Lactose Intolerance

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1- Introduction

2- Pathophysiology

3- Symptoms

4- Treatment


Lactose intolerance is a common condition where the body is unable to digest lactose, a sugar found in milk and dairy products. This is due to a deficiency of lactase, an enzyme produced by the cells lining the small intestine.



  1. Lactase Deficiency:

    • Primary Lactase Deficiency: This is the most common cause of lactose intolerance and develops over time. As people age, lactase production decreases, which can lead to symptoms of lactose intolerance. This condition is often genetic and varies significantly among different populations.
    • Secondary Lactase Deficiency: This can occur due to injury or illness affecting the small intestine, such as gastroenteritis, Crohn’s disease, celiac disease, or chemotherapy.
    • Congenital Lactase Deficiency: A rare genetic disorder where lactase production is absent from birth.
  2. Undigested Lactose:

    • When lactose is not adequately broken down in the small intestine, it passes into the colon undigested. In the colon, bacteria ferment the lactose, producing gases (hydrogen, methane, and carbon dioxide) and short-chain fatty acids, leading to symptoms.


Symptoms typically occur 30 minutes to 2 hours after consuming lactose-containing foods and can include:

  • Abdominal pain and cramping
  • Bloating
  • Gas (flatulence)
  • Diarrhea
  • Nausea


  • Dietary Management:

    • Lactose-Free or Low-Lactose Diet: Avoiding or reducing the intake of dairy products and other lactose-containing foods.
    • Lactase Supplements: Taking lactase enzyme supplements before consuming dairy products to aid in the digestion of lactose.
  • Alternative Foods:

    • Lactose-Free Dairy Products: These products have lactase added to them or have had the lactose removed.
    • Non-Dairy Alternatives: Such as almond milk, soy milk, rice milk, and coconut milk.
    • Fermented Dairy Products: Yogurt and kefir, which may be better tolerated due to the presence of lactase-producing bacteria.
  • Nutritional Considerations:

    • Calcium and Vitamin D: Ensuring adequate intake of calcium and vitamin D, either through lactose-free foods, supplements, or non-dairy sources, to prevent deficiencies.
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