Experimental design: Double-blind randomized controlled trial. Research location: Porto Alegre Clinical Hospital (HCPA), RS, Brazil. Participants: Medical residents of the HCPA. Intervention: The groups will be randomized to ezetimibe 10 mg for 5 days or placebo. On the fifth day, they should came after an overnight fast for blood tests collection [25(OH)D, PTH, calcium, albumin]. Next, all participants will receive orally a cholecalciferol 50,000 IU capsule and a snack containing 15g of fat. Participants will return 14 days after that for a second blood test.