[Kim Jaeho's Life Story]<264> Wise Coexistence with Ultraviolet Rays

When going to the mountains, you sometimes encounter people who cover their entire face except for their eyes. Seeing this often has made me somewhat accustomed to it, but the suffocating feeling remains hard to shake off.

Sunlight contains ultraviolet rays known to be harmful to the body, so many people wear hats, sunglasses, or apply sunscreen to block UV rays when going outside. Recently, some people cover their entire face except for their eyes with sunshields, similar to how Muslims wear hijabs.

How accurately do we understand ultraviolet rays? When electricity flows, electric and magnetic fields occur simultaneously around it, and the waves generated by their periodic changes are called electromagnetic waves or electromagnetic radiation. Sunlight contains electromagnetic waves such as X-rays, ultraviolet rays, visible light, and infrared rays. Among these, all except visible light are invisible to the human eye.

Ultraviolet rays have shorter wavelengths than infrared and visible light but longer wavelengths than X-rays. Solar ultraviolet rays are divided into UVA, UVB, and UVC based on wavelength. UVA has a wavelength of 320?400 nm, the longest among ultraviolet rays, so it is not absorbed by the ozone layer and mostly reaches the Earth's surface. It has little effect on living organisms but can pass through glass and, with prolonged exposure, contributes to wrinkles and skin aging.

UVB has a wavelength of 280?320 nm, a medium wavelength among ultraviolet rays, and less than 10% reaches the Earth's surface. Most UVB is blocked by glass. UVB has strong energy and can cause burns, skin cancer, photoaging, pigmentation, and cataracts with prolonged exposure. It also activates provitamin D, playing a crucial role in converting it into vitamin D, which is essential for the human body.

UVC has the shortest wavelength among ultraviolet rays, ranging from 100 to 280 nm, and is almost entirely blocked by the ozone layer, so it does not reach the Earth's surface. It has high energy and is very harmful to health; excessive exposure can cause burns, skin cancer, and cataracts. However, it is effective in sterilizing viruses and bacteria.

As seen above, ultraviolet rays have both beneficial and harmful effects on our health, so it is unwise to avoid UV rays too much or to be exposed excessively. Prolonged overexposure to UV rays is known to cause skin cancer, photoaging, pigmentation, cataracts, and burns. Skin cancer, in particular, affects many people and causes many deaths.

Due to the negative factors of ultraviolet rays, avoiding UV rays excessively can reduce the risk of various diseases, including skin cancer. However, insufficient UV exposure can cause serious problems, the most significant being the inadequate production of vitamin D, which plays an important role in our body.

Vitamin D is activated vitamin D3 produced when provitamin D in the skin of animals or humans absorbs UVB. Vitamin D helps regulate calcium and phosphate levels in the body, essential for maintaining healthy bones, teeth, and muscles. A deficiency in vitamin D can cause bone deformities such as rickets in children and bone pain due to osteomalacia in adults.

Vitamin D deficiency in our body can be supplemented through food. Foods rich in vitamin D include eggs, salmon, trout, mushrooms, and cod liver oil. In cases where outdoor activities are limited for special reasons and sufficient vitamin D synthesis through UV exposure is not possible, there are limits to supplying vitamin D through food alone, so vitamin D supplements can be used to compensate for the deficiency.

However, taking excessive vitamin D supplements over a long period can cause calcium accumulation in the body (hypercalcemia), weakening bones and damaging the kidneys and heart, so caution is necessary.

Humans were created to live while receiving sunlight, so problems arising from avoiding sunlight go beyond vitamin D deficiency. When exposed to sunlight, endorphins, the happiness chemicals, are produced in brain cells, improving mood and providing mental stability. Various beneficial reactions occur in the body, including vitamin D synthesis. Excessive avoidance of sunlight to evade UV rays prevents these effects.

Ultraviolet rays are used in treating various skin diseases such as rickets, psoriasis, vitiligo, atopic dermatitis, and localized scleroderma. Both natural sunlight and artificial ultraviolet rays are used for treatment. According to a study on the positive effects of ultraviolet rays, UV exposure induces the production of nitric oxide (NO) in the body, which lowers blood pressure, improves cardiovascular health, has antibacterial effects, and can act as a neurotransmitter.

So far, we have examined the problems caused by excessive and insufficient UV exposure. What is the best approach to protect our health? The answer is clear: maintain UV exposure at an appropriate level?not too much, not too little.

Since vitamin D is well produced when exposed to UV rays, health organizations generally recommend exposing oneself to sunlight for 10?30 minutes, 2?3 times a week, to prevent vitamin D deficiency. However, in Korea, the negative aspects of UV rays are excessively emphasized, leading to an over-avoidance of UV exposure.

According to data from the Korea Disease Control and Prevention Agency, the proportion of people with vitamin D deficiency is very high?87% in men and 93% in women?indicating that UV exposure time is generally insufficient and needs to be increased to some extent.

However, increasing UV exposure time raises the risk of diseases such as skin cancer, so it is necessary to limit excessive UV exposure to prevent these issues. Following the recommendations of health organizations, it is advisable to expose oneself directly to sunlight for 10?30 minutes several times a week. To minimize problems caused by excessive exposure, as recommended by the World Health Organization (WHO), it is best to avoid outdoor activities during peak UV hours from 10 a.m. to 4 p.m. When going outside, wearing hats with brims or protective clothing to shield the head, face, and neck from UV rays, or using appropriate sunscreen and reapplying it every two hours, is recommended.

Independent Researcher

This content was produced with the assistance of AI translation services.