Modern medicine continues to illuminate the observations recorded in the Donguibogam. Lactose intolerance is a prime example of what happens when the small intestine struggles to receive and filter properly. The small intestine produces a digestive enzyme called lactase, and when this enzyme is lacking, the body cannot properly break down lactose found in milk and dairy products. Undigested lactose passes through the small intestine into the large intestine, where bacteria ferment it and produce large amounts of gas. This gas causes abdominal distension and abdominal pain, while lactose exerts an osmotic effect that draws water into the intestine, leading to diarrhea. These symptoms typically appear within 30 minutes to 2 hours after consuming lactose, and in severe cases, they may be accompanied by nausea or dizziness.
Lactose intolerance generally falls into three types. The most common is primary lactose intolerance, where lactase secretion naturally declines with age. It is widespread enough to affect over 70% of people of Asian descent. Secondary lactose intolerance occurs when lactase secretion drops temporarily due to conditions that injure the small intestine, such as enteritis, Crohn's disease, or celiac disease, and it can improve once the underlying condition resolves. Finally, congenital lactase deficiency is an extremely rare condition in which no lactase is produced from birth.
In this way, lactose intolerance reflects both the hypofunction of small intestine enzymes and an imbalance in the gut microbiota. Rather than simple dyspepsia, it can be a broader indicator of intestinal health, making it important to listen to your body and respond thoughtfully. If drinking milk consistently causes distress, seeking an accurate diagnosis and learning how to support your small intestine is far better than simply enduring it.
