine which entraps fat and prevents intestinal absorption [35,36]. Chitosan forms a floccule in the duodenum which entraps dietary oil [37]. However, these effects are still controversial [31,38,39]. Actually, van Bennekum et al. [32] suggested that the incorporation of chitosan in the diet of rats reduces cholesterol (food) intake, but did not affect either intestinal cholesterol absorption or faecal sterol output. 

Pluronic L-101 is a potent inhibitor in vitro of human pancreatic lipase. Fed as 1 to 3 % of diet to rats, a dose-dependent decrease in body weight has been observed [162] without a change in food consumption. Excretion of dietary fat was increased in a dose-dependent manner suggesting some antiobesity function for this poloxamer. A related compound Pluronic F-68 - more hydrophobic than L-101 -a poor inhibitor of lipase, did not produce either decrease in body weight or increase in faecal fat excretion. 

Qiao and Classen (2003) also reported minor effects cansed by dietary treatment of sinapine on tissue measurements. The authors proposed that the hind gut might be an important metabolic site for sinapine because aU the diets containing sinapine reduced the empty weight of caeca. The ileal digestibility of SNP was 35-42%, 27-38% and 30-46% for sinapine bisulphate, sinapine ethanol extract and rapeseed meal sinapine, respectively, while faecal digestibility values were 68-72%, 65-75% and 54-63% for the same treatment groups. A major metabolic pathway of sinapine via hydrolysis into sinapic acid and choline in the digestive tract was identified. 

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