Study | Design | Exposure | Dietary component measured§ | Methodological quality score* | Geographical area | Population |
Aderele13 | Case-control | Plasma | C | 8 | Nigeria | Children |
Anetor14 | Case-control | Serum | C | 6 | Nigeria | Adult |
Arora15 | Case-control | Serum | A | 8 | India | Children |
Baker34† | Case-control | Serum, dietary | A, C, E | 8 | England | Adult |
Bodner36 | Nested case-control | Plasma, dietary | A, C, E | 8 | Scotland | Adult |
Burns49 | Cross-sectional | Dietary | C, E | 5 | USA and Canada | Children |
Cook37 | Cross-sectional | Plasma, dietary | C | 4 | England and Wales | Children |
De Luis16 | Case-control | Dietary | A, C, E | 7 | Spain | Adult |
Fogarty50‡ | Cross-sectional | Serum, dietary | E | 6 | England | Adult |
Ford17 | Cross-sectional | Serum, dietary | A, C, E | 4 | USA | Adult |
Garcia-Larsen43 | Cross-sectional | Dietary | A, C, E | 5 | Chile | Adult |
Gibson18† | Case-control | Serum | A | 7 | Australia | Adult |
Grievink38 | Cross-sectional | Dietary | A, C, E | 5 | Netherlands | Adult |
Hijazi45 | Case-control | Dietary | A, C, E | 7 | Saudi Arabia | Children |
Huang19 | Cross-sectional | Dietary | A, C, E | 5 | Taiwan | Children |
Kalayci20‡ | Case-control | Serum | A, C, E | 7 | Turkey | Children |
Kelly21 | Case-control | Plasma | C, E | 6 | Sweden | Adult |
Kelly39 | Cross-sectional | Serum | A, C, E | 7 | Scotland | Adult |
Kongerud22 | Case-control | Sputum | C, E | 3 | USA | Adult |
Mainous46 | Cross-sectional | Serum | C | 4 | USA | Adult |
Misso23 | Case-control | Serum, dietary | C | 8 | Australia | Adult |
Mizuno24 | Case-control | Serum | C, E | 7 | Japan | Children |
Murray40† | Case-control | Dietary | A, C, E | 7 | England | Children |
Nagel25* | Case-control | Dietary | A, C, E | 7 | Germany | Adult |
Olusi26‡ | Case-control | Serum | C | 5 | Nigeria | Not specified |
Omenaas41 | Cross-sectional | Dietary | C | 5 | Norway | Adult |
Patel35 | Population-based case-control | Dietary | A, C, E | 8 | England | Adult |
Picado27 | Case-control | Serum, dietary | A, C, E | 7 | Spain | Adult |
Powell28† | Cross-sectional | Serum | A, C, E | 6 | England | Children |
Romieu47 | Cross-sectional | Dietary | C | 5 | USA | Children |
Rubin48 | Cross-sectional | Serum | A, C, E | 6 | USA | Children |
Salam44 | Cohort | Dietary | A, C, E | 7 | USA | Children |
Schwartz42 | Cross-sectional | Serum, dietary | A, C | 6 | USA | Any age |
Shaheen29 | Case-control | Dietary | A, C, E | 5 | England | Adult |
Shidfar30 | Case-control | Serum | C | 7 | Iran | Adult |
Soutar51 | Case-control | Dietary | A, C, E | 8 | Scotland | Adult |
Tan-Un31 | Case-control | Serum, dietary | A, E | 6 | China | Adult |
Troisi32 | Cohort | Dietary | A, C, E | 7 | USA | Adult |
Vural33 | Case-control | Serum | C | 4 | Turkey | Adult |
Woods52 | Cross-sectional | Dietary | A, C, E | 5 | Australia | Adult |
*Methodological quality of studies based on the Newcastle-Ottawa Quality Assessment Scale. †Non-parametric data presented in article. ‡Excluded from meta-analysis due to insufficient data. §Constituent of vitamin A or E measured.