Title: Alternative Sweeteners

Xylitol 351
IX. USE OF XYLITOL IN PARENTERAL NUTRITION
The aim of parenteral nutrition is to optimize fluid, energy, nitrogen, and electrolyte
balance by the infusion of adequate solutions providing energy (e.g., glucose
or lipids), amino acids, and mineral salts (186,187). However, a stable metabolic
condition is often difficult to reestablish in severely injured patients because the
posttrauma metabolism may be seriously disturbed in various respects. In particular,
the use of glucose, which is the body’s normal energy source, is often impaired,
especially in patients with shock, severe trauma, burns, sepsis, and diabetes.
Under the conditions of such a general disturbance of metabolism and of
the hormone-regulated control mechanisms, insulin must be administered concomitantly
with the glucose to ensure sufficient use of this energy source. However,
this procedure requires careful regular monitoring of the blood glucose levels
to avoid severe complications. In addition, the infusion of glucose in excess
of 0.12–0.24 g/kg/hr may be generally questioned because higher infusion rates
lead neither to a further suppression of the endogenous gluconeogenesis at the
expense of physiologically important proteins nor to an increase of the peripheral
glucose use (188). Because with this recommended maximum rate of glucose
infusion, the energy requirement of the injured or stressed organism is not completely
covered, the infusion of fructose and xylitol in addition to glucose has
been advocated (12,13,189,190). In several studies, the positive influence of such
infusion regimens on nitrogen balance and visceral protein synthesis has been
demonstrated in stressed or post-trauma patients (13,189), as well as in an animal
model (190). However, these effects were not always reproducible (191,192).
More recently, it has been proposed to supplement lipid emulsions with
xylitol. In this combination, xylitol is preferred over glucose because it only marginally
stimulates insulin secretion and therefore does not suppress lipolysis, as
demonstrated by a positive adenosine triphosphate (ATP) balance. In this way,
xylitol could improve the metabolic situation (193,194).
At present, xylitol is used mainly as a glucose substitute in parenteral amino
acid solutions, as well as in combination with fructose and glucose in so-called
trisugar solutions. These products are frequently applied, particularly in Germany.
Solutions of xylitol alone are nowadays rarely used, except in Japan.
Most clinical investigations on the use of xylitol in parenteral solutions
have concentrated on the general energetic and amino acid–sparing effects. Other
potentially beneficial, metabolic effects have not yet been explored in detail. Because
xylitol is metabolized by way of the pentose phosphate pathway, it is conceivable
that the levels of phosphorylated nucleotides (ATP) might be enhanced.
This could be relevant in reperfused myocardial tissue, as has been suggested by
studies with ribose, which is subject to the same catabolic pathway (195–197).
Other potential advantageous effects include an increase of the 2,3-diphosphog-