Salt Flat Reflection

Parallel Universes of Salt

Salt Research Citation NetworkIf you poke around in the scientific literature trying to understand the evidence behind policies related to cutting the salt in food, you might feel like you are wandering between parallel universes. Some systematic reviews find little empiric evidence for trying to reduce salt intake. Others find the evidence compelling. A new analysis published in the International Journal of Epidemiology offers an explanation.

Ludovic Trinquart and colleagues say scientists have become so polarized on this subject that most of them are not working with or even considering the data of others who hold different views from their own. They illustrate this point with the citation network graph on the right. Their analysis found that publications were 50% more likely to cite other publications with conclusions matching their own. That’s why you see a preponderance of blue and red lines in the graph. They represents citations that that match the perspective of the publications making the citations. Trinquart et al concluded:

We documented a strong polarization of scientific reports on the link between sodium intake and health outcomes, and a pattern of uncertainty in systematic reviews about what should count as evidence.

This finding is disheartening, though not entirely surprising. The example of salt is not an isolated one. Think about the polarization related to sugar for another obvious example.

Good science and good policy require a full consideration of all the data. Certainty is never possible. But rigorous scientific dialogue and consideration of all available data can prevent mistakes and nasty surprises down the road.

Click here for the paper by Trinquart et al and here to read more in the Washington Post.

Salt Flat Reflection, photograph © Peter Nijenhuis / flickr

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February 19, 2016