5 reasons to cut back on animal foods

Red meat is in the hot seat these days. Experts call it a threat to both our health and the health of the planet our children will inherit. But it’s not just whether to cut back on red (and processed) meat. The question is: What will take its place? Here are five reasons to fill most of your plate with plants.

1. Help your heart.

How do researchers know that a “plant-forward” diet is good for the heart?

“There are layers of evidence,” says Walter Willett, professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health.

For starters, nuts, beans, soy, and other plant sources of protein have more polyunsaturated fat and less saturated fat than red meat and dairy.

“We’ve known for 50 years that polyunsaturated fats reduce LDL—or bad—cholesterol and saturated fats raise LDL,” says Willett. And “red meat is extremely low in polyunsaturated and quite high in saturated fats.”

Dozens of studies have demonstrated the impact of different fats on LDL.¹

“Trials clearly show that replacing red meat with plant-based protein sources like nuts, beans, and soy foods reduces LDL levels,” notes Willett.²

And it’s not just saturated vs. polyunsaturated fat. Last year, researchers fed people diets rich in red meat (beef), white meat (chicken and turkey), or non-meat proteins (largely beans, nuts, and soy foods) for four weeks each.³

To look beyond the impact of fats, the scientists made all three diets equal in saturated and polyunsaturated fat, largely by adding saturated fat from full-fat dairy foods and butter to the white meat and non-meat diets.

(That’s why LDL was equal on the red-meat and white-meat diets.)

The surprise: LDL was lowest on the non-meat diet.

“Detailed comparison suggests plant proteins are better for the heart,” said the National Heart, Lung, and Blood Institute (which funded but did not conduct the study) on its website.

“Ideally, if we wanted to know about the long-term health effects of plants, red meat, or other foods on heart attacks or other chronic disease, we’d randomly assign thousands of people to different diets for many years to see what happened to their rates of those diseases,” says Willett.

But few such studies have ever been done.

“It could be very hard to get thousands of people to sign up to be randomized, hard to keep them on those diets, and hard to get an ethics board to approve diets that have adverse effects on cardiovascular risk factors like LDL,” notes Willett.

So instead of assigning people to different diets, researchers ask people what they eat, then track their illnesses for years or decades. Recently, those studies have looked at people who eat diets rich in healthy plant foods.

“Soda and doughnuts are plant foods,” says Willett, “but they’re definitely not healthy.” So his team created an index for healthy and unhealthy plant foods.

People gained points for eating fruits, vegetables, nuts, beans, whole grains, oils, tea, and coffee more often. And they lost points for eating refined grains, potatoes, fruit juices, sugary drinks, sweets, and desserts more often.^4-6

“Diets high in healthy plant-based foods did best,” says Willett. That is, people eating them had a lower risk of both heart disease and type 2 diabetes. “The unhealthy plant-based diets did the worst.”

But people don’t have to go vegan—that is, avoid all animal foods.

“The further you go toward a plant-based diet, the lower your risk of these diseases,” says Willett. “But it’s not all or nothing.”

“In fact, we can’t say whether a very low intake of animal protein is better or worse than no animal foods at all. Having a little fish, poultry, or dairy may be a safety net to provide certain nutrients. That’s typical of many traditional diets like the Mediterranean diet.”

2. Sustain your brain.

“Another reason to keep your blood pressure down: It can lower your risk of dementia,” ran the Los Angeles Times headline in 2018.

The big news: In the SPRINT MIND trial, people with high blood pressure who were randomly assigned to reach a systolic blood pressure below 120 had a lower risk of mild cognitive impairment—which can lead to dementia—than people assigned to reach 140 systolic.⁷

“What SPRINT has shown is that what is good for your heart is also good for your brain,” co-author Jeff Williamson, professor of gerontology and geriatric medicine at the Wake Forest School of Medicine, told the Times.

SPRINT MIND cut blood pressure in the below-120 group by an average of 18 points using multiple drugs. But in some people, a DASH (Dietary Approaches to Stop Hypertension) diet can bring blood pressure into the normal range without drugs.

“In the DASH trial, a DASH diet lowered blood pressure by 11 points in people with hypertension,” says Frank Sacks, professor of cardiovascular disease prevention at the Harvard T.H. Chan School of Public Health.

“That’s as effective as some drugs.”

A key component of DASH: fruits and vegetables.

“Fruits and vegetables are important foods to protect us against hypertension,” says Sacks. But they only accounted for half of the diet’s impact in the DASH trial.

“Eating fish and chicken instead of beef and pork, vegetable oils instead of butter, and more low-fat dairy accounted for the other half,” says Sacks.

Could lowering blood pressure with diet protect the brain as well as lowering pressure with drugs?

The MIND trial is looking at whether a DASH-like diet—tweaked to include more of some foods like berries, olive oil, and nuts—can slow cognitive decline.

But even if the diet only prevents strokes, that’s a plus. Tiny, often undetected strokes are the underlying cause of what scientists call vascular dementia, the second most common cause of memory loss.

“We’re hoping the MIND diet can prevent both Alzheimer’s and vascular dementia, but there’s more reason to be optimistic about vascular dementia,” says Sacks. “Many people with memory loss have both.”

3. Cut your risk of cancer.

Willett’s studies didn’t find a link between the plant-diet index and deaths from cancer, possibly because cancer isn’t just one disease.

“Cancer is complicated because each cancer has a different set of risk factors acting at different ages,” he cautions.

But a plant-forward diet can help you dodge at least one cause of one cancer.

In 2015, the International Agency for Research on Cancer (IARC) put processed meats—like bacon, hot dogs, ham, sausage, and lunch meats—in the same evidence category as tobacco smoking and exposure to asbestos.⁸

“IARC had 22 experts from 10 countries evaluate over 800 studies, and they classified processed meats as carcinogenic to humans based on sufficient evidence for colorectal cancer,” says Marjorie McCullough, senior scientific director of epidemiology research at the American Cancer Society.

But that conclusion “does NOT mean that they [processed meats, tobacco, and asbestos] are all equally dangerous,” noted IARC.

Each daily serving of processed meat (2 oz., or roughly the size of a hot dog) increases the risk of colorectal cancer by about 18 percent, said IARC. In contrast, smoking raises the risk of lung cancer by 1,500 to 3,000 percent (that is, 15 to 30 times).

Burgers, steaks, pork chops, and other unprocessed red meats (beef, pork, lamb, and veal) are probable human carcinogens, concluded IARC, because the evidence was less certain than it was for processed meats.

What’s the evidence behind IARC’s conclusions? Most comes from studies that ask people what they eat and then track them for years to see who gets cancer.⁹

“The data suggests that there’s no threshold below which you can say that an amount of processed meat poses no risk of colorectal cancer,” notes McCullough.

(Last year, a meta-analysis concluded that there is too little evidence to recommend eating less red or processed meat, but the authors failed to consider all the evidence on meat and cancer.)

IARC also relied on “strong mechanistic evidence,” says McCullough. “How these foods increase cancer risk is not known, but there are several strong possibilities.” Among them:

■ N-nitroso compounds. “When you consume processed meat, you may consume pre-formed N-nitroso compounds, which are carcinogens,” says McCullough.

“Other processed meats contain nitrates and nitrites, which can form N-nitroso compounds in the gut.”

■ Heme iron. Red meats are rich in heme iron, which is part of the hemoglobin in blood. “Heme iron can catalyze the formation of N-nitroso compounds in the gut,” says McCullough.

Almost 20 years ago, researchers put people on a diet that included either beef and pork or poultry and fish.¹⁰

“When they ate the red meat, they had a greater output of N-nitroso compounds than when they ate the white meat,” says McCullough.

■ Mutagens. “Mutagens are formed when meats are cooked at high heat or when they’re exposed to smoke,” explains McCullough. “Mutagens can cause DNA damage, and that increases the potential for colorectal cancer.”

Beyond meat and colorectal cancer, the evidence on diet and cancer is intriguing but uncertain.

“Fruits and vegetables are related to lower ER-negative breast cancer,” says Willett. (ER-negative tumors are not responsive to estrogen.)

In a 24-year follow-up of roughly 182,000 nurses, the risk of ER-negative breast cancer was 12 percent lower for every two servings of fruits and vegetables eaten per day.¹¹

The links were clearest for orange or yellow vegetables (like carrots or winter squash) and berries.

“The association with ER-negative breast cancer is also seen in studies that look at blood carotenoid levels,” adds Willett. (Carotenoids like beta-carotene give many fruits and vegetables their orange or yellow color.)

And ER-negative tumors are more difficult to treat.

“It’s the most dangerous kind of breast cancer,” says Willett.

4. Keep antibiotics working.

“WHO warns that pipeline for new antibiotics is running dry,” reported the New York Times in January.

“Never has the threat of antimicrobial resistance been more immediate and the need for solutions more urgent,” said Tedros Adhanom Ghebreyesus, Director-General of the World Health Organization, in summing up the WHO report that led to the Times headline.

Each year, at least 2.8 million U.S. residents get an antibiotic-resistant infection, and more than 35,000 die, according to the Centers for Disease Control and Prevention.¹²

What makes bacteria resistant to antibiotics?

“It’s just a matter of evolution,” says Lance Price, professor of environmental and occupational health at George Washington University.

“Every now and then, a bacteria picks up a mutation or a gene from another bacteria that makes it resistant to some antibiotic. If that antibiotic is present, then the susceptible bacteria are going to die off and the resistant ones are going to multiply.”

And bacteria multiply fast.

“You can go from a single drug-resistant E. coli to more than a billion in 24 hours,” says Price.

What does that have to do with food?

Two-thirds of the 20 million pounds of medically important antibiotics sold every year in the United States are used in livestock (mostly cattle and pigs), according to the Natural Resources Defense Council.

“The antibiotics are being used to prevent or treat diseases that occur in part because we raise animals in concentrated animal feeding operations,” explains Price.

“When I see these operations, I don’t see factories making meat. I see factories making trillions and trillions of drug-resistant bacteria.”

And some of those drug-resistant bacteria end up in people. “We’re barreling toward a time when our antibiotics no longer work,” says Price.

5. Protect your children’s planet.

“Wildfires at all-time high. Arctic sea ice remains at record lows,” says the U.S. Environmental Protection Agency.¹³

“The Earth’s climate is changing.” The change shows up in virtually every indicator that the EPA and the National Climate Assessment track, from rising global greenhouse gas emissions, sea levels, and air and ocean temperatures to more heatwaves, heavy rains, persistent drought in the Southwest, and flooding on the coasts and in Northeast, Pacific Northwest, and Midwest rivers. ^14,15

And time is running out.

“The climate crisis has arrived and is accelerating faster than most scientists expected,” said a “climate emergency” warning from 11,000 scientists in 153 countries in January.¹⁶

“Especially worrisome are potential irreversible climate tipping points... that could lead to a catastrophic ‘hothouse Earth,’ well beyond the control of humans.”

Among the events that could trigger a tipping point: melting Antarctic or Greenland ice sheets, loss of Arctic sea ice, or drought in the Amazon rainforest (see map).¹⁷

And what we eat matters.

“Business as usual in the food system is not an option,” says Nicole Tichenor Blackstone, assistant professor of agriculture, food, and environment at Tufts University.

Eating more plants and fewer animal foods can help.¹⁸

“Globally, livestock systems are responsible for around 11 to 15 percent of greenhouse gas emissions, they occupy 80 percent of global agricultural land, and they use around 30 percent of agricultural water,” notes Blackstone.

Beef takes the greatest toll.

“The differences are not small,” says Harvard’s Walter Willett. “Beef produces far more greenhouse gas per serving than plant proteins like soy and nuts.”

Why? “Beef cattle have a much higher carbon footprint than non-ruminant animals like pork or poultry or plant-based proteins in part because cows consume grass,” explains Blackstone.

Digesting that grass makes cattle expel methane from both ends of their GI tracts (mostly from burps).

And “methane is a greenhouse gas that’s 25 to 28 times more powerful than carbon dioxide,” says Blackstone.

Greenhouse gasses aren’t the only problem. Growing enormous quantities of grain to feed livestock—and the animals’ manure—can pollute water with nitrogen and phosphorus.¹⁹

“Nitrogen and phosphorus have consequences, like the algal blooms in Lake Erie and the Gulf of Mexico,” says Blackstone.

What’s more, “plant-based proteins tend to use less water, which matters in places where water is scarce.” (Exception: In North America, almonds require about as much water per serving as beef.¹⁹)

What about plant-based “meats”?

“Life-cycle assessments commissioned by Beyond Meat and Impossible Foods show roughly 90 percent lower greenhouse gas emissions, 90 percent less water use, and 90 percent less land use compared to beef,” says Blackstone.^20,21

“If you eat plant-based meats in place of pork, the reductions are a little less dramatic.”

Overall, red meat has ripple effects throughout the environment.

“We’re cutting down forests and plowing under prairies to produce animal foods that are destroying our biodiversity and interfering with water systems,” explains Willett.

“We’re growing vast amounts of grain, much of it to feed to animals, not people. And the fertilizer that’s being used to grow that grain is poisoning our streams and oceans.”

“This bizarre food system is bad for the planet and bad for people.”

Worst of all, our children and grandchildren will face the consequences.

“When we talk about environmental sustainability, we’re not only talking about our ability to live now with clean water, clean air, et cetera,” says Blackstone.

“We’re talking about avoiding catastrophic warming and, in some cases, total ecosystem collapse.”

“If you don’t do it for today, do it for your kids and grandkids. The choices we make can build a more sustainable future for them.”

References

¹ who.int/nutrition/publications/nutrientrequirements/sfa_systematic_review.
²Circulation 139: 1828, 2019.
³Am. J. Clin. Nutr. 110: 24, 2019.
⁴Circulation 140: 979, 2019.
⁵J. Am. Coll. Cardiol. 70: 411, 2017.
⁶PLoS Med. 2016. doi:10.1371/journal. pmed.1002039.
⁷JAMA 321: 553, 2019.
⁸ iarc.fr/wp-content/uploads/2018/07/Monographs-QA_Vol114.pdf.
⁹ monographs.iarc.fr/wp-content/uploads/2018/06/mono114.pdf.
¹⁰J. Nutr. 132: 3522S, 2002.
¹¹Int. J. Cancer 144: 1496, 2019.
¹² cdc.gov/drugresistance/pdf/threats-report/2019-ar-threats-report-508.pdf.
¹³ epa.gov/climate-indicators.
¹⁴ epa.gov/climate-indicators/downloads-indicators-report.
¹⁵ science2017.globalchange.gov/downloads/CSSR2017_FullReport.pdf.
¹⁶Biosci. 70: 8, 2020.
¹⁷Nature 575: 592, 2019.
¹⁸ ipcc.ch/site/assets/uploads/2019/11/SRCCL-Full-Report-Compiled-191128.pdf.
¹⁹Science 360: 987, 2018.
²⁰ css.umich.edu/publication/beyond-meats-beyond-burger-life-cycle-assessment-detailed-comparison-between-plant-based.
²¹ impossiblefoods.com/mission/lca-update-2019.

Photos: stock.adobe.com: marrakeshh, Ramon Grosso, fotolia.com—© robynmac (hot dog, carrots, pork chop), © Elena Moiseeva (burger), © Stanislav Pepeliaev (cold cuts), © Spauln (water), ©OlgaLIS (bacon), © arnowssr (spinach), © Artyshot (steak), deyana, zi3000.

Graph source: Science 360: 987, 2018.

Illustration: Adapted from Nature 575: 592, 2019.