A new analysis suggests that shifting to a plant-based diet may reduce the environmental impact of what people eat. But the findings come from a tightly controlled clinical trial, and the real-world effects may vary depending on how diets are adopted and maintained.
In a study published in BMJ Nutrition Prevention & Health, researchers found that participants who followed a low-fat vegan diet for 12 weeks had an estimated 35% reduction in diet-related greenhouse gas emissions. The study analyzed dietary data from a randomized clinical trial of postmenopausal women.
The research was led by Physicians Committee for Responsible Medicine, an organization that promotes plant-based diets, and involved linking participants’ food intake to environmental impact databases to estimate emissions and energy use.
The reduction was largely driven by eliminating animal products, which tend to have higher environmental footprints than plant-based foods. Researchers estimated the change was comparable to avoiding about 600 miles of driving per year.
The analysis also found that the total energy required to produce participants’ food dropped by about 34% during the intervention. This measure includes energy used across the food system, from production and processing to transportation and storage.
It’s important to note that these environmental findings were based on a secondary analysis of dietary data from a clinical trial originally designed to study health outcomes. In that trial, participants in the vegan group also experienced weight loss and fewer severe hot flashes, but those outcomes were not the primary focus of this environmental analysis.
The study has several limitations. It focused on a specific group (postmenopausal women) and followed them for a relatively short period of time. Participants also were guided through a structured dietary intervention, which may not reflect how people typically change their eating habits on their own.
The environmental impact estimates were based on established databases that model the emissions associated with different foods. While widely used in research, these models cannot fully account for differences in how foods are produced, sourced and consumed in real-world settings.
More broadly, nutrition researchers emphasize that environmental impact can vary widely within both plant-based and animal-based diets. Factors such as food waste, processing, transportation and agricultural practices all play a role.
Taken together, the findings add to a growing body of research suggesting that dietary patterns can influence not only health but also environmental outcomes. However, the extent of those effects in everyday life will likely depend on the details of how diets are structured and sustained over time.
The study was funded by the Physicians Committee for Responsible Medicine, Alberta Pulse Growers Commission, Arkansas Children’s Hospital, Canadian Institutes of Health Research, Plant-Based Health Professionals UK, Protein Industries Canada, George Washington University and the United Soybean Board.