A systematic review and meta-analysis of previous cohort studies on the effects of chocolate consumption has found that chocolate may be linked to a reduction in the risk of developing heart disease. The paper was published overnight in the British Medical Journal.
We asked Dr Karin Ried, whose team is conducting a review of randomised controlled trials of chocolate’s positive health impact for the Cochrane Collaboration what to make of the findings:
The authors of the BMJ study did a meta-analysis, a systematic review of several studies – four cohort studies and one cross-sectional study – that followed people up over time and checked whether they were eating chocolate and how much.
At the end of the period – most of the studies were about five years in length - they looked at the rate of stroke, heart disease and diabetes (cardiometabolic symptoms) among participants. They found people who ate more chocolate or cocoa products had a lower rate of cardiovascular diseases.
What is it about chocolate that makes it good for cardiovascular health?
It’s known that cocoa flavanols are beneficial for vascular health.
A lot of studies done in animals as well as human cell and human studies have looked at the role of cocoa in chocolate. So it’s important that we distinguish chocolate from cocoa.
In order to answer the question of what makes chocolate good for health accurately, we have to know whether it’s dark chocolate, white chocolate or milk chocolate that we’re talking about.
And chocolate has other ingredients such as sugar and fat that might counter the positive effects of cocoa.
Basically, you have to be careful when you say consuming chocolate is good because the kind of chocolate is key - white chocolate has no flavanols while dark chocolate can have up to 70% or 80% cocoa.
We should probably talk more about cocoa than chocolate because the differences in chocolate are vast and the health benefits come from cocoa.
What other health benefits can cocoa confer?
My group is doing meta-analysis of randomized controlled trials looking into the effect of cocoa on blood pressure.
These trials are short – about two weeks to 18 weeks long – so you can’t look at the impact of chocolate on stroke or heart disease but you can look at other cardiovascular effects of chocolate, such as blood pressure.
What we’ve found is that the less sugar in the chocolate, the more beneficial it is. The positive effects are even more pronounced in overweight or obese people.
There are many more ingredients in chocolates and cocoa has other effects than cardiovascular health benefits. It’s quite well known, for instance that it can affect mood.
How much chocolate is the right amount?
One shouldn’t feel guilty about eating a little chocolate but when we look at heart health, we have to look at the dosage.
What’s consistent in our research and in what this new research found is that you have to eat lots and lots of cocoa to have beneficial effects.
The studies included in the meta-analysis had very broad categories – they asked people when they ate chocolate and the choices were once a month, once a week or never.
You really can’t pin down a daily dosage using those sorts of categories.
One of the studies went into more detail- asking whether people ate chocolate one to two times a day or one to two times a week. Already that’s a little bit more informative.
So the data gives us a hint but it’s really not detailed enough to draw any conclusions. But when we look at our randomized controlled trials, we can say a little more about dosage and daily intake.
The range of dosage they used went from one piece, which is six grams of chocolate, to a whole block, which is 100 grams, a day. The trials we are looking at ran from two weeks to 18 weeks and what we found in our analysis of these short studies was that it’s not really the dosage that matters.
Small doses may also have positive effects, which means if you have one piece of chocolate a day you can get beneficial effects without side effects like weight gain.
What is you advice to chocolate lovers?
Less is more if you want to have chocolate as a long-term treat and go for dark chocolates with less sugar or even cocoa that you can make a drink out of – without too much added sugar.
Having one piece of milk or dark chocolate a day can’t be bad for you, but it’s important to be careful of candy bars because when you look at their ingredients, cocoa content is small.
The first thing listed will be sugar – so there may be as much as 80% sugar in there and perhaps 15% cocoa. So with that kind of chocolate bar, you’re eating more sugar than cocoa.
The findings of the systematic review were presented at the European Society of Cardiology in Paris overnight.