Vitamin D, the sunshine vitamin is important for health. Those with fat malabsorption disorders malabsorb vitamin D and thus must rely on cutaneous production of vitamin D3. Vitamin D3 is generated secondary to exposure to ultraviolet B (UVB) radiation (whether from the sun or from an artificial source). Light emitting diodes (LEDs) have been developed to emit ultraviolet radiation. Little is known about the efficiency of UVB emitting LEDs tuned to different wavelengths for producing vitamin D3 in human skin. Ampoules containing 7-dehydrocholesterol were exposed to a LED that emitted a peak wavelength at 293, 295, 298 or 305 nm to determine their efficiency to produce previtamin D3. The 293 nm LED was best suited for evaluating its effectiveness for producing vitamin D in human skin due to the shorter exposure time. This LED was found to be 2.4 times more efficient in producing vitamin D3 in human skin than the sun in less than 1/60th the time. This has significant health implications for medical device development in the future that can be used for providing vitamin D supplementation to patients with fat malabsorption syndromes as well as patients with other metabolic abnormalities including patients with chronic kidney disease.

Aim: A commercially available light emitting diode (LED) that transmitted narrow band ultraviolet B (UVB) radiation was evaluated for its efficacy and efficiency to produce vitamin D 3 in human skin. Materials and Methods: Human skin samples were obtained from surgical procedures. The LED had peak emission wavelength of 295 nm. Skin samples were exposed to the UVB-LED for varying times and then were analyzed by high-pressure liquid chromatography (HPLC) to determine the vitamin D 3 content. Results: There was a statistically significant time-and dosedependent increase in the percent of 7-dehydrocholesterol that was converted to vitamin D 3 in the skin type II samples; 1. 3%±0.5, 2.3%±0.6 and 4.5%±1.67 after exposure to 0.75 (11.7 mJ/cm 2 ), 1.5 (23.4 mJ/cm 2 ) and 3 (46.8 mJ/cm 2 ) minimal erythemal doses (MEDs), respectively. Conclusion: The UVB-LED was effective and efficient in generating vitamin D 3 in human skin, in vitro. The amount of vitamin D 3 production increased in a dose-dependent fashion with increased UVB energy. UVB-LEDs can be developed for devices that can efficiently produce vitamin D 3 in human skin.Vitamin D is mainly obtained from sun exposure, as well as from few dietary sources (1, 2). Specifically, during sun exposure, epidermal 7-dehydrocholesterol (7-DHC or provitamin D 3 ) absorbs solar ultraviolet (UV) B radiation, which results in the thermodynamically unstable molecule, previtamin D 3 . Once formed, the triene system in previtamin D 3 rearranges to form the more thermodynamically stable product, vitamin D 3 (1-4). After its formation, vitamin D 3 enters the circulation from the skin and is transported to the liver to be metabolized into 25-hydroxyvitamin D 3 (25(OH)D), and to the kidneys to undergo additional metabolism to 1,25-dihydroxyvitamin D 3 (1, 3, 5-7).The Sperti lamp, which contained a mercury arc lamp, was produced in the 1940s in the United States, where it was available in pharmacies to treat and prevent the bone disorder known as rickets (1, 6, 7). Since then, there has been an evolution of improved, more user-friendly vitamin D-producing devices for the treatment and prevention of vitamin D deficiency. In particular, the modern version of the Sperti lamp, Sperti D/UV-Fluorescent lamp (KBD, Inc., Las Vegas, NV, USA), was designed with UVB emitting fluorescent bulbs, which have the benefit of a lower heat emission than the previously mercury arc lamps. Additionally, these new UVB-emitting bulbs allow for a larger area of the user's skin to be exposed (8-10). Indeed, the Sperti D/UV-Fluorescent lamp has been shown to be effective in raising blood levels of 25(OH)D in healthy adults, as well as in patients with fat malabsorption syndromes who may not benefit from oral vitamin D supplementation (8,9).The modern version of the Sperti lamp includes improved gallium nitride-based UV light-emitting diode (LED), and is commercially available for use in clinical application (11,12). These LEDs can also be designed to emit specific UV narrow band in order to be utilized therapeu...