Foods with the largest environmental footprint tend to also provide less nutrition and cost more per unit than foods with a smaller impact on the environment, a recent French study found. But that isn't the rule across the board.

Cutting meat intake has been one recommended strategy for curbing greenhouse gas emissions linked to global warming. For the first time, researchers aimed to compare the nutrient density, environmental impact and price of common foods.

"The food system accounts for approximately one-third of global greenhouse gas emissions, and global obesity is on the rise," said Gabriel Masset, lead author of the study and a research assistant at Aix-Marseille Universite in Marseille.

"Identifying foods more likely to be part of healthy and low-carbon diets could be an effective way to help consumers in their daily choices," Masset told Reuters Health in an email. The study was published in the Journal of the Academy of Nutrition and Dietetics.

Masset and his team used a French dietary survey conducted in 2006 and 2007 to identify the 391 foods and beverages most commonly consumed in that country by more than 1,900 people between the ages of 18 and 79. The environmental impact of these items was gauged based on three measures: greenhouse gas emissions, emissions to the atmosphere that lead to acid rain and ion buildup in water, which can cause the development of undesired algae.

Next, the researchers evaluated the nutritional quality of the foods by calculating a ratio of "good" nutrients, such as fiber, iron and protein, to "bad" ones, including sodium and added sugars. Food prices were assessed using information from a 2006 French consumer panel, which is based on 12,000 households.

The results reiterated previous findings that animal-based products are tougher on the environment than plant foods. Fruits and vegetables packed the most nutrition, while fruits, vegetables and meats tended to be pricy. Starchy foods, including pasta, cooked beans and mashed potatoes, were the cheapest, both by weight and calorie count.

Sugary foods with little nutritional value, including pastries and soft drinks, were inexpensive sources of calories with an environmental footprint on the average to smaller side.

"Our results highlighted that it would be overly simplistic and misleading to affirm that low-carbon foods and diets are healthier," Masset said.

The study "reinforces that we need to continue to focus on ways that the food sector affects our environment," said Alicia Romano, a dietitian at the Frances Stern Nutrition Center at Tufts Medical Center in Boston, in an email. Romano was not involved in the study.

The impact of animal products on the planet means that the "greenest" diet is one with less meat and dairy - or none at all. For the sake of the environment, the authors said, diets should include more plant-based foods.

"People should be aware that foods of animal origin, despite being essential sources of nutrients, do have a higher carbon footprint than plant-based foods," Masset said.

In addition, healthcare providers should be prepared to help patients make changes to their diets.

"They should be more inclined towards (meatless) choices and be ready to assist individuals trying to reduce their meat, fish and egg intake," Masset said.

SOURCE: bit.ly/1fpRplb Journal of the Academy of Nutrition and Dietetics, online April 7, 2014.