One cup won’t boost your memory, alas, but your tongue won’t be complaining (Image: Laurence Mouton/Corbis)

Here’s one for chocoholics to chew on. After consuming drinks enriched with compounds found in cocoa beans for three months, the performance of people aged 50 to 69 on a memory test was akin to someone several decades younger. Problem is, if you want such a benefit from eating chocolate, you would have to eat staggering amounts.

The small study is the latest to suggest that chemicals in cocoa called flavanols can have beneficial effects on the brain. Flavanols are a type of chemical found naturally in cocoa beans, blueberries, green tea and red wine. Previous studies have suggested that mice on a flavanol-rich diet showed enhanced memory and greater blood flow to certain areas of the brain. Scott Small, a neurologist at Columbia University in New York City, wanted to see what affect a similar regime might have on the human brain.

To find out, his team instructed 19 volunteers aged 50 to 69 to drink 900 milligrams a day of powdered cocoa flavanols mixed with water or milk. This dosage was spread over two drinks each day. Another 18 people had to drink a similar beverage that contained just 10 milligrams of the compounds.


Before and after the three months, people in both groups underwent fMRI scans. Comparing the scans revealed that after the regime, the high-dose flavanol drinkers had about 20 per cent more blood flowing to a particular section of their hippocampi, called the dentate gyrus, than they did before. The high-dose drinkers also had about this much more blood flow to the dentate gyrus than the low-flavanol group. Intriguingly, this region has been linked to age-related memory decline in people.

Now you see it

In addition, each person had to complete a memory test before and after the three-months. In each test, participants were shown 41 similar, abstract shapes, one after the other. Once these had all been presented, they were shown 82 more shapes and had to identify the ones they had seen before. Previous work by Small’s team has shown that from their twenties onwards, adults’ reaction times to identifying previously seen shapes decrease with age, by about 220 milliseconds for each decade of age.

On average, the high-flavanol group reacted to each shape 630 milliseconds faster than the low-dose group. This is equivalent to the high-dose group performing as though they were three decades younger than the low-dose group.

But don’t start stocking up on Mars bars just yet, cautions Small. “Yes, these flavanols exist in chocolate, but in a very miniscule amount,” he says. “You would have to consume so much chocolate to get it that you would damage your health.”

Public health issue

“Society is ageing, and we are always looking for interventions to delay the decline in cognition that goes with this,” says neurologist Madhav Thambisetty at Johns Hopkins School of Medicine in Baltimore, Maryland. “This study tackles what is a fundamental public health problem.”

He says he would like to see what affect drinking flavanols has on other types of memory test in a larger study – which is what Small plans to do next.

Sebastian Jessberger at the University of Zurich in Switzerland agrees that more work is needed to tease out what the flavanols are doing. For example, he points out that it would be good to find out how long the effect on memory lasts, how much is needed to be effective, and if the compounds are causing changes in other parts of the body.

“It’s naive to think that you take a drug or a compound and there’s only one area where something is changing,” says Jessberger.

Journal reference: Nature Neuroscience, DOI: 10.1038/nn.3850