Sustainable diets are diets that meet human nutritional requirements while maintaining food security, natural resources, and biodiverse ecosystems for present and future generations. Sustainable diets require agriculture, processing, transportation, and distribution practices that do not jeopardize the ability of current and future populations to meet their food needs. Designing sustainable diets for individuals, much less for communities, regions, and 7.5–10 billion people, is extremely complex.
Over the millennia, humankind has undergone three agricultural revolutions: the transition from hunting and gathering to settled agriculture beginning some 12,000 years ago; increased agricultural production spurred by the industrial revolution of the 18th and 19th centuries; and the so-called “green” revolution of the 20th century with improved crop varieties; synthetic fertilizers, pesticides, and herbicides; and concentrated animal feeding operations (CAFOs); which enabled centralized food production on a massive scale for feeding a burgeoning human population. Each of these revolutions ultimately proved unsustainable. In the 21st century, soil degradation, water depletion, deforestation to create agricultural land, conversion of agricultural lands to other uses, fossil-fuel-dependent food transportation costs, and the massive greenhouse gas (GHG) emissions of industrial-scale agriculture have resulted in environmental pollution and degradation, human health threats, and ongoing climate change that is disrupting agricultural production. According to the World Resources Institute (WRI), projected population growth to almost ten billion by 2050, with two-thirds of people living in urban areas and a greatly altered global environment, will require an increase of almost 70% in food calories over those available in 2006.
Diets in wealthy countries account for more than 30% of total GHG emissions and 20%–30% of total household GHG emissions. They require about half of Earth's ice-free land; use about 70% of available fresh water; pollute rivers with fertilizers, chemicals, and other waste, leading to vast marine dead zones; and have driven almost 90% of fish species to the brink of extinction or beyond. About 50% of fertilizer applied to crops leaches into the environment or escapes into the atmosphere as nitrogen oxides that contribute to smog. Furthermore, with urbanization and rising incomes, high-calorie, protein- and animal-based diets are spreading rapidly around the world. According to the WRI, worldwide protein consumption exceeds average dietary requirements by one-third. The average American man eats almost 3.5 oz. (100 g) of protein daily, almost twice the required amount. At present rates of increase, by 2050 animal-based food consumption is predicted to rise 80% over 2006 levels, with beef consumption increasing 95%.
Most animal-based foods are less sustainable than plant-based foods. It takes about twice as much land to raise animals for meat compared to plant foods. Beef production uses 20 times more land and emits 20 times more GHG per unit of edible protein than plant-based proteins such as beans, peas, and lentils. Chicken and pork require three times the land and emit three times the GHG of beans. Cows produce relatively few calories and protein for human food compared to the calories and protein they consume. One-quarter of the planet's land outside of Antarctica is used for pasture. Beef production accounts for one-third of the global water used for animal production. Meat, milk, and eggs together account for 40% of global agricultural gross domestic product, while using one-third of the Earth's water. Ruminants, especially cattle, accounted for almost half of agricultural GHG emissions in 2010.
Nevertheless, relatively small dietary changes could significantly reduce resource depletion and environmental destruction. For example, a shift to more sustainable diets with less meat and dairy could cut the dietary environmental impact of average Americans by 50%. According to the WRI, a 40% reduction in meat and dairy consumption by the two billion people who consume the most would prevent 168 billion tons of future GHG emissions—three times the total global emissions in 2009—and save land equal to twice the area of India, which could be used to grow food for 10 billion people without increasing GHG-emitting deforestation.
Other definitions of sustainable diets include:
All sustainable diets prioritize fruits and vegetables and minimize or eliminate meat and dairy. This promotes sustainability in multiple ways, including reducing deforestation and the use of freshwater resources, as well as improving health. Meat, especially beef, production is a major contributor to GHG emissions that drive climate change. Raising and transporting animals uses more land, water, food, and energy than growing plants such as nuts and legumes for protein. The Barilla Institute in Italy has designed a food-environment double pyramid for healthy, sustainable diets: fruits and vegetables form the base of the food pyramid, with sweets and beef at the narrow top; the inverted environmental pyramid places beef at the broad top for its high environmental impact, with low-impact fruits at the bottom tip. The Mediterranean diet has been suggested as a model of a healthy, sustainable diet, since its sociocultural basis creates strong links between local food production, cultural heritage, and identity, and contributes to rural development. Other recommendations for sustainability sometimes include:
The “Guide to Sustainable Food” from Sustain: The Alliance for Better Food and Farming lists seven principles of sustainable diets:
The World Wildlife Federation's “LiveWell” recommendations for healthy, low-carbon diets include:
Sustainable diets depend on sustainable agriculture. Smaller farms tend to be more sustainable over the long term than industrial farms, because they generally use fewer chemicals, cause less soil erosion, produce less animal waste and GHG, and maintain more wildlife habitat.
The U.S. Department of Agriculture defines sustainable agriculture as an “integrated system of plant and animal production practices” applied in a site-specific manner that over the long term:
Practices that promote agricultural sustainability include:
Sustainable diets require the integration of sustainable food production with sustainable processing, distribution, consumption, and waste management. Such food systems may require:
In 2015, the American National Standards Institute (ANSI) developed a comprehensive sustainable agriculture standard that encompasses food and nonfood crops in the entire supply chain from producers to consumers. ANSI-LEO-4000 is a third-party verification of sustainability for producers, processors, manufacturers, distributors, food-service providers, brands, retailers, and consumers.
The Sustainable Food Trade Association promotes the sustainability of organic products from growers, processors, handlers, distributors, brokers, and retailers. It aims to “systematically reduce and eventually eliminate dependence on:”
The Sustainable Food Trade Association promotes:
Sustainable diets are designed to address these problems by:
In addition to reducing GHG emissions and lessening impact on climate change and the environment, sustainable diets can reduce obesity and other health-related conditions. A 2017 French study reported that individuals, especially women, who were more concerned about food sustainability, including local production and environmental protection, appeared to follow healthier diets.
Designing sustainable diets is fraught with difficulties and contradictions. For example, nuts are considered a healthy, sustainable source of protein and fats, yet it takes 0.7 gal. (2.8 L) of water to produce a single almond, and 80% of the world's almonds are grown in frequently drought-stricken California. Some sustainable diets include fish once or twice per week, yet many fish populations are unsustainable.
Producing four hamburger patties requires 30 sq. yds. (25 sq m) of land, 55 lb. (25 kg) of animal feed, and about 59 gal. (220 L) of water. A 2017 study reported that even if all 320 million Americans switched to an exclusive plant-based (vegan) diet, agricultural GHG emissions would be reduced by only about 28%. In part, this is because agricultural waste currently fed to livestock would have to be burned, and fertilizing animal manure would have to be replaced with synthetic fertilizers, emitting millions of tons of carbon. Critics of the study have argued that its GHG reduction estimates were too low; for example, by not considering GHG emissions from currently imported meat from countries like Brazil.
One risk to sustainable diets is the possibility that individuals may not get all the vitamins and minerals they need if they eat only plant-based foods. A vegan diet could lead to deficiencies in calcium, some vitamins, and key fatty acids, because plant foods that supply these nutrients are not currently produced in sufficient amounts.
A 2016 study examined the feasibility of various food-production scenarios for feeding 2050's global population without expanding farmland. Diet was the largest determinant of feasibility. All of the scenarios with exclusively plant-based diets were feasible, whereas only 15% of scenarios with typical meat-heavy Western diets were feasible. The study concluded that, in theory, it would be possible to feed the global population without deforestation for creating additional farmland.
Scientists are researching other innovative means of creating sustainable diets, such as manipulating soil microbial communities to sustainably increase crop production. For example, microbes may be able to increase plants' phosphorus uptake from the soil, circumventing the need for chemical fertilizers. GM versions of fruits, oilseeds, and root crops can provide not only improved pest resistance, thereby reducing the need for pesticides, but also improved production via traits such as tolerance to drought and temperature extremes, improved nutrient content, or increased photosynthetic capacity.
Dietary guidelines in some countries such as the United Kingdom, the Netherlands, Brazil, and Sweden include sustainability. The U.S. Dietary Guidelines Advisory Committee's recommendation that sustainable diets be an integral component of the 2015–2020 Dietary Guidelines for Americans (DGA) met with political outrage. Although the DGA always recommends more plant-based and less animal-based foods, the 2015 committee argued that sustainable diets are not only healthier but also have less environmental impact and conserve resources to help ensure food security for present and future generations. Furthermore, the committee argued that future food insecurity was inevitable without sustainability. The U.S. meat industry, especially beef producers, as well as some conservative groups, responded angrily. In the end, federal officials rejected the proposal and refused to consider the impacts of diet on the environment. Proposed congressional legislation even included language that would prohibit consideration of sustainability in dietary recommendations. Nevertheless, the debate raised public awareness of sustainable diets.
See also Food waste ; Mediterranean diet ; Plant-based eating ; Veganism .
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Margaret Alic, PhD