Uncovering the keys to eye health

Age-related macular degeneration is the leading cause of blindness in the developed world. It happens when the macula-a yellow spot on the retina of the eye-is damaged, leading to progressive central vision loss.

In 2001, the Age-Related Eye Disease Study (ARMDS) found that taking an antioxidant supplement containing vitamin C, vitamin E, beta-carotene, and zinc could reduce the risk of macular degeneration progression by about 25% in people with the disease. Since then, other studies have suggested that additional nutrients might also help people with macular degeneration.

The first of these are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) found in fish oil. Observational studies have suggested that people who eat more fish containing these omega-3 fatty acids have a lower risk of macular degeneration.

Lutein and zeaxanthin are antioxidants found in green leafy vegetables, corn, egg yolks, and broccoli. These carotenoids are found in high concentrations in the macula and lend the macula its bright yellow appearance. A recent study showed that a combination of omega-3s and lutein and zeaxanthin could increase macular pigment density in people with macular degeneration, a factor associated with decreased risk of the disease.

Fine-tuning the formula

For the new study, called AREDS2, researchers decided to make some changes to the original AREDS supplement to see how different formulations would affect macular degeneration progression. Over 4,000 people aged 50 to 85 years who were at risk for advanced macular degeneration took part in the 5-year study.

• The control group took the standard AREDS formula.
• One group took the AREDS formula with 10 mg of lutein and 2 mg of zeaxanthin.
• One group took the AREDS formula with 650 mg of EPA and 350 mg of DHA.
• Another group took the AREDS formula with all four of these ingredients.

They also made some other changes to the formula, including decreasing the amount of zinc and swapping out the beta-carotene for lutein and zeaxanthin. High doses of zinc can cause stomach upset and beta-carotene may increase lung cancer risk in smokers, limiting its use in these people.

Here are the highlights of the study's findings:

• Adding lutein and zeaxanthin or DHA and EPA to the formula didn't change the supplement's effectiveness.
• Adding all four ingredients to the formula also didn't change the supplement's effectiveness.
• Lowering the zinc dose didn't change the effectiveness of the supplement, but it did decrease the likelihood of stomach upset.
• Substituting lutein and zeaxanthin for the beta-carotene didn't take away from the positive effects of the supplement on eye health.

"Because of potential increased incidence of lung cancer in former smokers, lutein and zeaxanthin could be an appropriate carotenoid substitute in the AREDS formulation," commented lead study author, Dr. Emily Chew of the National Eye Institute at the National Institutes of Health.

See the light

To help prevent macular degeneration, eye health experts recommend getting regular exercise, avoiding smoking, eating fish at least once a week, and consuming plenty of antioxidant-rich foods. Chopping, pureeing, and cooking carotenoid-containing foods in oil help make their beneficial compounds more absorbable.

(JAMA 2013;doi:10.1001/jama.2013.4997)