Abstract
BackgroundThe 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.ObjectiveWe sought to evaluate the 25-hydroxyvitamin D (25OHD) trend over 20 years.DesignWe 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.ResultsThe 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.ConclusionsVitamin 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.
Highlights
Vitamin D supply is changeable, being sourced from skin synthesis following solar exposure, which is curtailed seasonally in high-latitude countries, and from oral intake of natural foodstuffs, fortified foodstuffs and supplements [1]
The total group was divided into five ordered categories according to 25OHD levels http://www.endocrineconnections.org
Vitamin D status has improved immensely in Ireland over the past 40 years following the advent of fortification of foodstuffs and the ready availability of low-dose vitamin D supplements
Summary
Vitamin D supply is changeable, being sourced from skin synthesis following solar exposure, which is curtailed seasonally in high-latitude countries, and from oral intake of natural foodstuffs, fortified foodstuffs and supplements [1]. Sunlight exposure is the predominant natural source of vitamin D, the primacy of oral intake over sunlight exposure both in the prevention and correction of vitamin D deficiency has been known for some time [2]. This is apposite to the concerns about sunlight exposure and skin cancer. We conducted a time series analysis of the monthly averages for 25OHD using a simple sequence chart and a running median smoothing function. 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
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