INTERPRETATION Results indicate that vitamin D has a protective effect against RTI , and dosing once-daily seems most effective .
BACKGROUND Low levels of 25-OH vitamin D are associated with  respiratory tract infection ( RTI ) .
However , results from r and omized controlled trials are inconclusive .
Therefore , we performed a systematic review and meta- analysis to assess the preventive effect of vitamin D supplementation on RTI .
Effect of weekly vitamin D supplements on mortality, morbidity, and growth of low birthweight term infants in India up to age 6 months: randomised controlled trial
Objective To investigate whether vitamin D supplementation can decrease the mortality and morbidity of low birthweight infants in low income countries . Design R and omised controlled trial . Setting Large government hospital in New Delhi , India . Participants 2079 low birthweight infants born at term ( > 37 weeks ’ gestation ) . Main outcome measures Primary outcome was admission to hospital or death during the first six months of life . Main secondary outcome was growth . Interventions Weekly vitamin D supplements for six months at a dose of one recommended nutrient intake per day ( 35 µg/week ) . Infants were visited weekly at home for observed supplementation and were brought to the clinic monthly for clinical examination and anthropometric measurements . Results Between group differences were not significant for death or hospital admissions ( 92 among 1039 infants in the vitamin D group v 99 among 1040 infants in the placebo group ; adjusted rate ratio 0.93 , 95 % confidence interval 0.68 to 1.29 ; P=0.68 ) , or referral to the outpatient clinic for moderate morbidity  . Vitamin D supplementation result ed in better vitamin D status as assessed by plasma calcidiol levels at six months . In adjusted analyses , vitamin D treatment significantly increased st and ard deviation ( z ) scores at six months for weight , length , and arm circumference and decreased the proportion of children with stunted growth ( length for age z score ≤2 ) or with arm circumference z scores of 2 or less . Conclusion A weekly dose of vitamin D result ed in better vitamin D status and benefited the classic vitamin D function of bone growth but did not decrease the incidence of severe morbidity or death among young low birthweight infants . Trial registration Clinical Trials.gov NCT00415402
INTERPRETATION Results indicate that vitamin D has a protective effect against RTI , and dosing once-daily seems most effective .
BACKGROUND Low levels of 25-OH vitamin D are associated with  respiratory tract infection ( RTI ) .
However , results from r and omized controlled trials are inconclusive .
Therefore , we performed a systematic review and meta- analysis to assess the preventive effect of vitamin D supplementation on RTI .