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Lactose intolerance
OVERVIEW: Inability to digest lactose (the primary sugar in milk) into its constituents, glucose and galactose, due to low levels of lactase enzyme in the brush border of the duodenum
• Congenital lactose intolerance - very rare
• Primary lactose intolerance - common in adults in whom a low level of lactase has developed after childhood. Symptoms are experienced after consumption of milk. Intolerance varies with amount of lactose consumed.
• Secondary lactose intolerance - inability to digest lactose caused by any condition injuring the intestinal mucosa (e.g., diarrhea) or a reduction of available mucosal surface (e.g., resection). This is usually transient, with the duration of the intolerance determined by the nature and course of the primary condition.
• 50% or more of infants with acute or chronic diarrhea have lactose intolerance, especially with rotavirus disease. Also, fairly common with giardiasis and ascariasis, inflammatory bowel disease, and the AIDS malabsorption syndrome.
• Lactose malabsorption - inability to absorb lactose. This does not necessarily parallel lactose intolerance.
System(s) affected: Gastrointestinal, Endocrine/Metabolic
Genetics: Unknown
Incidence/Prevalence in USA:
• Primary lactose intolerance - varies according to race. 75-90% of American Indians, blacks, Asians, Mediterraneans and Jews, less than 5% of descendants of Northern and Central Europeans.
• Secondary lactose intolerance - 50% or more of infants with acute or chronic diarrheal disease have lactose intolerance, especially with rotavirus disease. Also fairly common with giardiasis and ascariasis, inflammatory bowel disease and the AIDS malabsorptive syndrome.
Predominant age:
• Primary - teenage and adult
• Secondary - depends on the underlying condition
Predominant sex: Male = Female. However, 44% of lactose intolerant women will regain the ability to digest lactose during pregnancy.
SIGNS AND SYMPTOMS: • Bloating
• Cramping
• Abdominal discomfort
• Diarrhea or loose stools
• Flatulence
• Rumbling (borborygmi)
• Only one-third to one-fifth of people with lactose malabsorption will develop symptoms. Degree of symptoms varies with lactose load and with other foods consumed at the same time.
• In children - vomiting is common; frothy, acid stools; malnutrition can occur
CAUSES: • Primary lactose intolerance - normal decline in the lactase activity in the intestinal mucosa after weaning which is genetically controlled and permanent
• Secondary lactose intolerance - associated with gastroenteritis in children
• Also nontropical and tropical sprue, regional enteritis, abetalipoproteinemia, cystic fibrosis, ulcerative colitis, immunoglobulin deficiencies in both adults and children
RISK FACTORS: • Race
• Age
DIAGNOSIS DIFFERENTIAL DIAGNOSIS: Sucrase deficiency, diseases listed under secondary lactose intolerance
LABORATORY: Low fecal pH and reducing substances only valid when stools are collected fresh and assayed immediately. Fairly insensitive.
Drugs that may alter lab results: None
Disorders that may alter lab results: None
PATHOLOGICAL FINDINGS: Lactase deficiency in intestinal mucosa - may be patchy or focal. Rarely used in clinical practice.
SPECIAL TESTS: • Lactose breath hydrogen test - especially in children
• Lactose absorption test - alternative to lactose breath hydrogen test in adults
IMAGING: None
DIAGNOSTIC PROCEDURES: Small bowel biopsy for assay of lactase activity - may be normal if deficiency is focal or patchy (not readily available and usually not necessary)
TREATMENT APPROPRIATE HEALTH CARE: Outpatient except severe cases of malnutrition
GENERAL MEASURES: No disease specific measures
SURGICAL MEASURES: N/A
ACTIVITY: Full activity
DIET: • Reduce or restrict dietary lactose to control symptoms
• Yogurt and fermented products such as hard cheeses are tolerated better than milk
• Supplement calcium in the form of calcium carbonate
• Commercially available lactase preparations (Lactaid or Lactrase) are effective in reducing symptoms in many people
• Prehydrolyzed milk (Lactaid) is available and effective
PATIENT EDUCATION: • Patients must read labels on commercial products since milk-sugar is used in many products and may cause symptoms
• Lactose intolerant patients may tolerate whole milk or chocolate milk better than skim
• Lactose consumed with other food products is better tolerated than when it is consumed alone
• Primary lactase deficiency is permanent; secondary lactose intolerance is usually temporary, though it may persist for several months after the inciting disease has been cured.
MEDICATIONS DRUG(S) OF CHOICE: • Lactase (Lactaid, Lactrase) tablets
• 1 to 2 capsules or tablets prior to ingesting milk products. These vary in effectiveness at preventing symptoms.
• Can add tablets or contents of capsules to milk before drinking
• Also available in milk in some areas
Contraindications: None
Precautions: Not effective for all people with lactose intolerance
Significant possible interactions: None
ALTERNATIVE DRUGS: None
FOLLOW UP PATIENT MONITORING: N/A
PREVENTION/AVOIDANCE: Avoidance of lactose in large quantities will relieve symptoms. Patients can learn what level of lactose is tolerable in their diet.
POSSIBLE COMPLICATIONS: Calcium deficiency
EXPECTED COURSE AND PROGNOSIS: • Normal life expectancy
• Symptoms can be controlled
MISCELLANEOUS ASSOCIATED CONDITIONS: • Tropical or nontropical sprue
• Giardiasis
• Immunoglobulin deficiencies
• Crohn's disease
• Cystic fibrosis
AGE-RELATED FACTORS:
Pediatric:
• Primary lactose intolerance occurs after weaning - usually beginning in late childhood
• Breast milk contains a large quantity of lactose but does not seem to worsen diarrhea associated with viral or bacterial diseases
• Lactose free formulas are available
Geriatric: No increase in lactose intolerance in this age group
Others: Secondary lactose intolerance can begin at any age
PREGNANCY: 44% of lactose intolerant women will be able to tolerate lactose while pregnant
SYNONYMS: Lactase deficiency
ICD-9-CM: 271.3 intolerance or malabsorption (congenital) of lactose
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