Devore and her colleagues also failed to find a connection between total diet antioxidant power and brain sizes among the 462 participants who got an MRI test.
These findings suggest that it is time to go back to studying individual antioxidants, but more comprehensively, Devore said.
A connection between vitamin C and vitamin E and reduced risk of stroke and dementia, respectively, has been found in a number of studies, but there are probably other antioxidants such as flavonoids found in foods including onions, peas and berries that could be important, Devore said.
For his part, Bowman thinks there could still be a connection between antioxidant capacity in the Dutch group and dementia and stroke risk, but the researchers are not seeing it because they used food questionnaires to evaluate antioxidant levels.
"An alternative approach would be to look at dietary signatures in the blood," Bowman said.
Measuring nutrient levels in the blood could not only give a direct indication of what is available to the brain, but it could help avoid the inaccuracies in what people say they eat and differences in how well individuals absorb what they eat, he added.
In a 2012 study, Bowman and his colleagues developed a test to measure the levels of a panel of nutrients in the blood and found a connection among elderly people between high levels of vitamins B, C, D, and E and improved cognitive function and larger brains.
Although this connection has to be studied more, Bowman is working to start a clinical trial to test whether increasing the level of vitamins C and E could indeed help protect the brain from diseases.
In the meantime, Bowman gives his patients the same advice: to cut out the junk, such as trans fats, and load up your diet with antioxidant-rich nutrients. He only recommends antioxidant supplements temporarily if someone has low blood levels.
Find out more about antioxidants at the U.S. National Institutes of Health Office of Dietary Supplements.
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