Methodological quality of public health guideline recommendations on vitamin D and calcium: a systematic review protocol

Introduction: Current recommendations for vitamin D and calcium in dietary guidelines and bone health guidelines vary significantly among countries and professional organisations. It is unknown whether the methods used to develop these recommendations followed a rigourous process and how the differences in methods used may affect the recommended intakes of vitamin D and calcium. The objectives of this study are (1) collate and compare recommendations for vitamin D and calcium across guidelines, (2) appraise methodological quality of the guideline recommendations and (3) identify methodological factors that may affect the recommended intakes for vitamin D and calcium. This study will make a significant contribution to enhancing the methodological rigour in public health guidelines for vitamin D and calcium recommendations. Methods and analyses: We will conduct a systematic review to evaluate vitamin D and calcium recommendations for osteoporosis prevention in generally healthy middle-aged and older adults. Methodological assessment will be performed for each guideline against those outlined in the 2014 WHO handbook for guideline development. A systematic search strategy will be applied to locate food-based dietary guidelines and bone health guidelines indexed in various electronic databases, guideline repositories and grey literature from 1 January 2009 to 28 February 2019. Descriptive statistics will be used to summarise the data on intake recommendation and on proportion of guidelines consistent with the WHO criteria. Logistic regression, if feasible, will be used to assess the relationships between the methodological factors and the recommendation intakes. Ethics and dissemination: Ethics approval is not required as we will only extract published data or information from the published guidelines. Results of this review will be disseminated through conference presentations and peer-reviewed publications. PROSPERO registration number: CRD42019126452.