What Is Lactose Intolerance? Learn the Causes, Symptoms, and How to Manage It

Lactose intolerance is a condition in which the body is unable to properly digest lactose, a natural sugar found in milk and dairy products. This usually happens due to a decrease in the enzyme lactase in the small intestine after infancy, or because of damage to the intestinal lining caused by certain illnesses. Lactase plays an important role in breaking down lactose so it can be absorbed by the body.

When someone with lactose intolerance consumes dairy products like milk, cheese, yogurt, or buttermilk, the lactose remains undigested and is fermented by bacteria in the colon. This fermentation process leads to symptoms such as bloating, abdominal pain, diarrhea, and other digestive issues.

This condition is relatively common and can significantly affect daily activities if not managed properly. In Indonesia, lactose intolerance is frequently found, especially in children. Based on data, the prevalence of lactose malabsorption varies by age:

• Children aged 3–5 years: 21.3%
• Children aged 6–11 years: 57.8%
• Children aged 12–14 years: 73%
  
  

Interestingly, lactose intolerance is found both in children who regularly drink milk and those who don’t. The prevalence is 56.2% and 52.1% respectively. This means that drinking milk regularly does not guarantee that the body can digest lactose well—especially if lactase production is insufficient.

Therefore, it's important to understand the symptoms of lactose intolerance and recognize lactose-containing foods to help manage your diet wisely.

What Causes Lactose Intolerance?

Lactose intolerance can be caused by various factors, and each type has a different underlying cause. Here are four common types:

1. Primary Lactose Intolerance
   This is the most common type and is usually genetic. It occurs when lactase production gradually decreases with age. Although the decline may begin around age 2, symptoms often appear during adolescence or adulthood.
2. Secondary Lactose Intolerance
   This type is caused by damage to the digestive system due to conditions such as celiac disease, Crohn’s disease, intestinal infections, or inflammation. It can also result from medical treatments like chemotherapy or long-term antibiotic use.
3. Developmental Lactose Intolerance
   Occurs in premature babies whose digestive systems, particularly lactase production, are not fully developed. This type is temporary and usually improves as the baby grows.
4. Congenital Lactose Intolerance
   A rare condition caused by a genetic mutation inherited from both parents. Babies with this condition are born with little or no lactase and are unable to digest lactose from birth.

Symptoms of Lactose Intolerance

Common symptoms of lactose intolerance include:

• Bloating
• Abdominal pain or discomfort
• Excessive gas (flatulence)
• Nausea or vomiting after consuming dairy
• Diarrhea
• Redness or irritation around the anus (especially in children)
  
  

These symptoms typically occur within a few hours after eating or drinking products that contain lactose. The severity varies depending on how much lactose is consumed and the level of lactase deficiency in the body.

Recognizing these symptoms early can help you adjust your diet and prevent further digestive problems. If symptoms occur frequently, it's advisable to consult a doctor for proper diagnosis and guidance.

How Is Lactose Intolerance Diagnosed?

Diagnosis is based on a combination of clinical symptoms and medical tests. Common diagnostic methods include:

1. Stool Analysis
   This is a simple test often used for screening. If acids or reducing substances are found in the stool after consuming lactose, it may indicate lactose intolerance.
2. Lactose Tolerance Test
   The patient fasts for 4–8 hours, then consumes a lactose solution based on body weight. Blood sugar levels are measured every 30 minutes for 2 hours. If blood sugar rises less than 20 mg/dL from baseline, it suggests lactose malabsorption.
3. Barium-Lactose X-Ray
   The patient drinks a lactose-barium mixture, then an X-ray is taken. Lactose malabsorption can be seen as diluted barium and distended intestines. However, this method is rarely used due to radiation exposure.
4. Urine Galactose Test
   After drinking a lactose solution, galactose levels in urine are measured. If levels are below 0.9 mmol/L, it may indicate lactose malabsorption.
5. Hydrogen Breath Test
   This is a preferred method because it's non-invasive and accurate. After fasting, the patient drinks a lactose solution. Breath samples are taken every 30 minutes for 2 hours. An increase of 20 ppm or more in hydrogen levels indicates undigested lactose.
6. Intestinal Biopsy and Lactase Activity Test
   This is the gold standard for measuring lactase enzyme activity. A small sample of intestinal tissue is taken and analyzed. This test is usually reserved for complex cases where other tests are inconclusive.

How to Manage Lactose Intolerance

Currently, there is no cure for lactose intolerance, and no treatment has been found to increase lactase production. However, symptoms can be effectively managed by making dietary adjustments and adopting a healthy lifestyle.

Doctors typically recommend limiting or avoiding foods that contain lactose. Key sources of lactose to watch for include:

• Dairy milk (cow’s milk, goat’s milk)
• Dairy products (cheese, yogurt, butter, ice cream)
• Processed foods (cakes, biscuits, chocolate, candy, mayonnaise, instant soups, French fries, processed meats, and some cereals or bread)
  
  

Lactose-Free Alternatives

To replace dairy, you can choose plant-based milk such as soy milk, almond milk, or oat milk. Non-dairy yogurt made from coconut or soy, lactose-free cheese, and products labeled “lactose-free” are also safe options.

Gradual Lactose Exposure

Some people may tolerate small amounts of lactose if introduced gradually. However, this approach should only be done under medical supervision.

Probiotics for Digestive Support

Probiotic supplements can also help improve digestion. In addition to treating conditions like diarrhea or irritable bowel syndrome (IBS), certain probiotics support the body in breaking down lactose. Always consult your doctor before starting any new supplement.

Sources:

• Wicaksono, Y., Fanani, M. Z., & Jumiono, A. (2022). Kajian Potensi Pengembangan Produk Susu Bebas Laktosa bagi Penderita Lactose Intolerance. Jurnal Pangan Halal, 4(1).
• Saputra, G. A. (2019). Intoleransi Laktosa: Variasi Pemeriksaan Penunjang dan Tatalaksana. Jurnal Ilmu Kedokteran dan Kesehatan, 6(2).
• Yohmi, E., Boediarso, A. D., Hegar, B., Dwipurwantoro, P. G., & Firmansyah, A. (2001). Intoleransi Laktosa pada Anak dengan Nyeri Perut Berulang. Sari Pediatri, 2(4), 198-204.
• Alodokter.com – Intoleransi Laktosa, accessed on July 14, 2025.