[Comparison of metabolic effects of infusions of glucose and glucose substitutes]

The side effects of high dosed infusions of glucose and glucose substitutes (fructose, sorbitol, xylitol) in metabolically healthy volunteers have been studied. Infusions of glucose or fructose in high dose cause an increase in blood lactate levels. This effect, to a lesser degree, is observed with sorbitol. No effect, however, was seen with xylitol. Following the termination of the glucose infusions the lactate levels remain elevated, whereas after termination of the fructose infusions the lactate concentration is normalized within a short time. A decrease in the serum phosphate levels was observed for all the substances used. The most active were glucose and xylitol, followed by fructose and sorbitol, respectively. Similarly, all these substances cause an elevation of the serum bilirubin levels, though enzyme activities in serum remain unaffected. Xylitol had the greatest effect on bilirubin levels, however, glucose was also effective. The only side effect caused by the glucose substitutes was the stimulation of uric acid synthesis. In this respect xylitol was most effective. Some of metabolic effects of glucose and glucose substitutes are not yet clearly understood. However, even at very high doses these effects are not to be regarded as true "side-effects".