US study shows ‘healthy food’ is sometimes worse for the environment

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A study by US researchers shows that ‘healthy foods’ – including certain fruit and vegetables – may sometimes be more damaging to the environment than meat.

The research team, from Carnegie Mellon University set out to study the food supply chain to determine how the obesity epidemic in the US was affecting the environment.

The team tested three different scenarios: a reduction in calories consumed but no changes in diet; a shift to a more vegetable-heavy diet but no caloric reduction; and a mix of the two, which is the diet recommended by the US Department of Agriculture (USDA).

The researchers considered three parameters for the scenarios: energy use for food production, blue water footprint (the amount of freshwater necessary to produce a product), and greenhouse gas (GHG) emissions. In scenario one, quantities of these variables were reduced by about nine percent – unsurprising, as the only change was the consumption of fewer calories. The diets in scenario two and three had more fish, vegetables, and fruit compared to the average US diet. The higher intake of these healthy foods was balanced by a reduction in meat, solid fats, and added sugars.

All three parameters – energy use, water and GHG – actually increased under scenarios two and three. In scenario three, energy use went up by 38 percent, water use by 10 percent, and greenhouse gas emissions by six percent. Scenario two resulted in further environmental impact. The reason for this is that per calorie production of vegetables requires more energy and water than meat, but generates around one-quarter of GHG emissions compared to beef.

Significantly, the vegetable-based diet studied was not vegan and included comparatively high amounts of dairy – “dairy, by far, has the greatest impact on increased GHG emissions because it has the third highest emissions intensity value,” the study’s authors note.

Paul Fischbeck, professor of engineering and public policy at Carnegie Mellon University, said he had been “very surprised by our results” – adding that they were “probably counter-intuitive” and that “we expected the exact opposite.”

Perhaps the simplest way to describe the findings is that some vegetables turn out to have higher environmental impacts than was thought, and some meats are less environmentally damaging.

But the media – in both the US and UK – have interpreted the study in typically black and white terms, claiming that it shows that a vegetarian diet is worse for the environment than a meat-based one. Some have suggested they were encouraged by official press release from Carnegie Mellon University (headlined ‘Vegetarian and “healthy” diets could be more harmful to the environment’) offered a rather simplistic – and, arguably, politically loaded – analysis of the study’s findings. One of the study’s co-authors. Michelle Tom, has since accepted that the press release’s headline was “not the best title for our study”. However, another member of the team, professor Paul Fishbeck, insisted: “You can’t just assume that a vegetarian diet will reduce your carbon footprint, which is what people think.”


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