Lactose intolerance

Disease Description (Causes and Symptoms)

• Definition/pathophysiology: Lactose is a disaccharide found in milk and dairy products. Lactase (the lactose-digesting enzyme) in the intestinal mucosa breaks lactose down into glucose + galactose for absorption. When lactase is deficient, lactose is not properly digested and absorbed in the small intestine and enters the colon, causing osmotic diarrhea and gas production (fermentation by bacteria in the colon), among other symptoms.
• Main causes
  • Primary (adult-type) lactase reduction: Occurs as enzyme activity naturally decreases with age (prevalence varies by ethnicity and age).
  • Secondary (acquired) deficiency: Temporary or persistent loss of the enzyme due to enteritis (e.g., rotavirus), damage to the small-intestinal mucosa, malabsorption disorders, and other causes.
  • Congenital (hereditary) deficiency: Rare, and causes severe diarrhea from the neonatal period.
• Main symptoms: Abdominal bloating, abdominal pain (cramping), diarrhea, gas (flatulence), nausea, and others after consuming milk or dairy products. Symptom severity varies depending on the amount consumed, the degree of enzyme deficiency, and the form of the food.
• Tests commonly used for diagnosis (performed in outpatient clinics or laboratories)
  • Hydrogen breath test: A noninvasive standard test.
  • Lactose tolerance test (blood glucose rise test), stool acidity test (useful in infants).
  • If necessary, genetic testing (related to lactase persistence) or evaluation for underlying intestinal disease.

Treatment Methods and Precautions

• Goal: Relieve symptoms and prevent nutritional deficiencies (especially calcium and vitamin D deficiency)
• Dietary therapy
  • Avoid or reduce the amount of lactose that triggers symptoms: Rather than completely avoiding it, identify and adjust to the amount each person can tolerate.
  • Lactose-free (or low-lactose) milk products (lactose-free milk) and fermented dairy products (yogurt, aged cheese, etc.) cause fewer symptoms in most cases.
  • Consuming dairy products in small amounts frequently and together with other foods may help relieve symptoms.
  • Newborns and infants: Continued breastfeeding is recommended whenever possible (stopping breastfeeding is not necessarily the answer). Special formula is required in severe congenital cases.
• Medications and supplements
  • Lactase preparations: Taking them before consuming dairy products may prevent symptoms (follow the prescribed instructions).
  • Calcium and vitamin D supplementation if necessary: Intended to prevent deficiencies caused by limiting dairy-product intake.
  • Probiotics: May help relieve symptoms in some patients, but consistent evidence is limited.
• Treatment of underlying diseases
  • In cases of secondary deficiency, treating the cause (enteritis, malabsorption, etc.) may restore lactase function.
• Precautions / risk of complications
  • Do not confuse it with milk allergy (immune-mediated) (the symptoms, tests, and age groups differ). Consult a specialist if an allergy is suspected.
  • Avoiding dairy products excessively over a long period may increase the risk of reduced bone density due to calcium, protein, and vitamin D deficiencies; supplementation and alternative foods are recommended.
  • Seek medical attention immediately if severe diarrhea or dehydration occurs in an infant or young child.

Outpatient Visit Checklist (What to Bring and Precautions Before Testing)

• Items to prepare/bring
  • A list of current medications and supplements (including lactase supplements, antibiotics, and probiotics)
  • A recent food and symptom diary (what foods were eaten, the time symptoms began, duration, and severity)
  • Previous test results (related blood tests, stool tests, endoscopy, etc.) and previous medical certificates or diagnostic records (if available)
  • For children, growth records and feeding/weaning-food records
• Precautions before the breath (hydrogen) test (factors affecting test accuracy)
  • Fast for 8–12 hours before the test (water is allowed). Avoid foods high in fermentable carbohydrates on the day before the test (bread, fruit, vegetables, etc.).
  • Report the use of antibiotics, probiotics, and antacids during at least the 2 weeks before the test (up to 4 weeks is recommended), and confirm whether they should be discontinued.
  • Do not smoke or exercise on the day of the test.
  • Discontinue existing lactase supplements according to the doctor's instructions.
• Information to tell the doctor at the outpatient visit
  • When symptoms began, their frequency, related foods and amounts, family history (especially similar symptoms), and other details
  • A recent history of enteritis or antibiotic use, or other digestive symptoms (blood in the stool, fever, weight loss, etc.)

Examples of General Questions to Ask the Doctor

• "What tests should I undergo to confirm that my symptoms are definitely lactose intolerance?"
• "Based on the test results, which dairy products can I eat in daily life? Is there a recommended food list?"
• "Would using a lactase supplement (tablets/liquid) help? How should I take it, and what are the side effects?"
• "If I limit dairy products, how should I supplement calcium and vitamin D?"
• "How can I tell whether my symptoms are temporary or persistent?"

Examples of Disease-Specific Questions

• "If I use a lactase supplement, how much should I take at one time and when (before or during a meal) for the greatest effectiveness?"
• "In the case of a young child (or a breastfed newborn), is it okay to continue breastfeeding? If necessary, what formula do you recommend?"

(Note: This information has been summarized based on the information provided and the latest standard clinical practice guidelines. Recommendations may vary depending on individual circumstances, so please consult the treating doctor regarding the final diagnosis and treatment.)