A plate of veggies is healthier for you, but calorie for calorie, it can emit as many greenhouse gases as a chicken dinner.

The world's food industry contributes up to 30 percent of the greenhouse gas emissions that are causing climate change and all its disastrous effects. Many of those emissions come from energy-intensive, highly polluting sectors of the industry like cattle and processed-food production. Not only that, but eating too much red meat increases your risk of cancer, heart disease, and early death. So if you want to be healthier and do the planet a favor, the thinking goes, you should go vegetarian.

However, according to a new study published in the American Journal of Clinical Nutrition, that logic may not hold up under closer scrutiny: The research found that, calorie for calorie, fruits and vegetables can be just as polluting as other sectors of the agriculture industry.

The authors used survey data from just under 2,000 adults and compared the foods those adults reported eating with scientific data on the levels of greenhouse gas emissions associated with those particular foods. The researchers then classified each individual's diet based on nutritional value. High-nutritional-quality diets were those full of fruits, vegetables, and lean meats and low in sweets and salty snacks, while low-nutritional-quality diets were just the opposite.

Surprisingly, the study found that higher-nutritional-quality diets were associated with higher levels of greenhouse gas emissions, whereas diets of poor nutritional quality were associated with lower emissions. On a per-calorie basis, the study found, growing fruits and vegetables emits more greenhouse gases than producing the same number of calories from starches, sweets, salted snacks, dairy products, and even vegetable oils. And emissions associated with growing fruits and vegetables were roughly equal to the greenhouse gases emitted by producing an equivalent number of calories from pork, poultry, and eggs.

"The main reason is that there is a positive relationship between the quantity of food eaten and the carbon impact of diets," says Nicole Darmon, PhD, one of the study's authors and research director at the National Research Institute of Agronomy in Marseilles, France. So it's not that vegetables are necessarily worse for the planet than beef. It's just that the study participants were eating more fruits and vegetables to get the same number of calories as people eating unhealthy foods and lots of red meat.

Darmon isn't suggesting that people resort to eating lots of refined sugars, red meat, and dairy in order to tread more lightly on the planet. When she and her colleagues drilled down into each individual's diet, they noticed that, in some cases, healthy diets did lead to fewer greenhouse gas emissions. For instance, for women, healthier diets included fewer animal fats and more vegetable fats, the latter of which are much easier on the planet.

That's why Darmon recommends the following if you want to eat a healthier diet that won't be worse for the planet:

• Eat one vegetarian meal per day that includes a variety of whole grains, legumes, and nuts, all of which contain things like fiber and fat that will help you feel full.

• Get milk…and eat less butter and cheese. Processed dairy items require more dairy, and by definition produce more greenhouse gases, than milk alone.

• Think less cow, more chicken. If you don't want to give up all meat, just limit your consumption of beef and lamb. Both are ruminant animals and produce the highest levels of greenhouse gases of any food source. In addition, higher consumption of red meat is linked to increased rates of colorectal cancer.