A new review from the UK suggests that vitamin C intakes greater than 500 milligrams per day may improve vascular function in patients with diabetes, atherosclerosis and heart failure.
The meta-analysis pooled the results of 44 clinical trials investigating the effects of vitamin C supplemen- tation on endothelial function among a total of 1129 healthy participants and patients (1). The analysis showed that participants with atherosclerosis, diabetes and/or heart failure who had received more than
500 milligrams of vitamin C a day showed an improved endothelial function, while in healthy ones no effect on vascular health was observed.
The researchers commented that the results support the idea that vitamin C may be a useful nutritional intervention for the secondary prevention of cardiovascular diseases. Future randomized controlled trialsshould test the effect of supplementary vitamin C on major outcomes of cardiovascular disease (morbidity and mortality) in patients likely to benefit. The endothelium – the thin layer of cells lining the blood vessels – performs many functions including maintaining the suppleness of blood vessels and regulating the activity white blood cells (neutrophils) that form a key part of the immune system. Dysfunction in the endothelium leads to arteries with little suppleness, raising the risk of high blood pressure, and arteries that are chroni- cally inflamed, which increases atherosclerosis risk.
Oxidative damage and vascular inflammation are known to affect endothelial function, while nitric oxide (NO) – a potent vasodilator – seems to preserve endothelial function. In addition to its direct reactive oxygen spe- cies (ROS) neutralizing function, the beneficial effects of vitamin C on endothelial function may be related to the increase in NO bioavailability due to an enhanced efficiency of the enzymatic and non-enzymatic synt- hetic NO pathways and reduced cross-reactivity with ROS.