A federal panel has concluded that ensuring healthful food for the nation isn't just a matter of nutrition. It also hinges on steering the American diet toward more environmentally sustainable choices.

In other words, it's important not just to eat your greens, but also to green your eats.

This is a significant departure for the Dietary Guidelines Advisory Committee, which every five years submits updates to two federal departments: Agriculture, and Health and Human Services. They, in turn, recommend a national diet. It used to be depicted as a food pyramid. Now, it's a sectioned plate.

The panel's report came out last month, but the food fight had already begun.

Congress got wind of the recommendations, and in December expressed official "concern" that the committee was straying to extraneous issues and directed it - in a nonbinding statement attached to the omnibus federal spending bill - to "only include nutrition and dietary information."

The panel went ahead anyway, noting in its final report that "promoting healthy diets that also are more environmentally sustainable now will conserve resources for present and future generations, ensuring that the U.S. population has access to a diet that is healthy as well as sustainable and secure in the future."

Rather than a checklist of specific dietary amounts, the panel put forth broad statements. "A diet higher in plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts, and seeds, and lower in calories and animal-based foods is more health-promoting and is associated with less environmental impact than is the current U.S. diet," it concluded.

It proposed three "dietary patterns," all of which involve less meat than Americans currently consume (as do current guidelines), although it did note that "no food groups need to be eliminated completely to improve sustainability outcomes over the current status." (Sorry, vegans.)

The panel's take on seafood also was interesting. Although concern has been raised about whether farm-raised fish are as nutritious and safe to eat as their wild-caught cousins, the panel said that both would be needed to supply enough seafood to meet dietary recommendations. For many commonly consumed species, farmed fish have as many beneficial fatty acids as the wild-caught, the panel found.

It also weighed in on mercury in seafood, a constant source of confusion: "For the majority of wild-caught and farmed species, neither the risks of mercury nor organic pollutants outweigh the health benefits of seafood consumption," which include a decreased risk of cardiovascular disease and improved infant neurodevelopment.

Environmental groups cheered the direction of the panel, if not every recommendation.

"The fact is that the environment and health are inextricably connected," said Erik Olson, senior strategic director for health and food at the Natural Resources Defense Council. "It's hard to say that if you are destroying the planet, you are doing good things for health."

The seafood industry was pleased as well. National Fisheries Institute president John Connelly said the report "reaffirms seafood's position as one of the healthiest options in the American diet."

But meat producers balked, claiming that the panel had ventured too far afield and that either way, its dissing of meat was misguided. Almost every facet of the industry, from chicken to pork to beef, has made huge strides in lessening its environmental impacts, the industry noted.

(The panel's advice increases the pressure on the American meat industry to continue those gains. On March 3, a group of meat producers, processors, and others launched the U.S. Roundtable for Sustainable Beef. The goal is to figure out how to define, verify, and increase sustainability.)

Another criticism: All 14 members of the government advisory committee were nutritionists, not agriculture or environmental experts. "It's like going to a dermatologist for cardiac care," said Janet Riley, spokeswoman for the North American Meat Institute.

"If our government believes Americans should factor sustainability into their choices, guidance should come from a panel of sustainability experts that understands the complexity of the issue and addresses all segments: transportation, construction, energy management and all forms of agriculture," the institute said in a statement.

So expect an escalation of the battle over the precise environmental impacts of various foods. Numerous studies have demonstrated the high environmental cost of meats compared to plants. But a recent study of the carbon footprint of foods found that the carbon footprint of meat was partly offset by its "nutrient density," the amount of nutrition per serving.

The public may comment on the report through April 8 at www.health.gov/dietaryguidelines/

The site contains additional information as well as the 571-page report. If that's a bit much to plow through, just remember the advice of eco-food guru Michael Pollan: Eat food, not too much, mostly plants.