Dr. Ron’s Research Review – April 15, 2015

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This week’s research review focuses on the RDA for vitamin D.

The RDA for vitamin D is 600 IU per day and is assumed to achieve serum 25(OH)D levels of 50 nmol/L or more in 97.5% of healthy individuals.
Several studies, however, show no benefit from doses of 400 IU, and minimal from 800 IU/day. Particularly at risk were pregnant and lactating women (70% took a prenatal vitamin, 90% ate fish, and 93% drank approximately 2.3 glasses of milk per day) - 73% of the women and 80% of their infants were vitamin D–deficient (25-hydroxyvitamin D level, <20 ng per milliliter) at the time of birth. (Holick, 2007)
The RDA was calculated based on plotting the dose-response of 32 studies and calculating a relationship curve followed by an upper and lower prediction limit. The new study, however, uses only eight of the 32 studies (25%) that reported both the average and standard deviation. The 2.5th percentile dose-response points were calculated by subtracting 2 standard deviations from the average for each study. In short, the RDA is an averaged dose to achieve levels in 97.5% of healthy individuals. Veugelers and Ekwaru adjusted the data using the reported margin of error (twice the standard deviation).  (Veugelers and Ekwaru, 2014)

Veugelers and Ekwaru, using the IOM's data, calculated an RDA of 8895 IU per day.  


A follow-up study uses data derived from the GrassrootsHealth (GRH) database, which shows similar results - 3875 IU intake needed to achieve at least 20 ng/mL (50 nmol/L) in 97.5%. They also note that the correctly calculated RDA is well below the cutaneous production of vitamin D from summer sun. (Heaney et al., 2015)

Doses of 10,000 IU of vitamin D3 per day for up to 5 months, however, do not cause toxicity. (Holick, 2007)

 

Dr. Ron


 

Articles

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.
            (Heaney et al., 2015) Download
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.[...].

Vitamin D deficiency
            (Holick, 2007) Download

A statistical error in the estimation of the recommended dietary allowance for vitamin D.
            (Veugelers and Ekwaru, 2014) Download

 

References

Heaney, R, et al. (2015), ‘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.’, Nutrients, 7 (3), 1688-90. PubMedID: 25763527
Holick, M. F. (2007), ‘Vitamin D deficiency’, N Engl J Med, 357 (3), 266-81. PubMedID: 17634462
Veugelers, PJ and JP Ekwaru (2014), ‘A statistical error in the estimation of the recommended dietary allowance for vitamin D.’, Nutrients, 6(10) (10), 4472-75. PubMedID: 25333201