 Demographics, Skin Pigmentation and UVB: Surveys at baseline with parents or legal guardians will be used to estimate socioeconomic status education and household income. Race will be collected to facilitate understanding of the relationships among culture, skin pigmentation and baseline vitamin D status 5,6. Data regarding sun exposure during the previous month will be collected as a percentage of body surface area BSA exposed frequency of sunscreen use and total hours spent in direct sunlight per day. Sun index will be calculated for each child as necessary i.e. travel, by multiplying the BSA exposed by the time spent outside minutes per day. This index does not consider use of sun block, which is captured by survey in event of travel. Skin type at baseline will be established by measuring pigmentation three times at each site for constitutive pigmentation at the inner upper arm and facultative pigmentation at the forehead, mid-forearm and lower leg using a spectrophotometer CM-700d600d, Konica Minolta, Ramsey, NJ, USA. 