Conclusions Vitamin D supplementation  was safe and it protected against acute respiratory tract infection overall .
Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit .
Objectives To assess the overall effect of vitamin D supplementation on  risk of acute respiratory tract infection  , and to identify factors modifying this effect .
Vitamin D3 supplementation and upper respiratory tract infections in a randomized, controlled trial.
BACKGROUND R and omized controlled trials testing the association between vitamin D status and upper respiratory tract infection ( URTI ) have given mixed results . During a multicenter , r and omized controlled trial of colorectal adenoma chemoprevention , we tested whether 1000 IU/day vitamin D(3 ) supplementation reduced winter episodes and duration of URTI and its composite syndromes , influenza-like illness ( ILI ; fever and ≥2 of sore throat , cough , muscle ache , or headache ) and colds ( no fever , and ≥2 of runny nose , nasal congestion , sneezing , sore throat , cough , swollen or tender neck gl and s ) . METHODS The 2259 trial participants were aged 45 - 75 , in good health , had a history of colorectal adenoma , and had a serum 25-hydroxyvitamin D level ≥12 ng/mL. They were r and omized to vitamin D(3 ) ( 1000 IU/day ) , calcium ( 1200 mg/day ) , both , or placebo . Of these , 759 participants completed daily symptom diaries . Secondary data included semiannual surveys of all participants . RESULTS Among those who completed symptom diaries , supplementation did not significantly reduce winter episodes of URTI ( rate ratio [ RR ] , 0.93 ; 95 % confidence interval [ CI ] , .79 - 1.09 ) including colds ( RR , 0.93 ; 95 % CI , .78 - 1.10 ) or ILI ( RR , 0.95 ; 95 % CI , .62 - 1.46 ) , nor did it reduce winter days of illness ( RR , 1.13 ; 95 % CI , .90 - 1.43 ) . There was no significant benefit according to adherence , influenza vaccination , body mass index , or baseline vitamin D status . Semiannual surveys of all participants ( N = 2228 ) identified no benefit of supplementation on ILI ( odds ratio [ OR ] , 1.14 ; 95 % CI , .84 - 1.54 ) or colds ( OR , 1.03 ; 95 % CI , .87 - 1.23 ) . CONCLUSIONS Supplementation with 1000 IU/day vitamin D(3 ) did not significantly reduce the incidence or duration of URTI in adults with a baseline serum 25-hydroxyvitamin D level ≥12
Conclusions Vitamin D supplementation  was safe and it protected against acute respiratory tract infection overall .
Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit .
Objectives To assess the overall effect of vitamin D supplementation on  risk of acute respiratory tract infection  , and to identify factors modifying this effect .