Eggs provide two important antioxidants—lutein and zeaxanthin—that have been shown to protect the retina and reduce the risk of cataracts and age-related macular degeneration (AMD), the leading cause of age-related blindness. AMD affects more than 13 million Americans or 5% of people 65 and older.

The two antioxidants are part of the carotenoid family (like beta-carotene in carrots) and the only carotenoids found in the eye. People can’t make these carotenoids on their own and must get them from foods such as egg yolks, fruits, and green-leafy vegetables. Previous research has shown that lutein in eggs may be better absorbed by the body than it is from other sources, such as dietary supplements or spinach.

“The two studies on lutein and zeaxanthin provide further validation that eggs provide important eye health benefits for baby boomers and aging adults, says Donald McNamara, executive director of the Egg Nutrition Center. “They also support the 30-plus years of research that show people can enjoy an egg or two a day without negatively impacting blood cholesterol levels, something that has been misunderstood by both health professionals and the public.”

In one of the studies published in the Journal of Nutrition, 24 women ages 24 to 59 were randomly assigned to one of three groups: a group that consumed a sugar pill daily or one of two egg groups. Women in both egg groups ate six eggs a week for six weeks. The eggs contained either 330 micrograms or 960 micrograms of lutein and zeaxanthin.

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Zeaxanthin levels significantly increased for both egg groups and lutein levels increased for the women in the first egg group. Eye pigments that help protect the retina by blocking out harmful light significantly increased in both egg groups. And interestingly, cholesterol levels significantly increased in the group that consumed the sugar pill but did not increase in either egg group.

The other random control study published late last month also showed that eating an egg a day significantly increases lutein and zeaxanthin levels without raising cholesterol. Thirty-three men and women over the age of 60 took part in each phase of a four-phase study. Lutein and zeaxanthin levels increased by 26% and 38%, respectively, after participants ate an egg a day for five weeks. There was no increase in levels of these nutrients during a five-week period when participants ate egg substitutes (that do not have the antioxidants) daily, nor during two, three-week periods when no eggs or egg substitutes were consumed. Cholesterol levels did not differ during any phase of the study.

“Many people think they are doing themselves a favor by only consuming egg substitutes or egg whites,” says Marcia Greenblum, a registered dietitian. “But the fact is, many of an egg’s nutrients are found in the yolk, including most of the choline and vitamin B12, and about 40% of the protein.”