Plant-based foods, such as fruits and vegetables, whole grains, beans, peas, nuts and lentils, generally consume less energy, land and water, and have lower greenhouse gas intensity than animal-based foods. A plant-based diet can have a significant positive impact on the environment and health. Fruits and vegetables have a very low environmental impact, although there are some exceptions. A sustainable diet is one that, in general, is healthy and has a low impact on the environment and food supply.
In addition to changing the environment through land clearing and other agricultural practices, food production has a major impact on greenhouse gases. A sustainable diet considers the impact it will have on the environment, the individual and the food chain as a whole. According to the EAT-Lancet Commission, adopting healthy diets with a diversity of plant-based foods and stopping consuming highly processed foods and diets rich in refined grains and added sugar could prevent up to a quarter of all adult deaths. The team looked at how the choice to eat or give up specific foods, not just categories, such as vegetables, could affect AVADs, and detailed the benefits of some foods and the harmful effects of others if a person's initial diet changed.
Farmers and producers can also use natural buffers, including hedges, to protect fields and pastures from inclement weather (such as winds) and help strengthen the natural habitats of beneficial organisms, including pollinators. A person who wants to eat more sustainably can make an effort to change the proportion of food on their plates, going from being mainly meat to mainly vegetables. So Jolliet and her colleagues created a system that combined both concerns and analyzed the health and environmental impacts of specific foods. Animal-based foods can still have a place in a sustainable diet, although there is no agreement on how much animal food a person can eat and remain sustainable.
The committee stated that “a dietary pattern that contains more plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts and seeds, and lower in animal foods, promotes more health and is associated with a lower environmental impact (GHG emissions and use of energy, land and water) than the current average. Unused food breaks down in landfills and releases methane gas, one of the most powerful greenhouse gases. Foods such as nuts and fruits have significant health benefits, but are often grown in places with water shortages, such as California. A study conducted by researchers from the Centers for Disease Control and Prevention and Emory University found that “current federal agricultural subsidies focus on funding the production of food products, much of which are converted into high-fat meat and dairy products and other items that increase the risk of cardiometabolic risks in American adults.
By supporting the transition to food systems that generate net positive impacts on nutrition, the environment and livelihoods, the United Nations Environment Programme (UNEP) contributes to the Sustainable Food Systems Programme of the One Planet Network and leads the development of a guide for collaborative policymaking and improving governance. The study found that 57% of global greenhouse gas emissions from food production come from meat and dairy products.