Background: There are numerous guidelines developed for bone health. Yet, it is unclear whether the differences in guideline development methods explain the variability in the recommendations for vitamin D and calcium intake. The objective of this systematic review was to collate and compare recommendations for vitamin D and calcium across bone health guidelines, assess the methods used to form the recommendations, and explore which methodological factors were associated with these guideline recommendations. Methods: We searched MEDLINE, EMBASE, CINAHL, and other databases indexing guidelines to identify records in English between 2009 and 2019. Guidelines or policy statements on bone health or osteoporosis prevention for generally healthy adults aged ≥40 years were eligible for inclusion. Two reviewers independently extracted recommendations on daily vitamin D and calcium intake, supplement use, serum 25 hydroxyvitamin D [25(OH)D] level, and sunlight exposure. They assessed guideline development methods against 25 recommended criteria in the World Health Organization (WHO) handbook for guideline development. Additionally, they identified types of evidence underpinning the recommendations. Results: we included 47 eligible guidelines from 733 records: 74% of the guidelines provided vitamin D (200~600–4000 IU/day) and 70% provided calcium (600–1200 mg/day) recommendations, 96% and 88% recommended vitamin D and calcium supplements, respectively, and 70% recommended a specific 25(OH)D concentration. On average, each guideline met 10 (95% CI: 9–12) of the total of 25 methodological criteria for guideline development recommended by the WHO Handbook. There was uncertainty in the association between the methodological criteria and the proportion of guidelines that provided recommendations on daily vitamin D or calcium. Various types of evidence, including previous bone guidelines, nutrient reference reports, systematic reviews, observational studies, and perspectives/editorials were used to underpin the recommendations. Conclusions: There is considerable variability in vitamin D and calcium recommendations and in guideline development methods in bone health guidelines. Effort is required to strengthen the methodological rigor of guideline development and utilize the best available evidence to underpin nutrition recommendations in evidence-based guidelines on bone health.

Objective: The present study aims to examine the relationship between study funding sources, author conflicts of interest and conclusions in studies supporting vitamin D and calcium intake cited in bone health guideline recommendations. Design: Cross-sectional Setting: 47 global bone health guidelines with vitamin D and/or calcium recommendations for adults aged 40 years and above Participants: The evidence cited to support the recommendations was extracted by two independent reviewers and classified by type of recommendation, article characteristics, study design, types of funding sources and conflict of interest (COI) disclosure and direction of study conclusions. Results: Of 156 articles cited to support the bone health recommendations, 120 (77%) disclosed a funding source, and 43 (28%) declared that at least one author had a COI. Compared with articles with non-commercial or no funding source, those funded by commercial sponsors tended to have a study conclusion favourable towards vitamin D/calcium [RR (95% CI): 1.32 (0.94, 1.87), p = 0.16], but the association was not statistically significant (Fisher’s exact test). Compared to those with a COI disclosure statement, articles with missing or unclear COI disclosure were more likely to have favourable conclusions [1.56 (1.05, 2.31), p = 0.017] (Fisher’s exact test). Conclusion: In the evidence underpinning a sample of global bone health guidelines, COI disclosure was low and studies with missing or unclear COI disclosures were more likely to have favourable study conclusions than those with disclosures, suggesting a need for greater transparency of COI in bone health guidelines.

There are numerous guidelines developed for bone health. Yet it is unclear the differences in guideline development methods explain the variability in recommendations for vitamin D and calcium intakes. The objective of this systematic review was to collate and compare recommendations for vitamin D and calcium across bone health guidelines, assess methods used to form the recommendations, and explore which methodological factors were associated with these guideline recommendations. We searched MEDLINE, EMBASE, CINAHL and other databases indexing guidelines to identify records in English between 2009 and 2019. Guidelines or policy statements on bone health or osteoporosis prevention for generally healthy adults aged ≥40 years were eligible for inclusion. Two reviewers independently extracted recommendations on daily vitamin D and calcium intake, supplement use, serum 25 hydroxy vitamin D [25(OH)D] level, and sunlight exposure; assessed guideline development methods against 25 recommended criteria in the World Health Organization (WHO) Handbook for Guideline Development; and, identified types of evidence underpinning the recommendations. We included 47 eligible guidelines from 733 records: 74% of the guidelines provided vitamin D (200∼600-4000 IU/day) and 70% provided calcium (600-1200 mg/day) recommendations; 96% and 88% recommended vitamin D and calcium supplements, respectively; and 70% recommended a specific 25(OH)D concentration. The mean of meeting 25 WHO methodological criteria per guideline was 10 (95% CI: 9-12; interquartile range: 6-15). There was uncertainty in the associations between the methodological criteria and the proportion of guidelines that provided recommendations on daily vitamin D or calcium. Various types of evidence, ranging from previous bone guidelines, nutrient reference reports, systematic reviews, observational studies, to perspectives/editorials were used to underpin the recommendations. In conclusion, there is considerable variability in vitamin D and calcium recommendation and in guideline development methods in bone health guidelines. Effort is required to strengthen methodological rigor of guideline development and utilize the best available evidence to underpin public health nutrition.HighlightsThis systematic review provides evidence on the variabilities in vitamin D and calcium recommendations as well as guideline development methods in 47 bone health guidelines globally.Our findings point to continued effort to utilize the best available evidence to underpin nutrition recommendations and strengthen methodological rigor of guideline development in bone health guidelines.Registration of protocolPROSPERO: CRD42019126452