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The effects of vitamin D3 supplementation on serum total 25[OH]D concentration and physical performance: a randomised dose–response study
  1. Graeme L Close1,
  2. Jill Leckey1,
  3. Marcelle Patterson1,
  4. Warren Bradley1,
  5. Daniel J Owens1,
  6. William D Fraser2,
  7. James P Morton1
  1. 1Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
  2. 2Faculty of Medicine and Health Sciences, Norwich Medical School, University of East Anglia, Norwich, UK
  1. Correspondence to Dr Graeme L Close, Research Institute for Sport and Exercise Sciences, Tom Reilly Building, Byrom St Campus, Liverpool John Moores University, Liverpool L3 3AF, UK; g.l.close{at}


Background Vitamin D deficiency is common in the general public and athletic populations and may impair skeletal muscle function. We therefore assessed the effects of vitamin D3 supplementation on serum 25[OH]D concentrations and physical performance.

Methods 30 club-level athletes were block randomised (using baseline 25[OH]D concentrations) into one of three groups receiving either a placebo (PLB), 20 000 or 40 000 IU/week oral vitamin D3 for 12 weeks. Serum 25[OH]D and muscle function (1-RM bench press and leg press and vertical jump height) were measured presupplementation, 6 and 12 weeks postsupplementation. Vitamin D deficiency was defined in accordance with the US Institute of Medicine guideline (<50 nmol/l).

Results 57% of the subject population were vitamin D deficient at baseline (mean±SD value 51±24 nmol/l). Following 6 and 12 weeks supplementation with 20 000 IU (79±14 and 85±10 nmol/l, respectively) or 40 000 IU vitamin D3 (98±14 and 91±24 nmol/l, respectively), serum vitamin D concentrations increased in all participants, with every individual achieving concentrations greater than 50 nmol/l. In contrast, vitamin D concentration in the PLB group decreased at 6 and 12 weeks (37±18 and 41±22 nmol/l, respectively). Increasing serum 25[OH]D had no significant effect on any physical performance parameter (p>0.05).

Conclusions Both 20 000 and 40 000 IU vitamin D3 supplementation over a 6-week period elevates serum 25[OH]D concentrations above 50 nmol/l, but neither dose given for 12 weeks improved our chosen measures of physical performance.

  • Sports and nutrition
  • Supplements
  • Nutrition
  • Muscle metabolism

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