Lots of newspapers have become very excited because a study has found that people who eat chocolate are less likely to have strokes and heart disease.
The Daily Telegraph / Via telegraph.co.uk
The Telegraph, Mirror, Independent, and Daily Mail have all reported that eating chocolate can actually reduce your risk of suffering from these diseases. But that’s not what the study says.
The research is a meta-analysis published in the journal Heart, and it has indeed found a link between eating chocolate and reduced risk.
The study found that people who say that they eat a moderate amount of chocolate a day – up to 100g, about the equivalent of two ordinary bars – tend to be less likely to suffer stroke or coronary heart disease than people who say they don’t eat any at all.
But that doesn’t mean that the chocolate is doing them good.
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It’s not clear whether the chocolate is protecting them, or whether people who are at less risk tend to eat chocolate, or whether people aren’t very good at remembering what they’ve eaten. Or something else entirely. The researchers have tried to compensate for these possibilities, but it’s impossible to rule them out with this kind of study.
The authors mention that chocolate “is an important dietary source of flavonoid antioxidants, which are hypothesised to have a beneficial effect on endothelial function and protect against cardiovascular disease”. But the research doesn’t, and can’t, show that, and the study says as much – both in the paper itself and in the University of Aberdeen’s press release.
There are other problems with the reporting. For instance, the papers say that eating chocolate is associated with a 25% drop in heart disease.
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And that’s true. But while “a 25% drop” in something sounds big and impressive, it often isn’t. In this case, 577 out of 4195 people who didn’t eat chocolate had suffered from stroke or coronary heart disease, compared to 407 out of 4178 who ate quite a lot of chocolate. That’s about 14% in the first case, and about 10% in the second.
In short, if you took up eating chocolate in order to avoid a stroke, you’d have about a 4% chance of it making a difference. And that’s assuming that the chocolate really is protecting people, and that nothing else is going on.
For some reason, it’s always chocolate that gets in the news like this.
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Chocolate and red wine. People love to think that they might be doing them good, and there is some ambiguous evidence that they could be, so they make the headlines every time a new study comes out.
One journalist even fooled news agencies around the world into running an entirely bogus story about how chocolate helps people lose weight, to show how eager newspapers are to run this stuff.
But this study really did contain good news.
The authors don’t claim that chocolate prevents heart disease, as we’ve seen. But they do say that “there does not appear to be evidence that chocolate should be avoided in terms of impact on cardiovascular risk”. If you’re worried about stroke, or worried about heart disease, you can probably still eat chocolate without it raising your chances of getting ill. That’s good news for millions of people.
Still, though, eating chocolate in large amounts probably isn’t good for you.
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Public Health England estimates that being obese reduces your life expectancy by three years, and being severely obese by eight to 10 years. Eating lots of anything high in calories isn’t a very good idea from that point of view, especially if you don’t do much exercise.
