Vitamin C Therapy in Type 2 Diabetes and Cardiovascular Risk

More than 70% of type 2 diabetic individuals will die of atherosclerotic disease (1). This is partially explained by the abnormal lipid profile frequently observed in type 2 diabetes. These patients are also frequently afflicted with "Syndrome X," an assortment of risk factors for atherosclerosis, including hypertension, abdominal obesity, hyperuricemia, prothrombotic and proinflammatory states, and increased plasminogen activator inhibitor type I (PAI-1) (2).

Several approaches have been suggested to reduce the risk of atherosclerosis in type 2 diabetic individuals. Changes in lifestyle leading to increased exercise and weight loss will result in the reduction of adipose stores (and restore tissue sensitivity to insulin). However, this approach is very difficult for many individuals to achieve. For them, this can be supplemented with medications such as aspirin, angiotensin inhibitors, angiotensin receptor blockers, and the statins. Unfortunately, each of these medications is either expensive and/or includes undesirable side effects (3). In addition, clinical experience shows that many patients are against taking medication for cultural reasons and/or fear of long-term unknown consequences.

For these reasons, there is great interest in using vitamins to reduce atherogenic risk. More than half of the U.S. adult population consumes vitamins on a regular basis. They are inexpensive and easily accessible in grocery stores and health food stores. The FDA does not consider them as "drugs" and they undergo a less rigorous approval procedure (4,5). Vitamins are natural compounds found in the body, and many individuals do not consider them drugs, but feel they are simply fortifying their bodies against disease.

There is currently a focus on vitamins that are antioxidants, including vitamin C. Patients with diabetes usually have a decreased antioxidant status, which leads to increased oxidative stress and vascular dysfunction (6,7). Oxidative stress refers to the excessive production of oxygen free radical species, which damage their surrounding molecules, and this leads to the increased release of inflammatory mediators, oxidation of low-density lipoproteins (LDL), and increased coagulation (7).

Vitamin C, another antioxidant, has been shown to regenerate Vitamin E, and in patients with increased oxidative stress (i.e. patients with conditions such as diabetes mellitus, coronary artery disease, and hypercholesterolemia), it restores endothelium-dependent artery vasodilation, and may reverse endothelial dysfunction in peripheral arteries (6). It has been hypothesized that supplementation of vitamin C may be more effective than vitamins taken together.