By Gary Schwitzer
The following is a guest post by Kevin Lomangino, one of our story reviewers on HealthNewsReview.org. He is an independent medical journalist and editor who is currently Editor-in-Chief of Clinical Nutrition Insight,
a monthly evidence-based newsletter which reviews the scientific
literature on nutrition for physicians and dietitians. He tweets as @Klomangino.
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Readers of this blog know that there can be a huge gap between what
scientific evidence tells us and what gets reported to the public by the
media. And perhaps nowhere does this chasm yawn as widely as it does in
the field of nutrition research, with its steady stream of
observational studies linking particular foods and nutrients with risk
of various diseases.
Even though they are not designed to prove cause and effect, these studies inevitably get reported with overblown headlines about how coffee, for example, "reduces cancer risk" (or maybe it "increases" risk?) and olive oil
"cuts stroke risk."
Gary has discussed the many reasons
why journalists tend to sensationalize these kinds of studies,
including the lack of time, space, and training needed to report more
thoroughly. An important, but less appreciated, factor is the influence
of press offices at scientific journals and at academic institutions. In
an effort to increase publicity for their authors and organizations,
they sometimes encourage journalists to pump up these studies beyond
what the evidence warrants.
Consider a press release put out last month by the BMJ – British Medical Journal – with the following headline: "It’s official – chocolate linked to heart health."
Intrigued by the headline (as the BMJ no doubt hoped I would be), I
searched the release for an indication that some prestigious independent
body – the Institute of Medicine? a World Health Organization expert
committee? — had come together to evaluate the evidence on chocolate’s
cardiovascular effects. As unlikely as I found that prospect, I
recognized that it could justify an "official" declaration of an
association between chocolate and heart disease outcomes.
But no: the "official" designation was apparently bestowed by a
headline writer in the BMJ press office. It was prompted by the
publication of a study that found a correlation between high levels of chocolate intake and lower risk of cardiovascular disease and stroke.
As with all observational studies (or, in this case, a meta-analysis
that pooled data from seven observational studies), the study had many
important limitations that were well catalogued by the authors in their
paper. They note that "the available literature on this topic is limited
and novel" and that more studies are required "to confirm or refute the
results" of the analysis. To its credit, the BMJ referred to some of
these limitations high up in the press release, which noted that the
results might be explained "by some other unmeasured (confounding)
factor" besides chocolate.
But why then trumpet the results in the headline as evidence of an
"official" and apparently conclusive link? Journalists might be swayed
by such language to give this study much more weight than it deserves.
A related question is whether a scientific organization should be
spending any of its limited resources to promote this kind of study to
the public. After all, the data are quite preliminary and the underlying
premise about chocolate is, in my opinion at least, dubious at best.
While there is certainly evidence that chocolate with a high cocoa
content can make heart disease risk markers move in the right direction,
most of the chocolate sold today has a lower concentration of cocoa
solids, but lots of sugar, fat, and calories. Eating more of it seems
just as likely to increase rather than decrease cardiovascular risk.
I hope that researchers will one day develop more conclusive evidence
that chocolate benefits heart health. In the meantime, isn’t there
something more important for one of the world’s top medical journals to
tell us about?