The role of the small intestine described in Donguibogam closely aligns with modern medicine's focus on nutrient absorption and the gut-brain axis. In particular, the nutritional deficiency in the brain and nerves caused by small intestine hypofunction presents symptoms very similar to vitamin B12 deficiency in modern medicine. Vitamin B12, or cobalamin, is an essential water-soluble vitamin that plays a vital role in erythropoiesis, DNA synthesis, and the formation and maintenance of the myelin sheath protecting nerve cells. It is also involved in neurotransmitter synthesis, significantly affecting cognitive function and mood regulation. However, vitamin B12 absorption is quite complex. It must bind with intrinsic factor secreted by the stomach to be absorbed in the terminal ileum, the final portion of the small intestine. A breakdown at any stage of this process can lead to vitamin B12 deficiency. Contributing factors include inadequate intake of animal-source foods such as meat, fish, and dairy due to a vegetarian diet, long-term use of proton pump inhibitors, a history of gastrectomy, autoimmune conditions such as pernicious anemia, small intestine conditions like Crohn's disease, and decreased gastric acid secretion from aging. Because symptoms of vitamin B12 deficiency develop gradually over a broad range, they are often mistaken for simple fatigue or aging. Common signs include chronic fatigue, lethargy, pallor, and shortness of breath resulting from megaloblastic anemia. More concerning are the nervous system symptoms. It can cause peripheral neuropathy, including numbness in the hands and feet, paresthesia, poor balance, and gait disturbance, as well as memory impairment, impaired concentration, depression, cognitive decline, and symptoms resembling dementia. If the deficiency persists, this nervous system damage can become irreversible, making early diagnosis and treatment essential. Vitamin B12 levels can be checked with a blood test, and metabolites such as methylmalonic acid or homocysteine can be measured for an accurate diagnosis when needed. Modern medicine continues to show how subtle nutritional imbalances impact the brain and nervous system. The role of the small intestine and its connection to the heart in Donguibogam finds a meaningful modern interpretation in the necessity of essential nutrients like vitamin B12.
