To be climate-friendly, food-based dietary guidelines must include limits on total meat consumption - modeling from the case of France.

Background: Although food-based dietary guidelines (FBDG) include guidelines for meat consumption, they most often do not explicitly include environmental considerations. For instance, in France, FBDG recommend consuming no more than 500 g of red meat and 150 g of processed meat per week. This study uses modeling to investigate the range of greenhouse gas emissions (GHGe) that can be achieved under FBDG compliance.

Methods: The study analyzed data collected in 2014 from 29,413 NutriNet-Santé participants to assess their adherence to the French FBDG. GHGe, cumulative energy demand (CED), and land occupation (LO) for organic and conventional foods were obtained from the DIALECTE database. First, diets adequate in nutrients, culturally acceptable, and consistent with FBDG were modeled while minimizing or maximizing GHGe. Then, the spectrum of diets between minimum and maximum GHGe was explored while minimizing total departure from the observed diet with a gradual constraint on GHGE using the same other constraints. Environmental, economic (monetary cost), nutritional, and health criteria (Health risk score denoting long-term risk for health associated with diet) were then estimated for each diet.

Results: The average observed adequacy to FBDG was low (19%, SD = 25%) and GHGe were 4.34 (SD = 2.7%) kgCO2eq/d. Under nutritional, acceptability and FBDG constraints, the GHGe range of the diets varied from 1.16 to 6.99 kgCO2eq/d, depending up to ∼ 85% on the level of meat consumption. A similar shape was observed for CED, LO, and Health Risk Score, but costs were consistently higher than in the observed diet, and exhibited a U-shape. A greater proportion of organic foods was noted in the lower-emission diet; however, this proportion was low in the meat-rich, high-emission diet. At isoenergetic diets, the diet with the lowest emissions had more vegetables, whole grains, and plant-based substitutes.

Conclusions: While French dietary guidelines contribute, on average, to mitigating climate change and promoting health, this study emphasizes levers in recommended food consumption to more efficiently reduce diets' GHGe and points to total meat as the critical issue to better account for pressure on climate change. Other environmental pressures should also be taken into account when designing dietary guidelines.