"Chocolate makes you smarter, proves 40-year study," claims the Daily Express. The news is based on research which found that people who ate chocolate at least once a week performed better in brain tests.
Researchers in the US looked at whether eating chocolate regularly – regardless of the type of chocolate or the amount – was linked to brain function, in about 1,000 participants.
They found that people who said they ate chocolate at least once a week performed better in a range of mental tests involving memory and abstract thinking (among other functions), compared to those who rarely or never ate chocolate.
Lead researcher Georgina Crichton was quoted in the media as saying that the benefits of this would make someone better at daily tasks, "such as remembering a phone number, or your shopping list, or being able to do two things at once, like talking and driving at the same time".
The researchers said their results suggest that the "regular intake of cocoa flavanols may have a beneficial effect on cognitive function".
There have been plenty of studies in recent years looking at the possible health benefits of chocolate, including preventing heart disease and stroke, and improving brain function.
Due to the nature of the study, researchers admit they are unable to say whether the chocolate was responsible for the improved performance in the tests. Plenty of other factors could have been involved.
Before getting too carried away with the supposed health benefits of chocolate, it's worth remembering that chocolate also contains lots of sugar and fat, so should only be eaten in moderation.
Where did the story come from?
The study was carried out by researchers from the University of South Australia, the University of Maine and the Luxembourg Institute of Health, and was funded by the National Institutes of Health. The study was published in the peer-reviewed journal Appetite.
The study received widespread and mostly uncritical coverage by the UK media. The Independent and Daily Express both said that the study gave "proof" that chocolate made people more intelligent, while The Daily Telegraph and Daily Mirror said chocolate "can make you smarter".
However, The Guardian took a more sceptical approach, saying the results were "very vague" and taking the opportunity to question other health claims made for chocolate.
What kind of research was this?
This was a cross-sectional analysis of data from a big cohort study, which follows people through time. However, in this case, the researchers used data from just one time point, giving a "snapshot" of people's diet and brain function tests.
Studies like this can point to links between factors, but cannot demonstrate cause and effect. For example, it could be that chocolate makes people clever – or that clever people tend to eat more chocolate.
What did the research involve?
Researchers looked at the data from about 1,000 people taking part in a US cohort study (the Maine-Syracuse Longitudinal Study, MSLS) which was set up to examine cardiovascular risk factors and brain function in community-dwelling adults. As part of this study, participants filled in food questionnaires and undertook brain function tests from 2001 to 2006.
The researchers adjusted the figures to take account of factors that could skew the results, including people's education level, age, cardiovascular risk factors, and overall diet. They then looked to see whether brain test results varied according to how often people said they ate chocolate.
They excluded people with dementia, a history of stroke and past problems with alcohol use. While the main analysis of 968 people was based on one-off data for each individual, they also looked at data from a sub-group of 333 people who had taken intelligence tests in the past, before providing dietary information. They wanted to see whether intelligence scores could predict whether or not people said they ate chocolate frequently.
People in the study underwent brain function tests in six main areas:
- visual-spatial memory and organisation
- scanning and tracking
- ability to remember spoken information, such as a story or a list
- working memory
- similarities test (to assess abstract reasoning)
- mini-mental state exam
The researchers combined the first five to create an overall score.
The researchers took account of a few variables that could affect the results – such as people's education level, age, sex, overall diet and cardiovascular risk.
What were the basic results?
After adjusting their figures for confounding factors, the researchers found that better-than-average scores on five of the brain function area tests, and the overall score, were linked to eating chocolate more often (at least once a week compared to rarely or never). Tests of verbal memory showed no link to chocolate consumption.
Eating chocolate once a week, or more than once a week, was also linked to above-average test results, compared to eating it less than once a week. However, it's not clear whether eating chocolate more than once a week was linked to better test results than eating it weekly.
When the researchers looked at the subgroup of people who'd had intelligence tests in the years before the dietary questionnaire, they found that intelligence scores did not predict whether or not people ate chocolate.
How did the researchers interpret the results?
The researchers said their results, along with those of other short-term studies, suggest that, "regular intake of cocoa flavanols may have a beneficial effect on cognitive function, and possibly protect against normal age-related cognitive decline."
They add that people will need to strike a balance between the supposed health benefits of eating chocolate and its high-calorie content.
Studies suggesting that chocolate is good for us always grab the headlines. However, as is so often the case, the reality is less clear than the headlines suggest.
The current study adds to information about the links between diet and brain function – the way our brain processes and manages information.
It found that people who scored better than average on these tests said they ate chocolate more often than people who scored worse than average on the tests. But we don't know why that is.
There are quite a few limitations to the study. It's cross-sectional, which means we don't know which came first: the chocolate habit or the better brain function scores. It only shows us results from one snapshot in time.
There are many factors that are hard to account for that could affect how much chocolate you eat, and how well you do on brain function tests – for example, the family you grew up in. We can't be sure chocolate was the only factor that mattered. We also don't know how much chocolate people ate (only how often they ate it) or what type – whether it was dark, milk or white chocolate.
It's not easy to do good-quality, long-term studies into the effects of diet on health or intelligence, but we need to see much more, and better, long-term research before we can conclude that chocolate makes you smarter.
And even if cocoa flavanols do have some benefits, it's worth remembering that chocolate also contains lots of fat and sugar, which can contribute to obesity.