An Eye on Nutrition

When faces become blurry, road signs get fuzzy and the fine print on a food label appears illegible, your eyes are telling you something: a visit to an eye care professional is in order. From birth, our eyes are constantly filtering light—from harsh sunlight to the more damaging blue light—and over time the effects can be damaging. Just like the skin, our eyes need sunscreen. The good news is your diet can make a difference. Certain nutrients, specifically antioxidants and omega-3 fats, can help keep your peepers healthy for life.

A Glance at the Research

The last two decades of research have generated vital data on ocular health and nutrition. Studies have shown that the macula of the eye is specifically responsive to two carotenoids, lutein and zeaxanthin. The macula is responsible for the sharpest central vision.

Lutein and zeaxanthin are collectively called macular pigment because they accumulate in macular cells and are found in the macula’s yellow coloration (Wenzel et al. 2006). Through its light-screening capacity and antioxidant activity, macular pigment may reduce photo-oxidation in the central retina (Bone et al. 2003). In addition, the outer retina may be negatively altered by free-radical production and oxidation; the proper nutrients may stave off the effects of free-radical damage (Seddon et al. 1994).

Eyeing Optical Conditions

It’s not surprising that our aging nation is experiencing age-related eye conditions. Chief among these is age-related macular degeneration (AMD), a progressive condition that attacks the macula of the eye. AMD currently affects 13 million Americans or 5% of people aged 65 and older (Goodrow et al. 2006). It is the leading cause of irreversible blindness among this age group (Seddon et al. 1994).

AMD presents in two forms: dry or wet. Dry AMD is the slow, insidious loss of central vision, which can be treated with vitamin and mineral supplementation. The common symptoms of dry AMD are slightly blurred vision and difficulty seeing faces clearly. Although dry AMD generally affects both eyes, one eye can be affected while the vision in the other eye seems normal. Wet AMD occurs when abnormal blood vessels develop under the retina; damage to the macula occurs rapidly and can lead to sudden vision loss. Wet AMD is typically treated with laser surgery, not diet.

According to Michael A. Rosenberg, MD, associate chair of the department of ophthalmology at the Feinberg School of Medicine Northwestern Memorial Hospital in Chicago, genetics may play a key role in AMD. “The current thinking is that AMD is a hereditary disease, and without a family history (of the disease), the chances of getting it are remote,” says Rosenberg. People with a family history or other risk factors for AMD (see “A Look at AMD Risk Factors” below) should have a comprehensive dilated eye examination at least once a year after age 50, according Rosenberg. “The best eye protection for children and teens is to wear sunglasses and avoid ultraviolet (UV) exposure as much as possible.”

Look to Your Diet

How can you safeguard your eyes with good nutrition? Research has shown that a high dietary intake of dark, leafy greens (e.g., kale, spinach and collard greens) is associated with a lower risk for AMD (Seddon et al. 1994). According to Seddon, subjects in this epidemiological study who ate foods with high concentrations of lutein and zeaxanthin had a 43% lower prevalence of AMD than those who consumed the lowest levels. The study found that just 6 milligrams (mg) of lutein per day was preventive against AMD. According to various scientific studies, the current clinical recommendation is 6-10 mg of lutein per day for eye health (Wenzel et al. 2006).

Unfortunately, the human body cannot synthesize lutein and zeaxanthin; both carotenoids must be obtained from the diet (Wenzel et al. 2006). Egg yolks, fruits and green, leafy vegetables are all good sources of lutein and zeaxanthin. “A fatty egg yolk is a perfect delivery vehicle for fat-soluble carotenoids,” according to Robert J. Nicolosi, PhD, director of the Center for Health and Disease Research at the University of Massachusetts, Lowell.

Nicolosi was one of the authors of a study that randomly assigned 24 women either to consume six eggs per week or to take a placebo pill (Wenzel et al. 2006). After 12 weeks, macular pigment optical density—which improves light filtering—was greater in the women who ate the eggs than in the controls. “This suggests that the carotenoids in egg yolks may be highly bioavailable to the eyes,” says Nicolosi.

But how do those fatty yolks affect blood cholesterol levels? Studies found that eating an egg daily for 5 weeks boosted blood levels of lutein and zeaxanthin but did not increase cholesterol or triglycerides levels (Goodrow et al. 2006; Wenzel et al. 2006). “Our data show that eating an egg a day isn’t a factor for raising cholesterol,” says Nicolosi. “In fact, people who avoid eggs may be missing an opportunity to consume vital nutrients that can help prevent AMD.”

One caveat: The research to date indicates that some level of dietary fat is helpful in maximizing absorption of fat-soluble carotenoids, particularly lutein (Roodenburg et al. 2000). One healthy and easy way to accomplish this would be to saut├® dark, leafy greens in a little olive oil or toss salads with 1 or 2 tablespoons of full-fat—not fat-free—dressing, which would increase the absorption of lutein.

A Peek at Supplementation

The standard for eye supplementation was set by the Age-Related Eye Disease Study (AREDS), a major clinical trial in 2001 sponsored by the National Eye Institute of the federal government’s National Institutes of Health. After observing about 3,600 people with all stages of AMD, AREDS concluded that people who took a high-potency antioxidant and zinc supplement reduced their chances of getting advanced AMD by 25% (Seddon, Cote & Rosner 2003). The specific nutrients included high doses of vitamin C; vitamin E; beta carotene equivalent to vitamin A; zinc as zinc oxide; and copper as cupric oxide (the latter was added to prevent copper deficiency anemia, a condition associated with high levels of zinc intake). Although the AREDS findings specifically noted that supplementation was not a cure for AMD, the nutrient formula did slow the progression of macular degeneration in patients who already had the disease.

The next generation study, AREDS2, will examine the effects of omega-3 fatty acids in addition to the AREDS1 nutrient formula. The addition of omega-3 fatty acids is significant, since research has found that consuming fish at least twice a week may reduce AMD risk compared with not eating fish at all (Liebman et al. 2007). Other studies have found that higher fish intake was associated with lower risk of AMD progression in older adults (Seddon, Cote & Rosner 2003).

Because it is almost impossible to get the eye-health nutrient megadoses used in the research, eye care professionals often recommend “eye vitamins” for their patients. “There is no downside to taking supplements, especially if you have a family history of eye disease,” states Rosenberg. Two age-specific formulas are Bausch & Lomb’s Ocuvite® Adult and Ocuvite® Adult 50+. Both supplements contain high concentrations of omega-3 fatty acids, lutein, vitamin C, vitamin E, zinc and copper.

How to Keep Your Eyes Fit

Advise your clients to maintain the health of their eyes by following these simple steps outlined in the National Eye Institute Resource Guide (www.nei.nih.gov/health/maculardegen/armd_facts.asp):

• Eat a healthy diet high in dark green, leafy vegetables and fish (and consider taking an eye vitamin, if advised by your physician).
• Don’t smoke!
• Maintain a normal blood pressure.
• Watch your weight.
• Exercise.

SIDEBAR: Load Up on Lutein-Rich Foods

Look for these sources of the carotenoid lutein, which has been linked with good eye health:
kale (raw) 26.5 mg per cup
kale (cooked) 11.9 mg per 1/2 cup
collards (cooked) 7.3 mg per 1/2 cup
spinach (fresh, raw) 3.7 mg per cup
spinach (cooked) 10.2 mg per 1/2 cup
eggs 0.3 mg in 2 large

Source: U.S. Department of Agriculture, Agricultural Research Service, USDA Nutrient Data Laboratory. 2005. USDA National Nutrient Database for Standard Reference, Release 18.

SIDEBAR: A Look at AMD Risk Factors

The following factors may increase a person’s risk of developing age-related macular degeneration (AMD), the leading cause of blindness in adults 65 and older (Seddon et al. 1994).

• smoking
• obesity
• race (more prevalent among Caucasians than African Americans)
• family history (those with immediate family members who have AMD are at a higher risk of developing the disease)
• gender (women appear to be at greater risk than men)

SIDEBAR: Top 5 Fish for Omega-3 Fatty Acids

Troll your grocery shelves for these sources of beneficial omega-3 fatty acids:
Atlantic salmon, farmed 3,650 mg*
Atlantic salmon, wild 3,130 mg*
coho salmon, farmed 2,180 mg*
rainbow trout, farmed 1,960 mg*
coho salmon, wild 1,800 mg*

*per 6-ounce serving of cooked fish
Source: Nutrition Action Health Letter, October 2007.

SIDEBAR: Eye Health Resources

www.dontlosesight.org—This public education program raises awareness about eye health and macular degeneration and allows users to submit macular degeneration-related questions to an ophthalmologist.

www.nei.nih.gov/AREDS2/—AREDS2 is a nationwide study that aims to determine whether a combination of vitamins and minerals can further slow the progression of age-related macular degeneration (AMD); nearly 100 clinical centers are now seeking 4,000 study participants ages 50-85 who have AMD.

www.preventblindness.org—Prevent Blindness America® is the nation’s leading volunteer eye health and safety organization dedicated to fighting blindness through education, advocacy, certified vision screenings, community programs and research.

Victoria Shanta Retelny, RD, LD, is a registered dietitian in private practice in Chicago. She operates a nutrition consulting business called LivingWell Communications (www.livingwellcommunications.com).

References

Bone, R.A., et al. 2003. Lutein and zeaxanthin dietary supplements raise macular pigment density and serum concentrations of these carotenoids in humans. The Journal of Nutrition, 133, 992-98.

Goodrow, E.F., et al. 2006. Consumption of one egg per day increases serum lutein and zeaxanthin concentrations in older adults without altering serum lipid and lipoprotein cholesterol concentrations. The Journal of Nutrition, 136, 2519-24.

Liebman, B. 2007. Omega medicine? Is fish oil good for what ails you? Nutrition Action Health Letter, 34 (8), 4-6.

Roodenburg, A.J.C., et al. 2000. Amount of fat in the diet affects bioavailability of lutein esters but not of alpha-carotene, beta-carotene or vitamin E in humans. American Journal of Clinical Nutrition, 71, 1187-93.
Seddon, J.M., Cote, J., & Rosner, B. 2003. Progression of age-related macular degeneration: Association with dietary fat, transunsaturated fat, nuts, and fish intake. Archives of Ophthalmology, 121 (12), 1728-37.

Seddon, J.M., et al. 1994. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Journal of the American Medical Association, 272, 1413-20.

Wenzel, A.J., et al. 2006. A 12-week egg intervention increases serum zeaxanthin and macular pigment optical density in women. The Journal of Nutrition, 136, 2568-73.