| 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.