Dear Dr. Dong-i subscribers, shall we explain the wisdom of Donguibogam in the language of modern science? Our body's biological rhythm is called the circadian rhythm, an internal clock that regulates sleep-arousal, hormone secretion, body temperature, and metabolism on an approximately 24-hour cycle. The conductor of all this is a small area located in the hypothalamus of the brain called the suprachiasmatic nucleus. The suprachiasmatic nucleus serves as the master clock of our body, receiving signals from the external environment, especially light information, to calibrate our biological rhythm.
When morning sunlight enters the eyes, this light signal is transmitted to the suprachiasmatic nucleus via the retina, and the suprachiasmatic nucleus signals the pineal gland in the brain to stop secreting melatonin. Melatonin is a sleep hormone secreted at night to help us fall asleep. Simultaneously, it promotes the secretion of the arousal hormone cortisol, preparing the body for activity. Conversely, when the sun sets and darkness arrives, the suprachiasmatic nucleus signals the body to restart melatonin secretion, and we gradually feel sleepy. In this way, light is the most powerful external stimulus that resets our biological clock.
However, modern people live a lifestyle far removed from this natural rhythm of light. When exposed late at night to the blue light emitting from smartphones, computers, TVs, and similar screens, the brain mistakes it for daytime and suppresses melatonin secretion. In the end, sleep does not come, and even if you manage to fall asleep, it becomes difficult to achieve deep sleep. Irregular meal times, shift work, and jet lag caused by frequent international travel are also primary culprits throwing the suprachiasmatic nucleus into confusion. In particular, in autumn and winter when daylight hours decrease, difficulties arise in regulating melatonin secretion due to a lack of sunlight, causing many people to experience depression such as seasonal affective disorder.
When the biological rhythm is disrupted, the problem goes beyond being unable to sleep. Sleep deprivation breaks the balance of the appetite-regulating hormones leptin and ghrelin, which can lead to overeating and weight gain, and raises insulin resistance, which is important for blood glucose control, increasing the risk of diabetes. It can also cause various physical and mental health issues, such as decreased immunity, increased risk of cardiovascular disease, reduced concentration and memory, and anxiety or depression. Every system in our body operates in tune with the biological clock. Modern medicine speaks with the same voice as Donguibogam regarding how important it is to listen to the rhythms of nature and live in accordance with them.
