A systematic review and meta-regression analysis of the vitamin D intake-serum 25-hydroxyvitamin D relationship to inform European recommendations.
Br J Nutr. 2011 Dec;106(11):1638-48. Epub 2011 Oct 14.
Cashman KD, Fitzgerald AP, Kiely M, Seamans KM.
School of Food and Nutritional Sciences, University College Cork, Republic of Ireland. k.cashman at ucc.ie
The present study used a systematic review approach to identify relevant randomised control trials (RCT) with vitamin D and then apply meta-regression to explore the most appropriate model of the vitamin D intake-serum 25-hydroxyvitamin D (25(OH)D) relationship to underpin setting reference intake values.
Methods included an updated structured search on Ovid MEDLINE; rigorous inclusion/exclusion criteria; data extraction; and meta-regression (using different model constructs).
In particular, priority was given to data from winter-based RCT performed at latitudes >49·5°N (n 12).
A combined weighted linear model meta-regression analyses of natural log (Ln) total vitamin D intake (i.e. diet and supplemental vitamin D) v. achieved serum 25(OH)D in winter (that used by the North American Dietary Reference Intake Committee) produced a curvilinear relationship (mean (95 % lower CI) serum 25(OH)D (nmol/l) = 9·2 (8·5) Ln (total vitamin D)).
Use of non-transformed total vitamin D intake data (maximum 1400 IU/d; 35 ?g/d) provided for a more linear relationship (mean serum 25(OH)D (nmol/l) = 0·044 × (total vitamin D)+33·035).
Although inputting an intake of 600 IU/d (i.e. the RDA) into the 95 % lower CI curvilinear and linear models predicted a serum 25(OH)D of 54·4 and 55·2 nmol/l, respectively, the total vitamin D intake that would achieve 50 (and 40) nmol/l serum 25(OH)D was 359 (111) and 480 (260) IU/d, respectively.
Inclusion of 95 % range in the model to account for inter-individual variability increased the predicted intake of vitamin D needed to maintain serum 25(OH)D ? 50 nmol/l to 930 IU/d.
The model used to describe the vitamin D intake-status relationship needs to be considered carefully when setting new reference intake values in the Europe.
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They appeared to not consider high risk groups such as: overweight, dark skin, pregnant
They did mention pregnant once: to say that the special needs during pregnancy was excluded from analysis
Elderly: The authors referenced a paper showing 800 IU resulted in 20 ng of vitamin D - which as considered adequate
- Published Recommendations both IU and ng - which has the following two graphs