Dietary fibre comprises the cell walls and supporting structures of vegetables and fruits. Most of the fibre in our diet is in the form of nonstarch polysaccharides (NSP),1 which are not digestible by human enzymes. Fibre may be soluble (pectins, guar, ispaghula) or insoluble (cellulose, hemicelluloses, lignin). Insoluble fibre has less effect than soluble fibre on the viscosity of gut contents but is a stronger laxative because it resists digestion in the small bowel and so enters the colon intact. In addition it has a vast capacity for retaining water; thus one gram of carrot fibre can hold 23 grams of water.2 It has been proposed that as humans have refined the carbohydrates in their diet over the centuries, so they have deprived themselves of fibre, the ensuing under-filling of the colon being an important cause of constipation, haemorrhoids and diverticular disease. Stool bulking agents, which add fibre to the diet, are the treatment of choice for simple constipation. They act by increasing the volume and lowering the viscosity of intestinal contents to produce a soft bulky stool, which encourages normal reflex bowel activity. The mode of action of stool bulking agents is thus more physiological than other types of laxative. They
1 The term 'unavailable complex carbohydrate' (UCC) is also used and refers to NSP plus undigested ('resistant') starch.
2 McConnell A A et al 1974 J Sci Food Agric 25:1427.
should be taken with liberal quantities of fluid (at least 2 litres daily).
Bran is the residue left when flour is made from cereals; it contains between 25% and 50% of fibre. The fibre content of a normal diet can be increased by eating wholemeal bread and bran cereals but over-zealous supplementation may cause troublesome wind (from bacterial fermentation in the colon).
Viscous (soluble) fibres, e.g. ispaghula, are effective and more palatable than bran. Ispaghula husk contains mucilage and hemicelluloses which swell rapidly in water. Methylcellulose takes up water to swell to a colloid about 25 times its original volume and sterculia,3 similarly, swells when mixed with water.
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Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.