Lactase Deficiency

Aka: Lactase Deficiency, Lactose Intolerance, Milk Intolerance, Hypolactasia, Alactasia

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II. Epidemiology: Incidence of Hypolactasia by ethnicity

  1. Northern european: 2 to 15%
  2. Latino patients: 50 to 80%
  3. Ashkenazi jews: 60 to 80%
  4. Black patients: 60 to 80%
  5. American Indians: 80 to 100%
  6. Asians: 95 to 100%
  7. References
    1. Sahi (1994) Scand J Gastroenterol 29(Suppl 202):7-20 [PubMed]

III. Pathophysiology

  1. Lactose deficiency is not a milk allergy
  2. Lactase enzyme present on Small Intestine brush border
    1. Lactase lyses lactose into Glucose and galactose
  3. Normal lactase physiologic changes
    1. Lactase is highest at birth
    2. Lactase levels start to decline by age 3.5 to 5 years
    3. 95% of birth lactase levels lost by early childhood
    4. Lactase continues to decrease with aging
  4. Lactase Enzyme Deficiency in the Small Intestine
    1. Lactose deficiency may be normal
    2. Europeans may be exception rather than the norm
      1. May have gene mutation that maintains lactase
  5. Lactase Deficiency results in lactose malabsorption
    1. Unabsorbed lactose draws water into Small Bowel
    2. Lactose is metabolized in the colon by Bacteria
      1. Short-chain Fatty Acids
        1. Reabsorbed with water
        2. Osmotic Diarrhea if reabsorption overloaded
      2. Gas production (Carbon dioxide, Hydrogen gas)
        1. Results in Flatulence, bloating, cramping

IV. Causes

  1. Idiopathic (most common)
    1. See Incidence per ethnicity above
    2. Physiologic waning of lactase activity in childhood
  2. Small Bowel secondary causes
    1. HIV Enteropathy
    2. Crohn's Disease
    3. Celiac Sprue
    4. Whiple's Disease
    5. Severe Viral Gastroenteritis
    6. Giardiasis
  3. Iatrogenic secondary causes
    1. Chemotherapy
    2. Radiation enteritis
    3. Oral Antibiotics (Clostridium difficile overgrowth)
  4. Miscellaneous secondary causes
    1. Carcinoid Syndrome
    2. Cystic Fibrosis
    3. Gastropathy of Diabetes Mellitus
    4. Kwashiorkor
    5. Zollinger-Ellison Syndrome
    6. Alcoholism

V. Symptoms with milk product ingestion

  1. Moderate dairy intake (e.g. 8-12 ounces milk)
    1. Bloating
    2. Flatulence or gas
    3. Cramping Abdominal Pain
    4. Foul smelling stools
  2. Large dairy intake or severe intolerance
    1. More significant symptoms of those listed above
    2. Osmotic Diarrhea

VI. Signs

  1. No weight loss associated with malabsorption

VII. Differential Diagnosis (See secondary causes above)

  1. Irritable Bowel Syndrome
  2. Inflammatory Bowel Disease
  3. Cystic Fibrosis
  4. Diverticulitis
  5. Celiac Sprue
  6. Acute Gastroenteritis
  7. Giardiasis

VIII. Evaluation

  1. Consider empiric trial off dairy products
    1. Also Consider Elimination Diet
  2. Lactose Breath Hydrogen Test
  3. Lactose Tolerance Test (replaced by hydrogen test)

IX. Management

  1. See Lactose-Free Diet
    1. Do not completely eliminate dairy products
    2. Risk of Vitamin Deficiency
  2. Lactase enzyme replacement (e.g. Lactaid, Dairy Ease)

X. References

  1. Melrad in Goldman (2000) Cecil Medicine, p. 719
  2. Swagerty (2002) Am Fam Physician 65(9):1845-50 [PubMed]

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