Nutritional supplements can play a role in managing ophthalmic patients

Studies have shown positive effects for patients with AMD or dry eye syndrome.

The practice of advising patients to use nutritional supplementation in eye care has met with some scrutiny within the medical community. Ample research demonstrates the positive benefits of nutritional supplements, particularly omega-3 fatty acids, as an adjunct to standard pharmacotherapy in the care and treatment of our patients with age-related macular degeneration and dry eye syndrome.

Timothy L. Schneider

Dietary omega-3 fatty acids can reduce AMD, according to a study published in American Journal of Clinical Nutrition. Findings in this study revealed that individuals who habitually consume oily fish or who consume 300 mg of docosahexaenoic acid and eicosapentaenoic acid daily were 70% less likely to have wet AMD.

AMD

In a study published in Archives of Ophthalmology, it was found that diets high in omega-3 fatty acids and fish were inversely associated with AMD risk when intake of linoleic acid was low. In a meta-analysis of 88,974 subjects, high dietary intake of omega-3 fatty acids was associated with an overall 38% reduction in the risk of late AMD. Further, consuming omega-3s from fish at least twice weekly was associated with reduced risk of both early and late AMD.

Report 20 of the Age-Related Eye Disease Study (AREDS) found that higher intake of omega-3s and fish was positively linked to decreased likelihood of having neovascular AMD. AREDS Report 23 recently suggested that omega-3 fatty acid intake was associated with a decreased risk of the progression from bilateral drusen to central geographic atrophy.

AREDS Report 22 revealed that high dietary intake of lutein and zeaxanthin were independently associated with a reduced likelihood of having neovascular AMD. Subjects consuming the highest amounts of lutein and zeaxanthin were 35% less likely to have neovascular AMD and 55% less likely to have geographic atrophy. The Lutein Antioxidant Supplementation Trial (LAST) found that visual function improved with lutein alone or together with antioxidants, vitamins and minerals in male patients with atrophic AMD. In another such study, the Carotenoids and Antioxidants in Age-Related Maculopathy Italian Study (CARMIS), it was found that short-term carotenoid and antioxidant supplementation in non-advanced AMD can improve a selective dysfunction in the central retina.

The Taurine, Omega-3 Fatty Acids, Zinc, Antioxidant, Lutein (TOZAL) study investigated the impact of the listed nutritional supplements on visual function in patients with atrophic AMD. Seventy-six percent of the subjects receiving the nutritional supplement demonstrated stabilization or improvement of best corrected visual acuity at 6 months. Although the study period was relatively short, these results align with both the LAST and CARMIS studies.

Dry eye syndrome

AMD is not the only ophthalmic disease that may benefit from nutritional supplements. The Women’s Health Study found a 68% reduction of dry eye syndrome in women who consumed five to six servings of tuna per week, one of the largest contributors of omega-3s in American diets. A high ratio of omega-6:omega-3 greater than 15:1 was associated with a greater than twofold prevalence of dry eye syndrome, suggesting that the ratio of inflammatory omega-6 fatty acids to anti-inflammatory omega-3 fatty acids is important.

Cataract development appears to be altered by nutritional supplementation as well. High dietary levels of lutein and zeaxanthin resulted in a 32% lower prevalence of nuclear cataract compared with lower levels of dietary intake in women studied in the Carotenoids in Age-Related Eye Disease Study.

How does it work?

The etiology of AMD and dry eye syndrome appears to be multifactorial, but inflammation likely plays a major role. One of the most potent inhibitors of inflammation is omega-3 fatty acid. Essential fatty acids are natural modulators of inflammatory activity via their interaction with eicosanoids, locally acting hormone-like lipids involved in the control of inflammatory and immune responses. Eicosanoids are derived from three fatty-acid precursors: dihomogammalinolenic acid, arachidonic acid and eicosapentaenoic acid.

The modulation of inflammatory activity is based on the balance of these precursors. Omega-3 fatty acids suppress the biosynthesis of arachidonic acid-derived eicosanoids. Dietary intake determines the balance of omega-3 fatty acids to omega-6 fatty acids in cellular membranes. High intake of omega-3 fatty acids results in displacement of the usually more abundant arachidonic acid with eicosapentaenoic acid and docosahexaenoic acid. Eicosanoids derived from arachidonic acid (prostaglandins E2 and leukotriene B4) are vigorously pro-inflammatory.

It is also thought that omega-3 fatty acids may exhibit cytoprotective and cytotherapeutic actions contributing to a number of anti-angiogenic and neuroprotective mechanisms within the retina.

Lutein and zeaxanthin protect the retina from oxidative stress by absorbing blue light, which can cause photochemical damage. It appears that nNOS and COX-2 expression are inhibited by lutein.

What does this mean for the medical community?

Dietary supplements are big business in the United States. Consumer sales in 2006 were estimated at $22.5 billion, with some 60% of Americans taking at least a daily vitamin. For many years, the American Medical Association deemed the use of vitamins unnecessary, assuming that most Americans received adequate nutrition in their daily food intake. However, in 2002, the AMA reversed its stance, claiming that scientific understanding of vitamins had advanced and that nutritional supplements may play a key role in preventing many common illnesses, including cancer, depression, heart disease, osteoporosis, dementia and AMD.

The estimated cost of a single Lucentis (ranibizumab, Genentech) injection for the treatment of neovascular AMD is in the neighborhood of $1,950. Some trials show 12 injections per year to be most effective in improving vision, totaling about $23,400 per eye per year, which can be cost-prohibitive. Consequently, AMD has a profound impact not only on one’s economic position, but also on quality of life. One-third of all patients with AMD were found to have clinical depression secondary to severe reduction in quality of life.

If only a small percentage of the ophthalmic community embraces the findings of the AREDS, CARMIS, TOZAL and LAST studies, and present nutritional supplementation as an adjunct to patient care, hundreds of thousands of patients’ lives may be positively affected. As physicians, we need to direct our patients to only the highest quality pharmaceutical-grade products with high bioavailability that have the highest likelihood for success.

Omega-3s have been suggested to decrease the risk of AMD, dementia, depression, coronary artery disease, arthritis, hyperlipidemia and even cancer. According to Greg M. Cole, PhD, a researcher at the University of California, Los Angeles, clinical trials lack funding to target the most promising patient population — people who have not yet started to show signs of those problems. “The risk of Alzheimer’s doubles with every 5 years after age 65, and we’ve got a generation of 75 million people heading into that,” he said. “We can’t afford to miss something that might help with prevention just because we couldn’t find the money to study it.”

Nutritional supplements pose little risk. The possible benefits in terms of maintaining independence, preserving vision, health care and personal cost savings, and easing the burden on family caregivers are positive beyond measure. There will always be skeptics who are wary as to whether it is the physician’s place to suggest or recommend nutritional supplements. As more research supports nutritional supplements, not recommending them may pose the biggest risk.

References:

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• Timothy L. Schneider, MD, can be reached at Schneider Eye Center, 1909 Beach Blvd., Suite 101, Jacksonville Beach, FL 32250; 904-247-5575; fax: 904-247-3375; e-mail: tschneider@schneidereye.com.