August 28, 2003

Double-blind chocolate

I read an interesting article yesterday about the possible health benefits of chocolate. Being a fan of the stuff, I was happy to find out that dark chocolate can indeed be healthy. Here's the article from New Scientist.

What I'm confused about is how they did the experiment. Here's a quote from the article:

"Dark chocolate contains about twice the amount of flavonoids as milk chocolate, so 12 healthy volunteers were given either 100 grams of plain chocolate or 200 grams of milk chocolate. Some were also given 200 ml of milk to drink in the double-blind experiment."

I had always thought a double-blind experiment meant that neither the researcher nor the subjects knew who was getting what treatment. Typically one set of subjects would get the actual drug, or a certain dose of it, and the other set would get a placebo (usually a sugar pill) or a different dose. Not until the experiment is over does anyone find out what they were getting.

I could see that perhaps the researchers wrapped the chocolate in foil so they wouldn't know who was getting milk or dark chocolate, which would satisfy one half of the double-blindness. But surely the participants would know if they were getting milk or dark chocolate. Gary suggested that maybe they didn't know what other participants were getting, just themselves. But I'm not sure that would qualify as double-blind.

I believe we get the journal Nature (where the original paper was published) at work, so I'll have to do more research on this when it arrives. All I can say is that I would gladly participate in such a study, no matter what kind of chocolate I had to eat!

Posted by Jen at August 28, 2003 08:10 AM

This is not new info - I have been hearing about the benefits of dark chocolate for a long time (by the way - my favorite) - and I think what they were trying to prove/disprove with the milk chocolate is that it does not have the benefits of dark chocolate - I would know if I was getting the dark - the milk - or just milk (yuck)- but would appreciate hearing more on the subject.

Posted by: Aunt Kathy at August 29, 2003 06:06 AM

I read the original paper in Nature; the experiment does not appear to be double-blind as reported in New Scientist. It was a crossover experimental design, which means the subjects are tested under both experimental and control conditions. In this case I assume it means all subjects tried all three chocolate doses during the course of the experiment: dark chocolate, milk chocolate, or dark chocolate with milk. Doing an experiment like this is useful because you can more easily rule out individual differences in reactions. And I'm sure the volunteers were more than happy to get three doses of chocolate!

Posted by: chocolate girl at September 2, 2003 04:45 PM