Table 2.
Summary of recent RCTs investigating the effect of vitamin D supplementation on RTIs in adults.
| References | Study population | Study type | Intervention | Infection definition/form | Main findings |
|---|---|---|---|---|---|
| Arihiro et al. (32) | n = 223 patients with inflammatory bowel disease | 6-month multicenter double-blind, placebo-controlled RCT | 500 IU (12.5 μg) vitamin D or control daily | Influenza infection diagnosed using influenza virus test kits. | Incidence of URTI was significantly lower in the vitamin D group (RR 0.59; 95% CI, 0.35–0.98) |
| Form: Viral | |||||
| Slow et al. (33) | n = 60 vitamin D group, n = 57 placebo | 6-week randomized, double-blind, placebo-controlled trial | Single high-dose vitamin D3 (200,000 IU) | Pneumonia that has been acquired outside of a hospital or health care setting. | Vitamin D increased the complete resolution of pneumonia in participants with baseline vitamin D levels <25 nmol/L (OR 17.0, 95% CI 1.40–549.4), but this was of modest statistical significance (p = 0.043) |
| Form: Not specified | |||||
| Jung et al. (34) | n = 25 male taekwondo athletes aged 19–22 years | 4-week double-blind, placebo-controlled RCT | 5,000 IU (125 μg) vitamin D3 or control daily | The Wisconsin Upper Respiratory Symptom Survey-11 (WURSS-11) was used. | Serum 25(OH)D levels increased by 256% and were inversely associated with total URTI symptoms (r = −0.435, p = 0.015) |
| Form: Not specified | |||||
| Ramos-Martinez et al. (35) | n = 86 patients with asthma aged 18–50 years | 6-month double-blind, placebo-controlled RCT | 10 IU (0.25 μg) calcitriol (1,25-(OH)2D3) or control daily | Respiratory infections in asthmatic patients. | Vitamin D supplementation reduced RTIs and reduced airways colonization by pathogenic bacteria |
| Form: Bacterial | |||||
| Shimizu et al. (36) | n = 428, aged 45–74 years | 16-week double-blind, placebo-controlled RCT | 400 IU (10 μg) vitamin D or control daily. | The Japanese version of Wisconsin Upper Respiratory Symptom Survey-21 (WURSS21) was used. | Vitamin D reduces the duration of URTI, the physical severity of URTI, and the quality of life when suffering from URTI |
| Form: Not specified | |||||
| Ginde et al. (37) | n = 107 longer-term care residents, aged over 60 years | 12-month double-blind, parallel group, randomized controlled phase II trial | High dose (3,000–4,000 IU/75–100 μg day) or standard dose (400–1,000 IU/10–25 μg day). | Measured both upper (common colds, sinusitis, pharyngitis, otitis media) and lower (acute bronchitis, influenza, pneumonia) ARIs that required medical attention | The high-dose group had 0.67 ARIs per person-year compared to 1.11 in the standard dose group (incidence rate ratio 0.60; 95% CI 0.38–0.94; p= 0.02) |
| Form: Not specified | |||||
| He et al. (38) | n = 39 athletes during winter training | 14-week placebo-controlled RCT | 5,000 IU (125 μg) vitamin D or control daily | Measured changes in antimicrobial peptides. | Blood and salivary analyses showed that serum 25(OH)D levels increased by 130% and vitamin D increased SIgA and cathelicidin, which could improve resistance to respiratory infections |
| Form: Bacterial |
UPTI, upper respiratory tract infection; CI, confidence interval; OR odds ratio.