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Mostly Plants: New Science Says a Healthier Diet is Best for the Climate

Good food advocates have long argued that what’s best for your health is also best for the planet, but new science now backs up the claim. A paper published today in the journal Nature by scientists at the University of Minnesota, presents hard numbers that suggest eating less meat, less refined fat, and less sugar will also reduce the climate change impacts of food production.

Using about 50 years’ worth of data from the world’s 100 most populous countries, UM Professor of Ecology G. David Tilman and graduate student Michael Clark show how current diet trends are contributing, not only to diet-related illnesses such as diabetes and heart disease, but also to dangerously increasing agricultural greenhouse gas emissions (GHGs).

“This is the first time this data has been put together to show these links are real and strong and not just the mutterings of food lovers and environmental advocates,” explains Tilman.

“Alternative diets that offer substantial health benefits could, if widely adopted, reduce global agricultural greenhouse gas emissions; reduce land clearing and resultant species extinctions; and help prevent such diet-related chronic non-communicable diseases,” write Tilman and Clark in the Nature article.

Agriculture currently contributes about 25 percent of the GHG emissions driving climate change. Grain-based livestock production–which involves clearing land and raising grain for animal feed, particularly in the world’s tropical regions–contribute more than 75 percent of those emissions.

As the rest of the world adopts American dietary habits, the rates of meat, sugar, and processed food consumption have been on to rise. (In China alone, the numbers have skyrocketed.) If the trend continues, all those burgers and pork chops are projected to cause an 80 percent increase in agricultural GHG emissions by 2050.

At the same time, thanks to the exporting of American dietary habits, more than 2.1 billion of the world’s 7.2 billion people are now either overweight or obese. Tilman explains that “empty calories”–sugar, fat, oils and alcohol–now account for almost 40 percent of food purchased in the world’s 15 wealthiest countries, which helps explain the resulting health effects.

According to the data Tilman and Clark examined, which corrected for other lifestyle factors, a vegetarian diet reduced incidence of type II diabetes by 41 percent, followed by a vegetarian diet that includes seafood (25 percent), and a Mediterranean diet that combines moderate meat consumption and is rich in fruit, vegetables, and seafood (16 percent). All three diets appeared to reduce coronary heart disease deaths between 20 and 26 percent and cancer rates by between 7 and 13 percent compared to diets that included at least twice as much meat and processed foods.

Tilman and Clark caution that while the links between what makes healthy diet and what will help lower agricultural greenhouse gas emissions are clear, it’s also possible to eat “a pure junk food diet,”–think French fries, donuts, and tortilla chips–that has low GHG emissions.

So the solution to what the scientists call the “diet-environment-health trilemma” will require choosing menus high in plant-based, whole foods like those that fit in a Meditarreanean, “pescetarian” or vegetarian diet. If these diets become the norm by 2050, Tilman and Clark say “there would be no net increase in food production emissions.”

But they also note that making such a change won’t necessarily be easy. “The dietary choices that individuals make are influenced by culture, nutritional knowledge, price, availability, taste and convenience, all of which must be considered if the dietary transition that is taking place is to be counteracted,” write Tilman and Clark.

So, how do we counter the trend toward eating more meat and fatty food? “There are lots of policy options,” says Doug Boucher, director of climate research at the Union of Concerned Scientists. These include carbon taxes that would include agriculture as New Zealand now does, shifting agricultural subsidies away from livestock and related feed production, and changing government dietary guidelines to include sustainability and climate change considerations, as the U.S. Department of Agriculture’s (USDA) 2015 guidelines are expected to.

The USDA’s climate change program director, William Hohenstein, explains that rather than addressing the “trilemma” by focusing on the menu, the agency’s preferred strategy is to work with growers and livestock producers on practices that will reduce GHGs. “Consumers always have a choice,” says Hohestein.

Tilman suggests “better education” is key to helping people of all income levels understand the impacts of their food choices. He also wonders if, given the clear trend toward convenience foods, it might be possible to develop new food that is healthy, low-carbon and he adds, “also tastes good.”

Meanwhile, the data strongly suggest that eating more like Bill Clinton post-heart surgery will not only improve personal and public health, but also help put the planet on a much needed version of a weight-reduction program for greenhouse gasses.

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9 thoughts on “Mostly Plants: New Science Says a Healthier Diet is Best for the Climate

  1. Being myself over 50, I’m a living proof that the switch towards a plant based diet is possible even for adults and generally for people of any age. I took a conservative approach – first, I started learning how to prepare my own meatless meals. Then I started cooking for myself, and slowly replacing all ingredients. In a one year span, I turned from frequent meat eater to a vegan. And guess what – nothing serious happened to me. I pay more attention to what I buy, I prepare my own food more often, I also cook for my family way more than I used to. And when people ask me if I miss meat, cheese or eggs, I feel confident in saying NO.

  2. Ironically I am currently reading “Defending Beef” which effectively counters all these allegations. Maybe this message should be more nuanced. Eating grass fed beef or pastured animal products is more expensive and will inherently lead to less meat intake. Less cropland will be used to grow the corn and soy that feeds the CAFO system. We can restore the soil and feed ourselves without demonizing animal protein and healthy fats in the diet while pointing to the far more harmful effects of too much refined grain and sugar in the diet–which also come from plants.

  3. It is important to compare available information. Certainly, pastured meat options are less detrimental to the environment (and healthier) than CAFO grain-fed versions.

    If I understand the above article correctly, it is not demonizing healthy fats nor grass-fed beef. It is simply suggesting eating “less meat, less refined fat, and less sugar” than the average American diet results in better health, and more resilient ecosystems.

    It is important to consider the sources of information. “Defending Beef” cites research, but it is opinion as well. The Nature article is more robust, comparing 50 years of data in 100 most populous countries. The DMII and cardiovascular disease rates in diets with less meat, sugar & fats are compelling.

  4. “Agriculture currently contributes about 25 percent of the GHG emissions driving climate change.” Is that correct? According to the EPA’s website agriculture contributes 10% in the US and 14% globally.

  5. I appreciate the mention of my book, Defending Beef. I deal with many of these same issues in my book, and I strongly agree with the preceding comment that they are far more complex than the headline suggests. I am currently getting a copy of the full study, which looks interesting, but it’s certainly not a simple condemnation of animals in the food system, which have both nutritional and environmental benefits WHEN PROPERLY RAISED. It is also worth noting the study authors considered sugar, refined oils, alcohol, and meat all to be important factors. I look forward to reading the full study.

  6. The hyperlink goes to an abstract and I’m disinclined to spend $32 for a pdf of the actual article. However I did read and click through on some of the papers cited in the bibliography. Several are “cohort studies” so in essense this paper appears to have gone back and assessed other researchers observational studies and like those studies has done no actual clinical research. Cohort studies are just the begiining of research. You get correlations from the analysis to base a hypothesis to test. It isn’t the end result,. There is no actual data. So all you really appear to have here is a lot of postulations if I’m correct on what appears to be the methodology used here. Makes good headlines, but it isn’t real science.

  7. I agree with Wynne. The piece isn’t demonizing animal-based food, just stating that a plant-based diet will have many interconnected benefits – health and the environment chief among them. What this piece doesn’t mention, nor do Bonnie or Nicolette above, is the ethical piece. Even if you could ensure free-range, grass-fed meat ensured a pain-free existence (which you can’t), raising animals to simply slaughter them has some ethical questions. Also, to suggest that the world can suddenly switch to grass-fed, free-range beef is simply untrue. There is too much profit in confinement systems and, as non-western countries continue to adopt the SAD, cheap meat is essential to fulfilling those needs. And, the animal waste problems still exist.