Eating a diet rich in antioxidants may not lower your risk of developing Alzheimer’s disease, according to a new study that found that overall antioxidant intake was not related to dementia risk. But as with all food research, the connection between what we eat and why we get sick remains complex.
Antioxidants, which include nutrients like vitamins C and E, selenium and lycopene, are found in a wide variety of fruits and vegetables and other foods. Antioxidants act to mop up the highly reactive oxygen molecules called free radicals that can build up during daily living and damage cells throughout the body, including the brain. They have been thought to contribute to a lower risk for heart disease, cancer and other ills.
The results of the study, published in the journal Neurology, counters earlier research that found that antioxidants may be good for the brain, lowering the risk for Alzheimer’s and stroke. The findings underscore some of the difficulties inherent in dietary studies, which typically rely on people’s reports of what they eat. Diet is also complex, involving hundreds of foods, making it difficult to separate out the impact of individual nutrients on disease and health.
"These results are interesting because other studies have suggested that antioxidants may help protect against stroke and dementia," said study author Elizabeth E. Devore of Harvard Medical School in Boston. "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."
For the study, researchers surveyed more than 5,000 men and women age 55 and older about how often they ate 170 foods over the course of the previous year. They were then grouped according to whether they consumed low, moderate or high amounts of antioxidants. None of the participants had signs of dementia at the start of the study.
They were then followed for an average of 14 years. During that time, about 600 developed Alzheimer’s or another form of dementia. Those in the high-antioxidant group were no less likely to develop dementia than those who consumed low total levels of antioxidants.
Dr. Devore noted that in this study, 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.
In other studies showing a link between antioxidants and stroke and dementia risk, she noted, there was less variation in tea and coffee consumption, and more of the differences in antioxidants levels were due to fruits and vegetables in the diet. It is possible that individual nutrients, such as vitamin E, may play more of a role in brain health than overall antioxidant levels, she said.
Other studies have been mixed on whether antioxidants protect the brain. Last year, a study of people with mild to moderate Alzheimer’s found that taking antioxidant supplements like vitamins C and E did not appear to be effective in altering the course of Alzheimer’s disease. [See the ALZinfo.org story, “Antioxidant Pills Ineffective in Alzheimer’s Study,” at http://www.alzinfo.org/08/articles/drugs-and-treatment/antioxidant-pills-ineffective-alzheimers-study .] That study, however, only lasted four months, and it did not address the question of whether taking antioxidant supplements by healthy people might affect their risk of developing Alzheimer’s.
Nutrition experts point out that many foods contain a rich mix of antioxidants, so that taking one or several supplements does not duplicate the benefits of eating healthful foods. Numerous studies suggest that eating a rich variety of fruits and vegetables may help to ward off Alzheimer’s and a range of other ailments. Other research shows that a Mediterranean-style diet rich in fish, olive oil, fruits, vegetables and red wine and low in red meat and butter may help protect against Alzheimer's, heart disease and other ills.
Source: Neurology, from the American Academy of Neurology, published online, Feb. 20, 2013