Table 1.
Data extraction elements
| Category | Items |
|---|---|
| Article characteristics | Names and numbers of authors |
| Title of study | |
| Year of publication | |
| Published journal | |
| 5-year journal impact factor | |
| Number of times article is cited | |
| Types of guideline recommendation | Dietary vitamin D |
| Vitamin D supplements | |
| Recommended serum 25(OH)D level | |
| Vitamin D from sun exposure | |
| Dietary Ca | |
| Ca supplements | |
| Study design | Randomised control trial (RCT) Non-randomised trial |
| Cohort study | |
| Cross-sectional study | |
| Case control study | |
| Systematic review of RCT | |
| Systematic review of non-RCT | |
| Others (e.g. opinion, commentary, editorial, narrative review) | |
| Funding source disclosure | Disclosed funding source |
| Disclosed no funding source | |
| Disclosure missing | |
| Unclear | |
| Author conflict of interest (COI) disclosure | No COI (explicitly stating none) |
| Missing COI declaration | |
| Uncertain | |
| Declared COI in at least one author | |
| Funding source/COI by commercial funding category | Supplement |
| Pharmaceutical | |
| Dairy | |
| Food | |
| Non-dairy | |
| Tanning industry | |
| Other | |
| Funding source/COI by non-commercial funding category | University |
| Government | |
| Other non-profit | |
| Charity/philanthropic organisation | |
| Direction of study conclusion | Favourable to vitamin D/Ca |
| Unfavourable to vitamin D/Ca | |
| Neutral about vitamin D/Ca |