High nutritional quality is not associated with low greenhouse gas emissions in self-selected diets of French adults.

BACKGROUND
Healthy diets are supposed to be more environmentally friendly because they rely mainly on plant-based foods, which have lower greenhouse gas emissions (GHGEs) per unit weight than do animal-based foods.

OBJECTIVES
The objectives were to estimate the GHGEs associated with the consumption of self-selected diets in France and to analyze their relation with the nutritional quality of diets.

DESIGN
For each adult in the national dietary Individual and National Survey on Food Consumption (n = 1918), the GHGEs of his or her diet were estimated based on the GHGEs of 391 foods. Highest-nutritional-quality diets were defined as those having simultaneously 1) an energy density below the median, 2) a mean adequacy ratio (MAR) above the median, and 3) a mean excess ratio (MER, percentage of maximum recommended values for nutrients for which intake should be limited) below the median.

RESULTS
MAR was positively correlated and MER was negatively correlated with diet-related GHGEs. High-nutritional-quality diets contained more plant-based foods, notably fruit and vegetables, and fewer sweets and salted snacks than did low-quality diets. After adjustment for age, sex, and energy intake, the consumption of sweets and salted snacks was negatively correlated with diet-related GHGEs, whereas the consumption of animal products and of fruit and vegetables was positively associated with them. After adjustment for energy intake, high-nutritional-quality diets had significantly higher GHGEs (+9% and +22% for men and women, respectively) than did low-nutritional-quality diets.

CONCLUSIONS
Despite containing large amounts of plant-based foods, self-selected diets of the highest nutritional quality are currently not those with the lowest diet-related GHGEs.