Influence of Vitamin D Supplementation by Simulated Sunlight or Oral D3 on Respiratory Infection during Military Training
Medicine & Science in Sports & Exercise: doi: 10.1249/MSS.0000000000002604
Harrison, Sophie E.1; Oliver, Samuel J.1; Kashi, Daniel S.1,2; Carswell, Alexander T.1,3; Edwards, Jason P.1,2; Wentz, Laurel M.1,4; Roberts, Ross1; Tang, Jonathan C. Y.3; Izard, Rachel M.5,6; Jackson, Sarah7; Allan, Donald8; Rhodes, Lesley E.9; Fraser, William D.3,10; Greeves, Julie P.3,7,11; Walsh, Neil P.2
1,000 IU of vitamin D daily for 4 weeks then 400 IU daily for 8 weeks
Note by Vitamin D Life:
probably get similar benefit by taking a 50,000 IU capsule once a month
Increasing the dose frequency to bi-weekly has been proven to prevent/treat 18 other health problems and is expected to reduce incidence of COVID-19
Download the PDF from Vitamin D Life
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.