Pediatric Exercise Science, 2015, 27, 113-119 http://dx.doi.org/10.1123/pes.2014-0030 © 2015 Human Kinetics, Inc.
Vitamin D Supplementation and Upper Respiratory Tract Infections in Adolescent Swimmers: A Randomized Controlled Trial Gal Dubnov-Raz
Barak Rinat
Edmond and Lily Safra Children’s Hospital
Hadassah Medical Center
Harri Hemilä
Lauryn Choleva
University of Helsinki
Tel Aviv University
Avner H. Cohen
Naama W. Constantini
Clalit Health Services
Hadassah Medical Center
Observational studies identified associations between vitamin D insufficiency (serum 25(OH)D < 30ng·ml–1) and risk of upper respiratory infection (URI). Swimmers are highly prone to URIs, which might hinder their performance. The aim of this study was to examine if vitamin D3 supplementation reduces URI burden in vitamin D-insufficient swimmers. Fifty-five competitive adolescent swimmers with vitamin D insufficiency were randomized to receive vitamin D3 (2,000IU·d·1) or placebo for 12 winter weeks. A URI symptom questionnaire was completed weekly. Serum 25(OH)D concentrations were measured by radio-immunoassay before and after supplementation. We used linear regression to examine the relation between the change in 25(OH)D concentrations during the trial, and the duration and severity of URIs. There were no between-group differences in the frequency, severity, or duration of URIs. Exploratory analyses revealed that in the placebo group only, the change in 25(OH)D concentrations during the trial was highly associated with the duration of URIs (r = –0.90,p < .001), and moderately associated with the severity of URIs (r = –0.65,p = .043). The between-group differences for duration were highly significant. Vitamin D3 supplementation in adolescent swimmers with vitamin D insufficiency did not reduce URI burden. However, larger decreases in serum 25(OH)D concentrations were associated with significantly longer and more severe URI episodes. Keywords: cholecalciferol, cold, swimming, athletes, pediatrics Upper respiratory tract infections (URIs) are among the most common causes of global disease (13). Very few established methods to prevent or treat URIs are available. Vitamin D plays a vital role in many physiological processes, including the activity of the immune system (14). Dubnov-Raz is with the Exercise, Lifestyle and Nutrition Clinic, Edmond and Lily Safra Children’s Hospital, Tel Hashomer, Israel. Rinat is with the Hadassah Medical Center, Jerusalem, Israel. Hemilä is with the Dept. of Public Health, University of Helsinki, Helsinki, Finland. Choleva is with the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. Cohen is with the Pediatric Ambulatory Center, Clalit Health Services, PetahTikva, Israel. Constantini is with the Dept. of Orthopedics, Hadassah Medical Center, Jerusalem, Israel. Address author correspondence to Gal Dubnov-Raz at [email protected].
A negative correlation between vitamin D concentrations and the risk of URIs had been previously identified. In several studies, it was found that serum 25-hydroxyvitamin D (25(OH)D) concentrations below 30 ng·ml–1 (i.e., vitamin D insufficiency) were associated with a higher URI risk (8,12,16,22,23). Few controlled trials of vitamin D supplementation and URI risk or severity have been published. The results of these studies showed either some protective effect (4,25) or no significant effect (17,19–21). In a recent systematic review on the associations between vitamin D status and risk of URIs, the results from randomized controlled trials were summarized as conflicting (15). The authors recommended additional supplementation studies in populations with a high prevalence of vitamin D deficiency at baseline, and using doses sufficient to induce a sustained elevation of serum 25(OH)D concentrations. 113
Downloaded by Univ of Hong Kong Libraries on 09/16/16, Volume 27, Article Number 1
114 Dubnov-Raz et al.
Athletes training indoors, such as swimmers, dancers, gymnasts and basketball players, have a high prevalence of both vitamin D insufficiency (serum 25(OH)D
Vitamin D Supplementation and Upper Respiratory Tract Infections in Adolescent Swimmers: A Randomized Controlled Trial Gal Dubnov-Raz
Barak Rinat
Edmond and Lily Safra Children’s Hospital
Hadassah Medical Center
Harri Hemilä
Lauryn Choleva
University of Helsinki
Tel Aviv University
Avner H. Cohen
Naama W. Constantini
Clalit Health Services
Hadassah Medical Center
Observational studies identified associations between vitamin D insufficiency (serum 25(OH)D < 30ng·ml–1) and risk of upper respiratory infection (URI). Swimmers are highly prone to URIs, which might hinder their performance. The aim of this study was to examine if vitamin D3 supplementation reduces URI burden in vitamin D-insufficient swimmers. Fifty-five competitive adolescent swimmers with vitamin D insufficiency were randomized to receive vitamin D3 (2,000IU·d·1) or placebo for 12 winter weeks. A URI symptom questionnaire was completed weekly. Serum 25(OH)D concentrations were measured by radio-immunoassay before and after supplementation. We used linear regression to examine the relation between the change in 25(OH)D concentrations during the trial, and the duration and severity of URIs. There were no between-group differences in the frequency, severity, or duration of URIs. Exploratory analyses revealed that in the placebo group only, the change in 25(OH)D concentrations during the trial was highly associated with the duration of URIs (r = –0.90,p < .001), and moderately associated with the severity of URIs (r = –0.65,p = .043). The between-group differences for duration were highly significant. Vitamin D3 supplementation in adolescent swimmers with vitamin D insufficiency did not reduce URI burden. However, larger decreases in serum 25(OH)D concentrations were associated with significantly longer and more severe URI episodes. Keywords: cholecalciferol, cold, swimming, athletes, pediatrics Upper respiratory tract infections (URIs) are among the most common causes of global disease (13). Very few established methods to prevent or treat URIs are available. Vitamin D plays a vital role in many physiological processes, including the activity of the immune system (14). Dubnov-Raz is with the Exercise, Lifestyle and Nutrition Clinic, Edmond and Lily Safra Children’s Hospital, Tel Hashomer, Israel. Rinat is with the Hadassah Medical Center, Jerusalem, Israel. Hemilä is with the Dept. of Public Health, University of Helsinki, Helsinki, Finland. Choleva is with the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. Cohen is with the Pediatric Ambulatory Center, Clalit Health Services, PetahTikva, Israel. Constantini is with the Dept. of Orthopedics, Hadassah Medical Center, Jerusalem, Israel. Address author correspondence to Gal Dubnov-Raz at [email protected].
A negative correlation between vitamin D concentrations and the risk of URIs had been previously identified. In several studies, it was found that serum 25-hydroxyvitamin D (25(OH)D) concentrations below 30 ng·ml–1 (i.e., vitamin D insufficiency) were associated with a higher URI risk (8,12,16,22,23). Few controlled trials of vitamin D supplementation and URI risk or severity have been published. The results of these studies showed either some protective effect (4,25) or no significant effect (17,19–21). In a recent systematic review on the associations between vitamin D status and risk of URIs, the results from randomized controlled trials were summarized as conflicting (15). The authors recommended additional supplementation studies in populations with a high prevalence of vitamin D deficiency at baseline, and using doses sufficient to induce a sustained elevation of serum 25(OH)D concentrations. 113
Downloaded by Univ of Hong Kong Libraries on 09/16/16, Volume 27, Article Number 1
114 Dubnov-Raz et al.
Athletes training indoors, such as swimmers, dancers, gymnasts and basketball players, have a high prevalence of both vitamin D insufficiency (serum 25(OH)D
