Survey of pulmonary tuberculosis in south and west Wales.

Fluid intake can increase or decrease the effect of dietary fibre on gastrointestinal function depending on the type (water, tea, coffee, etc,) and quantity of fluid consumed.Chocolate, coffee, tea, cocoa, and some carbonated beverages (usually colas) contain methylxanthines, caffeine, theophylline, and theobromine.1The methylxanthines cause stimulation of the central nervous system, diuresis, and relaxation of smooth muscle.The various methylxanthines differ greatly in the intensity of their actions on various structures.'Consumption of tea in large quantity causes a fall in faecal bile acid output and an increase in intestinal transit time, while water in the same quantity produces opposite effects.Theo- phylline present in the tea by inducing diuresis causes extracellular dehydration and an increase in intestinal absorption of water leading to constipation.2Coffee does not cause gall-bladder emptying.3The methylxanthines present in the coffee inhibit gall-bladder emptying.Ingestion of water causes gall-bladder emptying4 and a rise in total serum bile acids5 similar to a meal.Rise in total serum bile acids -is seen in a cholecystectomised patient also after ingestion of water (personal observation).The probable existence of a "gastrobiliary" reflex has been postulated,6 and ingestion of water may stimulate this reflex.Entry of food into the proximal part of small intestine initiates a "gastroileal" reflex,7 and water may initiate this reflex also.Dihydroxy bile acids inhibit colonic absorption of water.8Waterholding and bile salt binding are physical properties of dietary fibre.9Increase in water intake will allow increase in the amount of water presented to the large bowel, leading to an increase in the water content of faeces, which may help in more complete evacuation of faeces.Hence in dietary fibre therapy water intake at regular intervals in sufficient quantity should be advised.