October 5, 2021 — 12:05 PM
We’ve long known that eating more plants and fewer processed foods tends to be better for our health and the planet. But the specifics have been shaky: How, for example, does the environmental impact of a cheeseburger compare to that of a bowl of stew? Do bananas or carrots tend to be healthier for the average eater?
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We’ve lacked a way to directly compare individual foods—until now. A new study in the journal Nature Food, “Small Targeted Dietary Changes Can Yield Substantial Gains for Human Health and the Environment,” is the first to distill the health and environmental impacts of hundreds of our favorite dishes—from chicken to cheese to coffee creamer—down into minutes of healthy life lost.
Seven years in the making, this landmark publication found that a few mindful diet swaps can lead to a longer life and a more sustainable one at that.
How the study came together.
A group of food sustainability, environmental health, and nutrition experts teamed up for this multidisciplinary research.
Olivier Jolliet, Ph.D., a professor of environmental health sciences at the University of Michigan and a senior author on the study, tells mbg that this collaboration was unique and overdue.
After decades of working on environmental lifecycle analyses—i.e. studying the cumulative impact that food has over its lifecycle—he says that nutrition has always been one factor he’s overlooked.
“In a lifecycle assessment, you look at all the stages of your lifecycle: The raw material extraction, manufacturing, supply chain, then the use phase and disposal… Usually, people who are doing that don’t consider the impact for human health—which is a major impact,” Jolliet says on a call with mbg. Frankly, he says, “We were stupid not to do that from the start,” since a food’s nutritional value can really make or break how healthy it is for the planet overall.
He says that nutritionists have historically been similarly siloed, so joining forces on a more holistic database—one that measures both the human and environmental health impact of individual foods—was a refreshing new challenge for both parties.
Making down-to-the-minute calculations.
From the start, the team knew they wanted to present their findings in a way that people could immediately understand. So they pushed beyond calories and saturated fat content to estimate the number of healthy minutes a food could add or take off of a healthy life.
To do so, they applied to individual dishes data from the Global Burden of Disease, which measures how 15 categories of food affect mortality (i.e., those who eat diets high in processed meat are more likely to contract certain fatal cancers).
Take a hot dog: It contains processed meat, which has been shown to take years off life according to the Global Burden of Disease. Per gram, though, it can be said to take off a certain number of minutes—27, according to the team’s estimate. Its sodium and trans fat take off 10 more minutes, but its healthy polyunsaturated fats add one minute. That brings the total burden to 36 minutes of healthy life lost with every hot dog consumed, give or take a few minutes.
Jolliet’s team crunched these numbers on 5,853 foods to create their Health Nutritional Index. From there, they considered 18 environmental factors (ozone depletion, particulate matter emitted during transportation, water use, etc.) to come up with the short-term global warming impact of each food.
They published the findings on 167 of the most popular foods in America and color-coded each one green, orange, or red depending on its combined environmental-health score.
The results ranged from 36 minutes of healthy life lost to 33 minutes gained, and their shorter-term global warming impacts spanned from 0.0005 to 5.7 kg CO2 equivalents (CO2-eq). A serving of cheddar cheese, for example, was found to take 1.4 minutes off a healthy life and emit 0.3 kg CO2-eq, on average. A slice of pepperoni pizza snagged about five minutes and emitted 0.55 kg CO2-eq. An apple added 13 healthy life minutes and emitted 0.02 kg CO2 eq.
Since composing this database piece by piece since 2014, the study authors say they have found some key trends arise.
Unsurprisingly, the foods that scored the worst from an environmental perspective were processed meat, beef, and shrimp, followed by pork and lamb. Processed meat and red meat also had a heavy health toll.
“From a health standpoint, eliminating processed meat and reducing overall sodium consumption provides the largest gain in healthy life compared with all other food types,” the study authors write in a statement on their results. “Getting rid of beef, then pork and lamb, is really the priority,” Jolliet says.
As for what to replace these items with, field-grown fruits, vegetables, legumes, and low-environmental-impact seafood and nuts all scored high points for both health and environmental impact. While some nutritious foods came with a surprisingly high global warming impact in the report (such as greenhouse-raised vegetables, which can be energy-intensive to produce, and some farm-raised fish), for the most part, foods that are healthy for us also tend to be better for the environment.
“Finally, foods classified in the amber zone, such as dairy, poultry, and several grain-based dishes, offer acceptable alternatives if used to substitute foods from the dark red zone or to meet specific nutrient requirements (for example, vitamins and minerals),” the statement continues.
Now, the study’s authors didn’t set out to make us all obsess over the number of minutes we’re adding or taking off of our lives with each bite of food. Instead, Jolliet hopes that people use this research as inspiration to replace just a few of the red foods in their life with green ones—both for the sake of their health and the planet.
After all, swapping out just 10% of daily calories from nutritionally and environmentally detrimental foods (about half a serving of processed meat or beef) was found to result in a nutritional health gain of 48 minutes and a 33% carbon footprint reduction in the study. Not bad for one diet shift.
How to apply these findings for a healthier, more sustainable life.
While the nitty-gritty findings of this study aren’t airtight—researchers didn’t factor in other things that affect mortality, consider cultural connections to certain food groups, or account for alternative growing practices like regenerative farming and sustainable aquaculture—they provide a new way to think about what’s on your plate and what it means for you and the world at large.
After the food data is made available to the public, Jolliet is hoping it can live in an app or be displayed in the supermarket. “That would be a powerful label,” he says. Furthermore, the study points out the need for governments and decision-makers to take these factors into account when recommending and subsidizing certain food groups.
Jolliet says that this report, which was released in late August and has already reached 100 million people, has already been the most impactful of his career by far, and he’s hopeful that it will leave a legacy. In the process of writing it, he himself has basically given up processed meat (though, he smiles, he’s Swiss, so cheese is still prominently featured on the menu) and heard of others doing the same—if not for the environment, then for the 36 minutes of healthy life it could save them.
“Overall,” the authors conclude in their report summary, “we hope this work inspires and empowers a transition towards healthy and environmentally sustainable diets, changing one food at a time.”