title: Rising trend in vitamin D status from 1993 to 2013: dual concerns for the future.
abstract: BACKGROUND
  The Institute of Medicine 2011 Report on Dietary Reference Intakes for Calcium and Vitamin D specified higher intakes for all age groups compared to the 1997 report, but also cautioned against spurious claims about an epidemic of vitamin D deficiency and against advocates of higher intake requirements. Over 40 years, we have noted marked improvement in vitamin D status but we are concerned about hypervitaminosis D.
  
  
  OBJECTIVE
  We sought to evaluate the 25-hydroxyvitamin D (25OHD) trend over 20 years.
  
  
  METHODS
  We retrieved all results of serum 25OHD from 1993 to 2013 (n=69 012) that was trimmed to one sample per person (n=43 782). We conducted a time series analysis of the monthly averages for 25OHD using a simple sequence chart and a running median smoothing function. We modelled the data using univariate auto-regressive integrated moving average (ARIMA) and forecast 25OHD levels up to 2016.
  
  
  RESULTS
  The time series sequence chart and smoother function demonstrated a steady upward trend with seasonality. The yearly average 25OHD increased from 36.1 nmol/l in 1993 to 57.3 nmol/l in 2013. The ARIMA model was a good fit for the 25OHD time series; it forecasted monthly average 25OHD up to the end of 2016 with a positive stationary R(2) of 0.377.
  
  
  CONCLUSIONS
  Vitamin D status improved over the past 40 years, but there remains a dual problem: there are groups at risk of vitamin D deficiency who need public health preventative measures; on the other hand, random members of the population are taking unnecessarily high vitamin D intakes for unsubstantiated claims.
authors.affiliation: Metabolism LaboratoryDepartment of EndocrinologySt Vincent's University Hospital, Elm Park, Dublin 4, IrelandSchool of Medicine and Medical SciencesUniversity College Dublin, Belfield, Dublin 4, Ireland Metabolism LaboratoryDepartment of EndocrinologySt Vincent's University Hospital, Elm Park, Dublin 4, IrelandSchool of Medicine and Medical SciencesUniversity College Dublin, Belfield, Dublin 4, Ireland Metabolism LaboratoryDepartment of EndocrinologySt Vincent's University Hospital, Elm Park, Dublin 4, IrelandSchool of Medicine and Medical SciencesUniversity College Dublin, Belfield, Dublin 4, Ireland mjmckenn@iol.ie.
authors.forename: Malachi J
authors.initials: MJ
authors.lastname: McKenna
authors.affiliation: Metabolism LaboratoryDepartment of EndocrinologySt Vincent's University Hospital, Elm Park, Dublin 4, IrelandSchool of Medicine and Medical SciencesUniversity College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Barbara F
authors.initials: BF
authors.lastname: Murray
authors.affiliation: Metabolism LaboratoryDepartment of EndocrinologySt Vincent's University Hospital, Elm Park, Dublin 4, IrelandSchool of Medicine and Medical SciencesUniversity College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Myra
authors.initials: M
authors.lastname: O'Keane
authors.affiliation: Metabolism LaboratoryDepartment of EndocrinologySt Vincent's University Hospital, Elm Park, Dublin 4, IrelandSchool of Medicine and Medical SciencesUniversity College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Mark T
authors.initials: MT
authors.lastname: Kilbane
keywords: 25-hydroxyvitamin D; hypervitaminosis D; hypovitaminosis D; trend