Author: Wang Yanping Ding Hong
Unit: Department of Clinical Laboratory, Baodi District People's Hospital, Tianjin
In infants and young children with indigestion, doctors often ask for a urine galactose test to help diagnose whether the child is "lactose intolerant." So what exactly is lactose intolerance? Here are some related issues.
1. What is lactose?
Lactose is a disaccharide with the molecular formula C12H22O11. It is mainly found in the milk of mammals.
Lactose is the best sugar to eat in children, mainly to provide energy to the human body, promote the development of the nervous system, calcium absorption and the growth of lactic acid bacteria in the intestine.
In terms of lactose content, human milk > cow's milk > goat's milk.
2. How is lactose digested and absorbed?
The body cannot directly absorb disaccharides, which are first hydrolyzed to monosaccharides.
The lactose in milk is catalyzed by lactase in the small intestine and hydrolyzed into two monosaccharides: one molecule of glucose and one molecule of galactose. Galactose is a differential isomer of glucose, the same molecular formula as glucose, but in a different direction to the hydroxyl group on the fourth carbon.
3. Where does the lactose hydrolysis product go?
Both glucose and galactose, which are hydrolyzed by lactose, enter the bloodstream. Glucose is absorbed and utilized by the body to provide energy; while galactose is mostly converted into glucose in the liver, and what is not converted is excreted by the urinary tract.
4. What is "lactose intolerance"?
Lactose intolerance refers to a series of digestive symptoms caused by the inability of some people to absorb lactose after eating breast milk or milk, which generally occurs within half an hour to 2 hours after consumption.
Lactose intolerance occurs in infants and young children and is one of the leading causes of non-infectious diarrhea in infants and young children.
The main part of the body's lactase secretion is the small intestine, when lactase is deficient, a large amount of lactose can not be decomposed and remains in the small intestine, resulting in increased osmolality. According to the principle of osmotic equilibrium, the water and small molecules in the intestinal cells are inhaled into the intestinal lumen, which greatly increases the fluid in the intestinal lumen and causes diarrhea. After the undigested lactose enters the colon, it is decomposed by the intestinal flora, producing lactic acid, acetic acid and hydrogen, resulting in the child's stool being thin and foamy, accompanied by bloating, bowel sounds and other symptoms. Lactose intolerance is primary or secondary to rotavirus infection.
5. How to check lactose intolerance?
There are many test methods, among which the urine galactose experiment is non-invasive and is more suitable for infants and young children.
From the above, it can be seen that if the concentration of galactose in the urine is low, it means that the galactose content in the blood is low, and it can be inferred that lactase deficiency leads to lactose not being able to hydrolyze smoothly.
6. Is there any way to treat it?
Infants and young children are fed lactose-free milk powder or lactase to relieve symptoms, and adults may consume dairy products in small amounts and multiple times. As the child grows and develops, it may also gradually become normal.
7. Are there other diseases with similar symptoms?
Yes, such as cow's milk protein allergy and galactosemia.
People with milk protein allergy will have rashes, diarrhea, blood in the stool, etc. after drinking milk, but diarrhea stops after stopping milk and switching to breast milk; galactosemia is an autosomal recessive genetic disease, the cause is in the second step of lactose metabolism - galactose can not be smoothly converted into glucose, the main symptoms are vomiting, diarrhea, hypoglycemia (clinical blood glucose refers to glucose), cataracts and cirrhosis. Diagnosing lactose intolerance requires differentiation from other related disorders.
Edited by: Yeah Reviewer: Xiao Ran