Does chocolate reduce the risk of heart disease?

A recent study found that people who eat lots of chocolate are healthier than those who eat none.

A Mars a day?

Yet another study on the health benefits of chocolate hit the headlines in June, having found that people who ate lots of chocolate had better cardiovascular health than those who ate none.

The study, published in reputable journal Heart and involving thousands of people, compared rates of cardiovascular disease (CVD), including coronary heart disease and stroke, among different groupings of chocolate eaters. The quintile (20% of people) with the highest level of chocolate consumption were compared with the quintile who ate no chocolate, and were found to have lower rates of CVD.

The press release was duly sent out, and the media ran with it. Headlines included:

Two chocolate bars a day 'reduce risks of heart disease and stroke' [the Independent]

Chocolate lowers your heart disease and stroke risk []

New study suggests the more chocolate you eat, the lower your risk of heart disease []

In short, eating lots of chocolate is apparently healthier than eating none. Even better, it doesn't have to be dark chocolate, which actually has been shown in numerous clinical trials to have a positive effect on the cardiovascular system. It can be any chocolate, including bars merely containing chocolate – like a Mars bar (40% chocolate) or a Crunchie (62% chocolate). Two bars a day!

But before everyone hits the shops for their two bars a day, let's get that bit straight. The highest chocolate-eating group didn't all eat two chocolate bars a day. In fact, the amount of chocolate-containing foods in this group ranged from 16-99g per day, with a median of 25g. That's a range of around one bar per week, to two bars a day, every day – a big difference. It would have been interesting to see the CVD results of those at the higher end of this range compared with the lower end.

And what about reducing the risk of heart disease? This kind of study doesn't show cause and effect, it only shows an association between chocolate intake and reduced risk of heart disease – and most articles did point this out. Eventually.

While some headlines correctly stated chocolate is linked with reduced heart disease risk, medical media analyst, Dr Amanda Wilson, points out that many laypeople wouldn't appreciate the difference between 'Chocolate is linked with reduced risk of heart disease' and 'Chocolate reduces heart disease risk'.

However, she points out, people are more savvy about these sorts of stories now. "There are so many contradictory health stories these days – chocolate's good, chocolate's bad, chocolate's good again – that people take them with a grain of salt."

So what's the real story?

Supposing chocolate is not, in fact, the new miracle ingredient in heart health, how would we explain the findings? The authors suggested several reasons, including:

  • People who are generally healthy – and who are therefore at lower risk of cardiovascular disease – may be more likely to choose to eat chocolate than people with high blood pressure, high cholesterol, diabetes and so on, who may be more cautious about eating unhealthy foods. This is called reverse causality: eating chocolate doesn't cause good health; rather good health causes eating chocolate.
  • Unhealthy, overweight people at risk of CVD may have under-reported chocolate consumption – studies of dietary reporting have found some people, especially overweight women, tend to under-report foods such as snacks and sweets.
  • Active people are more likely than less active people to eat more food in general, including chocolate-containing food, and are also more likely to have lower rates of CVD. In this study, the highest chocolate-eating group consumed the most energy and were the most active, and were a similar weight to the non-chocolate eaters.

So, does eating lots of chocolate-containing food reduce heart disease risk? We don't know, and this study leaves us none the wiser.

The authors conclude, "There does not appear to be any evidence to say that chocolate should be avoided in those who are concerned about cardiovascular risk."

The Heart Foundation agrees it's not necessary to avoid chocolate for heart health. But spokesperson Shane Landon says: "Most sources of chocolate are high in sugar and saturated fat, which is not beneficial for heart health. The Heart Foundation would recommend people focus on increasing the amount of fruit and vegetables they consume, rather than the amount of chocolate."