• Kirsten V Knutsen, Ahmed A Madar, Per Lagerløv, Mette Brekke, Truls Raastad, Lars C Stene, and Haakon E Meyer.
• Department of General Practice (K.V.K., P.L., M.B.), Institute of Health and Society, University of Oslo, Oslo N-0318, Norway; Department of Community Medicine (A.A.M., H.E.M.), Institute of Health and Society, University of Oslo, Oslo N-0318, Norway; Division of Epidemiology (L.C.S., H.E.M.), Norwegian Institute of Public Health, Oslo N-0403, Norway; and Norwegian School of Sport Sciences (T.R.), Oslo N-0806, Norway.
• J. Clin. Endocrinol. Metab. 2014 Jan 1;99(1):194-202.

ContextThe effect of vitamin D on muscle strength in adults is not established.ObjectiveOur objective was to test whether vitamin D supplementation increases muscle strength and power compared with placebo.DesignWe conducted a randomized, double-blind, placebo-controlled trial.SettingThe setting was immigrants' activity centers.ParticipantsTwo hundred fifty-one healthy adult males and females aged 18-50 years with non-Western immigrant background performed the baseline test and 86% returned to the follow-up test.InterventionsSixteen weeks of daily supplementation with 25 μg (1000 IU) vitamin D3, 10 μg (400 IU) vitamin D3, or placebo.Main Outcome MeasuresDifference in jump height between pre- and postintervention. Secondary outcomes were differences in handgrip strength and chair-rising test.ResultsPercentage change in jump height did not differ between those receiving vitamin D (25 or 10 μg vitamin D3) and those receiving placebo (mean difference -1.4%, 95% confidence interval: -4.9% to 2.2%, P=.44). No significant effect was detected in the subgroup randomized to 25 μg vitamin D or in other preplanned subgroup analyses nor were there any significant differences in handgrip strength or the chair-rising test. Mean serum 25-hydroxyvitamin D3 concentration increased from 27 to 52 nmol/L and from 27 to 43 nmol/L in the 25 and 10 μg supplementation groups, respectively, whereas serum 25-hydroxyvitamin D3 did not change in the placebo group.ConclusionsDaily supplementation with 25 or 10 μg vitamin D3 for 16 weeks did not improve muscle strength or power measured by the jump test, handgrip test, or chair-rising test in this population with low baseline vitamin D status.

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