Lactose intolerance (Causes, Symptoms, Diagnosis and Treatment)

  • Among animals, generally man alone takes milk even after becoming adult.
  • Milk and other dairy products consist of sugar (Carbohydrate) in them called lactose.
  • There is secretion of an enzyme called lactase in our small intestine that breaks down or digests lactose into glucose and galactose which can be easily absorbed into the blood stream.
  • With age, secretion of lactase decreases or ceases in human beings that leads to lactose intolerance.
  • Hence, lactose intolerance or lactose malabsorption is a condition where a person becomes unable to digest milk sugar (lactose) in his body.
  • There are three types of lactose intolerance.
    • Primary lactose intolerance
    • Secondary lactose intolerance
    • Congenital lactose intolerance


  • Less secretion or no secretion of lactase in the small intestine, naturally or after any illness, injury or surgery involving the small intestine.
  • In lactose intolerant people, lactose is fermented in their large intestine by bacteria, producing gases and acids.


  • Lactose intolerance is usually harmless, but its symptoms can be uncomfortable and embarrassing.
  • The signs and symptoms of lactose intolerance usually begin 30 minutes to two hours after eating of drinking foods that contain lactose, which include;
    • Flatulence (distension of stomach and intestine)
    • Intestinal cramps
    • Abdominal pain
    • Diarrhea
    • Bloating
    • Nausea and sometimes, vomiting


Doctors may suspect lactose intolerance based on the signs and symptoms but they confirm the diagnosis by conducting one or more of the following tests:

  • Hydrogen breath test:
    • This test will find the high levels of hydrogen when we exhale.
    • Hydrogen is exhaled if a person is lactose intolerant.
    • Hydrogen is produced when lactose is broken down in the large intestine by bacteria which is then taken by blood up to the lungs and then exhaled.
  • Blood test:
    • A liquid containing high level of lactose is given to a person to drink.
    • Two hours after drinking the liquid, a blood test is done to measure the amount of glucose.
    • If glucose level doesn’t rise, it means the person isn’t properly digesting and absorbing lactose filled drink.
  • Stool acidity test:
    • This is for infants and children who can’t undergo other tests.
    • Fermentation of undigested lactose in the large intestine produces lactic acid and other acids that can be detected in the stool sample.

Prevention and treatment:

  • Less consumption of milk and milk products. Dairy products like yoghurt and curd can be consumed in small amount as they contain lactic acid in them.
  • Milk can be substituted by other foods like almonds, dried beans, tofu, egg yolks, collards etc. to supplement proteins and calcium.
  • If symptoms are shown, we should immediately go and consult a doctor.

Lactose intolerance (Causes, Symptoms, Diagnosis and Treatment)