Vitamin C May Aid People with Diabetes
Supplementing with vitamin C may help prevent some of the complications of diabetes by lowering blood pressure and reducing the stiffness of arteries, according to a report in Hypertension (2002;40:804–9). This new study adds to a growing body of evidence that people with diabetes can benefit by increasing their intake of vitamin C.
Thirty men and women with type 2 (adult onset) diabetes were randomly assigned to receive 500 mg of vitamin C per day or a placebo. After four weeks of treatment, the average blood pressure decreased significantly in the group taking vitamin C, whereas no change was seen in the placebo group. The systolic blood pressure (the higher number) decreased by an average of 9.8 mm Hg, while the diastolic blood pressure (the lower number) decreased by 4.4 mm Hg. These changes in blood pressure are nearly as great as one might expect from taking a prescription blood pressure-lowering medication. In addition, the stiffness of the arteries decreased significantly in the vitamin C group.
Heart disease is a common complication of diabetes. As high blood pressure and arterial stiffness are both risk factors for heart disease, the results of this study suggest that vitamin C supplementation can reduce the chance that a person with diabetes will develop this complication.
Previous research has shown that diabetics have higher requirements for vitamin C than healthy people. Vitamin C, which has a chemical structure similar to that of the common sugar glucose, appears to compete with glucose for entry into cells. When the blood glucose level is elevated, as in diabetes, more vitamin C than usual is needed in order for the vitamin to perform its functions in the body. In experimental animals, vitamin C deficiency causes hardening of the arteries (atherosclerosis).
Research has suggested that vitamin C might also help prevent other consequences of diabetes, such as damage to the eyes and nerves. Vitamin C inhibits all three of the biochemical reactions that are believed to contribute to the development of these complications: (1) the production of oxygen-derived free radicals, (2) the accumulation of sorbitol within cells, and (3) a tissue-damaging reaction called glycosylation. However, no long-term studies have been done in humans to determine whether supplementing with vitamin C actually does prevent eye and nerve damage.
Vitamin C supplementation is not entirely without risk for people with diabetes. People with advanced diabetes may suffer from kidney disease, which, if severe enough, could impair the body's capacity to excrete vitamin C. In people with severe kidney failure, supplemental vitamin C in excess of 100 mg per day can accumulate in the body and be converted to oxalate, which has the potential to damage the heart and other tissues. Fortunately, most diabetics can safely handle vitamin C supplements. However, to be on the safe side, individuals with diabetes should consult their doctor before taking large amounts of vitamin C.
Alan R. Gaby, MD, an expert in nutritional therapies, testified to the White House Commission on CAM upon request in December 2001. Dr. Gaby served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the author of Preventing and Reversing Osteoporosis (Prima, 1994), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Prima, 1999), the A–Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Prima, 1999), Clinical Essentials Volume 1 and 2 (Healthnotes, 2000), and The Patient’s Book of Natural Healing (Prima, 1999). A former professor at Bastyr University of Natural Health Sciences, in Kenmore, WA, where he served as the Endowed Professor of Nutrition, Dr. Gaby is the Chief Medical Editor for Healthnotes, Inc.
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