A new study of over 16,000 women over age 70, conducted by researchers at Harvard, has found that eating an average of one-half cup of blueberries or one cup of strawberries per week, over decades, may slow the memory and cognitive decline associated with aging by up to 2.5 years.
The study, conducted by Elizabeth E. Devore ScD, of Channing Laboratory, Brigham and Women’s Hospital, and Harvard Medical School in Boston, Massachusetts, and colleagues, was published in the April 25, 2012 online issue of the Annals of Neurology, the official journal of the American Neurological Association.
“What makes our study unique is the amount of data we analyzed over such a long period of time. No other berry study has been conducted on such a large scale,” explained Elizabeth Devore, the lead author. “We provide the first epidemiologic evidence that berries appear to slow progression of memory decline in elderly women,” noted Dr. Devore.
“Among women who consumed 2 or more servings [of one-half cup each] of strawberries and blueberries each week we saw a modest reduction in memory decline. This effect appears to be attainable with relatively simple dietary modifications,” she said.
The Study; Methodology
The data for the study was drawn from the large ongoing Nurses’ Health Study—including 121,700 female, registered nurses between the ages of 30 and 55—who completed health and lifestyle questionnaires beginning in 1976.
Since 1980, the participants completed questionnaires every four years regarding their frequency of food consumption. Between 1995 and 2001, 16,010 of the participants, who were over age 70 years, also took a battery of memory tests, at 2-year intervals.
Those approximately 16,000 women, who were included in the present study, had an average age of 74 and mean body mass index of 26.
The Harvard researchers conducted statistical analysis to compare the rates of mental decline (which is normally age-related) measured in those women who reported eating little or no berries to those women who ate the most blueberries and those who ate the most strawberries.
The results of the food frequency questionnaires answered by the women every four years were averaged over time to determine the extent of berry consumption for this purpose. For purposes of the study, a serving of berries was considered to be one-half cup.
The researchers found that the nurses who ate the most blueberries and strawberries delayed their memory and cognitive decline by 1.5 to 2.5 years, compared with those who did not report eating blueberries or strawberries.
The participants in the study who ate the most blueberries reported eating an average of one serving (one-half cup) or more of blueberries per week. Those who ate the most strawberries reported eating an average of two servings (two one-half cups) or more of strawberries per week.
The authors summarized their findings scientifically, as follows:
In addition, the researchers found that, while berries appeared to help memory and mental functioning the most, other foods rich in flavonoids such as other fruits and vegetables, tea, onions and red wine, may also be helpful for memory, Dr. Devore told Businessweek.
“Additionally, in further supporting evidence, greater intakes of anthocyanidins and total flavonoids were associated with slower rates of cognitive decline (p-trends = 0.015 and 0.053, respectively, for the global score),” the authors wrote.
“This is pretty compelling evidence to suggest that berries do appear to have memory benefits,” said Dr. Devore, the lead author.
“Our findings have significant public health implications as increasing berry intake is a fairly simple dietary modification to reduce memory decline in older adults,” she said in a news release issued by Harvard.
Dr. Devore explained that she and her colleagues focused on berries because previous studies conducted on mice showed that a flavonoid called anthocyanidin, the key compound found in berries, could transfer from the blood into brain tissues and become concentrated in the hippocampus, which is responsible for learning and memory.
Anthocyanidin and other flavonoids are antioxidents, which fight inflammation and oxidation, both processes that affect aging brain cells.
The study authors caution that their study does not prove that berries directly caused the slower mental decline observed in the highest berry-eaters.
In fact, the researchers found that the study participants who ate strawberries and blueberries regularly also got more exercise and had higher incomes. Both of those factors have also been associated with better health in previous studies.
However, the researchers report that even after controlling and adjusting for factors such as those, they found that eating a diet high in fruits and vegetables, especially berries, still correlated with slower mental decline with aging.
The study is the first to study the effects of berry consumption on long-term cognitive decline, and the authors call for further studies to repeat and confirm their findings.
In the meantime, however, it makes sense to add blueberries and strawberries to your diet, frozen or fresh, Dr. Devore told Time. “I don’t think there are many downsides to that. The availability of berries and access to this kind of intervention is great as a public health message,” said Dr. Devore.
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