The nation’s top nutritional panel is recommending for the first time that Americans consider the impact on the environment when they are choosing what to eat, a move that defied a warning from Congress and, if enacted, could discourage people from eating red meat.

Members of Congress had sought in December to keep the group from even discussing the issue, asserting that while advising the government on federal dietary guidelines, the committee should steer clear of extraneous issues and stick to nutritional advice.

But the panel’s findings, issued Thursday in the form of a 571-page report, recommended that Americans be kinder to the environment by eating more foods derived from plants and fewer foods that come from animals. Red meat is deemed particularly harmful because of, among other things, the amount of land and feed required in its production.

“Consistent evidence indicates that, in general, a dietary pattern that is higher in plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts, and seeds, and lower in animal-based foods is more health promoting and is associated with lesser environmental impact than is the current average U.S. diet,” the report says.

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Many scientists say animal-based foods are a poorer choice for the environment because they are associated with significantly larger carbon emissions than their plant-based counterparts. (Jayme Halbritter/AP)

The environmental recommendations are part of a report meant to provide the scientific basis for the next version of the Dietary Guidelines, the federal government’s publication on what to eat. The Department of Health and Human Services and the Agriculture Department will issue the guidelines later this year.

Those agencies could ignore the panel’s recommendations, but major deviations are rare, experts and former panel members said.

Overall, the committee’s report amounts to a scientific update regarding what is known about healthy eating. Although Americans don’t necessarily heed the dietary guidelines ahead of each meal, the guidelines are influential and can help dictate what is on the menu of school lunches and how foods are labeled.

The panel found that Americans are consuming too much salt, added sugars and foods rich in saturated fats. And for the first time, the panel addressed concerns about coffee, saying that there is strong evidence that moderate consumption is not associated with long-term health risks. The panel also reversed decades of warnings about eating foods high in cholesterol, such as eggs and liver.

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But the decision by the advisory panel to link the dietary guidelines to the environment will probably stir the most controversy.

In December, Congress approved language that expressed “concern” that the advisory committee was “considering issues outside of the nutritional focus of the panel” — alluding to the environmental discussions.

The nation's top nutritional panel released its report recommending changes to the U.S. dietary guidelines. Here are the main takeaways of what you should and should not eat. (Julio C. Negron and Jayne W. Orenstein/The Washington Post)

Moreover, Congress said at the time, the final Dietary Guidelines should “only include nutrition and dietary information.”

The advisory panel’s report prompted immediate criticism from Congress — as well as a warning from Rep. Robert B. Aderholt (R-Ala.), chairman of the Appropriations subcommittee that oversees the budget for the Agriculture Department.

“Chairman Aderholt is skeptical of the panel’s departure from utilizing sound science as the criteria for the guidelines,” according to Brian Rell, a spokesman. “Politically motivated issues such as taxes on certain foods and environmental sustainability are outside their purview.”

He warned that the panel committee would “keep this in mind” as it considers funding the agencies this spring.

Meat industry lobbyists also attacked the recommendation, asserting that the panel was stacked with health experts who know too little about environmental science.

“The Committee’s foray into the murky waters of sustainability is well beyond its scope and expertise. It’s akin to having a dermatologist provide recommendations about cardiac care,” Barry Carpenter, the chief executive of the North American Meat Institute, said in a statement.

He added that the recommendations “appear to be based on personal opinions or social agendas.”

In the past, federal bureaucrats have come under lobbying pressure from groups that discovered their particular product had been targeted for opprobrium by the Dietary Guidelines.

Americans are eating less meat than they have in the past, but they are still eating too much, according to the panel’s experts, and all that meat consumption is having detrimental effects on the environment.

Many scientists say animal-based foods are a poorer choice for the environment because they are associated with significantly larger carbon emissions than their plant-based counterparts. Animals generate a lot of methane, and the production of meat products requires large amounts of feed, fertilizer and fuel, all of which put stress on the environment.

Numerous studies have documented the outsize impact. A study published last year in the journal Climatic Change reported that meat eaters contributed more to global warming than do fish eaters, vegetarians and vegans.

Red meat in particular, which the committee says Americans need to scale back on for health reasons, has been linked to a larger carbon footprint than other meats. For instance, on a per-kilogram basis, beef is associated with more than twice the carbon emissions of pork, nearly three times that of turkey and almost four times that of chicken, according to the Environmental Working Group.

Red meat is also a comparatively inefficient source of calories and protein. The World Resources Institute has estimated that poultry, pork, shrimp, fish and eggs are all much better sources of those two nutrients relative to the amount of feed and land required to produce them.

“It’s pretty much a consensus view among global environmental scientists that we would be better off if we ate less meat,” said Timothy Searchinger, a research scholar at Princeton University who focuses on agriculture and climate change.

Miriam Nelson, a professor at Tufts University and one of the committee’s members, said the panel is not saying that people should become vegans.

“But we are saying that people need to eat less meat,” Nelson said. “We need to start thinking about what’s sustainable. . . . Other countries have already started doing this — including sustainability in their recommendations. We should be doing it, too.”