Real Evidence for Caution About Ultra-Processed Food

Will ultra-processed food kill you? Probably not, but two new studies provide some real evidence for caution about this dietary boogeyman. First, a large observational study in France finds a 14 percent higher risk of death in a people who eat more of the stuff. And then, an RCT from NIH shows that ultra-processed foods cause people to eat more and gain weight. It’s quite a one two punch.

Mortality and Processed Food

JAMA Internal Medicine published the French study yesterday. It’s a huge cohort of adults, 45 and older from the NutriNet-Santé Study. Laure Schnabel and colleagues followed 44,451 people for a median of seven years. Roughly one in a hundred of them died in those seven years. After adjusting for all of the confounding factors that they could,  Schnabel et al linked ultra-processed food consumption to a 14 percent increase in the risk of death.

So it’s not quite like smoking cigarettes. But it’s worth noting.

At the same time, it’s worth noting that this is still an observational study. French people don’t eat much ultra-processed foods compared to folks in other countries. It’s about 14 percent of the French diet. In the British diet, it’s more than half. Among other things, that means that French people who eat a lot of processed food are unusual. They’re poorer, they’re younger, they’re living alone, and they have a higher BMI.

Those are obvious confounders, but you have to worry about residual confounding. Those are undetected factors that might explain the mortality observations.

Weight Gain

That’s where the NIH study by Kevin Hall and colleagues provides an important piece of the puzzle. It’s a very tightly controlled study for only two weeks. The study randomly assigned 20 adults to receive either ultra-processed foods or unprocessed foods. They could eat as much or as little as they liked. But they were living in the NIH Clinical Center, so that was all the food they received. After two weeks, everyone crossed over to the opposite diet.

At the end of the two weeks, people eating ultra-processed foods gained almost two pounds. People eating unprocessed foods lost two pounds. Shazam. Two weeks of mac and cheese plus chicken nuggets for lunch (all you can eat) will make you gain more weight than two weeks of spinach salad with grilled chicken and bulgur. Not a huge surprise, we think.

However, it’s a very tidy study that proves a point with real data. These findings are preliminary, because Hall’s paper is in preprint status. That means peer-review is ongoing and incomplete. So take it with a small grain of salt for now

What to Do?

Hall advised caution in translating this information to policy. He says:

This study is the first randomized controlled trial of ultra-processed versus unprocessed diets and suggests that limiting consumption of ultra-processed foods may be an effective strategy for obesity prevention and treatment.

However, advocates of policies that discourage ultra-processed foods should be mindful that the time, skill, expense, and effort to prepare meals from minimally processed foods requires resources that are often in short supply.

Watch this space. You can be sure this will be a hot topic for years to come.

Click here for the Schnabel study and here for the Hall study. For further perspective on ultra-processed food, click here. Finally, you can find further reporting on the Schnabel study here and here.

From Apple to Gummy Bear, illustration © Nutritional Doublethink / flickr

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February 12, 2019