The fact that most MAs on results from RCTs did not show a beneficial effect does not disprove the hypothesis suggested by observational findings on adverse health outcomes of low 25OHD levels
Background A large number of observational studies have reported harmful effects of low 25-hydroxyvitamin D ( 25OHD ) levels on non-skeletal outcomes .
We performed a systematic quantitative review on characteristics of r and omized clinical trials ( RCTs ) included in meta-analyses ( MAs ) on non-skeletal effects of vitamin D supplementation .
Vitamin D status has a linear association with seasonal infections and lung function in British adults.
Higher vitamin D concentrations have been proposed as a protective ' seasonal stimulus ' against influenza , and there are suggestions for associations with other aspects of respiratory health . The aim of the present study was to investigate the relationship of current vitamin D status ( measured by 25-hydroxyvitamin D , 25(OH)D ) with  respiratory infections and lung function .  We used cross-sectional data from 6789 participants in the nationwide 1958 British birth cohort who had measurements of 25(OH)D , lung function ( forced expiratory volume in 1 s ( FEV1 ) and forced vital capacity ( FVC ) ) and respiratory infections available from the age of 45 years . In this population , the prevalence of respiratory infections had a strong seasonal pattern in the opposite direction to the pattern for 25(OH)D concentrations . Each 10 nmol/l increase in 25(OH)D was associated with a 7 % lower risk of infection ( 95 % CI 3 , 11 % ) after adjustment for adiposity , lifestyle and socio-economic factors . For FEV1 and FVC , each 10 nmol/l increase in 25(OH)D was associated with 8 ( 95 % CI 3 , 13 ) ml and 13 ( 95 % CI 7 , 20 ) ml higher volume , respectively , after controlling for covariates . Associations of 25(OH)D with FEV1 and FVC were only slightly attenuated after further adjustment for infection and other respiratory illness . In conclusion , vitamin D status had a linear relationship with respiratory infections and lung function . R and omised controlled trials are warranted to investigate the role of vitamin D supplementation on respiratory health and to establish the underlying mechanisms
The fact that most MAs on results from RCTs did not show a beneficial effect does not disprove the hypothesis suggested by observational findings on adverse health outcomes of low 25OHD levels
Background A large number of observational studies have reported harmful effects of low 25-hydroxyvitamin D ( 25OHD ) levels on non-skeletal outcomes .
We performed a systematic quantitative review on characteristics of r and omized clinical trials ( RCTs ) included in meta-analyses ( MAs ) on non-skeletal effects of vitamin D supplementation .