New Research Says Plant-based Diet Best for Planet and People

As cities grow and incomes rise around the world, more and more people are leaving gardens and traditional diets behind and eating refined sugars, refined fats, oils and resource- and land-intense agricultural products like beef. This global dietary transition is harming the health of both people and the planet, says new research.

But the study also shows that shifting away from this trajectory and choosing healthier traditional Mediterranean, pescatarian or vegetarian diets could not only boost human lifespans and quality of life, but also slash emissions and save habitat for endangered species.

And we better hurry; the scientists project that if the trend continues, the situation will be worse yet with greenhouse gas emissions up by 80 percent by 2050.

Examining almost 50 years’ worth of data from the world’s 100 most populous countries, University of Minnesota Professor of Ecology G. David Tilman and graduate student Michael Clark illustrate how current diet trends are contributing to ever-rising agricultural greenhouse gas emissions and habitat degradation.

On top of that, they write: “These dietary shifts are greatly increasing the incidence of Type 2 diabetes, coronary heart disease and other chronic non-communicable diseases that lower global life expectancies.”

In the study, published in the November 12 online edition of Nature, the researchers found that as incomes increased between 1961 and 2009 people began consuming more meat protein, “empty calories” and total calories per person. (“Empty calories” — sugar, fat, oils and alcohol — now account for almost 40 percent of food purchased in the world’s 15 wealthiest countries, according to the research.)

When the researchers combined the trends with forecasts of population growth and income growth for the coming decades, they were able to project that diets in 2050 will contain fewer servings of fruits and vegetables, about 60 percent more empty calories and 25 to 50 percent more pork, poultry, beef, dairy and eggs. These are changes that are known to increase the prevalence of type II diabetes, coronary heart disease and some cancers.

Using life-cycle analyses of various food production systems, the study also calculated that, if current trends prevail, these 2050 diets would also lead to an 80 percent increase in global greenhouse gas emissions from food production as well as habitat destruction due to land clearing for agriculture around the world.

“We showed that the same dietary changes that can add about a decade to our lives can also prevent massive environmental damage,” said Tilman, a professor in UM’s College of Biological Sciences and resident fellow at the Institute on the Environment.

“In particular, if the world were to adopt variations on three common diets, health would be greatly increased at the same time global greenhouse gas emissions were reduced by an amount equal to the current greenhouse gas emissions of all cars, trucks, planes, trains and ships. In addition, this dietary shift would prevent the destruction of an area of tropical forests and savannahs as large as half of the United States.”

The study compared health impacts of the global omnivorous diet with those reported for traditional Mediterranean, pescatarian and vegetarian diets. Adopting these alternative diets could reduce incidence of type II diabetes by about 25 percent, cancer by about 10 percent and death from heart disease by about 20 percent relative to the omnivore diet.

Adopting these or similar alternative diets would also prevent most or all of the increased greenhouse gas emissions and habitat destruction that would otherwise be caused by both dietary changes and increased global population.

The authors acknowledged that numerous factors go into diet choice — but also pointed out that the alternative diets already are part of the lives of countless people around the world.

“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,” Tilman said.

Noting that variations on the diets used in the scenario could potentially show even greater benefit, the authors concluded that “the evaluation and implementation of dietary solutions to the tightly linked diet-environment-health trilemma is a global challenge, and opportunity, of great environmental and public health importance.”

Meanwhile, the paper offers a number of nuanced findings about the environmental impacts of various dietary choices. Here are a few takeaways to keep in mind:

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Carol is a journalist with a green heart who believes that presenting information in a positive and accessible manner is essential to activating more people to join the search for equitable and sustainable solutions to global problems. A native of Montreal, Canada, she joined the UNU communications team in 2008 while living in Tokyo and, after relocating to Vancouver, continued to telecommute to Our World as writer/editor through 2015.

Join the Discussion

  • John Higson

    It’s rubbish really.The human animal evolved for a mixed diet with things like meat and offal featuring highly.I agree on refined oils,sugars and grain,these have no place in our diet.But,plant based? I don’t think so.

    • Too bad the science isn’t on your side on rubbishing this theory, John. Perhaps contemplating the meaning of the word ‘evolve’ prior to employing it would get you closer to confronting your bias?

      • John Higson

        I’m afraid the science is on my side,there are theories that we started to use tools only so we could get at the fat rich tissue inside the skulls of our prey,the fact that we have canines,the size of our brains(needing a more nutrient rich diet than can be got from plant based foods)etc,etc,etc. If you are happy eating vast amounts of carbs in a concentrated form which our bodies aren’t designed for,have at it.I’ll carry on eating like a hunter/gatherer,meat/fish of all descriptions,fruit,nuts and vegetables.

        Just exactly what do you think my biases are? If you mean the biases that come from having studied nutrition at university and knowing a bit of biochemistry whilst generally being a scientist,then ,yes, I’m biased.

      • John Higson

        Speaking of biases,it would seem to me that yours appear to be more obvious than mine.’Green Heart’ and ‘Journalist’ doesn’t qualify you to be an expert on nutrition now,does it? Having had these argument over the years ,over and over again,some people are ideologically against what most paleo-anthropologists would agree is the optimal diet for Homo Sapiens Sapiens.That diet was the one our hunter/gatherer ancestors ate,NOT a plant based one.Sure it had a lot of plants in it,but it would probably be called ‘animal based’ if anything.

        I know the world’s population as it stands can’t be fed that way,it’s just a matter of fact that grain rich diets are more calorie efficient,I know all this! But that doesn’t mean that it’s better for us.It simply isn’t.I refer you to the above paleo-anthropologists-humans were much healthier and taller and more robust as H/Gers and shrank and became much less robust when we became farmers(and adopted a carb /grain rich diet),these are the facts as I understand them,refute if you can!

        • Hi John. Sorry for sounding somewhat snarky in my original reply. Debates about meat eating often end up the perfect example of what happens when advocacy and promotion of absolute stances displace a (skeptical, in the true sense) effort to impartially judge a complex reality. So I hope you can forgive me for perceiving your comment as such. When it comes to my bias on this topic, I have to say that it is towards peer-reviewed science, as I too have had many debates on this issue with people who take an absolute stance without having ever read any of the science, let alone sampling what two sides of an issue contend!

          As to what I am assuming you are basing your arguments on — the evolutionary discordance hypothesis much employed by the now popular & trademarked “Paleo Diet” by Loren Corden (some aspects of which are indeed being reinforced by the very varied research routes having to do with the topic) — it is my understanding that the overall the validity of the evolutionary discordance hypothesis has been brought into doubt by recent science (it seems there is more and more evidence that humans can and have adapted dietarily – see for example To the extent that even the originators of the hypothesis stated in a 2010 update (on the 25th anniversary of the hypothesis):

          “Much more research needs to be done, but the past quarter century has proven the interest and heuristic value, if not yet the ultimate validity, of the model.”

          As the article we are commenting on highlights, this is an area of research that is uber-key to humanity’s future so research on human dietary evolution will no doubt continue to evolve and hopefully we humans will have an open mind on the topic and adapt to the best of our ability and comfort level (some for ethical reasons might choose a diet that may in the long run not allow as long a lifespan as say a meat-based one). That said, I wanted to say that, in my view (and to some extent, the research discussed in this article), “plant-based” does not mean everyone must go completely vegan (though there again, I hope research will continue on whether it is possible to find a truly and easily healthful way to allow that, should people choose that route). I myself have tended toward plant-based diet my entire adult life and at age 47 I am as fit (have always been physically active) and the same weight as I was when I was 20 and my only health issues are hereditary (eczema and migraines). My version of plant-based today is mucho local organic veg & fruit, other plant protein foods (legumes, quinoa, beans, nuts, seeds), whole grains, local organic dairy with occasional (2-3 times a week) local organic small-scale meat & fish. Oh, and chocolate, lol.

          So that’s my POV. In closing, I just want to say that I hope you won’t give up hope that there can be a solution to this conundrum. I recently came across the work of Vaclav Smil on the topic and have been meaning to see if the library has his book on the topic: Should We Eat Meat? Evolution and Consequences of Modern Carnivory. But I’ve just checked his website to give you the link and I now see he’s got a paper summarizing it so I’m going to put that on my reading list and here it is in case you’d like to do same:


        • I welcome findings based on serious study that we need to tilt towards more vegetarianism in our eating habits. I don’t think the point is about what some call an ‘omnivorous’ diet (I am Indian and we call it non-vegetarian) versus a vegetarian one, but how much meat (and fish) are consumed by households and at what cost. I agree that religious and faith reasons excepted, many households did consume meat products – how regularly is probably not known from archaeological evidence. What I find worrying is the rate of increase in the consumption of meat – especially in P R China and in metropolitan India – and the environmental costs of that much meat being provided. As far as I know there are two kinds of relationships to look for, which I think this article covers: the food calorific and nutritive value of staple cereals, vegetables and horticulture per some unit of arable land, and the energy need (in BTUs or any equivalent) to collect, process, transport and store meat to consumers. My experience and observation in India, where i live and work, is that the ‘BTU’ energy of doing so is prohibitive but is made possible by hidden subsidies, while the ecosystem value of providing, per arable land unit, a vegetarian diet is not recognised well enough. Regards, Rahul Goswami

          • Thanks very much for your thoughtful comments Rahul. It is definitely time that hidden subsidies are brought to light and people begin seriously discussing the caloric vs energy balance as you so succinctly describe.

      • John Higson

        Did my 2 comments really get moderated? For what? Why? Were they inappropriate? Or are just shutting down dissenting voices? If that’s the case you’re pathetic…..

        • BrendanBarrett

          Hi John, Sorry we were in a workshop all day so no one had the chance to moderate your comments.

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