"These results are interesting because other studies have suggested that antioxidants may help protect against stroke and dementia," said study author Elizabeth E. Devore, ScD, of Harvard Medical School in Boston and Erasmus Medical Center in Rotterdam, Netherlands. "It's possible that individual antioxidants, or the main foods that contribute those antioxidants-rather than the total antioxidant level in the diet-contribute to the lower risk of dementia and stroke found in earlier studies."
The study involved 5,395 people age 55 and older who had no signs of dementia at the start of the study. Participants completed questionnaires about how often they ate 170 foods over the past year at the start of the study. Then the participants were followed for an average of nearly 14 years.
Participants were divided into three groups: low, moderate and high levels of antioxidants in the diet. About 600 people developed dementia during the study and about 600 people had a stroke. But researchers found that people with high levels of antioxidants were no more or less likely to develop brain disease than people with low levels of antioxidants.
Devore noted that about 90 percent of the difference in antioxidant levels in the study was due to the amount of coffee and tea people drank. Coffee and tea contain high levels of nontraditional antioxidants such as flavonoids.
"This differed from an Italian study that found the higher total antioxidant levels were associated with a lower risk of stroke, where the variation from coffee and tea was lower, and the contribution from alcoholic beverages, fruits and vegetables was higher," Devore said.
The study was supported by the Netherlands Organization for Scientific Research and the U.S. National Institutes of Health.