March 24, 2006 -- Your eyes may be a window to your body's health, a new study shows.

The report, published in Nutrition, shows that diet and lifestyle might sway the odds -- for better or worse -- of developing age-related macular degeneration (AMD).

AMD is America's leading cause of vision loss. More than 13 million people in the U.S. show some signs of AMD, which is uncommon in people younger than 55. A new study shows that diet, smoking, and BMI (body mass index) may affect the chances of getting AMD.

Eating healthfully, not smoking, and not being overweight could help keep age-related macular degeneration at bay, according to the new study. The reverse also appears to be true, write the researchers. They included Johanna Seddon, MD, of Harvard Medical School and the Harvard School of Public Health.

Tracking AMD

Seddon and colleagues studied 934 people who were 67 to 71 years old, on average. Half of the participants were screened at a Boston eye and ear clinic. The others were screened at an eye clinic in Portland, Ore.

A total of 184 participants didn't have AMD. The rest had mild AMD (201 patients), moderate AMD (326 patients), or advanced AMD (223 patients).

Participants completed surveys about their diet and lifestyle. They also gave blood samples, which Seddon's team checked for levels of C-reactive protein (CRP) and homocysteine, which have been linked to increased risk of heart disease.

The researchers had previously reported that CRP and homocysteine are associated with age-related macular degeneration. This time, they checked how diet and lifestyle affected levels of CRP and homocysteine, as well as AMD risk.

None of the participants were asked to change their diets or lifestyles. The researchers just looked for patterns among the participants' habits, blood chemicals, and AMD diagnosis.

Eye-Opening Data

The researchers found that people who smoked, were overweight, and consumed fewer antioxidants (natural chemicals found in many fruits and vegetables) tended to have higher levels of CRP and homocysteine.

For instance, people who reported eating fish more than twice per week had lower CRP levels. This was also true for people who consumed higher levels of vitamin C, beta-carotene, and the antioxidants lutein and zeaxanthin.

CRP levels were higher for people who smoked or had higher BMI, the study also shows.

Lower homocysteine levels were seen in people with more vitamin E in their blood and those who consumed more antioxidants and vitamin B-6. But higher blood levels of vitamin E were also tied to higher CRP levels. That contradiction should be studied further, note Seddon and colleagues.

"Overall, these findings suggest that sick eyes may occur in sick bodies related to smoking, being overweight, and other unhealthy behaviors," they write.

"AMD is associated with immune, inflammatory, and other cardiovascular mechanisms, and these results emphasize the need to adhere to healthy lifestyles for your eyes and your body overall," Seddon says in a news release.