Blood galactose in infants and children:

It is commonly assumed that when infants ingest milk, lactose is degraded completely to glucose and galactose in the gastrointestinal tract, and that the galactose that is absorbed is extracted in the first pass, by the liver, and converted to glucose. This is far from the truth—a fact that is better known to older, than to contemporary, physicians. In the days when urinary-reducing substances were determined in total, and separated by paper or thin layer chromatography, it was not uncommon to find both lactose and galactose in the urine of children, particularly those with diarrhea or gastrointestinal disturbances. The use of specific glucose measuring reagents has tended to obscure this fact for the modern physician. In this paper, Hartman and his colleagues use the relatively crude and laborious methods available to them at the time to demonstrate that in the infant who is taking formula every three to four hours, the galactose level in blood may be as high as that of glucose, and in fact, could in certain circumstances, mask hypoglycemia if a specific measurement of glucose is not made. In galactosemia, the ingestion of milk may lead to galactose levels as high as 110 mg/100 mL and actually depress glucose levels in blood. Because galactose is metabolized in the liver, galactose levels were one way of measuring the severity of liver dysfunction. Neither Hartmann et al nor I can speculate as to whether there are circumstances in which blood galactose accumulation may have an adverse effect, even in patients who do not have inherited forms of deficient galactose metabolism.