Vitamin C may slow progress of cataracts

A diet rich in the antioxidant vitamin C appears to help keep cataracts away, according to a study published March 23 in the journal Ophthalmology. Genetics play a part, too, though a much smaller role by comparison.

In the study, researchers at King's College London analyzed the development of cataracts in 324 sets of twins living in the United Kingdom. They looked at whether particular nutrients—in food and dietary supplement forms—could slow the progression of cataracts. The nutrients included vitamins, A, B, C, D and E, copper, manganese and zinc. Questionnaires were used to determine the twins' vitamin C consumption, and digital imaging was used to assess cataract progression.

Researchers also considered the impact of genetics versus environmental factors in the progression of cataracts.

"Genetic factors explained 35% of the variation in progression of nuclear cataract over a 10-year period," the study concludes. "Environmental factors accounted for the remaining variance, and in particular, dietary vitamin C protected against cataract progression assessed approximately 10 years after baseline."

Significance of the study

The study confirmed previous research: Vitamin C (ascorbate acid) can help prevent the oxidation that clouds the lens as we age, says Stuart Richer, O.D., Ph.D., director of ocular preventive medicine at the James Lovell Federal Health Care Facility in North Chicago, associate professor of family and preventative medicine at Chicago Medical School and assistant clinical professor in the University of Illinois at Chicago department of ophthalmology and visual science. Dr. Richer also is president of the Ocular Nutrition Society.

"While there are multiple positive studies associating ascorbate and lowered risk of cataract, this was a particularly good study in that it teased out the genetic susceptibility factor," Dr. Richer says.

One past study linking vitamin C and the progression of cataracts produced conflicting results. However, there is sufficient evidence to indicate vitamin C has a positive impact on cataract progression and overall health, and doctors of optometry can play a role in educating patients about its benefits.

Educate patients about nutrition

Vitamin C is naturally abundant in the fluids and tissues of the eye—from the cornea to the retina. However, its concentration can decline with "environmental assault" and age, if not supplemented, Dr. Richer says.

"A lack of plant food (vegetables and fruit); excessive smoking; chronic aspirin and acetaminophen use; and high dietary sugar or excessive, simple carbohydrate consumption all deplete and disrupt the cellular ascorbate redox state," he says. "Diabetes also increases the need for ascorbate within the body and eyes. The resulting cellular damage from ascorbate deficiency is indistinguishable from radiation damage."

Vitamin C, taken intravenously or orally, has been associated with benefits to the eye but also in medical literature with the prevention of cancer, cardiovascular disease, stroke, atherosclerosis and infectious diseases.

"Doctors of optometry, in their primary care eye physician role, should query every patient concerning micronutrient-rich plant food consumption, and then encourage patients to consume the government-recommended nine to 13 portions of vitamin-C-rich plant food per day," Dr. Richer says. "The average American only consumes three portions per day, and 30% of the African American community fails to eat a single daily fruit or vegetable."

He adds that for those who cannot meet U.S. dietary recommendations, supplements can be prescribed. "Educating our patients in established nutritional science, while they are in the exam room, in my opinion, is a primary care directive."

Learn more about talking to patients about nutrition.

The AOA follows all research closely, including potential cataract treatments. Although diet and nutrition are interesting treatment possibilities for patients, more research is needed regarding their influence on visual health. For more information or help for better vision, please visit the AOA website.