AMD is the leading cause of blindness in people older than 50, and affects more than 10 million Americans. The disease affects the central part of the retina -- the macula -- which is responsible for controlling fine vision, leaving sufferers with limited sight.
The first study, led by Elizabeth Goodrow of the University of Massachusetts, examined the effects of eating one egg per day on blood levels of lutein and zeaxanthin in 33 men and women older than 60. The participants were fed one egg or an egg substitute per day for a five-week period before switching to a period where the participants did not eat eggs. The researchers found that lutein levels increased by 26 percent, while zeaxanthin levels increased by 38 percent compared to the no-egg weeks. Goodrow's team also noted that the egg-a-day diet did not increase total, LDL or HDL cholesterol, or triglycerides.
"These findings indicate that in older adults, five weeks of consuming one egg per day significantly increases serum lutein and zeaxanthin concentrations without elevating serum lipids and lipoprotein cholesterol concentrations," the researchers wrote.
The second University of Massachusetts study, led by Adam Wenzel, examined the effects of a 12-week diet of six eggs per week on blood levels of lutein and zeaxanthin on 24 women aged between 24 and 59.
The women were randomly assigned to one of three groups: The first ate six eggs per week containing 330 micrograms of lutein and zeaxanthin each; the second ate six eggs per week containing 965 micrograms of the nutrients each; and the third was given placebo.
At the study's end, the researchers found that blood levels of zeaxanthin -- but not lutein -- increased in the two groups that ate eggs, but not in the placebo group. Wenzel also found that the egg groups' cholesterol levels were unaffected by the eggs, though the placebo group -- which took a sugar-filled capsule -- experienced increases in total cholesterol and triglycerides.
"This study once again shows the power of natural medicine found in wholesome foods," says Mike Adams, author of The Honest Food Guide, a free downloadable nutrition guide for consumers. "Eggs are also a good source of protein, sulfur compounds and essential fatty acids."