Table 1.
Randomized controlled trials investigating the association between vitamin D supplementation and increased risk of respiratory illness as an outcome
| Author(s) | Year | Sample size and participants | Location | Dose and duration of supplementation | Outcome measure | Strength of association |
| Jorde et al. (93) | 2011 | n = 569 adults 32–84 y old | Norway, Austria, USA, Scotland, Denmark, and Belgium | 1111–6800 IU/d cholecalciferol for at least 12 wk during influenza season | Risk of influenza-like illness, measured by self-report | RR of influenza-like illness1: 0.88 (95%CI: 0.58–1.32) Median increased duration of ILI2: 3 d (P < 0.01) |
| Urashima et al. (12) | 2010 | n = 334 school-children | Japan | One 200-IU tablet cholecalciferol 3 times/d for 120 d | PCR-confirmed influenza A | RR of infection1: 0.58 (95%CI: 0.34–0.99) |
| Li-Ng et al. (22) | 2009 | n = 162 adults 18–80 y old | USA | 2000 IU cholecalciferol/ d for 12 wk | Risk of URTI | RR of URTI1: 0.96 (95%CI: 0.75–1.23) |
| Wejse et al. (100) | 2009 | n = 281 adults with TB | Guinea-Bissau | 100,000 IU of cholecalciferol at inclusion and again at 5 and 8 mo after TB treatment | Clinical severity and mortality of tuberculosis | RR of mortality1: 1.19 (95%CI: 0.58–1.95) |
| Aloia and Li-Ng (14) | 2007 | n = 208 postmenopausal African American women | USA | 800 IU cholecalciferol/d for 2 y, then increased to 2000 IU/d for an additional year (3 y total) | Risk of self-reported cold or influenza | RR of cold or influenza1: 0.31 (95%CI: 0.15–0.65) |
| Avenell et al. (92) | 2007 | n = 3444 adults ≥70 y old | England and Scotland | 800 IU/d cholecalciferol, 1000 mg calcium, both, or placebo, for 24–62 mo | Risk of any infection, measured by self-report | Relative odds of any infection1: 0.90 (95%CI: 0.76–1.07) |
| Martineau et al. (78) | 2007 | n = 131 adults >17 y old | England | Single dose of 100,000 IU ergocalciferol at beginning of study | Immunity to TB mycobacteria measured by BCG-lux luminescence ratio at 24 h postinfection | Relative increase in immunity3: 20.4% (95%CI: 1–25%) |
| Nursyam et al. (17) | 2006 | n = 67 TB patients 15–59 y old with moderately advanced TB lesions | Indonesia | 10,000 IU vitamin D (unspecified)/d | Rate of sputum conversion | Relative odds of conversion4: 1.32 (95%CI: 1.09–1.60) |
| Morcos et al. (18) | 1998 | n = 24 children with TB, 1–13 y old | Egypt | 1000 IU cholecalciferol/d for the length of tuberculosis treatment | Concentration of serum vitamin D in supplemented vs. unsupplemented groups | Difference in vitamin D (pg/mL) between supplemented and unsupplemented groups was not significant (data not shown) |
| Rehman (102) | 1994 | n = 47 children 3–12 y old | India | 60,000 IU vitamin D (unspecified)/wk for 6 wk, plus 650 mg calcium/d | Frequency of any infection in children | No difference in frequency seen between supplemented and control groups (data not shown) |
RR refers to the risk of illness while being supplemented with vitamin D compared with being supplemented with placebo. TB, tuberculous; URTI, upper respiratory tract infection.
“Relative increase in duration” refers to the extra number of days that participants in the placebo group reported experiencing ILI symptoms, compared with the number of days that supplemented participants reported; -value is a chi-square value comparing the 2 proportions.
“Relative increase” refers to the increase in immunity in vitamin D-supplemented compared with placebo-supplemented participants.
“Relative conversion” refers to the conversion proportion of vitamin D-supplemented compared with conversion proportion of placebo-supplemented participants.