The first aim of this study will be to evaluate the efficacy of an FDA approved artificial source of UVB radiation (Sperti® lamp) in raising serum 25(OH)D levels in patients with fat malabsorption due to Crohn's disease, ulcerative colitis, or cystic fibrosis or gastric bypass surgery and other causes. The second aim of the study is to compare the rise in serum 25(OH)D over the repeated measures in this study in patients with the 4 different skin types (types II-V).