Explain the Stool weight and laxation?

The amount of stool excreted varies markedly from individual to individual and in an individual over a period of time. Faeces are complex and consist of water, unfermented fibre, excreted compounds and bacterial mass. Of the dietary constituents, dietary fibre has been shown to influence the stool weight to a great extent, The ability of different types of fibres to increase faecal bulk depends on a complex relationship between the chemical and physical properties of the fibre and the bacterial population in the colon. In general, faecal bulk increases as fibre fermentability decreases.

The mechanism by which a fibre increases stool weight is through the water- holding capacity of unfermented fibre. Animal and human studies have indicated that cereal fibres have the greatest faecal bulking power. Wheat bran added to the diet increases stool weight in a predictable linear manner and decreases intestinal transit time. Besides quantity, the particle size is also important. Coarsely ground wheat bran has little or no effect and may even be constipating. Fibre may influence faecal output by another mechanism. Colonic microbial growth may be stimulated by ingestion of fermentable fibre sources. Bacteria are an important component of faecal mass. However, increase in weight does not always occur from eating these fibres. Some laxative effects may be due to volatile SCFAs produced during fermentation. Osmotic effects of these fermentation products may also be important but this mechanism is not yet well defined.