College swimmers helped by daily 5,000 IU of Vitamin D in the fall – RCT

Created February 2020

Effects of Seasonal Vitamin D3 Supplementation on Strength, Power, and Body Composition in College Swimmers

Int J Sport Nutr Exerc Metab, 1-9 2020 Feb 4, DOI: 10.1123/ijsnem.2019-0250

Michelle S Rockwell 1, Madlyn I Frisard 1, Janet W Rankin 1, Jennifer S Zabinsky 1, Ryan P Mcmillan 1, Wen You 1, Kevin P Davy 1, Matthew W Hulver 1

* NCAA trainers are getting on board the Vitamin D train (40-50 ng)– Nov 2019 * Vitamin D is not considered to be doping * Athletes helped by weekly 50,000 IU Vitamin D – RCT Aug 2019 * 4,000 IU of Vitamin D is OK - 19 organizations agree - 2018 * Need 40 to 60 ng of Vitamin D – 48 scientists call for action – 2015 Indoor Athletes have lower Vitamin D levels * NFL team less likely to cut players with high levels of vitamin D – Feb 2015 * NHL discovers Vitamin D – their ideal is 40-120 ng – 2016 * Every single Taekwondo (indoor) Korean teen had low Vitamin D – Sept 2019 * Dark skinned NCAA basketball players were 15X more likely to have low vitamin D – Feb 2014 Overview Sports and vitamin D has the following summary {include} Sports category in VitaminDWiki starts with {include} The Meta-analysis of Sports and Vitamin D are listed here: {category}

The purpose of this study was to evaluate the impact of fall season vitamin D3 supplementation on strength/power, body composition, and anabolic hormones in swimmers with optimal vitamin D status at summer's end. Male and female National Collegiate Athletic Association Division I swimmers (N = 19) with optimal 25-hydroxyvitamin D [25(OH)D] randomly received 5,000 IU of vitamin D3 (VITD) or placebo (PLA) daily for 12 weeks while participating in swimming and strength and conditioning training (August-November). Before and after the intervention, the participants underwent blood sampling for analysis of serum 25(OH)D, parathyroid hormone, total testosterone, free testosterone, sex hormone-binding globulin, and insulin-like growth factor 1, dual-energy X-ray absorptiometry, and strength/power testing (bench press, squat, dead lift, standing broad jump, vertical jump, and dips and pull-ups). Sex was used as a covariate for analyses.

  • The 25(OH)D was decreased by 44% in PLA (p < .05) and increased by 8% in VITD over the 12 weeks.

  • Fat-free mass increased in VITD (56.4-59.1 kg; p < .05), but not PLA (59.4-59.7 kg; p < .01).

    • Appears that added 2.7 kg of muscle if take Vitamin D, but only added 0.3 kg if placebo

  • Significant Group × Time interaction effects were observed for dead lift (F = 21.577, p < .01) and vertical jump (F = 11.219, p < .01), but no other strength/power tests.

  • Total testosterone decreased similarly in both groups, but free testosterone decreased and sex hormone-binding globulin increased only in PLA (p < .01).

  • There were no group differences or changes in insulin-like growth factor 1 with the intervention.

The findings suggest that vitamin D supplementation is an efficacious strategy to maintain 25(OH)D during the fall season training and to enhance some aspects of strength/power and fat-free mass in swimmers. Further research on the relationship between vitamin D and anabolic hormones is needed.

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Tags: Intervention Sports