Studies show nutrition impacts cataracts, glaucoma and AMD

A growing body of evidence suggests that antioxidants can protect against the development and progression of degenerative eye diseases.

Issue: June 15, 2000

ByRochelle Nataloni

WILMINGTON, Del. — Ophthalmologists are waking up to the fact that many of their patients are eager to embrace nutrition-based preventive eye care strategies and conventional therapy alternatives. Lutein and zeaxanthin, vitamins A, C and E and Ginkgo biloba are just a few of the antioxidants, vitamins and herbal extracts researchers are showing that have a positive impact on degenerative eye diseases.

In his book The Eye Care Revolution, ophthalmologist Robert Abel Jr., MD, describes a host of natural remedies to avoid or improve cataract, glaucoma and macular degeneration. “The criticism, of course, is that this is all anecdotal medicine,” Dr. Abel told Ocular Surgery News, “but quite frankly, when you see an anecdote twice, you’ve got a hypothesis, and once you have a hypothesis, then you have something that you can scientifically study.”

Ophthalmologist Steven G. Pratt, MD, also is a strong proponent of the nutrition/eye health connection. He provides a handout to each of his adult patients describing the benefits of increased consumption of fruits and vegetables, and he recommends a general supplement that includes vitamins, minerals, antioxidants, carotinoids and polyphenolic flavonoids. “The information illustrating the benefits of good nutrition is in the scientific peer-reviewed journals,” Dr. Pratt said. “What has to happen now is that we need the government and the medical schools and the pharmaceutical companies to educate physicians and all health care professionals about the benefits of good nutrition in preventing disease, because right now the public knows more about this than physicians do. There are always going to be cataracts and macular degeneration, but we have to start cutting back on the prevalence, or we are going to go down under a sea of disease with not enough money to treat it. The future,” he said, “is in prevention.”

Cataract studies

Researchers at Harvard University offer a piece of compelling evidence that lutein may help prevent cataracts. (Am J Clin Nutr. 1999;70:509-516). A 12-year prospective study of 77,466 female nurses ranging in age from 45 to 71 illustrated that nurses with the highest intake of lutein and zeaxanthin had a 22% lower risk of cataract extraction compared with those in the lowest quintile of intake. No association between cataracts and other carotenoids — alpha-carotene, beta-carotene, lycopene and beta-cryptoxanthin — was detected. The study also showed that high intake of spinach and kale, which are rich in lutein, may reduce the risk of cataract extraction. In a similar study of men (Am J Clin Nutr. 1999;70:517-524), it was found that men with the highest consumption of lutein and zeaxanthin had a 19% lower risk of cataract extraction compared to men with the lowest consumption. These studies were completed by Johanna M. Seddon, MD, the same epidemiologist who did the pivotal lutein study published in 1994, which showed a 43% reduction in risk of age-related macular degeneration (AMD) among women with high dietary intake of fruits and vegetables containing lutein. She later published an article linking smoking to increased risk for AMD.

A population-based cross sectional study of 2,900 people in Australia showed that the intake of polyunsaturated fats may reduce the prevalence of cortical cataracts, while consumption of foods high in protein and some of the B vitamins such as thiamin (B₁) and riboflavin (B₂) and niacin significantly reduced the risk of developing nuclear cataracts. “As with other studies, we established that vitamin A may protect against nuclear cataract and that spinach — a good source of lutein — may play a role,” said Robert G. Cumming, MBBS, PhD, of the University of Sydney. “However, our study indicates that the B vitamins also may play a role in protecting against nuclear cataracts.” The study also showed that people who consumed the highest amount of sodium were twice as likely as those consuming the lowest amounts to develop a posterior subcapsular cataract. The study concludes that further research on nutrition and the development of cataracts should extend beyond the antioxidants.

Researchers also are suggesting that vitamin C, an important water-soluble antioxidant normally present in high concentrations in the lens of the eye, may provide protection against the development of cataract. The study (J Clin Epidemiol. 1999;52(12):1207-1211) comprised dietary and disease data from the Second National Health and Nutrition Examination Survey including 4,001 men and women between 60 and 74 years of age. Joel Simon, MD, MPH, assistant professor of medicine and epidemiology at the University of California, found a 26% decrease in the development of cataract for each 1 mg increase in blood vitamin C levels among men and women who reported a history of cataract. These findings agree with several other studies that have found that individuals with high blood levels of vitamin C, high dietary intake of vitamin C and long-term, daily C supplementation have a lower risk of developing cataract.

Glaucoma

Smoking cessation and moderate exercise, such as walking, are two lifestyle changes that may aid in glaucoma management, and Ginkgo biloba has been shown to improve blood flow. “While medications are the first line of therapy, with surgery used to complement the therapeutic regimen, lifestyle changes including exercise and smoking cessation, as well as food or vitamin supplements, may [complement] the treatment scheme,” Murray Fingeret, OD, reported in Primary Care Optometry News. A study in Archives of Ophthalmology (1991;109:1096-1098) showed that by the end of a 3-month exercise training period, study participants had a 20% decrease in intraocular pressure, which returned to pre-exercise levels within 3 weeks when the conditioning program stopped.

Dr. Abel considers glaucoma a disease of stress. “You have to step outside the paradigm to recognize the bigger picture and to recognize that glaucoma is a disease of stress,” he said. “Of course there are variations to that, but the main theme is that if you relax, it helps.”

The Glaucoma Research Foundation (GRF) is funding research on carotenoids, vitamin C and vitamin E in relation to open-angle glaucoma with visual field loss not due to any other condition. The Antioxidant Intake and Primary Open Angle Glaucoma Study has followed 120,000 women for 22 years and about 50,000 men for 10 years. One of the lead researchers, told GRF, “Antioxidants as treatment and/or cure is certainly within the realm of possibility.” Apoptotic cell death is mediated by oxidative stress, and antioxidants produced by the body have been shown to protect against apoptotic cell death. The connection: well-established data suggest that oxidation may influence glaucoma risk.

Macular degeneration

Researchers theorize that lutein and zeaxanthin protect the macula pigment in two ways: by absorbing harmful blue light from the sun’s rays and by acting as antioxidants that neutralize free radicals. Population-based studies have demonstrated a link between low dietary intake and serum levels of lutein and zeaxanthin and risk for AMD. A study by the National Eye Institute of the National Institutes of Health, The Eye Disease Case Control Study, found that those with AMD tended to have lower serum concentrations of lutein and zeaxanthin. A second report from the same study found that the lowest intakes of dietary lutein and zeaxanthin were associated with a higher risk of AMD. John T. Landrum, PhD, of the department of chemistry at Florida International University in Miami, and colleagues demonstrated that large doses of supplemental lutein and zeaxanthin, approximately 30 mg per day, resulted in large increases in serum and macular carotenoid levels. They also tested the outcome with low levels of supplemental lutein. In a small-scale pilot study, subjects took 2.4 mg of lutein daily for 6 months. Even with these low intakes, serum levels increased between 20% and 300% in study participants. More than one-half of the participants also exhibited a statistically significant increase in macular pigment level. In his research, Dr. Landrum said he has observed that the presence of high levels of lutein and zeaxanthin in the macula were associated with 75% reduction in the risk of AMD.

For Your Information:

Steven G. Pratt, MD, can be reached at 9850 Genessee Ave., Ste. 310, La Jolla, CA 92037-1205; (858) 457-3010; fax: (858) 457-0028; e-mail: spratt71@hotmail.com. Dr. Pratt has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for Alcon.

Robert Abel Jr., MD, can be reached at Concord Plaza, Naamans Bldg., 3501 Silverside Road, Wilmington, DE 19810; (302) 477-2600; fax: (302) 477-2650; e-mail: docrmabel@aol.com. Dr. Abel has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Robert G. Cumming, MBBS, PhD, can be reached at the University of Sydney, A27 – Edward Ford Bldg., NSW 2006 Australia; (61) 2-9351-4822; fax: (61) 2-9351-7420; e-mail: bobc@pub.health.usyd.edu.au. Dr. Cumming has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Johanna M. Seddon, MD, can be reached at Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, 243 Charles St., 3rd Floor, Boston, MA 02114; (617) 573-3285; fax: (617) 573-3570; e-mail: johanna_seddon@meei.harvard.edu.

Joel Simon, MD, MPH, can be reached at General Internal Medical Section (111A1), San Francisco VA Medical Center, 4150 Clement St., San Francisco, CA 94121. Dr. Simon has no direct financial interest in any of the products mentioned in this article. He receives research funding from Roche Vitamins Inc.

Murray Fingeret, OD, can be reached at St. Albans VA Hospital, Linden Blvd. & 179th St., St. Albans, NY 11425; (718) 526-1000; fax: (516) 569-3566. Dr. Fingeret has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

John T. Landrum, PhD, can be reached at Florida International University, Department of Chemistry, Miami, FL 33199; (305) 348-2606; fax: (305) 348-3772. Dr. Landrum has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.