Table 5.
Efficacy of vitamin and antioxidant supplements given singly or combined with other vitamin or antioxidant supplements in prevention of major cardiovascular events in subgroup meta-analysis
| Factor | No of trials | Relative risk (95% CI) | Heterogeneity, I2 (%) | Model |
|---|---|---|---|---|
| All | 50 | 1.00 (0.98 to 1.02) | 42 | Fixed effects |
| Vitamin A: | ||||
| Given singly | NA | — | — | — |
| Combined with others | 2 | 0.98 (0.45 to 2.16) | 87 | Random effects |
| Vitamin B6: | ||||
| Given singly | NA | — | — | — |
| Combined with others | 16 | 0.96 (0.92 to 1.01) | 33 | Fixed effects |
| Low quality trials | 5 | 0.94 (0.73 to 1.21) | 66 | Random effects |
| High quality trials | 11 | 0.96 (0.91 to 1.01) | 1 | Fixed effects |
| Vitamin B12: | ||||
| Given singly | NA | — | — | — |
| Combined with others | 17 | 0.99 (0.95 to 1.02) | 37 | Fixed effects |
| Low quality trials | 5 | 0.94 (0.73 to 1.21) | 66 | Random effects |
| High quality trials | 12 | 0.98 (0.95 to 1.02) | 18 | Fixed effects |
| Folic acid: | ||||
| Given singly | 4 | 1.02 (0.84 to 1.23) | 47 | Fixed effects |
| Combined with others | 17 | 0.99 (0.95 to 1.02) | 37 | Fixed effects |
| Given singly or combined | 21 | 0.99 (0.95 to 1.02) | 35 | Fixed effects |
| Low quality trials | 8 | 0.99 (0.90 to 1.08) | 49 | Fixed effects |
| High quality trials | 12 | 0.98 (0.95 to 1.02) | 18 | Fixed effects |
| Vitamin C*: | ||||
| Given singly | NA | — | — | — |
| Combined with others | 7 | 0.99 (0.94 to 1.06) | 16 | Fixed effects |
| Low quality trials | 4 | 0.99 (0.94 to 1.04) | 44 | Fixed effects |
| High quality trials | 3 | 0.99 (0.88 to 1.11) | 0 | Fixed effects |
| Vitamin D | ||||
| Given singly | 2 | 0.95 (0.86 to 1.05) | 11 | Fixed effects |
| Combined with others | 5 | 1.04 (0.99 to 1.10) | 0 | Fixed effects |
| Given singly or combined | 7 | 1.02 (0.98 to 1.07) | 23 | Fixed effects |
| Low quality trials | 5 | 1.02 (0.98 to 1.08) | 47 | Fixed effects |
| High quality trials | 2 | 1.01 (0.45 to 2.27) | 0 | Fixed effects |
| Vitamin E*: | ||||
| Given singly | 10 | 0.93 (0.85 to 1.01) | 57 | Random effects |
| Combined with others | 7 | 0.99 (0.94 to 1.04) | 15 | Fixed effects |
| Given singly or combined | 17 | 0.97 (0.94 to 1.01) | 44 | Fixed effects |
| Low quality trials | 9 | 0.99 (0.95 to 1.03) | 43 | Fixed effects |
| High quality trials | 8 | 0.95 (0.90 to 1.00)† | 45 | Fixed effects |
| β carotene: | ||||
| Given singly | 5 | 1.02 (0.96 to 1.08) | 31 | Fixed effects |
| Combined with others | 6 | 1.00 (0.81 to 1.23) | 70 | Random effects |
| Given singly or combined | 11 | 1.04 (0.96 to 1.12) | 55 | Random effects |
| Low quality trials | 6 | 0.99 (0.95 to 1.03) | 30 | Fixed effects |
| High quality trials | 5 | 1.13 (0.98 to 1.29) | 64 | Random effects |
| Selenium: | ||||
| Given singly | 3 | 0.34 (0.06 to 2.05) | 70 | Random effects |
| Combined with others | 4 | 0.88 (0.72 to 1.08) | 26 | Fixed effects |
| Given singly or combined | 7 | 0.91 (0.77 to 1.06) | 47 | Fixed effects |
| Low quality trials | 4 | 0.91 (0.73 to 1.12) | 43 | Fixed effects |
| High quality trials | 1 | 0.98 (0.77 to 1.24) | NA | NA |
NA=not applicable.
*For subgroup meta-analysis of vitamin C and vitamin E, we used data from 2008 PHS2 article83 because data were not available in 2012 PHS article.
†P≤0.05.