Good, Bad, Ugly: Planetary Health and Ultra-Processed Foods

Keeping up with virtues and vices in food just keeps getting harder. Planetary health is a virtue to pursue, but ultra-processed food is a vice, and plant-based foods are virtuous unless they are ultra-processed. Then perhaps they become virtuous vices. So confusing.

A series of publications this week adds to the confusion. In the American Journal of Clinical Nutrition, Linh Bui and colleagues tell us a diet with a high planetary health diet index has an association with lower risk for mortality and for environment impacts. Throwing concerns for scientific accuracy out the window, CNN says it more plainly: “Planet-first diet cuts risk of early death by nearly a third.”

Then we have a publication in Lancet Regional Health – Europe telling us not to rely on the health benefits of earth-friendly plant-based foods if those foods are ultra-processed. Again, the news media steps in and says it plainly: “When plant foods are ultra-processed, the health benefits disappear.”

Poof – all the virtue of plant-based diets goes up in smoke when ultra-processing taints it.

Trolling for Correlations in Big Datasets

We note that these two studies are both exercises in seeking correlations from large datasets.

In the AJCN paper, researchers report on a Planetary Health Dietary Index to quantify adherence to the EAT-Lancet reference diet. They use data from the Nurses Health Studies and the Health Professionals Follow-up Study to look for correlations between this index and mortality. Not surprisingly, they found what they sought. People who scored high on this index had a 23% reduction in mortality compared to those with low scores. In all, they dug through data on about 200,000 individuals.

But of course, finding a correlation is not the same thing as establishing causality. The authors concede this, writing:

“Residual and unmeasured confounding cannot be completely controlled in this observational study.”

The Lancet paper reminds us that simple formulas for healthy eating can break down. The planetary and personal health benefits of plant-based foods might not hold up if those foods are ultra-processed. Of course, the same cautions about residual confounding apply to this study. We have observations about correlations in this study, too. Not evidence that ultra-processing wipes out the benefits of plant based foods.

In sum, whether someone is selling us personal health, planetary health, or just food that promotes healthy profits, we remain skeptical. There are many ways to follow a healthy pattern for eating. There are also many ways to stray from a healthy pattern. Simple answers often raise many questions.

Click here for the AJCN paper and here for a commentary to go with it. For the Lancet paper, click here. For further perspective, click here and here.

Smartfood, photograph by Ted Kyle / ConscienHealth

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June 11, 2024

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