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Relative effectiveness of oral 25-hydroxyvitamin D₃ and vitamin D₃ in raising wintertime serum 25-hydroxyvitamin D in older adults¹,²,³,⁴

1. Kevin D Cashman,
2. Kelly M Seamans,
3. Alice J Lucey,
4. Elisabeth Stöcklin,
5. Peter Weber,
6. Mairead Kiely, and
7. Tom R Hill

- Author Affiliations

1. ¹From the School of Food and Nutritional Sciences (KDC, KMS, AJL, MK, and TRH) and the Department of Medicine (KDC), University College Cork, Cork, Ireland, and DSM Nutritional Products Ltd, Kaiseraugst, Switzerland (ES and PW).

- Author Notes

• ↵2 Supported by the Irish Department of Agriculture, Food and the Marine under its Food Institutional Research Measure (grants to KDC and MK). DSM Nutritional Products Ltd supplied the vitamin D₃ and 25-hydroxyvitamin D₃ for supplements.
• ↵3 Present address for TRH: School of Agriculture, Food and Rural Development and Human Nutrition Research Centre, Newcastle University, Newcastle-Upon-Tyne, United Kingdom.
• ↵4 Address correspondence to KD Cashman, School of Food and Nutritional Sciences and Department of Medicine, University College Cork, Cork, Ireland. E-mail: k.cashman@ucc.ie.

Abstract

Background: The relative potency of 25-hydroxyvitamin D₃ to vitamin D₃ 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 D₃ is 5 times more potent in raising serum 25-hydroxyvitamin D [25(OH)D] during winter compared with an equivalent amount of vitamin D₃.

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 D₃, or 7 or 20 μg 25-hydroxyvitamin D₃ 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 D₃/d and 7- and 20-μg 25-hydroxyvitamin D₃/d groups, respectively. A comparison of the 7- and 20-μg 25-hydroxyvitamin D₃/d groups with the 20-μg vitamin D₃/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 D₃ was about 5 times more effective in raising serum 25(OH)D in older adults in winter than an equivalent amount of vitamin D₃. This conversion factor could be used in food-compositional tables for relevant foods. This study was registered at clinicaltrials.gov as NCT01398202.

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