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 .
Treatment of Vitamin D Deficiency Increases Lower Limb Muscle Strength in Institutionalized Older People Independently of Regular Physical Activity: A Randomized Double-Blind Controlled Trial
Aims : To investigate the effects of a 6-month supplementation with calcium and cholecalciferol on biochemical parameters and muscle strength of institutionalized elderly . Methods : This prospect i ve , double-blind , placebo-controlled , r and omized trial included Brazilian institutionalized people ≥60 years of age receiving a 6-month supplementation ( December to May ) of daily calcium plus monthly placebo ( calcium/placebo group ) or daily calcium plus oral cholecalciferol ( 150,000 IU once a month during the first 2 months , followed by 90,000 IU once a month for the last 4 months ; calcium/vitamin D group ) . Fasting blood sample s for 25(OH)D , PTH and calcium determination were collected ( n = 56 ) and muscle tests were performed ( n = 46 ) to measure the strength of hip flexors ( SHF ) and knee extensors ( SKE ) before ( baseline ) and after the 6-month intervention ( 6 months ) . Results : Due to seasonal variations , serum 25(OH)D significantly enhanced in both groups after treatment , but the calcium/vitamin D group had significantly higher 25 (OH)D levels than the calcium/placebo group ( 84 vs. 33 % , respectively ; p < 0.0001 ) . No cases of hypercalcemia were observed . While the calcium/placebo group showed no improvement in SHF and SKE at 6 months ( p = 0.93 and p = 0.61 , respectively ) , SHF was increased in the calcium/vitamin D group by 16.4 % ( p = 0.0001 ) and SKE by 24.6 % ( p = 0.0007 ) . Conclusions : The suggested cholecalciferol supplementation was safe and efficient in enhancing 25(OH)D levels and lower limb muscle strength in the elderly , in the absence of any regular physical exercise practice
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 .