If you have a low level of vitamin D, taking this inexpensive supplement may help prevent diabetic retinopathy. This is one of the most serious complications of diabetes and the most common reason why some people with the disease lose their vision.
A meta-analysis just presented at the Annual Scientific and Clinical Congress of the American Association of Clinical Endocrinologists, in Orlando, Florida, from May 25 to 29, found “a statistically significant association between diabetic retinopathy and vitamin D deficiency.” Three researchers presented their findings in an abstract, “The Relationship Between Vitamin D Deficiency and Diabetic Retinopathy: A Systematic Review and Meta-Analysis.” The Canadian Journal of Ophthalmology is expected to publish the full report soon, Dr. Sikarin Upala of Bassett Medical Center in Cooperstown, New York, one of the study’s co-authors, told me.
The role of vitamin D in the origin and development of diabetic retinopathy is still an area of debate, as another co-author, Dr. Anawin Sanguankeo of Bassett Medical Center, recently noted. (The third co-author is Jason Zhang of Yale University.) Dr. Sanguankeo stressed, however, that the evident connection between vitamin D deficiency and diabetic retinopathy indicated by the trio's meta-analysis suggests that people with low vitamin D levels should be screened for diabetic retinopathy.
The optimal vitamin D level
The meta-analysis analyzed data from 13 studies involving 9,350 people with diabetes who had been tested for both diabetic retinopathy and vitamin D deficiency -- defined as a serum level less than 20 ng/ml. The researchers cited the optimal vitamin D level as greater than 30 ng/ml.
(An optimal vitamin D level of greater than 30 ng/ml is consistent with the latest evidence that we may need only a level of 26 ng/ml, not the long-recommended higher levels of the supplement, as I wrote in "A Vitamin D Surprise for People With Diabetes.")
The new meta-analysis recommended that elderly women, in particular, look into taking a vitamin D supplement to protect against the development and progression of diabetic retinopathy. “Elderly women have high risk of having vitamin D deficiency based on the epidemiology and physiology,” Dr. Upala wrote me in an email.
Women over 70 have the lowest average level of vitamin D of all age-gender groups in the U.S. population, according to the 2005-2006 National Health and Nutrition Examination Survey, while people with diabetes in general often have lower levels of vitamin D than the rest of the population.
The benefits of vitamin D
Vitamin D is so important for those of us who have diabetes that I have already written 11 articles about it here. It might also help prevent everything from heart disease and cancer to the pain of neuropathy.
Now those of us with diabetes have another important reason to make sure that we have the right level of vitamin D. If your doctor will not prescribe a vitamin D test at a reasonable cost, you can get one from GrassrootsHealth, as I recommend in "Vitamin D Testing."
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David Mendosa is a journalist who learned in 1994 that he has Type 2 diabetes, which he now writes about exclusively. He has written thousands of diabetes articles, two books about it, created one of the first diabetes websites, and publishes the month newsletter, “Diabetes Update.” His very low-carbohydrate diet, current A1C level of 5.3, and BMI of 19.8 keeps his diabetes in remission without any drugs.