Now, how does modern science explain these teachings of the Donguibogam filled with ancestral wisdom? These symptoms that become especially challenging in winter are commonly called seasonal affective disorder. This is a form of depression characterized by beginning mainly in autumn and winter and improving in spring. The greatest cause is simply a lack of sunlight.
Sunlight stimulates the suprachiasmatic nucleus located in the hypothalamus of our brain, playing a key role in regulating our body's biological clock, known as the circadian rhythm. In winter, as daylight hours shorten and sunlight exposure decreases, the function of this hypothalamus becomes disrupted. As a result, two significant changes occur.
First, the secretion of the hormone melatonin increases excessively. Melatonin is a sleep hormone secreted when it becomes dark that makes us feel sleepy. In winter, however, due to a lack of sunlight, melatonin secretion increases even during the day, leading to drowsiness and lethargy throughout the day. The term hibernation did not come out of nowhere; your body is constantly sending signals to rest.
Second, levels of serotonin, known as the happiness hormone, decrease. Serotonin affects mood regulation, appetite, and sleep. When sunlight is deficient, it also affects the metabolic pathway of tryptophan, an essential amino acid required for serotonin production, causing serotonin levels to drop. This leads to depressed mood, lethargy, impaired concentration, and even heightened cravings for carbohydrates that result in weight gain. There is a clear reason why staying cooped up inside because of the cold makes you crave sweet foods.
In addition, a deficiency in vitamin D, synthesized in our body through sunlight, is also an important factor. Vitamin D plays a vital role not only in bone health but also in immune function and mood regulation. When vitamin D levels drop due to lack of sunlight, feelings of depression can worsen. In this way, we can see that the concepts of yang qi deficiency and storing and sealing mentioned in the Donguibogam are very closely linked to modern science's excess melatonin, serotonin deficiency, and vitamin D deficiency. Understanding this as a gentle signal that your body wants to rest quietly in harmony with nature's rhythm, and making good use of the finest medicine called sunlight, can be seen as essential wisdom.
