Letter to Veugelers, P.J. and Ekwaru, J.P., A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D. Nutrients 2014, 6, 4472–4475; doi:10.3390/nu6104472

Recently Veugelers and Ekwaru published data [1] indicating that, in its dietary reference intakes for calcium and vitamin D, the Institute of Medicine (IOM) had made a serious calculation error [2]. Using the same data set as had the IOM panel, these investigators showed that the Recommended Dietary Allowance (RDA) for vitamin D had been underestimated by an order of magnitude. Veugelers and Ekwaru, using the IOM's data, calculated an RDA of 8895 IU per day. They noted that there was some uncertainty in that estimate, inasmuch as this value required an extrapolation from the available data, which did not include individuals receiving daily vitamin D inputs above 2400 IU/day. In this communication, we present data from a different cohort entirely, including many individuals with vitamin D intakes spanning a range from zero to above 10,000 IU per day. The data presented here are derived from the GrassrootsHealth (GRH) database, which had been characterized elsewhere [3]. Here we examine the probability range for the previously published GRH data at all supplement intakes across the relevant range. Figure 1 plots the 25(OH)D values for 3657 individuals as a function of their own intakes of vitamin D, showing both the best fit regression line through the data [3] and the 95% confidence limits for the total data set. The horizontal dashed lines in the figure are for serum 25(OH)D values of 20, 30, and 40 ng/mL (50, 75, and 100 nmol/L). The points at which these lines intersect the lower bound of the 95% probability band for serum 25(OH)D reflect the inputs necessary to ensure that 97.5% of the cohort would have a vitamin D status value at or above the respective 25(OH)D concentration. These three OPEN ACCESS