If Dwyer's results were indeed true, then people who take vitamin C supplements should die of heart attacks and strokes at a much greater rate than non-supplement users. However, there is no scientific evidence to support this concept. Many epidemiological studies and some clinical trials have suggested that dietary intake or supplementation of vitamin C is associated with a reduced risk of heart disease and stroke. Although this study indicated that vitamin C supplements provide cardiovascular benefits above and beyond the vitamin C obtained from the diet, two other large epidemiological studies published in 1996 found no effect on heart disease risk in people who take regular vitamin C supplements. Importantly, not a single epidemiological study or clinical trial has found an increased risk of heart attacks or strokes in people taking vitamin C supplements.
Impaired vasodilation is an important risk factor for angina, heart attacks, and strokes.
Vasodilation in patients with heart disease is significantly improved following daily supplementation with 500 mg of vitamin C for thirty days and is comparable to vasodilation seen in healthy people. Beneficial effects of vitamin C supplements leading to normalization of vasodilation have also been observed in patients with angina, heart failure, high cholesterol levels, hypertension, diabetes, high homocysteine levels, and in smokers. Additionally, a recent study published in Lancet demonstrated that 500 mg of vitamin C given daily for thirty days lowers blood pressure in patients with mild to moderate hypertension. High blood pressure is a major risk factor for heart disease and strokes. The salubrious effects of vitamin C were comparable to those derived from conventional anti-hypertensive medications.