Participant recruitment and randomization.
Cancer
RECRUITMENT, CANCER
Healthy adult participants of any Fitzpatrick skin type were recruited from March 2017 to June 2018 by IRB-approved advertisements (approved by IRB of Case Western Reserve University and Case Comprehensive Cancer Center [CASE 3416]) posted throughout the hospital and university and by referrals from other dermatologists. Ineligibility criteria included individuals aged < 17 years; individuals who were pregnant, nursing, or anticipate becoming pregnant within 3 months; individuals taking ketoconazole, colestipol, cholestyramine, phenobarbital, phenytoin, mineral oil, warfarin, aspirin, > 400 mg/day ibuprofen, > 220 mg/day naproxen sodium, ≥ 4,000 IU/day or 20,000 IU/week of VitD supplements, or illicit drugs; individuals undergoing treatment with chemotherapy, antibiotics, biologics, or immunosuppressants; or individuals with a BMI > 40. Thirty-one adults were screened for eligibility, and 28 were consented to participation. Given the pilot nature of the study design and the high level of involvement required of study participants, the sample size was determined primarily by recruitment constraints.Participants were block randomized into either the VitD group (VitD[+]) or placebo group (VitD[–]) using a balanced assignment (