- Lactose intolerance is defined as the inability to digest the ingested disaccharide lactose, secondary to a deficiency of the intrinsic enzyme lactase, resulting in clinical symptoms.
- Lactase deficiency is an intrinsic low level of lactase production which may or may not be associated with clinical symptoms.
- Lactose is a disaccharide composed of glucose and galactose.
- Lactose is important as a source of energy; it is the major carbohydrate in human and other mammalian milks; promotes the absorption of calcium, phosphorus, and iron; and has a probiotic effect on the gut flora.
- Four types of lactase deficiency
- Congenital lactase deficiency
- Extremely rare
- Presents during the newborn period
- Will cause severe diarrhea and failure to thrive and risk the newborn’s life
- Primary lactase deficiency (adult-type hypolactasia)
- Due to relative or absolute absence of lactase
- Develops during childhood at different ages in different racial groups
- Most common cause of lactose intolerance
- Secondary lactase deficiency
- Results from small bowel injury (acute gastroenteritis, persistent diarrhea, small bowel bacterial overgrowth, chemotherapy)
- Can present at any age, more common in infancy
- Developmental lactase deficiency
- A relative lactase deficiency observed in premature infants <34 weeks’ gestation
- Congenital lactase deficiency
- ~70% of the world’s population is prone to developing primary lactase deficiency by adulthood.
- The prevalence of primary lactase deficiency in northern Europeans, who have a diet rich in dairy, is 2%.
- In Hispanic populations, the prevalence of primary lactase deficiency is 50–80%.
- In Ashkenazi Jewish and African American populations, the prevalence is 60–80%.
- In Asian populations, the prevalence of primary lactase deficiency is nearly 100%.
- Nearly 20% of children <5 years from Hispanic, Asian, or African American descent have lactase deficiency and lactose malabsorption.
- Caucasian children usually do not develop symptoms until after 5 years of age.
- Posttranslational regulatory mechanisms in primary lactase deficiency or adult-type hypolactasia
- Correlation between the genetic polymorphism of mRNA and persistence of lactase activity with early loss at 1 to 2 years in Thai children and late loss at 10 to 20 years in Finnish children
- Symptoms depend on the amount of lactose ingested.
- Malabsorbed lactose creates an osmotic load that draws fluid and electrolytes into the bowel lumen, leading to an osmotic diarrhea.
- Nonabsorbed lactose acts as a substrate for intestinal bacteria.
- In the colon, bacteria metabolize lactose, producing volatile fatty acids and gases leading to flatulence, bowel distension, pain, and low pH.
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Cabana, Michael D., editor. "Lactose Intolerance." 5-Minute Pediatric Consult, 8th ed., Wolters Kluwer, 2019. Pediatrics Central, peds.unboundmedicine.com/pedscentral/view/5-Minute-Pediatric-Consult/617644/all/Lactose_Intolerance.
Lactose Intolerance. In: Cabana MDM, ed. 5-Minute Pediatric Consult. Wolters Kluwer; 2019. https://peds.unboundmedicine.com/pedscentral/view/5-Minute-Pediatric-Consult/617644/all/Lactose_Intolerance. Accessed June 8, 2023.
Lactose Intolerance. (2019). In Cabana, M. D. (Ed.), 5-Minute Pediatric Consult (8th ed.). Wolters Kluwer. https://peds.unboundmedicine.com/pedscentral/view/5-Minute-Pediatric-Consult/617644/all/Lactose_Intolerance
Lactose Intolerance [Internet]. In: Cabana MDM, editors. 5-Minute Pediatric Consult. Wolters Kluwer; 2019. [cited 2023 June 08]. Available from: https://peds.unboundmedicine.com/pedscentral/view/5-Minute-Pediatric-Consult/617644/all/Lactose_Intolerance.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Lactose Intolerance ID - 617644 ED - Cabana,Michael D, BT - 5-Minute Pediatric Consult UR - https://peds.unboundmedicine.com/pedscentral/view/5-Minute-Pediatric-Consult/617644/all/Lactose_Intolerance PB - Wolters Kluwer ET - 8 DB - Pediatrics Central DP - Unbound Medicine ER -