What causes lactose intolerance?

    Last Updated: October 25, 2023

    There are three types of lactose intolerance: primary, secondary, and congenital.[1]

    • Primary lactose intolerance is the most common. This is the normal drop in intestinal lactase production that occurs for most people between ages two and five.
    • Secondary lactose intolerance is a sudden decrease in lactase production due to damage to the small intestine. This is usually a transient condition resulting from conditions like infection, celiac disease, Crohn’s disease, food allergy, or small intestinal bacterial overgrowth (SIBO).[1]
    • Congenital lactase deficiency (CLD) refers to an inability to produce lactase from birth. It’s an autosomal-recessive disorder, caused by a mutation in the LCT gene, and it is extremely rare.[2]

    References

    1. ^Di Costanzo M, Berni Canani RLactose Intolerance: Common Misunderstandings.Ann Nutr Metab.(2018)
    2. ^Fazeli W, Kaczmarek S, Kirschstein M, Santer RA novel mutation within the lactase gene (LCT): the first report of congenital lactase deficiency diagnosed in Central Europe.BMC Gastroenterol.(2015-Jul-28)