Nutritive sweeteners
Other alternative sweeteners are low-energy, bulk, sugar (sucrose) substitutes which are used not only for their sweet taste, but also to replace intrinsic functions of sugar in baked products, ice cream, frozen desserts, and other processed foods. These sugar substitutes are carbohydrates and are usually classified as nutritive sweeteners. They include glucose (dextrose), liquid glucose, high fructose syrups, liquid fructose, crystalline fructose, corn syrup, corn syrup solids, concentrated grape juice, invert sugar, invert syrups (174,175), and polyols, which are polyhydric alcohols produced by the hydrogenation of the corresponding reducing sugars.
The benefits of carbohydrate loading before prolonged submaximal exercise have been shown mainly during cycling. A link was demonstrated between endurance performance during cycle ergometry and pre-exercise muscle glycogen concentration (184). The importance of muscle glycogen during prolonged exercise was confirmed in subsequent studies which showed that fatigue occurs when muscle glycogen concentrations are reduced to low values (185-187). Therefore, it is not surprising that attempts were made to find methods of increasing muscle glycogen stores in preparation for prolonged exercise. One study (188) examined the influence of different nutritional states on the resynthesis of glycogen during recovery from prolonged exhaustive exercise. It found that a diet low in carbohydrate, and high in fat and protein for 2 to 3 days after prolonged submaximal exercise, produced a delayed muscle glycogen resynthesis, but when this was followed by a high carbohydrate diet for the same period of time, glycogen supercompensation occurred (see Figure 7). This dietary manipulation not only increased the pre-exercise muscle glycogen concentration but also resulted in a significant improvement in endurance capacity (see Figure 8). Although this original method of carbohydrate-loading was recommended as part of the preparation for endurance competitions, the low carbohydrate, high fat and protein phase of the diet is an unpleasant experience. Therefore, alternative ways were explored to increase the pre-exercise glycogen stores without including a period on a diet high in fat and protein (189). It was found that a carbohydrate-rich diet consumed for 3 days prior to competition, accompanied by a decrease in training intensity, resulted in increased muscle glycogen concentrations of the same magnitude as those achieved with the traditional carbohydrate loading procedure.