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How Diet Affects Climate Change

UCLA Health interviewed Dr. Dana Hunnes, UCLA Fielding School of Public Health assistant professor of community health sciences, about how diet affects climate change

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Monday, September 20, 2021
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An effective step toward reducing climate change is literally on your plate.

Filling your daily diet with more plants and fewer animal products has more impact on the environment than taking shorter showers or switching to energy-efficient lightbulbs, said Dr. Dana Hunnes, UCLA Fielding School of Public Health assistant professor of community health sciences and UCLA Health dietitian.

Hunnes believes so strongly in the power of food choices to affect climate change that she wrote a book about it. “Recipe for Survival: What You Can Do to Live a Healthier and More Environmentally Friendly Life” is due to be published by Cambridge University Press in January.

“When we think about climate change, we think about emissions from cars, from planes and from our houses. And all too often, we're not also thinking about what we eat,” she said. “The most powerful action you can take as an individual right now is to change your eating habits to be more sustainable.”

How animal agriculture affects the environment

Food production is a significant source of global greenhouse gases, Hunnes said. Animal agriculture — particularly the cultivation of beef and dairy cows — is the leading culprit, as cows emit millions of tons of methane each year.

Americans consume an average of 200 pounds of meat per person per year, an eating pattern being adopted around the world as developing nations gain wealth.

It takes a lot of land to grow food for these animals that people eat and for the planet’s human population of 7.8 billion — half of the ice-free land on Earth. The growing need for grazing lands leads to deforestation, which eliminates habitat for wild animals and trees that would otherwise remove carbon dioxide from the atmosphere and keep moisture in the ground, further exacerbating climate change.

That’s why eating less meat and dairy is a meaningful way to curb individual environmental impact, Hunnes said.

“A vegan or plant-based diet can grow 10,000 times as many calories on one acre of land as growing an animal,” she said.

The impact of aquaculture

“There are plenty of plant-based foods out there that have plenty of protein and you absolutely can get enough, if not more than enough, from plant-based sources,” Hunnes said.

While eating fish instead of red meat may be healthier for our bodies, the cost to the planet is still unsustainable, she said.

Commercial fishing methods, including gill nets and bottom trawling, sweep up large swaths of animals, many of which were never destined for the marketplace and get tossed overboard – dead. This leads to overfishing, with as much as 90% of the world’s seas being depleted faster than fish can reproduce, she says.

Some of the most commonly eaten species have become “critically endangered and threatened with extinction,” Hunnes said, including grouper, swordfish and the Patagonian toothfish, better known as Chilean sea bass.

Farm-raised fish also have environmental costs as they can pollute and contaminate wild-fish environments and often require large amounts of feed, she said.

Where would the protein come from?

One question many have: Does a diet free of meat, fish and poultry have enough nutrients, particularly protein? Hunnes said most Americans can get ample daily protein without eating animals.

“Everything has a little bit of protein in it. Even an apple has half a gram of protein,” she said. “There are plenty of plant-based foods out there that have plenty of protein and you absolutely can get enough, if not more than enough, from plant-based sources.”

Popular plant-based sources of protein include peanuts, tofu and beans.

Packaged foods: Bad for you and the planet

Reducing consumption of packaged foods is another way to help the environment, Hunnes said, as these foods tend to rely on two things that harm the planet: palm oil and plastic.

Palm oil, which is an efficient crop and shelf-stable fat that is cheaper to produce than other oils, is found in foods such as crackers, cookies, cereals, breakfast bars and cake mixes, among other packaged products. Palm oil production leads to clear-cutting forests in Indonesia and Malaysia, Hunnes said, to make room for palm-oil trees. This drives orangutans and other species from their natural habitats.

“Unfortunately, our appetite for palm oil is only growing,” nearly doubling over the past 12 years, Hunnes said.

Packaged foods often rely on plastic, which pollutes the oceans and, ultimately, animal bloodstreams. Plastic photo-degrades in ocean waters, becoming micro-plastics that are consumed by marine animals. These materials release toxins, called persistent organic pollutants, which bio-accumulate up the food chain and into many of the fish that people eat, Hunnes said, adding that most Americans have residue of these toxic pollutants in their blood.

Solutions for sustainable eating

Simple swaps and gradual changes can make a big difference, Hunnes said.

Consider buying staple foods in bulk and packaging them in reusable containers. Reduce food waste destined for landfills by freezing leftovers and composting what you can’t eat.

Choose plant foods more often and reduce consumption of animal foods. “Crowd out the meat with everything else on the plate,” Hunnes said. “If you’re going to eat it, make it a condiment and not the main.”

Let the future of the planet be your motivation, she said, and consider the words of Albert Einstein.

“Albert Einstein is known for many great things,” Hunnes said. “But one thing I like to attribute to him is the idea that, ‘Nothing will benefit human health and increase the chances for survival of life on Earth more than the evolution to a vegetarian diet.’"

Hunnes has also recently been inteviewed by UCLA Health about "Do fitness enthusiasts really need supplements?" and "Food smarts: separating nutrition myths from facts."

By Sandy Cohen