One of my favourite foods is chocolate, especially the milky stuff, but I will eat dark chocolate. So this particular headline cheered me up no end: “People who eat dark chocolate are less likely to be depressed”. It was based on a study carried out by researchers from University College London, published in the journal Depression & Anxiety. They compared the chocolate-eating habits of more than 13,000 adults (based on dietary questionnaires), with their depression scores (based on something called the Patient Health Questionnaire).
After adjusting for confounders such as height, weight, marital status, ethnicity, education, income, physical activity, smoking, etc, they found that eaters of dark chocolate had 70 per cent lower odds of being clinically depressed than those who reported not eating chocolate at all.
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Dr Sarah Jackson, lead author of the study, was rightly cautious about claiming too much. As she explained, from this sort of a study you can’t infer causality. It could be that when people get depressed they lose interest in eating chocolate (which strikes me as a bit implausible), “or there could be other factors that make people both less likely to eat dark chocolate and to be depressed.”
But let’s assume, for the moment, that eating dark chocolate might enhance your mood. What could be the mechanism? Dark chocolate has a high concentration of flavonoids – these are antioxidants which have been shown to reduce inflammation. Chocolate also contains a surprising amount of fibre. The dark chocolate I am currently staring at is 10 per cent fibre, while the cocoa powder in my cupboard says it is 30 per cent fibre.
This combination of flavonoids and fibre have been shown to boost levels of ‘good’ bacteria in the gut. In turn, these bacteria produce short-chain fatty acids, which have a powerful anti-inflammatory effect. As there is mounting evidence that depression, at least in part, is due to inflammation in the brain, you can begin to put together a plausible case for dark chocolate mediating depression via the microbiome.
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There are no randomised controlled trials showing that dark chocolate really does improve depression, but there was one that showed it could boost blood flow to the brain and other organs. In a small study published in the journal Cardiovascular System, Portuguese researchers took 30 healthy adults and allocated them to either eating eight grams – about one small square – of 70 per cent cocoa chocolate a day for a month, or to a control group. Those eating the chocolate saw their arterial blood flow increase, on average, by over 50 per cent.
While I can’t see dark chocolate being prescribed for depression or heart failure any time soon, it does make me feel better about having a nibble every now and then.