Winter vitamin D3 supplementation does not increase muscle strength, but modulates the IGF-axis in young children
European Journal of Nutrition, pp 1–10. DOI
Mortensen, C., Mølgaard, C., Hauger, H. et al.
- Handgrip strength dropped by 20 percent in the last generation (perhaps due to lower vitamin D) - Feb 2017
- Muscle strength in youth increased with 60,000 IU vitamin D per week and 1 g Calcium – April 2010
- Muscle strength not increased by raising vitamin D to only 30 ng – RCT Aug 2012
- Overview Sports and vitamin D
- More than 40 ng vitamin D for Athletes – July 2010 nice tables
- Slow walking speed of youths 14 times more likely if low vitamin D - Dec 2016
- Vitamin D increased muscle strength by 1% to 19% (varied with dose and duration) – review June 2016
- Poor handgrip strength in 5-year-old girls 3X more likely if low vitamin D – May 2018
800 IU is not nearly enough
- 800 IU of vitamin D got most white Danish children to 20 nanograms – RCT Oct 2016
- Vitamin D needed to get children to just 20 ng in winter 800 IU white skin, 1100 IU dark (Sweden) – RCT June 2017
- Infants getting up to 1600 IU did not increase blood level of vitamin D – RCT March 2016
- Sports benefits from up to 50 ng (click on chart for details)
To explore whether muscle strength, the insulin-like growth factor axis (IGF-axis), height, and body composition were associated with serum 25-hydroxyvitamin D [25(OH)D] and affected by winter vitamin D supplementation in healthy children, and furthermore to explore potential sex differences.
We performed a double-blind, placebo-controlled, dose–response winter trial at 55ºN. A total of 117 children aged 4–8 years were randomly assigned to either placebo, 10, or 20 µg/day of vitamin D3 for 20 weeks. At baseline and endpoint, we measured muscle strength with handgrip dynamometer, fat mass index (FMI), fat free mass index (FFMI), height, plasma IGF-1, IGF-binding protein 3 (IGFBP-3), and serum 25(OH)D.
At baseline, serum 25(OH)D was positively associated with muscle strength, FFMI, and IGFBP-3 in girls only (all p < 0.01). At endpoint, baseline-adjusted muscle strength, FMI and FFMI did not differ between intervention groups. However, baseline-adjusted IGF-1 and IGFBP-3 were higher after 20 µg/day compared to placebo (p = 0.043 and p = 0.006, respectively) and IGFBP-3 was also higher after 20 µg/day compared to 10 µg/day (p = 0.011). Children tended to be taller after 20 µg/day compared to placebo (p = 0.064). No sex interactions were seen at endpoint.
Avoiding the winter-related decline in serum 25(OH)D may influence IGF-1 and IGFBP-3 in children. Larger trials are required to confirm these effects, and the long-term implication for linear growth.