Dietary cocoa flavanols --
naturally occurring bioactives found in cocoa -- reversed age-related memory
decline in healthy older adults, according to a study led by Columbia
University Medical Center (CUMC) scientists. The study, published today in the
advance online issue of Nature Neuroscience, provides the first direct
evidence that one component of age-related memory decline in humans is caused
by changes in a specific region of the brain and that this form of memory
decline can be improved by a dietary intervention.
The researchers point out that the product used in the study is
not the same as chocolate, and they caution against an increase in chocolate
consumption in an attempt to gain this effect.
As people age, they typically
show some decline in cognitive abilities, including learning and remembering
such things as the names of new acquaintances or where one parked the car or
placed one's keys. This normal age-related memory decline starts in early
adulthood but usually does not have any noticeable impact on quality of life
until people reach their fifties or sixties. Age-related memory decline is
different from the often-devastating memory impairment that occurs with
Alzheimer's, in which a disease process damages and destroys neurons in various
parts of the brain, including the memory circuits.
A cocoa flavanol-containing test
drink prepared specifically for research purposes was produced by the food
company Mars, Incorporated, which also partly supported the research, using a
proprietary process to extract flavanols from cocoa beans. Most methods of
processing cocoa remove many of the flavanols found in the raw plant.
In the CUMC study, 37 healthy
volunteers, ages 50 to 69, were randomized to receive either a high-flavanol
diet (900 mg of flavanols a day) or a low-flavanol diet (10 mg of flavanols a
day) for three months.
Brain imaging and memory tests were administered to each
participant before and after the study. The brain imaging measured blood volume
in the dentate gyrus, a measure of metabolism, and the memory test involved a
20-minute pattern-recognition exercise designed to evaluate a type of memory
controlled by the dentate gyrus.
"When we imaged our research
subjects' brains, we found noticeable improvements in the function of the
dentate gyrus in those who consumed the high-cocoa-flavanol drink," said
lead author Adam M. Brickman, PhD, associate professor of neuropsychology at
the Taub Institute.
The high-flavanol group also
performed significantly better on the memory test. "If a participant had
the memory of a typical 60-year-old at the beginning of the study, after three
months that person on average had the memory of a typical 30- or
40-year-old," said Dr. Small. He cautioned, however, that the findings
need to be replicated in a larger study -- which he and his team plan to do.
Flavanols are also found
naturally in tea leaves and in certain fruits and vegetables, but the overall
amounts, as well as the specific forms and mixtures, vary widely.
The precise formulation used in
the CUMC study has also been shown to improve cardiovascular health. Brigham
and Women's Hospital in Boston recently announced an NIH-funded study of 18,000
men and women to see whether flavanols can help prevent heart attacks and
strokes.
The researchers point out that
the product used in the study is not the same as chocolate, and they caution
against an increase in chocolate consumption in an attempt to gain this effect.
Two innovations by the
investigators made the study possible. One was a new information-processing
tool that allows the imaging data to be presented in a single,
three-dimensional snapshot, rather than in numerous individual slices. The tool
was developed in Dr. Small's lab by Usman A. Khan, an MD-PhD student in the
lab, and Frank A. Provenzano, a biomedical engineering graduate student at
Columbia. The other innovation was a modification to a classic neuropsychological
test, allowing the researchers to evaluate memory function specifically
localized to the dentate gyrus. .
Besides flavanols, exercise has
been shown in previous studies, including those of Dr. Small, to improve memory
and dentate gyrus function in younger people. In the current study, the
researchers were unable to assess whether exercise had an effect on memory or
on dentate gyrus activity. "Since we didn't reach the intended VO2max
(maximal oxygen uptake) target," said Dr. Small, "we couldn't
evaluate whether exercise was beneficial in this context. This is not to
saythat exercise is not beneficial for cognition. It may be that older people
need more intense exercise to reach VO2max levels that have therapeutic
effects."
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