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Randomized Controlled Trial
. 2017 Mar;28(3):841-851.
doi: 10.1007/s00198-016-3833-y. Epub 2016 Dec 16.

Optimum Dose of Vitamin D for Disease Prevention in Older People: BEST-D Trial of Vitamin D in Primary Care

Free PMC article
Randomized Controlled Trial

Optimum Dose of Vitamin D for Disease Prevention in Older People: BEST-D Trial of Vitamin D in Primary Care

H Hin et al. Osteoporos Int. .
Free PMC article


This trial compared the effects of daily treatment with vitamin D or placebo for 1 year on blood tests of vitamin D status. The results demonstrated that daily 4000 IU vitamin D3 is required to achieve blood levels associated with lowest disease risks, and this dose should be tested in future trials for fracture prevention.

Introduction: The aim of this trial was to assess the effects of daily supplementation with vitamin D3 4000 IU (100 μg), 2000 IU (50 μg) or placebo for 1 year on biochemical markers of vitamin D status in preparation for a large trial for prevention of fractures and other outcomes.

Methods: This is a randomized placebo-controlled trial in 305 community-dwelling people aged 65 years or older in Oxfordshire, UK. Outcomes included biochemical markers of vitamin D status (plasma 25-hydroxy-vitamin D [25[OH]D], parathyroid hormone [PTH], calcium and alkaline phosphatase), cardiovascular risk factors and tests of physical function.

Results: Mean (SD) plasma 25(OH)D levels were 50 (18) nmol/L at baseline and increased to 137 (39), 102 (25) and 53 (16) nmol/L after 12 months in those allocated 4000 IU, 2000 IU or placebo, respectively (with 88%, 70% and 1% of these groups achieving the pre-specified level of >90 nmol/L). Neither dose of vitamin D3 was associated with significant deviation outside the normal range of PTH or albumin-corrected calcium. The additional effect on 25(OH)D levels of 4000 versus 2000 IU was similar in all subgroups except for body mass index, for which the further increase was smaller in overweight and obese participants compared with normal-weight participants. Supplementation with vitamin D had no significant effects on cardiovascular risk factors or on measures of physical function.

Conclusions: After accounting for average 70% compliance in long-term trials, doses of 4000 IU vitamin D3 daily may be required to achieve plasma 25(OH)D levels associated with lowest disease risk in observational studies.

Keywords: Clinical trial; Markers of vitamin D status; Optimum dose; Vitamin D.

Conflict of interest statement

Compliance with ethical standards All participants provided written informed consent, and the study was approved by the National Research Ethics Service Committee (Oxford B), UK. Conflicts of interest None. Funding Tishcon Corporation (Westbury, NY, USA) donated the active and placebo vitamin D capsules. The British Heart Foundation (PG/12/32/29544) and British Heart Foundation Centre for Research Excellence provided partial funding for the study. The Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU) at the University of Oxford receives funding from the UK Medical Research Council, the British Heart Foundation and Cancer Research UK. Informed consent Informed consent was obtained from all individual participants included in the study. Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.


Fig. 1
Fig. 1
CONSORT flow diagram for the BEST-D trial
Fig. 2
Fig. 2
Effect of vitamin D allocation on mean plasma levels of 25(OH)D, intact parathyroid hormone and albumin-corrected calcium. The vertical axis represents about 8 baseline SDs for 25(OH)D and about 4 baseline SDs for iPTH and albumin-corrected calcium. Arithmetic means are shown for 25(OH)D and albumin-corrected calcium and geometric means for iPTH. The p values for tests of difference between the groups at each time point are given in Table 2
Fig. 3
Fig. 3
Additional effect on 12-month vitamin D level of 4000 IU daily compared with 2000 IU daily, overall and in pre-defined subgroups. Mean and SE estimates are adjusted for baseline 25(OH)D by analysis of covariance, with any missing values imputed through multiple imputation. The chi-square tests for trend shown for each subgroup test the null hypothesis of there being no linear trend in the difference in adjusted means across levels of the subgroup (as ordered) and are derived from standard formulae. The white diamond represents the overall estimated difference in baseline-adjusted 12-month mean 25(OH)D concentration between all patients allocated 4000 IU daily and all patients allocated 2000 IU daily. Asterisk: among patients allocated 4000 or 2000 IU daily

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