Evaluation of a novel light-emitting diode device for producing vitamin D
Ravichandran, Ajay Kumar
MetadataShow full item record
Vitamin D is a fat-soluble hormone essential for humans as it is a key player in calcium and phosphorus homeostasis for bone mineralization, and is linked to many nonskeletal health outcomes such as autoimmune diseases and cardiovascular disease as well. The primary source of vitamin D is the conversion of 7-dehydrocholestrol (7-DHC), which naturally exists in the plasma membranes of skin cells, to previtamin D3 by the exposure to the ultraviolet-B (UV-B) portion of sunlight. Despite humans’ ability to cutaneously synthesize vitamin D, many factors limit this process, and consequently vitamin D deficiency has become a common medical issue worldwide. Deficient individuals may not respond well to traditional vitamin D replacement through dietary supplementation if suffering from fat malabsorption syndromes while unable to get sufficient vitamin D from sun exposure due to location, sunscreen use, or cultural practices, among other reasons. It has been previously reported that exposure to artificial sources of UV-B radiation (UV lamps, tanning beds, among others) produces cutaneous vitamin D, but heat generation, poor portability, and other inconveniences to the deficient patient limit therapeutic use of these devices. In addition, broad-spectrum sources of UV radiation reduce the production of vitamin D compared to narrow-band sources because of the photoequilibrium that is established. The advent of the light-emitting diode (LED) provided a compact, energy-efficient, high-intensity, low-heat alternative radiation source, and the recent development of the UV LED offers a viable alternative for developing a personalized vitamin D-producing device. This thesis presents evidence that UV LEDs have the capacity to efficiently synthesize vitamin D3 in vitro and in human skin. Ampoules of 7-DHC were irradiated in triplicate with LEDs at 280, 285, 290, 295, 298, 300, and 310 nm. The 298 nm LED was found to have the most efficient previtamin D3 production of 7.0% in vitro at the equivalent of 0.75 minimal erythemal dose (MED, rated at 1 MED = 32 milliJoules per centimeter squared for type II skin), compared to all other assessed LEDs. Irradiation of human skin samples (IRB-exempt) with the 298 nm diode (~39 seconds of radiation) indicated that 1.5% of the original 7-DHC in type II (Caucasian) skin could be converted to vitamin D3 in situ after exposure to 0.75 MED. These results imply that manufacturing a cuff containing 298 nm LEDs that covers 3.8% of the total surface area of skin could provide 600 IUs of vitamin D3 if operated for just 39.0 seconds. The data provide a promising new approach to treat vitamin D-deficient patients suffering from fat malabsorption syndromes.