- By sahlhealth
- May 18, 2021
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People with lactose intolerance are unable to fully digest the sugar (lactose) in milk. As a result, they have diarrhea, gas and bloating after eating or drinking dairy products. The condition, which is also called lactose malabsorption, is usually harmless, but its symptoms can be uncomfortable
A deficiency of lactase â€” an enzyme produced in your small intestine â€” is usually responsible for lactose intolerance. Many people have low levels of lactase but are able to digest milk products without problems. If you’re actually lactose intolerant, though, your lactase deficiency leads to symptoms after you eat dairy foods.
Most people with lactose intolerance can manage the condition without having to give up all dairy foods
The signs and symptoms of lactose intolerance usually begin 30 minutes to two hours after eating or drinking foods that contain lactose. Common signs and symptoms include:
- Nausea, and sometimes, vomiting
- Abdominal cramps
When to see a doctor
Make an appointment with your doctor if you frequently have symptoms of lactose intolerance after eating dairy foods, particularly if you're worried about getting enough calcium.
Your doctor may suspect lactose intolerance based on your symptoms and your response to reducing the amount of dairy foods in your diet. Your doctor can confirm the diagnosis by conducting one or more of the following tests:
- Lactose tolerance test: The lactose tolerance test gauges your body's reaction to a liquid that contains high levels of lactose. Two hours after drinking the liquid, you'll undergo blood tests to measure the amount of glucose in your bloodstream. If your glucose level doesn't rise, it means your body isn't properly digesting and absorbing the lactose-filled drink.
- Hydrogen breath test: This test also requires you to drink a liquid that contains high levels of lactose. Then your doctor measures the amount of hydrogen in your breath at regular intervals. Normally, very little hydrogen is detectable. However, if your body doesn't digest the lactose, it will ferment in the colon, releasing hydrogen and other gases, which are absorbed by your intestines and eventually exhaled. Larger than normal amounts of exhaled hydrogen measured during a breath test indicate that you aren't fully digesting and absorbing lactose.
- Stool acidity test: For infants and children who can't undergo other tests, a stool acidity test may be used. The fermenting of undigested lactose creates lactic acid and other acids that can be detected in a stool sample.
There's currently no way to boost your body's production of lactase, but you can usually avoid the discomfort of lactose intolerance by:
- Avoiding large servings of milk and other dairy products
- Including small servings of dairy products in your regular meals
- Eating and drinking lactose-reduced ice cream and milk
- Drinking regular milk after you add a liquid or powder to it to break down the lactose
Lactose intolerance occurs when your small intestine doesn't produce enough of an enzyme (lactase) to digest milk sugar (lactose).
Normally, lactase turns milk sugar into two simple sugars â€” glucose and galactose â€” which are absorbed into the bloodstream through the intestinal lining.
If you're lactase deficient, lactose in your food moves into the colon instead of being processed and absorbed. In the colon, normal bacteria interact with undigested lactose, causing the signs and symptoms of lactose intolerance.
There are three types of lactose intolerance. Different factors cause the lactase deficiency underlying each type.
Primary lactose intolerance
This is the most common type of lactose intolerance. People who develop primary lactose intolerance start life producing plenty of lactase â€” a necessity for infants, who get all their nutrition from milk. As children replace milk with other foods, their lactase production normally decreases, but remains high enough to digest the amount of dairy in a typical adult diet.
In primary lactose intolerance, lactase production falls off sharply, making milk products difficult to digest by adulthood. Primary lactose intolerance is genetically determined, occurring in a large proportion of people with African, Asian or Hispanic ancestry. The condition is also common among those of Mediterranean or Southern European descent.
Secondary lactose intolerance
This form of lactose intolerance occurs when your small intestine decreases lactase production after an illness, injury or surgery involving your small intestine. Among the diseases associated with secondary lactose intolerance are celiac disease, bacterial overgrowth and Crohn's disease. Treatment of the underlying disorder may restore lactase levels and improve signs and symptoms, though it can take time.
Congenital or developmental lactose intolerance
It's possible, but rare, for babies to be born with lactose intolerance caused by a complete absence of lactase activity. This disorder is passed from generation to generation in a pattern of inheritance called autosomal recessive, meaning that both the mother and the father must pass on the same gene variant for a child to be affected. Premature infants may also have lactose intolerance because of an insufficient lactase level.
Factors that can make you or your child more prone to lactose intolerance include:
- Increasing age: Lactose intolerance usually appears in adulthood. The condition is uncommon in babies and young children.
- Ethnicity: Lactose intolerance is most common in people of African, Asian, Hispanic and American Indian descent.
- Premature birth: Infants born prematurely may have reduced levels of lactase because the small intestine doesn't develop lactase-producing cells until late in the third trimester.
- Diseases affecting the small intestine: Small intestine problems that can cause lactose intolerance include bacterial overgrowth, celiac disease and Crohn's disease.
- Certain cancer treatments: If you have received radiation therapy for cancer in your abdomen or have intestinal complications from chemotherapy, you have an increased risk of lactose intolerance.