Lactose Intolerance


Lactose intolerance, also known as lactose malabsorption, is a common condition that affects people’s ability to fully digest the sugar (lactose) found in milk. As a result, consuming dairy products can lead to unpleasant symptoms such as diarrhea, gas, and bloating. This discomfort is caused by a deficiency of lactase, an enzyme produced in the small intestine that is responsible for breaking down lactose. While low levels of lactase may not cause any noticeable symptoms, individuals with significantly low lactase production will experience digestive distress after consuming dairy.

Fortunately, lactose intolerance can be effectively managed without eliminating all dairy products from one’s diet. Many individuals with lactose intolerance can still enjoy dairy products by choosing lactose-free or low-lactose alternatives, such as lactose-free milk or yogurt. Additionally, digestive aids, such as lactase enzyme supplements, can help break down lactose and reduce symptoms. With careful management strategies, individuals with lactose intolerance can continue to enjoy dairy products without experiencing significant discomfort.


The symptoms result from the presence of undigested lactose in the large intestine. Normally, it takes six to 10 hours for food to reach the large intestine after consumption, with an additional 24-36 hours for complete traversal. Consequently, symptoms may appear a day or two after lactose ingestion. Key signs of lactose intolerance include:

  • Abdominal swelling.
  • Excessive intestinal gas.
  • Nausea and vomiting.
  • Abdominal pain and cramps.
  • Audible stomach gurgling or rumbling.
  • Diarrhea.

Schedule a doctor’s appointment if you often experience lactose intolerance symptoms post-consuming dairy, especially if calcium intake concerns you.


Lactose intolerance arises when the small intestine lacks sufficient lactase enzyme to digest milk sugar (lactose). Typically, lactase breaks down lactose into glucose and galactose, which are then absorbed into the bloodstream through the intestinal lining. In the absence of enough lactase, undigested lactose moves into the colon, where normal bacteria interact with it, giving rise to the signs and symptoms associated with lactose intolerance.

Lactose intolerance comprises three types, each characterized by distinct factors contributing to the underlying lactase deficiency:

  • Primary lactose intolerance: Primary lactose intolerance is the most common type, occurring when individuals start life producing sufficient lactase but experience a sharp decline in lactase production by adulthood. This deficiency makes it challenging to digest milk products.
  • Secondary lactose intolerance: Secondary lactose intolerance develops when the small intestine reduces lactase production following an illness, injury, or surgical procedure affecting this organ. Conditions linked to this form of lactose intolerance encompass intestinal infection, celiac disease, bacterial overgrowth, and Crohn’s disease. Addressing the underlying disorder may lead to the restoration of lactase levels, potentially alleviating associated signs and symptoms, although the process may require a significant amount of time.
  • Congenital or developmental lactose intolerance: This rare type occurs in babies born with lactose intolerance due to a genetic lack of lactase. The disorder follows an autosomal recessive pattern, requiring both parents to pass on the same gene variant for the child to be affected. Premature infants may also experience lactose intolerance due to insufficient lactase levels.

Risk factors

Factors contributing to an increased susceptibility to lactose intolerance include:

  • Age: Lactose intolerance typically manifests in adulthood and is uncommon in infants and young children.
  • Ethnicity: Individuals of African, Asian, Hispanic, and American Indian descent are more prone to lactose intolerance.
  • Small intestine disorders: Conditions affecting the small intestine, such as bacterial overgrowth, celiac disease, and Crohn’s disease, can lead to lactose intolerance.
  • Premature birth: Premature infants may have lower levels of lactase due to the delayed development of lactase-producing cells in the small intestine.
  • Cancer treatments: Undergoing radiation therapy for stomach cancer or experiencing intestinal complications from chemotherapy increases the risk of developing lactose intolerance.