Lactose Intolerance 101: A Beginner’s Guide To Types, Causes, Symptoms, And Treatment.

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1. How common is lactose intolerance?

Lactose intolerance is a clinical syndrome caused by ingestion of lactose or lactose-containing foods such as milk and dairy products.

It is a surprisingly common condition. Here are some basic facts about the prevalence of lactose intolerance:

  • On average, about 65% of the world population is lactose intolerant.
  • The prevalence of lactose intolerance is extremely variable among different age groups and races.
  • The highest rates of lactose intolerance are found in African Americans, Hispanics/Latinos, and Asians.
  • The lowest rates are found in people of European descent, and in young children (less than 6 years old).
  • The most common form of lactose intolerance is primary lactose intolerance (also called lactose non-persistence).

2. Causes of lactose intolerance.

Lactose is the primary carbohydrate source for infants and young children. It is the main sugar found in milk and dairy products.

As you grow, your dependence on lactose begins to fall as you consume other foods than breast milk.

Lactose is primarily digested inside your small intestine by the enzyme (lactase). The lactase enzyme is abundant during the breastfeeding period (babies are wired to digest lactose more than adults).

As you grow older, Most people experience a gradual decline in the lactase enzyme activity. This results in the most common type of lactose intolerance which is primary lactase deficiency or (lactase non-persistence).

Primary lactase deficiency is genetically regulated and often starts to cause symptoms during adolescence and early adulthood. Genetics explains the differences in the prevalence of lactose intolerance among different races (reference).

Moreover, Lactase deficiency can result from other causes such as destruction of the small intestine lining (by disease or drugs). This type of lactose intolerance is called Secondary lactase deficiency. It can affect any age group and its onset is linked to the cause.

Other rare causes are explained below in the section types of lactose intolerance.

3. Types of lactose intolerance (types of lactase deficiency)

A. Primary lactase deficiency (lactose intolerance).

  • The most common form (more than 90%)  of lactose intolerance.
  • results from the gradual decline of lactase enzyme activity with age.
  • Symptoms start to develop during adolescence and early childhood.

B. Secondary lactase deficiency.

Secondary lactose intolerance develops when a disease or drug causes destruction of the small intestine lining cells (which produce the lactase enzyme). It is a less common form, and it can develop at any age even later in life.

Common causes include:

  • An attack of severe gastroenteritis.
  • Celiac disease.
  • Crohn’s disease (a type of inflammatory bowel disease).
  • Ulcerative colitits.
  • Chemotherapy.
  • Antibiotic use.

C. Congenital lactase deficiency.

An autosomal recessive disease (genetic disease) that causes early absence or decreased lactase in infants. It is different from primary lactase deficiency.

The baby with congenital lactase deficiency develops symptoms soon after birth due to the absence or deficiency of the enzyme. It is a rare and more severe form and it doesn’t go away when the baby grows older.

D. Developmental lactase deficiency.

Developmental lactase deficiency occurs as a result of incomplete maturation of the small intestine (the site of lactase enzyme).

Developmental lactase deficiency affects preterm babies born between 28 to 73 weeks of pregnancy. The symptoms of lactose intolerance develop soon after birth. However, it improves with age (due to the maturation of the small intestine).

4. Symptoms.

Not all people with lactose malabsorption have symptoms. you may have lactose intolerance and don’t have symptoms at all (reference).

Symptoms of lactose intolerance start after eating lactose-containing foods (mainly mild and dairy products). The symptoms often develop 30 minutes to two hours after eating a lactose-containing meal.

Symptoms include:

  • Abdominal pain.
  • Bloating.
  • Distension and excessive passing of gas.
  • Nausea.
  • Diarrhea.
  • In children, the stools are bulky, frothy, and watery.
  • Vomiting is common among adolescents with lactose intolerance.

The symptoms are often variable depending on the severity of lactase deficiency and the amount of lactose ingested.

6. Treatment.

  • Restrict lactose from your diet.
  • Calcium and vitamin D supplementation.
  • Lactase enzyme supplementation.
  • No need to avoid lactose-containing food.