Some factors influencing absorption rates of the digestion products of protein and carbohydrate from the proximal jejunum of man and their possible nutritional implications.

Some factors influencing absorption rates of the digestion products of protein and carbohydrate from the proximal jejunum of man and their possible nutritional implications Ideal requirements of dietary energy (calories) and protein and its amino-acid ratio are difficult to determine'. At least one essential ingredient is frequently present in an inadequate concentration in the diet of a vast proportion of the world's human population. Ever since the demonstration in the early 1930s by Dr Cecily Williams that kwashiorkor is associated with a low protein intake and a low serum protein concentration, malnutrition in tropical countries has been considered to be entirely dietary in origin. Clearly that is an exaggerated view which has dominated the scene, and other factors, especially malabsorption of dietary constituents, are also important in the pathogenesis of malnutrition. In developing countries energy and protein are often present in low amounts in the average diet. For example, the majority of Zambian Africans live on a carbohydrate diet which contains a marginally adequate amount of protein. The staple diet in most areas is nshima, a porridge which is prepared from ground maize or millet2. Although childhood malnutrition there is very common, adults are usually moderately well nourished compared with those in many other tropical countries. Throughout this report, which deals with intestinal absorption of carbohydrates , amino acids and dipeptides, the technique used for measuring the proximal jejunal absorption rate in a 30-cm segment involves a double-lumen tube perfusion system, without proximal occlusion. The infused fluid was introduced into the jejunum at 12.0 ml min-l. Below that rate siphonage is difficult, and higher rates are undoubtedly unphysiological. Polyethylene glycol 4000 was used as a non-absorbable marker. Although the repro-ducibility of the method for solutes is good3 4'5 results for net water transfer are generally less exact. In most of the studies cited, the concentrations of mono-and disaccharides, amino acids and dipeptides in the perfusing fluid were probably greater than are likely to be present at the luminal surface of the enterocyte in the proximal jejunum of man, although there are very few data on that in vivo6. Whether or not absorption rates in the proximal jejunum bear a significant relationship to total absorption of dietary protein and carbohydrate is not entirely clear. A significant correlation has been demonstrated between the absorption rate of glucose from the proximal jejunum, and the weight of D-xylose excreted after a 25 g oral …