A mug of cocoa is not a cure for memory problems

"Cup of cocoa could give the elderly the memory of a 'typical 30 or 40-year-old'," The Independent reports.

Before you race down to the supermarket to pick up a tub of chocolatey powder, you might want to pause to consider some facts that rather undermine this headline.

The news is based on a small study that found a specially formulated cocoa-based drink high in "flavanols" made older people slightly faster, but no more accurate, in memory tests.

The research, which happened over a period of just three months, also looked at brain scans of the test subjects. It found increased activity in an area of the brain thought to be involved in cognition and memory – the dentate gyrus.

It is difficult to gauge whether the modest improvements seen in testing would have a significant impact on a person's daily life or functioning.

The prospect of halting or reversing dementia or age-related cognitive decline through simple changes in your diet is incredibly appealing. But while the results of this study suggest the particular product tested could improve cognition and memory, it certainly does not prove this.

Where did the story come from?

The study was carried out by researchers from universities based in New York, and was funded by US National Institutes of Health grants, as well as what was described as an "unrestricted grant" from Mars Incorporated.

One of the study authors declared a financial conflict of interest as they were also employed by Mars. As Mars is one of the globe's leading makers of chocolate products, this may represent a potential conflict of interest.

The study was published in the peer-reviewed journal, Nature Neuroscience.

The majority of the media coverage portrayed this study as showing cocoa was effective at improving memory, which you might assume means a better and more accurate recall of things. In reality, the research was more limited and the improvements were only seen in the speed of memory tasks, not in the accuracy of tasks.

The most frivolous headlines came from The Independent, with "Cup of cocoa could give the elderly the memory of a 'typical 30 or 40-year-old'," and the Daily Express, with its front page headline claiming that, "new study proves cup of cocoa can boost the brain". These statements are premature, potentially misleading and are not justified by this research alone.

The Independent's unfortunate headline may simply have parroted a press release on the research from Columbia University. In the press release, one of the researchers was quoted as saying, "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."

The study did not recruit anyone aged 30 to 40 to test this directly, so it appears to be an assumption. The main study publication itself also did not make these bold claims – they were confined to the press release.

Larger long-term trials may show whether more rounded improvement in cognitive ability and memory are possible using high flavanol supplements.

What kind of research was this?

This was a small randomised control trial testing the effect of a low- or high-cocoa diet on age-related memory decline in older adults.

The researchers state the function of a brain region called the dentate gyrus declines as people age, and is therefore considered to be a possible source of age-related memory decline.

This study first looked to find evidence that lower dentate gyrus function was indeed related to memory decline and, secondly, to test an intervention to stop the decline or reverse it.

A randomised control trial is one the best study designs to investigate whether dietary interventions such as this can influence cognitive ability.

The downside is that they tend to be very expensive to set up and run, so are often short and involve small numbers (as was the case with this study), which limits the applicability of the results to other populations.

What did the research involve?

The study involved asking volunteers aged 50 to 70, who were free from cognitive impairment, to follow a three-month lifestyle intervention containing diet and exercise elements.

Before and after the intervention, the research team compiled brain scans of the dentate gyrus region of the volunteers and tested their cognitive abilities to see if the diet, exercise or both elements together were influencing signs of age-related cognitive decline.

The study participants were free from illness, but were selected to be physically inactive and not to be above-average fitness. They were also excluded if they had a medical condition that didn't allow them to undertake aerobic activity. Anyone who routinely took dietary or herbal supplements was also excluded from the study.

The volunteers were randomised into one of four groups:

• high flavanol with aerobic exercise (eight people)
• high flavanol without aerobic exercise (11 people)
• low flavanol with aerobic exercise (nine people)
• high flavanol without aerobic exercise (nine people)

The people in the groups were similar in terms of age, educational level and gender.

The prescribed anaerobic exercise was one hour a day, four days a week. The high-flavanol intake group took 900mg cocoa flavanols with 138mg of epicatechin (another flavanol) every day, compared with the low-flavanol group, who consumed 10mg cocoa flavanols and less than 2mg epicatechin per day.

It isn't completely clear how the diet supplement element was delivered, but the researchers describe how participants were given the flavanols as a packet, possibly to dissolve in water like an instant chocolate drink.

Brain scans used a high-resolution variant of functional magnetic resonance imaging (fMRI) to map the precise site of age-related dentate gyrus dysfunction. fMRI allows scientists to see blood flow and volume in the brain as a sign of activity.

Cognitive abilities were assessed using a test called ModBent. ModBent has a matching element that involves showing complex images and asking people to "Click on the figure that looks exactly like the one you just saw as quickly as possible".

It also has a recognition element, which also shows complex images and asks people, "Is this one of the figures you saw earlier?"

The test scores are built up using both the speed of the answer (reaction time) and how many were recalled correctly (delayed retention). ModBent score was used in this study because it has previously been shown to deteriorate with age.

What were the basic results?

The study was completed by 37 people.

The main finding was that people given high-flavanol supplements had a significantly faster ModBent reaction times, but showed no improvement in retention tests. People who were given high flavanols were, on average, 630ms faster than the low-flavanol group after the intervention.

This was mirrored by a higher dentate gyrus function in the high-flavanol group compared with the low-flavanol group, as assessed in the brain scans.

Interestingly, this effect was unrelated to the exercise component. This was a surprise to the researchers, as previous research suggested regular exercise could reduce cognitive decline.

They investigated this further and found the exercise had not led to any physiological changes in VO2 max, one of many measures of cardiovascular fitness, which measures the amount of oxygen you use while exercising at maximum capacity.

From this, the researchers concluded people had not stuck to the exercise component of the intervention, so the results related to this were not valid. 

How did the researchers interpret the results?

The researchers stated that, "Our results indicate that dietary cocoa flavanol consumption enhanced DG [dentate gyrus] function," and the cognitive test and brain scan results "provide evidence that age-related changes in the DG observed in aging humans underlie and drive a hippocampal-dependent component of cognitive aging."

Conclusion

This small randomised control trial found giving people a supplement high in cocoa flavanols for three months appeared to improve the function of a brain area – the dentate gyrus.

Decreased activity in the dentate gyrus is thought to be involved in age-related memory decline. People who had high-flavanol supplements performed tests assessing cognitive ability more quickly than those who had low-flavanol supplements.

The prospect of halting or reversing age-related cognitive decline through simple changes in your diet is very appealing, and this study suggests one way it might be possible. However, this study alone does not prove this as it has a number of limitations, including:

• The group sizes were small. Only 37 people took part and they were further subdivided into groups of less than 10 for most comparisons.
• There were tiny differences in caffeine and theobromine levels in the high- and low-flavanol cocoa packets, making it possible that substances other than flavanols mediated the effects seen.
• Only reaction times, and not accuracy of performance, improved. Memory improvements weren't shown directly – participants may have improved their reaction times by simply paying more attention to the task. It is not known whether the observed changes in reaction times would have had any meaningful difference in terms of the person's daily life and functioning.
• Participants who exercised regularly or took regular herbal or vitamin supplements were excluded from the study, meaning results in this group might be different.
• None of the participants in this trial were reported to have any cognitive impairment, and longer-term diagnoses of cognitive impairment or dementia were not assessed, so it is not known whether high flavanol intake is of any benefit in preventing these outcomes.

It is also important to point out that the cocoa supplement used was specially formulated for the trial. You shouldn't be led to believe that drinking lots of hot chocolate bought in a supermarket, which can be very high in sugar, will necessarily boost your brain power: it may just boost your waistline. In fact, lots of hot chocolate could raise your blood pressure and increase your risk of tooth decay.