Lactose intolerance: Diagnosis and diet strategies

June 1, 2017

Diarrhea, abdominal pain, and flatulence following ingestion of milk or products containing milk are common complaints in pediatric practices. The pediatrician needs to be aware of the management of lactose intolerance to help guide a reasonable workup and plan.

Diarrhea, abdominal pain, and flatulence following ingestion of milk or products containing milk are common complaints in pediatric practices. The pediatrician needs to be aware of the management of lactose intolerance to help guide a reasonable workup and plan. Additionally, parental decisions about intake and avoidance of milk products impact not only the calcium and vitamin D intake of children but also other dietary choices such as intake of protein fat.

Pathophysiology of lactose intolerance

It is important for the pediatrician to understand the clinical spectrum of lactose problems.1,2 Generally, the syndrome incidence is lower in younger children and begins to increase around school age. The following definitions are important for the pediatrician to understand:2

·      Lactase deficiency-decreased lactase enzyme activity in the intestinal brush border.

·      Lactose malabsorption-failure to absorb lactose in the small bowel.

·      Lactose intolerance-clinical syndrome resulting from malabsorption.

Lactose intake is generally highest during infancy and then decreases with age. About 25% of lactose is absorbed in the small intestine by hydrolyzation with intestinal lactase. In the colon, the remainder of unabsorbed lactose is converted into short-chain fatty acids and hydrogen by the bacterial flora so that it can be absorbed. In some people, a certain degree of lactase deficiency can be mediated by this conversion process.2,3


The exact prevalence of lactose intolerance is not able to be determined, but it is more common among some pediatric populations such as those with recurrent abdominal pain.4,5

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Ethnicity significantly impacts risk with worldwide incidence, ranging from 5% to nearly 100%. European and white Americans have the lowest incidence. African Americans, Hispanic Americans, Asian Americans, and Native Americans all have higher incidences, but not nearly as high as is seen in parts of Asia and South America.6 This genetic reduction in lactase enzyme activity is a primary lactose malabsorption problem and is most common in mid-childhood.7 Congenital lactase deficiency, also a cause of primary lactose malabsorption, is a rare autosomal recessive disorder.

Lactose malabsorption also may occur secondary to other gastrointestinal processes such as bacterial overgrowth, intestinal infection (eg, rotavirus, Giardia, and other parasites) or inflammatory processes such as celiac disease, Crohn disease, and immune-related enteropathies.2

Clinical symptoms

Symptoms can be highly variable between individual patients (Table2,6-8). Children with faster transit times through the colon may be more likely to develop more significant symptoms.9 Similarly, foods that decrease gastric emptying times (eg, yogurt) may reduce symptoms of lactose intolerance.2 There is also a small group of patients that demonstrate lactose malabsorption but do not manifest any symptoms.10


Pediatricians take a varied approach to the diagnosis of lactose intolerance. Many pediatricians make a presumptive diagnosis based on history alone with the presence of symptoms with ingestion of lactose products. The diagnosis is often buttressed by symptom resolutions with avoidance and recurrence upon lactose challenge. The 2006 guideline from the American Academy of Pediatrics (AAP) states that a strict lactose-free, 2-week trial with resolution of symptoms and recurrence upon reintroduction is sufficient for diagnosis.2

More objective measures are sometimes preferred, and other indications for testing may include:

·      Diagnostic uncertainty.

·      Parental concern.

·      Desire to avoid lactose-restricted diets.

·      Patients in whom the diagnosis may clinically look like lactose intolerance, but the patient is at low risk based on ethnicity.

·      Patients with unexplained or severe symptoms.

·      Patients in whom the pediatrician suspects lactose intolerance, but the patient does not improve on a lactose-free diet.

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Lactose hydrogen breath test

This is a simple, noninvasive test wherein the patient receives a lactose load and the breath is measured for hydrogen every 15 to 30 minutes for up to 3 hours. The test looks for increased levels of hydrogen, which normally peaks in 90 to 120 minutes following the load. At 78% and 98%, respectively, the sensitivity and specificity are superior to the absorption test.11 It is considered the most reliable and cost-effective test for diagnosing lactose malabsorption.12 This test has largely replaced the lactose tolerance test if testing is needed.

The test is noted to be more reliable than history alone because patients think they are lactose intolerant and turn out not to be, and vice versa.2

Recent antibiotics, high-fiber diets, small intestinal bacterial overgrowth, intestinal motility disorders, and a lack of hydrogen-producing bacteria in the gut can lead to false-positive and false-negative results.2

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Postprandial hypoglycemia is considered a contraindication. Although uncommon, migraines, stomach cramping, panic attacks, dizziness, and allergy-like reactions all have been reported as adverse effects of testing, and anyone performing these tests should be prepared to address them.12

Lactose tolerance test

In this more-invasive test, children are administered a lactose load (2 g/kg). Blood glucose levels are monitored at 0, 60, and 120 minutes. Development of symptoms with an increased blood sugar of 20 mg/dL is diagnostic. In adult populations, the sensitivity and specificity are reported as 75% and 96%, respectively.13 In general, the lactose tolerance test is no longer deemed appropriate for clinical practice.6

Other testing

Small bowel biopsy and genetic testing are also available. Small bowel biopsies are rarely performed because of the availability of the sensitive and specific noninvasive tests mentioned above. Likewise, genetic tests for malabsorption are rarely performed because of cost.

Ruling out other causes

Because symptoms of lactose intolerance are vague, children should be evaluated for secondary causes, including:

·      Bacterial overgrowth;

·      Infectious (eg, Giardia);

·      Celiac disease;

·      Inflammatory bowel disease such as Crohn disease; and

·      Prematurity/developmental lactase deficiency.

Ingestion of large amounts of sorbitol or other simple carbohydrates can lead to osmotic diarrhea and symptoms similar to lactose intolerance. In older adolescents, the pediatrician may need to also consider surreptitious laxative use. Finally, the pediatrician should consider cow’s milk allergy in patients who continue symptoms after lactose restriction.

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The pediatrician has several means with which to manage lactose intolerance in pediatric patients.

Dietary restriction

For most patients with lactose intolerance, avoiding milk and dairy products results in improvement of symptoms. However, this is generally not necessary or advised. Most patients with lactose intolerance are able to tolerate 1 to 2 cups of milk or the equivalent per day without significant symptoms. Routine consumption of lactose over the entire day may be better tolerated than intermittent, daily bolusing of lactose. Patients may slowly increase intake after a period of restriction to determine each individual’s threshold for symptoms.8,14,15 Children intolerant of milk may tolerate milk chocolate and also yogurt, which often results in fewer symptoms because of its semisolid state. Aged cheeses also tend to produce fewer symptoms because of lower lactose content.2

The pediatrician wants patients to maintain calcium and vitamin D intake as much as possible. It is important for parents and caregivers to be educated that ingestion of lactose does not lead to damage of the gastrointestinal tract even if the child develops symptoms.

Enzyme replacement

If a child ingests more than 2 cups of milk per day or its equivalent, a child or adolescent may take one of the commercially available lactase enzyme preparations that are available as liquid or sprinkles. According to its website, Lactaid may be taken daily by children aged 4 years and older (

Lactose-free formulas

Lactose-free formulas, although commercially available in the United States, are generally not needed because enough enzyme activity remains to preserve digestion and absorption. Lactose-free formulas have not demonstrated an outcome advantage in terms of growth, development, or behavioral issues such as colic.2 If needed, lactose-free or reduced milk is available for children aged older than 1 year, and the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) will provide vouchers when needed.

Maintaining calcium and vitamin D intake

The pediatrician should warn parents against total lactose-free diets because this practice is associated with lower calcium absorption and potential problems with bone mineralization.

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The pediatrician should encourage intake of calcium-rich foods and consider calcium supplementation (liquid calcium gluconate for younger children and calcium carbonate for older children are readily available) if this is not possible. Vitamin D status should be monitored and intake replaced when appropriate as well. Dietary consultation may greatly assist the pediatrician and the family in identifying and monitoring both calcium and vitamin D intake.


Lactose intolerance is a common problem in pediatric practice. The pediatrician needs to be aware of practical strategies for diagnosis and management as well as when further workup needs to be done, in addition to preventing deficiency of calcium and vitamin D.


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2. Heyman MB, Committee on Nutrition. Lactose intolerance in infants, children, and adolescents. Pediatrics. 2006;118(3):1279-1286.

3. Hertzler SR, Savaiano DA. Colonic adaptation to daily lactose feeding in lactose maldigesters reduces lactose intolerance. Am J Clin Nutr. 1996;64(2):232-236.

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9. Serra J, Azpiroz F, Malagelada JR. Intestinal gas dynamics and tolerance in humans. Gastroenterology. 1998;115(3):542-550.

10. Glatstein M, Reif S, Scolnik D, et al. Lactose breath test in children: relationship between symptoms during the test and test results. Am J Ther. August 17, 2016. Epub ahead of print.

11. Gasbarrini A, Corazza GR, Gasbarrini G, et al; 1st Rome H2-Breath Testing Consensus Conference Working Group. Methodology and indications of H2-breath testing in gastrointestinal diseases: the Rome Consensus Conference. Aliment Pharmacol Ther. 2009;29 suppl 1:1-49.

12. Eisenmann A, Amann A, Said M, Datta B. Implementation and interpretation of hydrogen breath tests. J Breath Res. 2008;2(4);046002.

13. Newcomer AD, McGill DB, Thomas PJ, Hofmann AF. Prospective comparison of indirect methods for detecting lactase deficiency. N Engl J Med. 1975;293(24):1232-1236.

14. Suarez FL, Savaiano D, Arbisi P, Levitt MD. Tolerance to the daily ingestion of two cups of milk by individuals claiming lactose intolerance. Am J Clin Nutr. 1997;65(5):1502-1506.

15. Montalto M, Curigliano V, Santoro L, et al. Management and treatment of lactose malabsorption. World J Gastroenterol. 2006;12(2):187-191.