Priya Bansal MD

Asthma and Allergy Wellness Center


2435 Dean Street, Unit C
 St. Charles, IL 60175-4827

Lactose Intolerance

Lactose intolerance, also known as lactase deficiency, is the inability to fully digest lactose, a milk sugar found in dairy products. While lactose intolerance is not usually a serious condition, it can produce uncomfortable symptoms. In order to manage or eliminate such symptoms, certain dietary changes are necessary. Patients with lactose intolerance, depending on the severity of the condition, have to limit or eliminate their intake of dairy products, take supplements of the enzyme their bodies fail to produce, or consume lactose-free dairy products. Lactose intolerance is a common condition, affecting more than half of adults as they age.

Causes of Lactose Intolerance

Lactose intolerance is caused by a shortage of lactase, a digestive enzyme normally found in the lining of the small intestine. Lactase helps to break down milk sugar into glucose and galactose, both of which can be easily absorbed into the bloodstream. There are three types of lactose intolerance.

Primary Lactose Intolerance

The body normally produces a great deal of lactase in newborns, infants, and young children, during the period they depend on milk for sustenance. As children grow older and their diet becomes more varied, their bodies produce less lactase. During aging, therefore, some individuals become increasingly lactose intolerant.

Secondary Lactose Intolerance

Secondary lactose intolerance results from an external factor that causes the small intestine to reduce lactase production. Abdominal surgery or injury to the region may be to blame. The problem can also stem from gastrointestinal disorders such as celiac disease, gastroenteritis, or inflammatory bowel diseases, such as Crohn's disease or ulcerative colitis.

Congenital Lactose Intolerance

While it occurs rarely, infants can be born with lactose intolerance. The disorder in this case is hereditary and the newborn must inherit a recessive gene from each parent. Premature infants may also be lactose intolerant because they have not yet developed a sufficient lactase level. In either case, the babies are intolerant to their mothers' breast milk as well as to cow's milk. These infants experience diarrhea from birth and must be switched to formulas that are lactose-free.

People who received prior radiation therapy in the abdomen or have intestinal complications from chemotherapy, may have an increased risk of lactose intolerance.

Symptoms of Lactose Intolerance

Individuals with insufficient levels of lactase usually experience symptoms as the lactose that has been consumed moves into the digestive tract. The symptoms of lactose intolerance include:

  • Diarrhea
  • Nausea
  • Bloating
  • Abdominal pain
  • Flatulence (gas)

These symptoms usually occur about 30 minutes to 2 hours after the consumption of the offending products. The severity of the symptoms depends on the patient's age, intolerance level and rate of digestion.

Diagnosis of Lactose Intolerance

Lactose intolerance can be difficult to diagnose because the symptoms mimic other conditions. The doctor may perform specific tests to confirm the diagnosis. Tests that may be conducted include the following:

  • Lactose tolerance test
  • Hydrogen breath test
  • Stool acidity test

If these tests are negative, further investigation must be undertaken to find the cause of the patient's symptoms.

Treatment of Lactose Intolerance

There is no cure for lactose intolerance. Symptoms of the condition can be controlled to a large degree by dietary modification. A wide variety of lactase enzyme tablets and drops are available so that some patients can enjoy lactose products without symptoms. Also, there are now a great many lactose-free dairy products available that are digestible by many patients who suffer with this condition.

Additional Resources