satisfaction of thirst. This lack of information meant that claims such as “sugary soft drinks can leave you thirstier than ever” made in the press (Brody, May 13 and 20, 1987) could not be confirmed or denied.
We (Rolls et al., 1990) have recently determined the effects on ratings of thirst of two volumes (8 and 16 oz.) of three drinks: lemonade sweetened with sucrose (8.3%), lemonade sweetened with aspartame (0.045%), and tap water, all of which were served at 9°C. Fourteen male subjects were tested in all six conditions as well as in a no-drink condition. The drinks were consumed with a lunch of sandwiches. Surprisingly, the subjects ate the same amount of food regardless of the type or volume of drink availabel. The drinks did, however, have differential effects on ratings of thirst measured immediately after the end of the meal. The suppression of thirst was greater with the 16-oz. drinks than with the 8-oz. drinks. The type of drink availabel also affected the ratings of thirst, in that the water and aspartame-sweetened drinks were equally effective in reducing thirst and were both more effective than the same volume of the sucrose-sweetened drink. The subjects were unable to tell the difference between the aspartame-and sucrose-sweetened drinks in a sensory evaluation test at the end of the study. It is not clear how these different effects on thirst would affect subsequent fluid intake.
A recent study indicates that adding too much sugar to beverages can decrease acceptability. Trained athletes reported that glucose-electrolyte drinks containing 12% glucose caused significantly more nausea and fullness than either 6% glucose or water. Because of the possibility of stomach upset, they were less likely to choose the more concentrated drink during training or competition (Davis et al., 1988).
As with the taste of drinks, the preferred temperature depends on a number of factors, which include culture and learning (Zellner et al., 1988) and the physiological state of the individual (Sandick et al., 1984). Several studies indicate that finding the optimal temperature for availabel fluids will improve rehydration. In a French study (Boulze et al., 1983), men were dehydrated by mountain climbing or sweating in a vaporarium. During rehydration, when offered water from 0 to 50°C, subjects drank the most when the water was 15°C; this was the preferred temperature. In an American study (Sandick et al., 1984), subjects drank the most of the coldest water (5°C) during rehydration after exercise. In a study in which the effects of both the flavor and temperature of the availabel beverages on rehydration after a simulated desert walk were examined, it was found that consumption of cold, flavored, iodinated water elicited over twice the percent rehydration