Still Life with Fish

PREDIMED and the “Corpse” of Nutrition Science

Last year, the New England Journal of Medicine retracted and then published a revised analysis of the landmark PREDIMED study. With that action, it shook the world of nutrition science. Even now, there’s still a whole lot of shakin going on.

What About 267 Secondary Publications?

Just last week in the BMJ, Arnav Agarwal and John Ioannidis write that we still have a mess on our hands. That’s because simply retracting and republishing a single paper isn’t enough. It doesn’t resolve the issues of trust and transparency that this incident raises. For one thing, the PREDIMED study spawned a mind-boggling array of 267 secondary publications before the retraction.

On top of that, thousands of other papers have cited the study and its secondary publications. Thus, Agarwal and Ioannidis see a huge task ahead:

Republication may not solve multiple problems that remain, including the inappropriateness of stopping early given the revised results and the effects on over 200 secondary publications.

Multiple contradictions between data reported across PREDIMED publications suggest a more generic problem with the trial’s quality. PREDIMED may provide useful lessons on how to reassess and correct large volumes of published literature and on what methodological safeguards are needed for pivotal multicenter trials.

Writing in Vox, Julia Belluz quotes Ioannidis dismissing nutrition epidemiology as “a field that’s grown old and died.” He says, “At some point, we need to bury the corpse and move on to a more open, transparent sharing and controlled experimental way.”

Dean and Professor David Allison offers us a more measured assessment:

I do not share the view that nutrition epidemiology is beyond repair. I think it is often overused, poorly executed, and poorly conveyed. However, that does not mean it cannot not be appropriately used when needed, executed well, and reported well in principle. That a tool is often misused is usually taken as a sign of a need for reform, not abolition.

A Constructive Way Forward

Clearly, many people in the field agree. We need to get serious about increased scientific rigor in nutrition research. Of course, it’s hardly the only field facing scrutiny on this issue.

A distinguished list of nutrition scientists recently published a roadmap for this task. Cynthia Kroeger and colleagues suggest that renewed focus on core principles of science is key. “Science does not look into the souls of people to determine who is a truth teller,” they write. Instead, what really matters in science is the data, the methods for producing it, and the logic for connecting it to conclusions. Everything else is a distraction.

In the end, the issues that PREDIMED raises are all about trust. To trust the science of nutrition, we need high standards for rigorous, transparent, and reproducible research. Nothing less will do.

Click here for the paper by Agarwal and Ioannidis, and here for the recommendations of Kroeger et al.

Still Life with Fish, painting by Konstantin Korovin / WikiArt

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Month x, 2019