This is the time of year when chocolate rains down on our medical office in the form of holiday gifts for our staff, medicine nurses and doctors. That produces lots of groans about holiday weight gain and guilt about unhealthy eating.
But a study from earlier this year joins several others that have been published over the past decade that suggest that chocolate consumption has an upside: it lowers our risk for cardiovascular disease (heart attack and stroke). According to the data from nearly 21,000 people followed over 11 years, the likelihood of developing cardiovascular disease was 14% lower among the highest consumers of chocolate than among those who consumed none.
The same researchers also combined data from nine previous studies of chocolate consumption with over 150,000 participants and found similar reductions in disease risk. And in the three studies that measured deaths from cardiovascular disease the observed effect was even greater: consuming higher amounts of chocolate lowers our chance of dying from heart attack or stroke by almost 50%.
How does chocolate do its good work? Earlier research demonstrated two ways in which chocolate, or more correctly cocoa, can create health benefits.
First, it contains high levels of flavanols, a group of natural nutrients that are antioxidants. Antioxidants help our bodies’ cells resist damage, which decreases the tendency to form cholesterol blockages in our blood vessels.
Second, flavanols lower blood pressure, reduce the tendency for blood to clot inappropriately and improve blood flow. Each of these effects is known to lessen the likelihood of stroke and heart attack.
When we first learned of the connection between eating chocolate and healthier hearts and brains it appeared that dark chocolate produced better results than milk chocolate. That’s because milk can reduce the absorption of some antioxidants and because the cocoa concentration is greater in dark chocolate.
But additional research has found that the type of cocoa beans, their handling and their processing are also responsible for the variability in flavanols. As a result, a high percentage of cocoa in a given product isn’t a guarantee that the flavanol levels are equally high.
A problem with the chocolate research done thus far is that it’s all observational: we look at what people eat and then follow their health over time.
But to prove that cocoa consumption truly reduces cardiovascular disease we need to run experiments where participants are randomly assigned to get cocoa or no cocoa. And the most rigorous type of scientific study is also “double blind”, which requires that neither the subject (the chocolate consumer) nor the observer (the scientist) be aware of whether or not a given participant is getting cocoa or a placebo that passes for cocoa.
The last requirement is generally impossible when studying foods: what could a scientist possibly concoct that looks, smells and tastes like chocolate but is in fact something different?
In such circumstances we’re left with two choices.
First, we can try to extract the component of a food that we think creates the benefit that we identified in observational studies. Unfortunately, that tactic has a history of humbling researchers.
For example, when dietary studies showed that eating fish was associated with lower risk of cardiovascular disease, studies using fish oil capsules vs placebo showed no benefit for fish oil. The same negative trial result occurred when we theorized that omega-3 fatty acids were the magic ingredient in fish.
Somewhat surprisingly, those unfruitful experiences haven’t stopped researchers from starting a large and costly study of cocoa extract that will last five years, finishing in the year 2020.
However, the study has a significant problem: much of the money comes from Mars (the candy maker) and Pfizer (the pharmaceutical company). And industry support has a history of creating conflict of interest that biases the reported outcomes. That’s why physicians are wary of research results that arise from corporate funding.
The alternative to a double-blind trial is to simply accept the observational findings that have already accumulated. In fact, that’s what’s behind most food recommendations, including the present advice to follow a “Mediterranean diet” (see this post on Healthy eating: Best evidence and the Mediterranean diet).
But when it comes to chocolate, doctors are more hesitant to recommend it. That’s because chocolate is created by mixing sugar and fat with cocoa, adding calories and excesses of both these undesirable nutrients (see this post on Avoiding fat, sugar and salt). It’s another reason to prefer darker chocolate: higher amounts of cocoa reduce the place available for fat and sugar.
So what’s my best advice?
Sadly, I think that our reluctance to promote chocolate consumption arises more from the archaic moral view that pleasing things can’t be good for us than it comes from science. That’s why I make up to 50 grams (2 oz.) of chocolate with at least 70% cocoa part of my daily food intake. And it’s why I suggest that you go ahead and enjoy a healthful pleasure, both during the holidays and year round.