Nutritional Looks at Eye Health

Until recently, scientists were in the dark about nutrients’ role in preventing eye disease, but that’s no longer the case. A spotlight is shining on several important nutrients and their potential effects on eye health.

It’s a big deal; an estimated 16 million Americans over age 45 have some reported vision loss, with cataracts and age-related macular degeneration (AMD) causing much of the havoc. The lens moves on a path from transparent to opaque in cataract formation. AMD occurs as light-sensitive cells within the retina, particularly in the macula lutea, break down. It is one of the leading causes of blindness and vision impairment among people aged 55 and over.

Eye damage may start out early with exposure to sunlight, as ultraviolet light appears to damage the eye’s lens, and blue light affronts the retina. Free radicals also mount their destruction of the lens over time.

So how do nutrients protect against such assaults on eye health? Scientists have found high levels of vitamins C and E in the lens. These antioxidant nutrients seem to protect protein-digesting enzymes that seek out and destroy damaged and oxidized proteins accumulating on the lens that can lead to cataracts. Scientists have also found that lutein and zeaxanthin are concentrated in the retina. These carotenoids appear to protect the retina by absorbing blue light and neutralizing free radicals.

An eye on research

A number of studies during the past decade have looked at the effects of these and other nutrients on eye health. These found that people with high intakes of vitamins C and E, riboflavin, folate, beta-carotene, lutein, and zeaxanthin experience a lower prevalence of lens opacification than those with lower intakes of the nutrients. In addition, long-chain omega-3 fatty acids from fish are also associated with a decreased risk of advanced AMD. Results from the Age-Related Eye Disease Study (AREDS), published in the Archives of Ophthalmology (2001; 119(10):1,417-36), revealed a 25% lower risk of developing AMD when people took high-dose combinations of vitamins C and E, beta-carotene, and zinc for more than six years.

Researchers have continued to dig deeper into eye health and nutrition during the past year. The intake of antioxidants, beta-carotene, zinc, and vitamins A, C, and E were evaluated in 2,464 people aged 49 or older who took part in the Blue Mountains Eye Study, published in the American Journal of Clinical Nutrition in June 2008 (87(6):1,899-1905). It was discovered that higher intakes of vitamin C, or the combined intake of antioxidants, had long-term protective associations against the development of nuclear cataracts. Associations between age-related nuclear cataracts and lutein and zeaxanthin in the diet and serum were explored in the Carotenoids in the Age-Related Eye Disease Study, published in Archives of Ophthalmology (2008;126(3):354-364). Among a total of 1,802 women ages 50 to 79 studied, it was found that diets rich in lutein and zeaxanthin were linked with decreased prevalence of nuclear cataract. Prospective observational data from a large cohort of female health professionals published in the Archives of Ophthalmology (2008; 126(1):102-109) shows higher dietary intakes of lutein, zeaxanthin and vitamin E from food and supplements were associated with significantly decreased risks of cataracts. In a 2008 systematic review and meta-analysis of dietary omega-3 fatty acid and fish intake in the primary prevention of AMD published in the Archives of Ophthalmology (126:826-833), researchers concluded that consumption of fish and foods rich in omega-3 fatty acid may be linked with lower AMD risk, but additional research is needed to support recommendations for consumption. Researchers eagerly await the upcoming Age-Related Eye Disease Study 2, which will further evaluate nutritional factors, specifically, lutein, zeaxanthin and omega-3 fatty acids, in a multicenter, controlled, randomized trial.

Eating up eye nutrients

The National Eye Institute, Bethesda, MD, one of the government’s National Institutes of Health, suggests that people with intermediate risk of AMD in one or both eyes, or advanced AMD in one eye, should take the formulation used in the AREDS (vitamins C and E, beta-carotene, and zinc) to prevent AMD development by 25%. Plus, many experts believe that lutein, zeaxanthin and omega-3 fatty acids may have protective effects worth focusing on. Lutein and zeaxanthin are two of the most-abundant carotenoids in the American diet. These carotenoids both have yellow pigments, but are also found in many foods with green pigmentation. Common sources include dark-green leafy vegetables, broccoli, oranges, peppers, corn, peas, persimmons and tangerines. Eggs from chickens fed marigold petals have also been found to contain high levels of lutein. Look for more research results to bring the role of nutrition in eye health into focus in the near future.

Sharon Palmer, a registered dietitian with 16 years of experience in health-care and foodservice management, writes about food and nutrition for newspapers, magazines, websites and books. She makes her home in Southern California and can be reached at [email protected].

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