Numerical estimations of the daily amount of skin-synthesized vitamin D by pre-school children in Poland.

According to Polish guidelines, children need a daily dose of 600-1000 I·U. vitamin D, which could be skin-synthesized in the period May to September, after at least 15 min solar exposure between 10 am and 3 pm with uncovered forearms and lower legs. In Poland, doctors only prescribe oral supplementation to infants and small children up to 2 years old, rarely for the older children. Numerical estimates of the daily amount of vitamin D (expressed in I.U. vitamin D taken orally) due to the solar exposure for preschoolers have been made on the basis of an observation campaign in Warsaw, Poland. In the period from April to September, the observations of children's clothing of age 4-6 years and the measurements of UV index were carried out in the kindergarten playground and a nearby park (52.31N, 21.06°E). It appears, that longer exposures (~45 min) are needed to gain the recommended dose. However, the estimation is burden with large uncertainties. The alternative scenario is to allow children to play outside for as long as possible without getting sunburn, i.e. until the personal erythemal threshold is reached. Then, sunscreens should be applied.