People who closely follow the Mediterranean diet -- especially by eating fruit -- may be more than one-third less likely to develop age-related macular degeneration (AMD), a leading cause of blindness. The study, presented at the annual meeting of the American Academy of Ophthalmology is also the first to identify that caffeine may be especially protective against AMD.
What causes age-related macular degneration?
Macular degeneration is a chronic disease that attacks the central part of the retina called the macula, which controls fine, detailed vision. The condition results in progressive loss of visual sharpness making it difficult to drive a car, read a book and recognize faces.
The exact cause of AMD is unclear, but factors such as genetics, family history, cigarette smoking, high blood pressure, excessive sunlight exposure, and a diet low in antioxidants are linked with a greater risk. (Antioxidants are thought to protect cells in the retina from the harmful effects of free radicals, unstable molecules formed from cigarette smoke, pollution and ultraviolet light.)
The Mediterranean diet, which emphasizes eating fruits, vegetables, whole grains, legumes, nuts, healthy fats and fish, and limits red meat and butter, has been shown to improve heart health and reduced risk of cancer, but there has been little research on whether its benefits extend to eye health.
To determine this, researchers studied 883 Portuguese people, age 55 or older, to see whether adherence to the diet impacted their risk of AMD. Their findings revealed a significant reduction in risk in those who ate a Mediterranean diet most frequently, and particularly among those who consumed more fruit and caffeine.
Higher Mediterranean diet scores meant lower AMD risk
Researchers assessed their diets based on a questionnaire asking how often they ate foods associated with the Mediterranean diet. The more they ate foods associated with the diet, the higher the score, from 0-9. Those who closely followed the diet scored a 6 or greater.
Of those who did not closely follow the diet (scored below a 6), 50 percent had AMD. Of those who did closely follow the diet (scored 6 or above), only 39 percent had AMD. This represents a 35 percent lower risk compared to those who did not adhere to the diet.
Fruits especially beneficial
Researchers analyzed consumption of foods and found that people who consumed higher levels of fruit were significantly less likely to have AMD. Of those who consumed 150 grams (about five ounces) or more of fruit a day: 54.5 percent did not have AMD and 45.5 percent had AMD. Overall, people who ate that much fruit or more each day were almost 15 percent less likely to have AMD, based on an odds ratio calculation.
Caffeine and antioxidants also protective
Researchers used a computer program to analyze the participants' consumption of micronutrients, according to their answers on the questionnaire. They found higher consumption of antioxidants such as beta-carotene and vitamins C and E was protective against AMD. Of those who consumed high levels of caffeine (about 78 mg a day, or the equivalent of one shot of espresso): 54.4 percent did not have AMD and 45.1 percent had AMD.
While caffeine is not considered part of the Mediterranean diet per se, consumption of coffee and tea is common in Mediterranean countries. The researchers opted to look at caffeine because it is a powerful antioxidant that is known to be protective against other conditions, such as Alzheimer's disease.
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