Lactose is a sugar found in dairy products, like milk and cheese. To help digest it, our small intestine contains an enzyme called lactase. Lactase turns lactose into glucose, which our bodies use for energy. However, for children and adults with lactose intolerance, this digestive process doesn't occur properly, which can result in uncomfortable gastrointestinal (GI) symptoms.
"Lactose intolerance is when your intestine is lacking lactase," explains Charina Ramirez, M.D., a pediatric gastroenterologist at Children's Health℠ and Associate Professor at UT Southwestern. "If you don't have lactase, you can't break lactose down properly."
What are lactose intolerance symptoms in kids?
When a child cannot properly digest lactose, it can cause many symptoms. Signs your child may be lactose intolerant include:
- Stomach pain and cramping
Babies with lactose intolerance may be very fussy and may not gain weight or grow well. Lactose intolerance symptoms can range from mild to severe, depending on the amount of lactose a child consumes and how much lactase a child's body makes.
Is there a difference between lactose intolerance and milk allergy?
Lactose intolerance is not the same as a milk protein allergy, the most common food allergy in babies. Infants who have milk protein allergy are allergic to the protein in cow's milk. Children who are lactose intolerant cannot properly digest lactose, which is a sugar. While both groups of children may experience similar symptoms, the two conditions are very different. Learn more about symptoms of a food allergy in children.
What causes lactose intolerance in kids?
Lactose intolerance can occur in children for different reasons depending on their age. Reasons can include prematurity, congenital lactase deficiency, primary lactase deficiency and secondary lactase deficiency.
Prematurity and lactase deficiency
Though lactose intolerance is not common in babies, some babies who are born before 34 weeks don't have a fully functional gastrointestinal tract. They may lack lactase and other enzymes they need to digest food, though these can develop later as the child grows. Interestingly, these premature infants may still tolerate intact milk protein based formulas.
Congenital lactase deficiency
In rare cases, babies are born with lactose intolerance, which is known as congenital lactase deficiency.
"Infants with congenital lactase deficiency are born without any lactase enzyme," explains Dr. Ramirez. "These babies are diagnosed early in life because they have severe diarrhea and do not gain weight. You'll know right away if your child has it."
Primary lactase deficiency
The most common cause of lactose intolerance in kids is primary lactase deficiency. These children don't have enough lactase enzyme, and the amount of lactase they have may decline as they get older. While it may seem like lactose intolerance starts suddenly, it gradually worsens over time and the symptoms become more obvious.
About 65-70% of the world's population is affected by primary lactase deficiency, which is a genetic condition. It is extremely common among people of Asian and African descent, as well as Native Americans. While primary lactase deficiency can start as early as age 2, symptoms may not be noticeable until the adolescent and young adult years.
Secondary lactase deficiency
Other children may develop secondary lactase deficiency, which can occur suddenly after an illness.
"Any illness that injures the small intestine, such as gastroenteritis, can result in temporary or long-term lactase deficiency," says Dr. Ramirez. "Infants younger than 3 months are more at risk of being adversely affected by this. They may experience severe diarrhea and poor growth."
How is lactose intolerance diagnosed in children?
One simple way to determine if your child is lactose intolerant is to stop giving them dairy products (such as milk, cheese, ice cream, pizza) and see if their symptoms go away. To ensure your child still eats a well-rounded diet, you can offer your child dairy replacements such as vitamin D and calcium supplements. Your child's pediatrician can also offer additional recommendations and provide a referral to a specialist for further help.
A pediatric gastroenterologist can diagnose lactose intolerance in children by performing a hydrogen breath test. "We can perform a hydrogen breath test in the GI lab," says Dr. Ramirez. "Increased amounts of hydrogen on the test after drinking a lactose-containing product indicates lactose intolerance."
Your child may also be diagnosed after an endoscopy, a minimally invasive procedure to take samples of the tissues in the esophagus, stomach and small intestine. The tissue sample from the small intestine can be tested for lactase and other sugar enzymes.
What to do if your child is lactose intolerant
If your child is lactose intolerant, there are many solutions that allow your child to have a healthy, well-rounded diet. With the right foods and treatments, you can help stop your child's symptoms.
For true lactose intolerant babies, it is recommended that parents seek the help of a pediatric gastroenterologist to manage this condition. Because these infants are often "failure to thrive" and have diarrhea, they may need a special formula and should be closely monitored for adequate weight gain.
Older children have multiple options, such as choosing dairy-free milk and dairy-free cheese products or using Lactaid tablets, which contain lactase enzymes. Lactaid tablets come in a chewable form for children ages 4 years and up.
"You can take Lactaid tablets with the first sip or bite of dairy," says Dr. Ramirez. "It gives you the enzyme needed to break down the lactose for 45 minutes of eating or drinking. Taking a Lactaid tablet should help prevent symptoms such as bloating, stomach pain and diarrhea."
If children have temporary secondary lactase deficiency, you can help them avoid dairy for about two weeks, then reintroduce dairy products. Transient lactose intolerance can sometimes occur after a viral or bacterial gastroenteritis.
If your child has unexplained gastrointestinal symptoms like diarrhea, a Children's Health pediatric gastroenterologist can help you find answers. Learn more about our pediatric gastroenterology program and services.
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