WEDNESDAY, Aug. 7, 2013 (HealthDay News) -- A preliminary new study links two cups of hot cocoa per day to improved memory skills in seniors who had low levels of blood flow in their brains.
So, should you start stocking up on Swiss Miss? Not necessarily.
The research is too limited to prove that cocoa directly boosted the brainpower of those with lower blood flow in the brain, and the findings don't say anything about long-term effects. In addition, drinking two cups of a sweet drink each day could cause or worsen obesity, which is linked to declines in brain function.
"Before we recommend cocoa, it's important to go back and figure out what's in it that's doing this and make sure it's sustainable," said study author Dr. Farzaneh Sorond, an assistant professor of neurology at Harvard Medical School. "I'd prefer people wait until we figure out how to get the benefit without the calories, sugar and fat that comes in cocoa."
Still, the research is allowing scientists to get a better handle on a somewhat mysterious topic -- the flow of blood in the brain. The brain cells known as neurons need fuel to do their job, and blood provides it.
"The brain is a greedy organ, with just 2 percent of body mass and 20 percent of energy requirements," explained Andrew Scholey, director of the Center for Human Psychopharmacology at Swinburne University in Australia. "It requires a constant supply of blood to deliver the metabolic fuels of glucose and oxygen. Blood flow to the brain reduces with aging, and this correlates with cognitive [mental] decline."
Previous research has linked cocoa, which is found in chocolate, to health benefits. In the new study, researchers wanted to find out if it would affect blood flow in the brain, and brainpower itself.
The researchers recruited 60 people with an average age of 73 and assigned them to 30 days of either drinking cocoa rich in flavanol -- which is linked to improved blood flow -- or drinking cocoa low in flavanol. The special cocoa was provided by Mars Inc., but the company didn't have any other role in the study.
Eighteen people had impaired blood flow in the brain when the study began. Almost all of the 60 participants had high blood pressure and half had a form of diabetes. Almost all -- 85 percent -- were white.
Brain blood flow improved by an average of 8 percent by the end of the study in those participants whose levels were low at the beginning. There was no effect among the others who had normal blood flow.
Those with lower blood flow also performed better on memory tests, improving the time they needed to complete tasks (dropping from an average of 167 seconds to 116 seconds), but it's not clear what this would mean in day-to-day life. Again, those with regular blood flow levels didn't improve.
The levels of flavanol in the drinks didn't seem to matter, suggesting that flavanol has no effect or works in very small doses, Sorond said. It's also possible that another ingredient, like caffeine, is responsible for the changes, she said.
It's hard to know exactly what's happening in the brain, she said, but it may have something to do with the widening of vessels so more blood gets through.
The Alzheimer's Association issued a statement on the study Wednesday, noting several caveats about the research.
"This is a very small and very preliminary study, and it is not well-designed as a test of an intervention or therapy," said Maria Carrillo, vice president of medical and scientific relations at the association. "No one should start drinking cocoa with the expectation that it will provide cognitive benefits based on this study."
"There was no control group in this study to compare to the group that drank the cocoa," Carillo continued. Also, "factors that could possibly impact brain blood flow and/or cognition were not controlled, tracked or accounted for -- as far as we can see in the article."
Can Ozan Tan, an instructor at the Harvard Clinical and Translational Science Center who co-wrote a journal commentary about the research, said the study is important for more than what it seems to reveal about cocoa. It also shows a "convincing link" between blood flow in the brain, the physical makeup of the brain and brainpower, Tan said, and this connection could lead to better treatments for brain diseases and declines in brainpower.
The study was published in the Aug. 7 online issue of the journal Neurology.
For more about dementia, visit the U.S. National Library of Medicine.