Many large population studies have found that people who consume the most vitamin C from foods have a reduced risk of heart disease and various cancers. Some population studies have found similar protective effects from C or E supplements. But other elements in foods rich in C, or something about the life-style of people who consume high levels of C or E as supplements, may account for their lower risk. What the clinical trials show Some well-designed clinical trials, using human subjects under carefully controlled experimental conditions, have found that vitamins C and E do have the proposed health benefits. But others have found no effect.
Different studies use different doses of vitamins, so it's often hard to compare the results.
Most have focused on coronary artery disease. The results have been inconclusive. But the Heart Outcomes Prevention Evaluation Study, a Canadian study published last year, found no benefit when those at high risk for cardiovascular disease took 400 IU of E a day for four years. An Italian study published in the Lancet in 1999 found no significant reduction in coronary risk from 300 IU of E. These studies, and several others, raised more questions than they answered. Most of the clinical trials have been done on patients with heart disease.