The scientists randomly assigned 60 people with an average age of 73 to drink two cups of flavanol-rich or flavanol-poor cocoa every day for a month. Flavanols are a type of polyphenol -- antioxidants found in dark-colored foods including cocoa, tea, berries and wine. Flavanol-rich foods have been shown in past studies to benefit the heart and brain. The problem with these earlier studies, however, is they were based on food-consumption questionnaires, rather than having people actually eat certain foods and then measuring the biological results. The findings were published in the journal Neurology.
Subjects in the current study were tested for memory and thinking skills before, during and after the "cocoa intervention." Their levels of blood flow in the brain also were measured.
After a month of cocoa drinking, the researchers didn't find any overall differences between the high- and low-flavanol groups in terms of cognitive abilities, so they looked a little deeper. What they found was that people who had compromised blood flow to the brain and white matter damage at the beginning of the study did show a difference after drinking hot chocolate for a month: Blood flow in their brains improved by 8.3 percent and the time it took them to complete a memory test dropped from 167 seconds to 116 seconds.
These results support earlier evidence that cocoa's benefits may stem from its capacity to improve blood flow to the brain.
"We're learning more about blood flow in the brain and its effect on thinking skills," said study author Dr. Farzaneh A. Sorond, of Harvard Medical School. "As different areas of the brain need more energy to complete their tasks, they also need greater blood flow. This relationship, called neurovascular coupling, may play an important role in diseases such as Alzheimer's."
But scientists still don't know what it is in the chocolate that is beneficial. There was no difference in outcome between the high- and low-flavanol groups. So they don't know if it is the flavanols, the caffeine or another compound called theobromine. The researchers' hunch is that just a little flavanol is enough to make a big difference.
The researchers say that in the future, "Regular cocoa consumption may be a strategy to minimize (perhaps even reverse) cerebral vascular pathology in neurodegenerative disorders, regardless of its flavanol content," but "more work is needed to prove a link between cocoa, blood flow problems and cognitive decline."
The upshot is that more chocolate studies need to be done. Alas.
Want more Squid Ink? Follow us on Twitter or like us on Facebook, and follow Samantha Bonar at @samanthabonar.