Table 5.
Effect of vitamin C supplementation in major randomized controlled trials. Major limitations of the presented studies are that they mostly i) allowed concurrent supplementation in the placebo group, ii) included vitamin C sufficient individuals and iii) used multi-vitamin supplements with inadequate amounts of vitamin C.
| Study | Linxian Study [88] | Heart Protection Study [75] | Physicians Health Study II [76] | SU.VI.MAX Study [90] | Women's Antioxidant Cardiovascular Study [74] |
|---|---|---|---|---|---|
| Population | 29,584 men and women from Linxian County, Henan Province, China, aged ≥40 yrs | 20,536 British men and women aged ≥40 yrs with CHD or other occlusive arterial disease or diabetes | 14,641 US male physicians age ≥50 yrs | 13,017 French men and women aged ≥35 yrs | 8171 US women aged ≥40 yrs and with prior CVD or high risk |
| Design | ½ (2 × 2 x 2 × 2) | 2 × 2 | 2 × 2 ( × 2 × 2) | Parallel | 2 × 2 × 2 |
| VitC conc at entry (μmol/L) | 11.4a | Not reported | Not reported | 54.5 | Not reported |
| VitC conc in placebos (μmol/L) | 30.7 | 43.2 | Not reported | 58.0 | 71.5 |
| VitC group vs placebo (Δμmol/L) | 15.3 | +15.7b | Not reported | +11.3c | +35.2d |
| Fasted blood samples (Yes/No) | Not reported | No | Not reported | Yes | Not reported |
| Subjects allowed to take concurrent supplements (placebos taking suppl.) | Not reported | Yes, but not high dose vitE (Not reported) | Yes, up to the RDA (4.4% for 1 month/yr or more) | No | Yes, up to the RDA (27.5%) |
| Intervention | Various vitamin/mineral combinations including Vitamin C (120 mg/d) + Mo | Multivitamin containing Vitamin C (250 mg/d) | Vitamin C (500 mg/d) or other antioxidants | Multivitamin containing Vitamin C (120 mg/d). | Vitamin C (500 mg/d) or other antioxidants |
| Study period (years) | 5.25 | 5 | 8 | 7.5 | 9.4 |
| Endpoint | Mortality and cancer incidence | Major coronary events and fatal or non-fatal vascular events | Cardiovascular events, myocardial infarction, stroke, or CVD death | Ischemic cardiovascular disease and all-cause mortality | Myocardial infarction, stroke, coronary revascularization, or CVD death |
| Outcome | No effect of vitamin C + Mo supplementation | No effect of vitamin C supplementation | No effect of vitamin C supplementation | No effect on CVD but lower all-cause mortality in men | No effect of vitamin C supplementation |
Assessed in a98 individuals, babout 5% of the participants, can unselected subsample, d30 local participants. Abbreviations: CVD, cardiovascular disease; Mo, molybdenum.