건강한 삶을 위하여

햇빛에 오래 노출되면 (악성)피부암에 걸리는 것으로 알고 있는데 아래의 자료를 보니 반드시 그런건 아닌 것 같다. 자외선에는 UVA와 UVB가 있는데 UVB를 쬐면 비타민D의 생성이 촉진되어 그것이 항암작용을 하는 반면, UVA만 쬘 경우 비타민D 생성이 안되고 피부암에 걸리기 쉬운 것으로 나타났다고 한다. 그 예로 1940년 이후로 실내근무자에게 멜라노마라는 악성 피부암이 많이 발생했다고 한다. 유리창을 통해 들어오는 자외선은 UVA만 있고, 인체에 유익한 UVB는 다 걸러지기 때문이란다. 자세한 내용은 아래 참조.

* Dear Dr. Mirkin: You recommend sunlight for vitamin D, but isn't skin cancer a greater concern?
A single sunburn can cause malignant melanoma, but since 1940, the greatest increase in melanomas has occurred in office workers, not in people who work outdoors. FDA researchers believe that low vitamin D levels may be responsible (Medical Hypothesis, January 2009). Ultraviolet light is classified by wavelength into UVA and UVB. UVB rays cause skin to make vitamin D which helps the body to prevent cancers by inhibiting uncontrolled cell growth and restoring programable cells death called apoptosis. Since window glass block UVB almost completely, indoor office workers get up to nine times less UVB than people who spend more time outside and therefore, have far lower levels of vitamin D.

Since window glass allow UVA to pass through it, indoor workers have exposure to UVA which causes DNA damage and also breaks down what little vitamin D indoor workers get. The authors found indoor solar UVA irradiation to be 25 percent of what a person gets outdoors. So being indoors and exposing skin to the sun mostly through window glass reduces exposure to UVB that causes skin to make the vitamin D that prevents cancer, and increases relative exposure to UVA that destroys vitamin D in the skin and therefore increases cancer risk.

From Dr. Gabe Mirkin's Fitness and Health E-Zine at:http://www.drmirkin.com