Vitamin C is an antioxidant with significant physiologic actions. For instance, it has been reported to lower erythrocyte sorbitol concentrations, which may make it useful in treating diabetes.1 Data from the 3rd National Health and Nutrition Examination Survey showed that mean serum vitamin C concentrations were significantly lower in people with newly diagnosed diabetes than in people who did not have diabetes,2 lending support to the earlier belief that diabetes mellitus may be associated with decreased serum vitamin C concentrations. These results support the contention of Sebastian Padayatty and Mark Levine that subclinical vitamin C deficiency is more common than is generally recognized.3 An inverse association has been reported between plasma vitamin C concentration and glycosylated hemoglobin,4 suggesting that measures to increase plasma vitamin C levels may help to reduce the prevalence of diabetes. A colleague and I reported that 1500 mg of vitamin C, when given orally, reduces plasma glucose levels in patients with type 2 diabetes.5
Other studies have suggested that vitamin C reduces blood pressure.6,7 It may augment prostaglandin F and nitric oxide synthesis,8,9 which could account for its beneficial actions in diabetes and hypertension. The interactions of vitamin C with eicosanoids, nitric oxide, platelets, leukocytes and endothelial cells, among other types of molecules and cells, may account for some of its hitherto-unexplained beneficial actions. As suggested by Padayatty and Levine, more studies should be conducted on vitamin C's actions in various tissues, including cancerous ones.3 Until further studies are completed, however, caution should be exercised in advocating its use as an anticancer compound.