The practice of indoor tanning has led to the development of a large artificial tanning industry. In addition to
psychological benefits, exposure to UVB light helps the body produce the activated form of vitamin D, which is
necessary for many cellular functions. But uncontrolled tanning and UV overexposure can increase the risk of skin
cancer. For direct checkout of the vitamin D synthetic capacity of a UV source the bio-equivalent UV dosimeter has
been developed that is based on the same molecular photochemistry from which vitamin D is photosynthesized in
human skin and makes possible both instrumental and visual indication of vitamin D synthesis.
Excessive UV doses have adverse effects on human health, but proper amount of UV is beneficial for people and is
essential in the natural production of vitamin D# in skin. Most of broadband UV-radiometers that have an output in
sunburn units are incapable to record correctly the vitamin D synthetic capacity of sunlight because of the difference
between the CIE erythema and 'Vitamin D synthesis' action spectra. The liquid-crystalline UV sensor based on
provitamin D photoconversions has been developed for direct observation of vitamin D synthesis under UV irradiation.
UV-induced transformation of provitamin D in cholesteric liquid-crystalline matrix is accompanied by the change of
cholesteric pitch value in the LC cell. The developed UV biosensor makes possible both instrumental and visual
monitoring of the vitamin D synthetic capacity of sunlight and/or artificial UV source.
UV irradiation is widely used in phototherapy. Regardless of the fact that UV overexposure is liable to cause adverse health effect, in appropriate doses UV radiation initiates synthesis of vitamin D in skin that is absolutely essential for human health. As it proved, most people in northern industrial countries have a level of vitamin D in their bodies that is insufficient for optimum health, especially in winter. These low levels of vitamin D are now known to be associated with a wide spectrum of serious disease much of which leads on to premature death. The diseases associated with D deficiency involve more than a dozen types of cancer including colon, breast and prostate, as well as the classic bone diseases: rickets, osteoporosis and osteomalacia. Irradiation with artificial UV sources can prevent the vitamin D deficiency. However, in view of different irradiation spectra of UV lamps, their ability to initiate vitamin D synthesis is different. The reliable method based on an in vitro model of vitamin D synthesis has been developed for direct measurement in situ of the vitamin D synthetic capacity of artificial UV sources during a phototherapeutic procedure
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