Poor Diets Cause One Fifth of the World’s Deaths?

It’s a impressive factoid. According to a new study in Lancet, poor diets are a factor in one fifth of the world’s deaths every year. The biggest culprits are too much salt, along with too little fruit and whole grains. All of this comes from the Global Burden of Disease project at the University of Washington.

The study is carefully written in the language of associations with risk factors. But predictably, the headline writers are not so careful. “Poor diet kills more people than tobacco or high blood pressure” would be a prime example. That was the headline from the GBD newsroom.

Another favorite comes from USA Today:

One in Five People Are Eating
Themselves to an Early Death

Black Box Causality

Writing in a commentary to accompany this paper, Nita Forouhi and Nigel Unwin caution us.

First and foremost, they note that causal inference from nutritional epidemiology is “challenging.” On top of that they say the study has a bit of “black box methodology” that makes it hard to evaluate the results.

Dietary risk data comes mostly from populations with European origins. So applying those risk factors to the whole wide world is a little iffy. Asian diets, for example, are pretty high in refined carbs. So it’s reasonable to think that the risks linked to few whole grains might be different in these cultures.

On a side note, our favorite boogeyman – sugar-sweetened beverages – is pretty low on the list. Fourth from the bottom. So you can bet that the zealots at the UCSF sugar-is-poison project won’t be big fans of this study. That’s a mere guess, based on the likelihood of motivated reasoning.

A Good Thought Starter

Take away all the sensation and we still have a good study and a good thought starter. However, let’s not get too literal about causes of death. What we have here is nothing more than contributing factors. There’s a big difference.

Click here for the study, here for the commentary, and here for more from the New York Times. For reporting from NPR, click here.

A Big World, photograph © Sera Tü / flickr

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April 4, 2019