Influence of vitamin D supplementation by simulated sunlight or oral D3 on respiratory infection during military training

Harrison, Sophie, Oliver, Samuel J., Kashi, Daniel S., Carswell, Alexander T., Edwards, Jason P., Wentz, Laurel M., Roberts, Ross, Tang, Jonathan C Y, Izard, Rachel M., Jackson, Sarah, Allan, Donald, Rhodes, Lesley E., Fraser, William, Greeves, Julie P. and Walsh, Neil P. (2021) Influence of vitamin D supplementation by simulated sunlight or oral D3 on respiratory infection during military training. Medicine and Science in Sports and Exercise. ISSN 0195-9131

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Purpose: To determine the relationship between vitamin D status and upper respiratory tract infection (URTI) of physically active men and women across seasons (study 1). Then, to investigate the effects on URTI and mucosal immunity of achieving vitamin D sufficiency (25(OH)D ≥50 nmol·L-1) by a unique comparison of safe, simulated-sunlight or oral D3 supplementation in winter (study 2). Methods: In study 1, 1,644 military recruits were observed across basic military training. In study 2, a randomized controlled trial, 250 men undertaking military training received either placebo, simulated-sunlight (1.3x standard erythemal dose, three-times-per-week for 4-weeks and then once-per-week for 8-weeks) or oral vitamin D3 (1,000 IU·day-1 for 4-weeks and then 400 IU·day-1 for 8-weeks). URTI was diagnosed by physician (study 1) and Jackson common cold questionnaire (study 2). Serum 25(OH)D, salivary secretory immunoglobulin A (SIgA) and cathelicidin were assessed by LC-MS/MS and ELISA. Results: In study 1, only 21% of recruits were vitamin D sufficient during winter. Vitamin D sufficient recruits were 40% less likely to suffer URTI than recruits with 25(OH)D <50 nmol·L-1 (OR (95% CI) = 0.6 (0.4–0.9)); an association that remained after accounting for sex and smoking. Each URTI caused on average 3 missed training days. In study 2, vitamin D supplementation strategies were similarly effective to achieve vitamin D sufficiency in almost all (≥95%). Compared to placebo, vitamin D supplementation reduced the severity of peak URTI symptoms by 15% and days with URTI by 36% (P < 0.05). These reductions were similar with both vitamin D strategies (P > 0.05). Supplementation did not affect salivary SIgA or cathelicidin. Conclusion: Vitamin D sufficiency reduced the URTI burden during military training.

Item Type: Article
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: LivePure Connector
Date Deposited: 13 Jan 2021 00:54
Last Modified: 10 May 2021 00:11
DOI: 10.1249/MSS.0000000000002604

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