Meals served in the National School Lunch Program are developed with nutrition, cost, and youth preferences in mind, with little room or direction to consider environmental impact. Using data from over 2.2 million real-world lunches, researchers at Tufts quantified the environmental footprint of each lunch served to see if they could determine patterns and form recommendations for more sustainable lunches. They found that low impact school lunches had “20% more whole grains, nearly 20 times more nuts and seeds, and four times less animal protein than high impact lunches.” As a result, the authors concluded that “increasing whole grain requirements and providing serving size or frequency limits for beef” are the two most effective recommendations for reducing the environmental impacts of the National School Lunch program. 
Nature. 2022 June 23;3(138). doi: 10.1038/s43247-022-00452-3. (Stern AL et al.)

High income nations tend to have diverse food options that are disproportionally based on high-carbon footprint foods like meat and could be a great starting point when considering where to introduce climate-friendly diets. In this study, researchers used models to determine that if 54 high-income nations shifted to the EAT-Lancet diet (a primarily plant-based, healthy diet) and restored the resulting spared land to natural vegetation, they would have the potential to reduce their carbon emissions by 61%, which is equivalent to 14 years’ worth of current global agricultural emissions.
Nature Food. 2022 Jan 10;3:29-27. doi: 10.1038/s43016-021-00431-5. (Sun Z et al.)

As stress on our food system increases, certain dietary patterns may increase harmful environmental impacts. Diets that are nutritious and sustainable, such as those low in animal products and higher in plant-based foods, have been proposed as a solution to this issue which still meets dietary needs. In this study, researchers analyzed 150 different dietary patterns from varying countries and regions by pairing an estimate of food demand with an estimate of commodity prices in different years, with consideration of any food-system and socioeconomic changes. Across the dietary patterns sampled, the most affordable and sustainable were vegan/vegetarian diets that replaced meat with legumes or whole grains. The least affordable were pescetarian diets that centered around fish, fruits, and vegetables. Staple crops, such as cassava, maize, plantains, potatoes, rice, soybeans, sweet potatoes, and wheat, tend to be the most affordable aspect of these dietary patterns. Household food waste accounted for 29% of all food costs, so helping people to reduce food waste could improve both affordability and environmental sustainability.
Lancet Planetary Health. 2021 Dec;5(12):e861. doi: 10.1016/S2542-5196(21)00316-8. Epub 2021 Nov 24. (Springmann M et al.)

Food production accounts for roughly ⅓ of total greenhouse gas emissions, meaning that small shifts in food choices can make a big impact. In this study, researchers calculated the greenhouse gas emissions of 3,233 different foods, as well as example diets from 212 adults. In general, diets that are better for people also tended to better for the planet. For example, people who kept to the recommended levels of sodium, saturated fat, and carbohydrates had lower greenhouse gas emissions than those who exceeded those levels. Further, non-vegetarian diets produced 59% more greenhouse gas emissions than vegetarian diets. When looking at individual food categories, 32% of diet-related greenhouse gas emissions were from meat, 15% from drinks, 14% from dairy, and 8% from cakes/cookies/confectionary.
PLoS One. 2021 Nov 23;16(11):e0259418. doi: 10.1371/journal.pone.0259418. (Rippin HL et al.)

Diet is intimately linked both to human and environmental health. In this article, a commission of distinguished scientists from different fields set out to examine the components of a healthy diet and the link between diet and environmental health. Through an extensive review of literature, the researchers found that an ideal diet that meets basic nutritional needs and can be sustainably produced is mostly plant-based. Specifically, this diet is based around about 11 ounces vegetables, 9 ounces of dairy foods (a little over a cup of milk) 8 ounces of whole grains (about 8 servings, such as a slice of bread or a ½ cup cooked grains), 7 ounces of fruit, 3 ounces of legumes, 2 ounces of nuts, and an optional 2 ounces of other animal foods (like eggs, poultry, or meat) per day. The authors suggest that a global shift towards these dietary principles can prevent approximately 11 million deaths per year, and can sustainably produce enough food for the growing population without further damage to the environment.
Lancet.  2019 Feb 2;393(10170):447-492. doi: 10.1016/S0140-6736(18)31788-4. (Willett W et al)

Scientists are beginning to discover that eating choices that are best for people also happen to be best for the planet. Researchers from the European Commission’s Directorate for Sustainable Resources analyzed national food surveys, water footprint databases, and other datasets across the UK, France, and Germany to determine how the water footprint changes when people shift their diet. They found that shifting from the current eating pattern to a healthy eating pattern (that contains meat) cut reduce the water footprint by 11-35%, and that even larger reductions could be made by shifting to a healthy pescatarian (vegetarian with fish) diet (33-35% reduction) or a healthy vegetarian diet (35-55% reduction).
Nature Sustainability. 2018 Sept 1. doi: 10.1038/s41893-018-0133-x. (Vanham D et al.)

Forests are an important harbor of biodiversity and carbon storage, so cutting into forests to create more cropland could be very harmful to the ecosystem. To see how we can feed a growing world without cutting into forests, Austrian researchers analyzed 500 different scenarios with varying levels of cropland expansion, dietary patterns, and crop yields.  They found that “a large range of options exist to feed a no-deforestation world,” by 2050, but greatly varied based on what types of foods we’d choose to eat. For example, their models found that if the current North American diet (lots of meat and highly processed foods) continues to expand globally, only 15% of the scenarios involving this eating pattern are feasible. However, “all vegan scenarios and 94% of the vegetarian scenarios are feasible,” indicating the overall sustainability of plant based diets.
Nature Communication. 2016 Apr 19;7:11382. (Erb KH et al.)