Dark Chocolate Study Flimsy

Dark Shadows
Health Sciences Institute e-Alert
September 3, 2003

Dear Reader,

"Finish your dark chocolate! It's good for you!"

I wonder if that's a line children are hearing since we learned last week that dark chocolate is "healthy." According to the headlines, sound bites and 20-second reports from chirpy newscasters, dark chocolate can help reduce high blood pressure. So back up the chocolate truck and enjoy!

Well… as much as I would love for it to be true, it's time for a reality check.

Because 1) you know it's too good to be true, and 2) there were actually two chocolate studies released last week, and the second one (the one that was not as widely reported) contains a detail that would have made a far more important headline.

Cocoa Puff

It's funny how the mainstream press seems to take glee in reporting on flimsy studies that indicate drawbacks of dietary supplements, and yet they announce the "health" benefits of dark chocolate as if this were a genuine medical breakthrough.

And the fact is: the chocolate study that was most widely reported last week could hardly be flimsier.

Researchers at the University of Cologne recruited a group of 13 adults. Except for mild hypertension, all the subjects were healthy, none were obese, and none took supplements or medications. Every day for two weeks, half the group ate 3-ounces of dark chocolate, and half ate 3-ounces of white chocolate. When blood pressure was checked, the white chocolate group showed no change in blood pressure. But subjects in the dark chocolate group reduced their systolic blood pressure by 5 points (on average), and their diastolic blood pressure by 2.

Were these results significant? Using only 13 subjects for such a short trial falls short of anyone's definition of "significant." Especially when you consider that treating hypertension is not the same as treating a disease; high blood pressure is a symptom that indicates the presence of a larger health problem. Nevertheless, several news reports described the results as "significant." But they were possibly giving the study more credit than it was due, because it didn't appear in The Medical Journal of Short Studies Using Very Few Subjects – it appeared in the Journal of the American Medical Association.

So an insignificant study in a significant journal somehow adds up to "significant" results. And I guess that's especially so when you're reporting a fantasy that so many people apparently want to hear: Chocolate is good for you.

Got antioxidants?

Both of last week's chocolate studies were based on the common knowledge that chocolate contains polyphenols – antioxidants that we've frequently written about at HSI. Polyphenols are the heart-healthy compounds found in fruits, vegetables, tea, red wine, and in the primary ingredient of chocolate: cocoa beans.

The "other" chocolate study focused specifically on the antioxidant value of chocolate. It was conducted by Scottish and Italian researchers who used only 12 subjects for their trial. (Are chocolate mini-studies becoming a fad?) On different days, each of the subjects ate 3-ounce portions of either milk chocolate, dark chocolate, or dark chocolate taken with a serving of whole milk. Blood tests showed that subjects who ate dark chocolate alone experienced an average increase in antioxidant levels of 18 percent. But when the same subjects ate milk chocolate, or ate dark chocolate with milk, their antioxidant level increase was very slight.

The lead author of the study, Mauro Serafini, speculated that milk proteins may bind with antioxidants, impeding their absorption.

Now THAT'S a headline!

Both of the chocolate studies called for further research, and in the case of the second study I think more research is essential. If milk products inhibit the absorption of antioxidants beyond those found in chocolate, that's a critical nutrition issue that everyone needs to know about – even if it doesn't come with a sexy headline.

The wrong message

In the wake of last week's reports, the core message that "dark chocolate reduces blood pressure" has probably already become a bit of modern folk wisdom. You know there are many people out there already swearing by it because they heard it on TV. "Give me another Special Dark bar – it's good for my blood pressure."

Meanwhile, the obesity epidemic that we hear about so much in the U.S. is becoming a worldwide epidemic, with the UK, Canada, Mexico, and countries in Latin America and Europe now applying the term to their own populations. In light of all the health problems that come along with this epidemic, it's a ludicrous situation when news anchors encourage people to eat candy for a supposed health benefit based on a paper-thin study.

The Globe and Mail, a Canadian newspaper, included a "health" insight in its reporting on the chocolate studies last week. The article ended by referencing a recent statement from "a group of U.S. dietitians" who advised doctors to recommend dark chocolate to their patients "as part of a healthy diet." The U.S. dietitians weren't identified, so apparently we're supposed to be sufficiently impressed that we won't question who they are. Are they employed by the sugar industry? Are any of them on the payroll of a candy company? The Globe and Mail doesn't say.

No matter. The damage is done. And another chapter is added to the mythology that a candy product can do more good for our health than bad.

"Chocolate and Blood Pressure in Elderly Individuals With
Isolated Systolic Hypertension" Journal of the American
Medical Association, 2003;290:1029, jama.ama-assn.org

"Plasma Antioxidants from Chocolate" Nature, 424, 1013,
8/28/03, nature.com

"Study: Dark Chocolate may have Benefit" Lindsey Tanner,
Associated Press, The Miami Herald, 8/27/03, miami.com

"It Turns out Sinful Dark Chocolate is Healthy" Anne McIlroy,
The Globe and Mail, 8/28/03, globeandmail.com

"The Dark Side of the Great Chocolate Debate" The Cape Argus,
8/28/03, iol.co.za

"Skip the Milk Chocolate, Dark Is Better for You" Reuters
Health, 8/27/03, reutershealth.com

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Sandy Mintz


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