title: Vitamin D Supplementation and Physical Performance in Adolescent Swimmers.
abstract: It is hypothesized that vitamin D insufficiency in athletes might negatively affect sport performance. The objective of this study was to examine the effect of vitamin D3 supplementation on physical performance of adolescent swimmers with vitamin D insufficiency. Fifty-three adolescent competitive swimmers with vitamin D insufficiency (serum 25-hydroxyvitamin-D concentrations (25(OH)D) < 30 ng/ml, mean 24.2 ± 4.8 ng/ml) were randomized to receive 2,000 IU/day of vitamin D3 or placebo for 12 weeks. Swimming performance at several speeds, arm-grip strength, and one-legged balance, were measured before and after supplementation. The age-adjusted changes in performance variables during the study were compared between groups. 25(OH) D concentrations at study end were significantly higher in the vitamin group compared with the placebo group (29.6 ± 6.5 ng/ml vs. 20.3 ± 4.2 ng/ml, p < .001), yet only 48% of the vitamin group became vitamin D sufficient with this dosing. No between-group differences were found in the changes of the performance variables tested. No significant differences in performance were found between participants that became vitamin D sufficient, and those who did not. No significant correlation was found between the change in serum 25(OH)D and age-adjusted balance, strength or swimming performance at study end. Vitamin D3 supplementation that raised serum 25(OH)D concentrations by a mean of 9.3 ng/ml above placebo in adolescent swimmers with vitamin D insufficiency, did not improve physical performance more than placebo.
authors.affiliation: Exercise, Nutrition and Lifestyle Clinic, The Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Tel Hashomer, Israel.
authors.forename: Gal
authors.initials: G
authors.lastname: Dubnov-Raz
authors.forename: Netachen
authors.initials: N
authors.lastname: Livne
authors.forename: Raanan
authors.initials: R
authors.lastname: Raz
authors.forename: Avner H
authors.initials: AH
authors.lastname: Cohen
authors.forename: Naama W
authors.initials: NW
authors.lastname: Constantini
mesh_terms: D000293:Adolescent; D017195:Adolescent Nutritional Physiological Phenomena; D054874:Athletic Performance; D002112:Calcifediol / Q000097:blood; D002648:Child; D002664:Child Nutritional Physiological Phenomena; D002762:Cholecalciferol / Q000627:therapeutic use*; D015331:Cohort Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007557:Israel; D008297:Male; D053580:Muscle Strength; D004856:Postural Balance; D012720:Severity of Illness Index; D064133:Sports Nutritional Physiological Phenomena; D013550:Swimming; D014808:Vitamin D Deficiency / Q000097:blood / Q000178:diet therapy* / Q000503:physiopathology
chemical_list: D002762:Cholecalciferol; D002112:Calcifediol