Metabolic defect. Galactosemia is also a genetic disease caused by a missing enzyme, which controls a step in the conversion of galactose to glucose. Milk, the infant’s first food, contains a large amount of the disaccharide lactose (milk sugar), which is acted on by the intestinal digestive enzyme lactase to produce the monosaccharide’s glucose and galactose. When the subsequent conversion of galactose to glucose cannot be made because of the absence of the specific cell enzyme necessary for this conversion, galactose rapidly accumulates in the blood and in various body tissues.
Clinical symptoms. The rapid accumulation of galactose in tissues causes damage to the untreated infant. The child fails to thrive, and clinical evidences are apparent soon after birth. Liver damage brings jaundice, cirrhosis, enlargement of the spleen, and ascites – accumulation of fluid in the abdominal cavity. Death usually results from liver failure. If the infant survives, the continuing tissue damage in the optic lens and the brain cause cataracts and mental retardation.
Dietary management. The main indirect source of dietary galactose is milk. Therefore all forms of milk and lactose must be removed from the diet. A galactose-free diet is used, such as that given on p.233. The milk substitute usually used for infant feeding is Nutramigen, a complete protein compound that is free of galactose. Careful attention must be given to avoid lactose from other food sources as solid foods are added to the infant’s diet. Parents must be carefully instructed to check labels on all commercial products. Gives products that normally contain lactose. Even drugs contain lactose occasionally as an ingredient.
A deficiency of any of the enzymes that act on the disaccharides in the intestine-lactase, sucrose, maltase, or isomaltase-may produce a wide range of gastrointestinal problems and abdominal pain. The missing enzyme results in the inability to digest the specific sugar involved. Of these clinical problems, lactose intolerance is perhaps the most common. It is often seen in adults of certain racial backgrounds and may also occur in childhood. A diet similar to that used for galactosemia is required. Milk and all products containing lactose are carefully avoided. For children a milk substitute is used – Nutramigen, soy milk, or a meat-based formula.
The characteristic symptoms of lactose intolerance include a severe watery diarrhea after drinking milk, which results in an excessive loss of fluid from the intestine. If not treated, dehydration and serious illness may result.
In the United States population roughly 100% of Orientals past the teens, 60% to 80% of American blacks, about 100% of American Indians have lactose intolerance. Northern European Caucasians and their descendents, who comprise a large majority of the American population, maintain lactase enzyme activity until late in life. Many persons with lactose intolerance can still drink some milk. They may get intestinal gas and softening of the stools with a large intake but can usually handle from ½ to 1 cup of milk at a time, or they can tolerate cooked products containing milk.
The second most common disaccharide intolerance is that of sucrose. This condition should show up the first time that a young child is given any fruit containing sucrose – canned fruits and puddings, for example. Most mothers do not sweeten cereals. However, if sugar is used, such as in an evaporated milk formula, it is likely to show up at the time that the formula is first used. This is not too common a disorder. A good history could pinpoint exactly what food causes the symptoms, and then it can be verified with dietary measures. Most persons can tolerate a small amount of the sugars to which they are intolerant – about 5 or 6 gm. Of the sugar at a time. These small amounts will not precipitate an acute case of diarrhea. There may be minor softening of stools or a slightly bulkier stool, but the gastrointestinal result will not be sufficient to eliminate a great number of nutrients with the stools.