The song ‘First Love’ sung by singer Lim Hyun-jung, released in 1998, begins with the lyrics, ‘You who came and woke me up like the sun shining brightly~’. When I try to write an article about sunlight, this song comes to mind. Sunlight plays a dazzling role not only in waking us up, but also in waking up various aspects of our health.
Humans are animals that evolved to sleep at night when the sun goes down and be active during the day. The dialogue between day and night is different. These biological fluctuations that occur in our body are called circadian rhythms. This rhythm regulates our impulses, behaviors, and biochemistry. Light is at the heart of our bodies, including sleep, for rhythmic operation. In order to operate the circadian rhythm well, it is recommended to get enough sunlight during the day and reduce artificial light sources at night as much as possible. In 2007, the International Agency for Research on Cancer officially registered night shifts as ‘possible’ carcinogens.
As is widely known, exposure to sunlight produces vitamin D. Maintaining blood calcium levels is important for bone growth, maintaining bone density, and for the normal functioning of the nervous system. This regulation is achieved through a complex system called the vitamin D endocrine system. Vitamin D deficiency can lead to rickets in children, which results in brittle bones, retarded growth and deformed bones, and osteomalacia in adults. Osteomalacia is ambiguous, but it is often characterized by severe bone and muscle pain and is frequently misdiagnosed as fibromyalgia, chronic fatigue syndrome, or arthritis. Vitamin D deficiency also affects heart disease, diabetes, and brain cell development. Vitamin D helps various immune cells play a role in protecting the body against invading bacteria.
Vitamin D is important to our health in many ways, and while supplements are one way to provide vitamin D to people living in high latitudes who don’t get enough sunlight in the winter, they are no substitute for year-round sun exposure. Vitamin D expert Dr. Michael Hollick said that it is not easy to raise the level of vitamin D to at least 30 ng/mL, a healthy range with supplements alone. Many people’s quality of life has been lowered by the misunderstanding that their skin must be unconditionally protected from sunlight.
So, how much sunlight is appropriate? Dr. Michael Holick suggests different times of sun exposure in his book 『Vitamin D Solutions』 by considering the type of skin, the area of the skin exposed to sunlight, the latitude in which you live, and the intensity of sunlight depending on the time of day. According to this, if a Korean, an East Asian living in Seoul and Gyeonggi-do, whose skin is rarely red and always brown, who lives in Seoul and Gyeonggi-do, is exposed to 25-50% of their body surface area, August 8:11:30 a.m. 30-40 minutes, and 11 a.m.-pm Between 3 o’clock, 20-25 minutes of sunlight 2-3 times a week is appropriate and safe. However, sunscreen is not recommended during this time. This is because sunscreen almost completely blocks the body from making vitamin D from sunlight.