March 8, 2008 - Modern Medicine
Some foods may reduce glaucoma risk, study finds
Including certain fruits and vegetables in one's diet may reduce a person's risk of getting glaucoma, according to a study of older African-American women reported here at the American Glaucoma Society meeting.
JoAnn A. Giaconi, MD, assistant clinical professor of ophthalmology, Jules Stein Eye Institute, Los Angeles, reported on a study of 662 African-American women who participated in the Study of Osteoporotic Fractures. All of the women underwent disc photography and suprathreshold visual field testing to ascertain glaucoma; discs subsequently were graded by two masked and trained readers, and a glaucoma specialist reviewed all test results. Another glaucoma specialist confirmed glaucoma diagnoses.
Researchers ascertained diet through the Block Food Frequency Questionnaire (BFFQ), examined relationships between food and nutrient consumption and glaucoma using logistical regression, and looked for dose-response trends using the Cochran-Armitage trend test.
Mean age of the study population was 75 years. The investigators had disc and BFFQ data on 584 women (88.2%). Glaucoma was diagnosed in 77 (13%) of them.
"Subjects in the study who tended to consume more fruits and fruit juices had a lower likelihood of having glaucoma," Dr. Giaconi said. "Women who ate one serving a day of fruit compared with those eating less than one per day had a 65% decreased likelihood of glaucoma, and this increased to 79% if they were eating three or more servings. Women who ate more vegetables overall did not have this association."
When researchers looked at data pertaining to specific fruits and vegetables, they found that patients eating more oranges, peaches, spinach, green collards, and kale were less likely to have glaucoma.
"Women who consumed the highest quartile of oranges and peaches had an 82% and 70% decreased likelihood, respectively, of glaucoma compared with those who consumed less than a serving per week," Dr. Giaconi said. "And with the collard greens, it appears that just one serving per month was protective compared with subjects who ate less than a serving a month."
One study limitation is that the results cannot be generalized to men, other ethics groups, or younger patients, she said. Also, because the participants completed the questionnaire at the same time that glaucoma was being diagnosed, researchers can establish only that a relationship exists between diet and the disease; they cannot establish causation. Other limitations include the possibility of confounding by other variables such as family history, the issue of multiple comparisons, and the possibility that findings were obtained by chance.
"Further exploration of diet and glaucoma is warranted in different populations," Dr. Giaconi said. "At this time, it may be worthwhile to recommend fruits and green leafy vegetables to our patients who are risk for glaucoma or to patients who ask, 'What else can I do about my glaucoma?' At a minimum, we may be helping them, and we're probably not hurting them. There is evidence in other fields that these food items are beneficial to health in general."