Leiper J B
University Medical School, Foresterhill, Aberdeen, United Kingdom.
Int J Sports Med. 1998 Jun;19 Suppl 2:S129-32. doi: 10.1055/s-2007-971977.
Absorption of ingested water and most solutes occurs in the proximal small intestine, therefore the rate at which beverages are emptied from the stomach is an important factor in determining the rate of water absorption. In the small intestine, water absorption is brought about by the creation of suitable osmotic gradients that promote net uptake of water from the intestinal lumen. The absorption of solute, especially that brought about by active carriers, are highly effective in creating the osmotic gradients that promote net water uptake. The activation of these transporters also increases the permeability of the mucosa which helps absorption. Moderate hypotonicity of the luminal contents potentiates solute-induced water absorption while hypertonicity slows fluid absorption. Dilute hypotonic glucose-sodium solutions are highly effective oral rehydration solutions, and the type of carbohydrate used does not appear to be important. The addition of other actively absorbed solutes gives little benefit in potentiating water uptake. The inclusion of sodium in rehydration solutions may not be required to stimulate water absorption but probably assists the overall rehydration process. The amount of glucose required to stimulate water absorption is relatively small and for rehydration purposes ingestion of an adequate amount of a dilute solution is more beneficial than drinking a smaller volume of a more concentrated beverage.
摄入的水分和大多数溶质在近端小肠被吸收，因此饮料从胃中排空的速度是决定水分吸收速度的一个重要因素。在小肠中，水分吸收是通过建立合适的渗透梯度来实现的，该梯度促进水分从肠腔的净摄取。溶质的吸收，尤其是由主动载体介导的吸收，在建立促进水分净摄取的渗透梯度方面非常有效。这些转运蛋白的激活还会增加黏膜的通透性，有助于吸收。肠腔内容物的适度低渗会增强溶质诱导的水分吸收，而高渗则会减缓液体吸收。稀释的低渗葡萄糖 - 钠溶液是高效的口服补液溶液，所用碳水化合物的类型似乎并不重要。添加其他主动吸收的溶质对增强水分摄取几乎没有益处。补液溶液中钠的存在可能不是刺激水分吸收所必需的，但可能有助于整体补液过程。刺激水分吸收所需的葡萄糖量相对较少，为了补液目的，摄入适量的稀释溶液比饮用少量更浓缩的饮料更有益。
