Lactase deficiency (See: Lactose intolerance)

Lactose intolerance, also called Lactase deficiency, means you aren't able to fully digest the milk sugar (lactose) in dairy products. It's usually not dangerous, but symptoms of lactose intolerance can be uncomfortable.

A deficiency of lactase — an enzyme produced by the lining of your small intestine — is usually responsible for lactose intolerance. Many people have low levels of lactase, but only those who also have associated signs and symptoms have, by definition, lactose intolerance.

You can control symptoms of lactose intolerance by carefully choosing a diet that limits dairy products.

SYMPTOMS
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:

Diarrhea Nausea, and sometimes, vomiting Abdominal cramps Bloating Gas

Symptoms are usually mild, but may sometimes be severe.

Make an appointment with your doctor if you or your child has any signs or symptoms that worry you.

CAUSES
Lactose intolerance is usually caused by low levels of the enzyme lactase in your small intestine that lead to signs and symptoms.

Normally, the cells that line your small intestine produce an enzyme called lactase. The lactase enzyme attaches to lactose molecules in the food you eat and breaks them into two simple sugars — glucose and galactose — which can be absorbed into your bloodstream.

Without enough of the lactase enzyme, most of the lactose in your food moves unprocessed into the colon, where the normal intestinal bacteria interact with it. This causes the hallmarks of lactose intolerance — gas, bloating and diarrhea.

There are three types of lactose intolerance.

Normal result of aging for some people (primary lactose intolerance)
Normally, your body produces large amounts of lactase at birth and during early childhood, when milk is the primary source of nutrition. Usually your lactase production decreases as your diet becomes more varied and less reliant on milk. This gradual decline may lead to symptoms of lactose intolerance.

Result of illness or injury (secondary lactose intolerance)
This form of lactose intolerance occurs when your small intestine decreases lactase production after an illness, surgery or injury to your small intestine. It can occur as a result of intestinal diseases, such as celiac disease, gastroenteritis and an inflammatory bowel disease like Crohn's disease. Treatment of the underlying disorder may restore lactase levels and improve signs and symptoms, though it can take time.

Condition you're born with (congenital 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. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected. Infants with congenital lactose intolerance are intolerant of the lactose in their mothers' breast milk and have diarrhea from birth. These babies require lactose-free infant formulas. Premature infants may also have lactose intolerance because of an insufficient lactase level. In babies who are otherwise healthy, this doesn't lead to malnutrition.

COMPLICATIONS
Lactose intolerance, also called lactase deficiency, means you aren't able to fully digest the milk sugar (lactose) in dairy products. It's usually not dangerous, but symptoms of lactose intolerance can be uncomfortable.

A deficiency of lactase — an enzyme produced by the lining of your small intestine — is usually responsible for lactose intolerance. Many people have low levels of lactase, but only those who also have associated signs and symptoms have, by definition, lactose intolerance.

You can control symptoms of lactose intolerance by carefully choosing a diet that limits dairy products.


DIAGNOSIS
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.

TREATMENT
No treatments can cure lactose intolerance. There's currently no way to boost your body's production of the lactase enzyme. People with lactose intolerance usually find relief by reducing the amount of dairy products they eat and using special products made for people with this condition.