[Jackie07]

A couple of abstracts on Vitamin D3 (looks like there's not only a difference bet. Vitamin D3 and other Vitamin D, the 2nd abstract even points out the better result of taking '25-hydroxyvitamin D3'):

J Clin Endocrinol Metab. 2012 Jun 14. [Epub ahead of print]
A Systematic Review: Influence of Vitamin D Supplementation on Serum 25-Hydroxyvitamin D Concentration.
Autier P, Gandini S, Mullie P.
Source
International Prevention Research Institute (P.A., P.M.), 69006 Lyon, France; and European Institute of Oncology (S.G.), 20139 Milano, Italy.
Abstract
Context:Few studies in subjects over 50 yr of age have evaluated the influence of variable doses of vitamin D supplementation on serum 25-hydroxyvitamin D levels.Objective:We performed a meta-analysis of changes in circulating 25-hydroxyvitamin D level associated with vitamin D supplementation in Caucasian subjects over 50 yr old.Data Sources:We conducted a systematic search in literature databases and in references of past reviews.Study Selection:Randomized placebo or open-label trials that evaluated the influence of vitamin D supplementation on clinical outcomes were included in the study.Data Extraction:We reviewed trial characteristics and serum 25-hydroxyvitamin D concentrations at baseline and during the trial.Data Synthesis:Seventy-six trials published from 1984 to March 2011 included 6207 subjects allocated to 101 intervention groups that tested supplement doses ranging from 5 to 250 μg/d (median, 20 μg/d). For similar doses, trials could obtain increases in 25-hydroxyvitamin D three to four times lower than other trials. A meta-regression showed that in the absence of concomitant use of calcium supplements, the average increase in serum 25-hydroxyvitamin D concentrations was 0.78 ng/ml (1.95 nmol/liter) per microgram of vitamin D3 supplement per day. Compared to the vitamin D3, the vitamin D2 was associated with significantly lower increases (P = 0.03). Concomitant use of calcium supplementation and high 25-hydroxyvitamin D concentration at baseline was nonsignificantly associated with lower increases in 25-hydroxyvitamin D concentrations.Conclusionsietary recommendations and randomized trials on vitamin D supplementation should evaluate whether increases in circulating 25-hydroxyvitamin D levels match expectations-for instance, the average increases obtained by trials on vitamin D3 without concomitant calcium supplements.


Am J Clin Nutr. 2012 Jun;95(6):1350-6. Epub 2012 May 2.
Relative effectiveness of oral 25-hydroxyvitamin D3 and vitamin D3 in raising wintertime serum 25-hydroxyvitamin D in older adults.

Cashman KD, Seamans KM, Lucey AJ, Stöcklin E, Weber P, Kiely M, Hill TR.
Source

School of Food and Nutritional Sciences and the Department of Medicine, University College Cork, Cork, Ireland, and DSM Nutritional Products Ltd, Kaiseraugst, Switzerland.

Abstract

BACKGROUND:

The relative potency of 25-hydroxyvitamin D(3) to vitamin D(3) needs to be better defined so that food-composition tables can better reflect the true vitamin D nutritive value of certain foods.
OBJECTIVE:

We performed a randomized, controlled intervention study in apparently healthy, free-living adults to investigate whether the intake of 25-hydroxyvitamin D(3) is 5 times more potent in raising serum 25-hydroxyvitamin D [25(OH)D] during winter compared with an equivalent amount of vitamin D(3).
DESIGN:

A randomized, placebo-controlled, double-blind intervention study was conducted in adults aged ≥50 y (n = 56) who consumed a placebo, 20 μg vitamin D(3), or 7 or 20 μg 25-hydroxyvitamin D(3) daily throughout 10 wk of winter. Serum 25(OH)D was measured by using an enzyme-linked immunoassay, and serum albumin-corrected calcium (S-Ca) was assessed colorimetrically at the baseline, midpoint, and endpoint of the study.
RESULTS:

The mean (±SD) increases (per microgram of vitamin D compound) in serum 25(OH)D concentrations over baseline after 10 wk of supplementation were 0.96 ± 0.62, 4.02 ± 1.27, and 4.77 ± 1.04 nmol · L(-1) · μg intake(-1) for the 20-μg vitamin D(3)/d and 7- and 20-μg 25-hydroxyvitamin D(3)/d groups, respectively. A comparison of the 7- and 20-μg 25-hydroxyvitamin D(3)/d groups with the 20-μg vitamin D(3)/d group yielded conversion factors of 4.2 and 5, respectively. There was no effect of treatment on S-Ca concentrations and no incidence of hypercalcemia (S-Ca >2.6 nmol/L).
CONCLUSIONS:

Each microgram of orally consumed 25-hydroxyvitamin D(3) was about 5 times more effective in raising serum 25(OH)D in older adults in winter than an equivalent amount of vitamin D(3). This conversion factor could be used in food-compositional tables for relevant foods. This study was registered at clinicaltrials.gov as NCT01398202.