Chemicals in cocoa can boost memory abilities in older people, a new study suggests.
US researchers found flavanols – plant chemicals that are abundant in cocoa beans – improved performance in a list-learning task for people aged between 50 and 75.
Flavanols belong to a group of compounds called polyphenols, which are also abundant in red wine, tea, olive oil, onions, leeks, broccoli and blueberries.
Flavanols are ‘bioactive food constituents’ that protect against cognitive ageing, enhance cognitive performance and boost blood flow to the brain, studies suggest.
Researchers advise caution, however, as chocolate ‘is a treat and not health food’ and is generally low in flavanols.
Popular commercially available chocolate brands like Mars bars are ‘not a reliable source’ of flavanols, according to one expert, although flavanols do tend to be abundant in dark chocolate.
Dr Susan Kohlhass, director of Research at Alzheimer’s Research UK, who was not involved with the study, pointed out that Mars bars are not the best sources of flavanols in the supermarkets.
Sadly for chocolate lovers, the chocolate’s high fat and sugar content means it should be eaten in moderation as part of a balanced diet.
‘Chocolates are not a reliable source of flavanol compounds and this study does not suggest that eating chocolate is good for our cognitive health,’ she said.
Mars Inc, the US chocolatier which backed the research project, pointed out that the experts tested flavanols, not chocolate.
‘Unfortunately, flavanols are destroyed when cocoa is processed into chocolate, making chocolate an unreliable source of these compounds,’ a Mars spokesperson told MailOnline.
Previous research has already linked higher dietary intakes of flavonols with reduced risk of developing dementia – the ongoing decline of brain functioning.
Other research has credited flavanols with cutting the inflammation linked to heart disease, and with reducing the odds of dangerous blood clots.
They are also said to help keep diabetes and high blood pressure under control.
‘Now that we are living into our nineties, an emerging field is looking into what the right diet is for an ageing brain,’ study author Scott Small, a professor at Columbia University, told the Times.
‘I’d like to think there’s a way to tailor a diet to include flavanols, which are found in many foods.’
A 2014 study by Professor Small’s team, also backed by Mars Inc, found dietary cocoa flavanols reversed age-related memory decline in healthy older adults.
For this 2014 study, 37 healthy volunteers, ages 50 to 69, received either a high-flavanol diet or a low-flavanol diet for three months.
With the world’s population ageing, researchers wanted to replicate their initial findings at greater scale.
The researchers recruited 211 healthy people aged between 50 and 75 for the new trial, which lasted for 12 weeks.
At the start and end of the study, participants undertook a series of cognitive tests to assess their thinking and memory and a subset of the participants were given a magnetic resonance imaging (MRI) scan to measure blood flow in the brain.
During the trial, the participants were divided into four groups and given one of three different levels of a supplement containing cocoa flavanols – ‘low intake’ (260 mg per day) ‘medium intake’ (510 mg a day) and ‘high intake’ (770 mg a day).
Some participants also received a placebo (0 mg of flavanols per day) as a baseline.
They then were tasked with three different tests related to memory and brain function – a list-learning test, involving learning different letters in sequence and relaying them, and a list-sorting test, involving sorting images of objects, like banana and elephant.
The third, newly-developed object-recognition task was specific to a region of the brain called the dentate gyrus (DG).
The DG is in the hippocampus and is thought to play a major role in episodic memory formation.
Previously established list-learning and list-sorting tasks targeted the hippocampus and prefrontal cortex, respectively.
The diet supplemented with cocoa flavanols seemed to improve performance only on the memory task specific to learning a list, the team found.
There was no effect of 12 weeks of flavanol supplementation on blood flow to the DG, the region of the brain the researchers had identified in advance of the study.
‘Flavanol intake did not improve performance on the object-recognition task, the study’s primary endpoint, failing to replicate our previous findings,’ the researchers say in their paper, which has been published in the journal Scientific Reports.
‘Object-recognition and list-sorting performance did not correlate with baseline diet quality and did not improve after flavanol intake.
‘However, the hippocampal-dependent list-learning performance was directly associated with baseline diet quality and improved after flavanol intake.’
The findings suggest cocoa helps older people to recall information in their short-term memory, but less so for quickly identifying visual similarities between objects and patterns.
Analysis suggested newly-developed object-recognition task may have been too difficult for older participants
Dr Kohlhass highlighted the need for longer large-scale studies ‘to fully understand whether a diet high in these flavanols could boost cognition in old age’ and pointed out that the team effectively failed to replicate their findings from 2014.
‘We also don’t know how meaningful the improvements measured in the tests used here would be for people in their daily lives,’ Dr Kohlhass said.
‘While the researchers found that by the end of the study, those on a high-flavanol diet performed better in a list-learning task compared to the placebo group, they did not find a relationship between flavanol intake and performance on two other cognitive tests, one of which was the primary endpoint for the study.’
Another limitation were the fact the team used cocoa flavanol supplements provided to participants in capsule form, rather than pure cocoa.
Dr Kohlhass couldn’t say whether a diet high in cocoa would have any effect in either preventing or delaying the onset of dementia from the study’s findings.
‘Continued investment in research is crucial to find ways to protect the brain and reduce the risk of diseases that cause dementia,’ she said.
‘Although there’s currently no certain way to prevent dementia, research shows that a healthy lifestyle can help keep our brains health as we age.
‘A healthy diet, regular exercise, not smoking, and keeping blood pressure and weight in check can all help lower the risk of dementia.’