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Consumers equate healthy with sustainable food. But is it always true?


Consumers equate healthy with sustainable food. But is it always true?

Researchers call this the ‘halo effect; where positive impressions about one trait inform another.
December 15, 2023

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It’s green, it’s leafy, it makes you feel good: it must be good for the planet too, right? This is a common line of reasoning that many people use when they choose their meals. And yet according to new research, it doesn’t hold up to scrutiny. In fact, the foods that consumers perceive to be healthy and good for the planet were in reality almost never both, the study found.

The discovery could help us develop better ways of communicating the true sustainability of meal choices—instead of leaving people to just trust their own guts.

To understand how people choose their food, what better place to start than in a university canteen with thousands of hungry students and dozens of menu options, where the team of German and Austrian scientists could watch these dynamics play out in real time. They enrolled over 5,000 students from this captive audience, and asked them to separately rank both the sustainability, and the nutritional value, of 29 meals available to them at the canteen. These ranged from vegan and vegetarian dishes, to meals that were heavy on red meat, dairy, and fried foods. 

Separately, the researchers also did their own ranking of the 29 meals, using a unique algorithm that drew on the exact ingredients in each recipe to develop a profile of its sustainability (based on associated greenhouse gas emissions and other factors) and health value. 


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When the team compared their algorithmic rankings with the students’, they were struck by the emergence of a powerful pattern: where students gave a meal option a higher health ranking, it was almost always accompanied by a similarly high sustainability ranking, too. It seemed they were making a causal link between these two traits. 

For a handful of meals, this did chime with reality: for instance, students similarly ranked a tomato and basil pasta as both healthy and sustainable, and this matched the algorithm which gave the dish the same high health and sustainability score, too. 

But for almost all other meals, the students’ intuition failed. Take a stew of Asian glass noodles and beef: students thought this was quite healthy and similarly sustainable, but in fact it received a low sustainability ranking from the algorithm. 

Meanwhile, students rated a stew of peppers and gyro as both relatively healthy and sustainable—but this dish had the largest discrepancy between the two features, ranking very high nutritionally, but very low on the sustainability scale. A dish of creamy mushroom soup was one rare case where students ranked the dish higher for sustainability but lower for health—when in fact, the inverse was true. Creamy mushroom soup received one of the lowest sustainability ratings, but one of the higher nutritional ratings from the algorithm. 

These discrepancies can be explained by things that many of us intuitively understand: a food might be healthy but require lots of resources, like fertilizers, to grow, which enlarges its footprint. Likewise, a dish could contain lots of processed unhealthy food, but have a small ecological footprint. 

And yet, despite these logical points, it’s as if the desire to eat healthily creates a blind spot, or perhaps some wishful thinking, about the choices we make. The researchers describe this as a ‘halo effect’, where the perceived benefits of one thing diffuse out into other domains.

The researchers also examined the findings according to the type of meal, like vegan or vegetarian, and the age of the people who participated in the survey. Interestingly, they found that vegan and vegetarian meals didn’t significantly change the rating on sustainability and health, but the respondents’ age did play a role, with older participants showing a greater tendency to perceive healthy food as sustainable too.

So, what’s the takeaway from all of this? Namely, that if we want to shift the dial on sustainable food choices, we’ll need more than consumers’ intuition alone. Instead, choices should be guided by more robust indicators like sustainability labeling that specifically tells people what’s in their meal.

“The findings clearly indicate that we consumers need better and more readily accessible information about the sustainability and healthiness of foods,” the researchers say. After all, trying to be healthy and save the planet: that’s a tall order on a hungry stomach. 

Sproesser et. al. “The “healthy = sustainable” heuristic: Do meal or individual characteristics affect the association between perceived sustainability and healthiness of meals?PLOS Sustainability & Transformation. 2023. 

Image: PxHere

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