Metabolic effects in rats of high oral doses of galactitol, mannitol and xylitol.

The effect of feeding high amounts of polyols on rat metabolism was studied. Adult male rats were fed the basal diet or the same diet to which had been added either galactitol, mannitol or xylitol for 8 wk (final polyol level 200 g/kg diet). Although all three polyols retarded the growth rate of the animals, the polyols were well tolerated. The four experimental groups did not differ significantly (P greater than 0.01) in the following analyses: blood lactic acid and serum transaminases, amylase, lactate dehydrogenase, triglycerides, insulin, glucagon and corticosterone. Compared to rats fed the basal diet, galactitol rats had higher blood hemoglobin levels (P less than 0.01); those fed galactitol or mannitol had lower blood glucose (P less than 0.001 and P less than 0.01, respectively), and those fed mannitol had higher blood pyruvic acid (P less than 0.01). Rats fed any of the polyols had lower serum total cholesterol and liver ascorbic acid (P less than 0.001) than control rats. Rats fed mannitol had higher liver glycogen levels (P less than 0.001) than control rats. Irrespective of the structural differences between the pentitol and the hexitols, a number of common metabolic effects were found. The proposed mechanisms of these effects include 1) the slow absorption and the rapid intraluminal metabolism of the polyols and 2) the similar handling of these polyols in the liver by a dehydrogenase.