The amount of vitamin D produced from winter sunlight and dietary sources will negligibly raise blood 25-hydroxy vitamin D levels. People living in areas that receive less sunlight have lower circulating 25-hydroxyD (the major circulating form used to measure vitamin D status) levels. Vitamin D deficiency (defined as a serum 25(OH)D level < 20 ng/ml) in the general population is treated with oral supplementation of vitamin D at a dose of 50,000 IU given once weekly for eight weeks. (1) However from clinical experiences, oral supplementation has limited efficacy in vitamin D deficiency patients with malabsorption syndromes likely due to the inability to efficiently absorb vitamin D. *(1-3) A variety of UV light sources have been developed and sold as in-home tanning devices and to produce vitamin D in reptiles. In a pilot study, the investigators have observed that 5 out of 8 subjects had significant increased circulating 25(OH)D after exposure to a Sperti® lamp for 24 weeks. However, the possibility of correcting vitamin D deficiency by the skin exposure to artificial source of UVB radiation in patients with fat malabsorption has not been studied.