What Is Lactose Intolerance?


Lactose intolerance or lactose malabsorption is a condition in which the digestive system fails to break down the sugar lactose present in milk and milk-based products.

Lactose on consumption is broken down into two sugars, glucose & galactose, which can be easily absorbed into the body via the intestinal lining. The enzyme ‘lactase’ facilitating the breakdown of lactose is found in the small intestine. When the small intestine is unable to produce adequate amounts of lactase or if lactase production is completely halted, then the undigested lactose is processed by the gut bacteria present in the colon. These bacteria ferment the undigested lactose resulting in the release of hydrogen and gases. The production of these gases in in the colon result in the occurrence of some of the most common symptoms associated with lactose intolerance; these symptoms usually begin about 30 minutes to 2 hours after eating or drinking dairy products.

  • Abdominal cramps
  • Bloating
  • Gas
  • Diarrhea
  • Nausea

Types of Lactose Intolerance

  • Primary lactose intolerance – This is a condition in which an individual is born with a normal supply of lactase enzyme and can easily digest lactose from birth until early childhood; but as time progresses and milk is replaced by other supplements then production of lactase enzyme also decreases and the individual begins experiencing symptoms of lactose intolerance.
  • Secondary lactose intolerance – This type of lactose intolerance is not associated with metabolic changes in the body; rather, the incidence of diseases like celiac disease or inflammatory bowel disease, injury to the small intestine or a surgery can result in the depletion in the lactase enzyme production levels. This type of lactose intolerance is generally temporary and can be treated on the treatment of the underlying condition.
  • Congenital or developmental lactose intolerance – This condition occurs due to genetic anomalies caused by the passing of defective genes from the parents to the child. This is an autosomal recessive condition i.e.; both the parents have to transfer a copy of the defective gene to the child for the condition to occur. Babies born with this condition are unable to digest breast milk and if the condition is not detected soon, the life of the child will be threatened.
  • Developmental lactose intolerance – This is a rare type of lactose intolerance which affects children who are born prematurely; usually before 34 weeks of gestation (lactase production in the fetus begins at the 34th week of pregnancy).

Symptoms of lactose intolerance associated with infants

  • Swelling & pain in the abdomen
  • The milk doesn’t settle on feeding & come on and off the breast
  • Weight gain is negligible
  • Diarrhea
  • Feces are bulky, frothy & watery
  • Hips gain a reddish hue with the skin torn in some places
  • Farting & crying when passing feces
  • Increased fussiness


There are 3 common tests performed by clinicians to confirm lactose tolerance in individuals. These are:

  • Lactose intolerance test – It is a blood test that measures the body’s reaction to liquids with high lactose levels.
  • Hydrogen breath test – This is a test which measures the amount of hydrogen in the breath after consumption of foods with high lactose content (Fermentation of undigested lactose produces hydrogen gas).
  • Stool acidity test – This test measures the amount of lactic acid accumulated in the stool as a result of lactose fermentation. It is more commonly performed in infants and children.


  • Decreasing or removing dairy products from the diet – milk, curd, cheese, butter, casein, some packaged foods, etc.
  • Supplementing the diet with lactase enzyme on consumption of dairy products
  • Milk products are rich in calcium. Lactose intolerance renders an individual unable to consume milk. Taking calcium supplements or eating calcium fortified foods can compensate the deficiency in calcium, vitamin D, riboflavin and some proteins in lactose intolerant people.
  • Dairy milk can be substituted with alternatives such as almond, flax, soy, oat or rice milk.

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