In addition to its effects on biodiversity and the environment, agriculture has many direct and indirect effects on human nutrition and health. The number of people who are overweight or obese has been increasing rapidly throughout the world.1 In the United States, about 42 percent of adults and 18 percent of children and adolescents are overweight or obese—up from 10 percent and 5 percent, respectively, in the 1970s—and the percentages are higher in the United Kingdom. At the same time, more than 2 billion people lack micronutrients like iron and vitamin A because of inadequate diets. The consumption of processed foods with added salt, sugar, and fats is too high in many countries, while the consumption of fruits, vegetables, nuts, and legumes is too low. Furthermore, consumption of unhealthy foods is increasing as incomes rise and as processed foods become more widely available.
Many of the foods associated with a higher risk of chronic diseases like diabetes and heart disease, such as red meat and highly processed foods, also have the highest environmental impacts. Eating less of these foods and more locally produced fruits, vegetables, legumes, and nuts would reduce greenhouse gas emissions while also reducing the number of years of life lost to diet-related diseases.2,3 More sustainable and healthier diets could also have many other benefits, including increased support for farmers, greater resiliency of food systems, and increased equity among consumers.
One prominent effort to understand what a healthier and more sustainable global diet would look like was the detailed study undertaken by the EAT-Lancet Commission on Food, Planet, Health, which in 2019 issued a report titled “Food in the Anthropocene: The EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems.”4 The goal of the commission, which consisted of 37
1 Hales, C. M., M. D. Carroll, C. D. Fryar, and C. L. Ogden. 2020. Prevalence of Obesity and Severe Obesity Among Adults: United States, 2017–2018. NCHS Data Brief, No. 360. Hyattsville, MD: National Center for Health Statistics.
2 Milner, J., R. Green, A. D. Dangour, A. Haines, Z. Chalabi, J. Spadaro, A. Markandya, and P. Wilkinson. 2015. Health effects of adopting low greenhouse gas emission diets in the UK. BMJ Open 5:e007364.
3 Scheelbeek, P., R. Green, K. Papier, A. Knuppel, C. Alae-Carew, A. Balkwill, T. J. Key, V. Beral, and A. D. Dangour. 2020. Health impacts and environmental footprints of diets that meet the Eatwell Guide recommendations: Analyses of multiple UK studies. BMJ Open 10(8):e037554.
4 Willett, W., J. Rockström, B. Loken, M. Springmann, T. Lang, S. Vermeulen, T. Garnett, D. Tilman, F. DeClerck, A. Wood, M. Jonell, M. Clark, L. J. Gordon, J. Fanzo, C. Hawkes, R. Zurayk, J. A. Rivera, W. De Vries, L. Majele Sibanda, A. Afshin, A. Chaudhary, M. Herrero, R. Agustina, F. Branca, A. Lartey, S. Fan, B. Crona, E. Fox, V. Bignet, M. Troell, T. Lindahl, S. Singh, S. E. Cornell, K. Srinath Reddy, S. Narain, S. Nishtar, and C. J. L. Murray. 2019. Food in the Anthropocene: The EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems. The Lancet 393(10170):447–492.
scientists from 17 countries representing multiple disciplines, was to chart a course toward feeding a global population of 10 billion people by 2050 with a healthy and environmentally sustainable diet.
Using the best available evidence, the commission defined a healthy reference diet that could be available to everyone. For example, it considered the ratio of polyunsaturated to saturated fat in various foods, which is a factor in cardiovascular disease. Using this information, it defined the composition and total average calorie content of diets divided by food groups: whole grains, tubers and starchy vegetables, vegetables, fruits, dairy, protein sources, added fats, and added sugars.
The commission also defined planetary boundaries for six key environmental systems and processes: greenhouse gases, cropland use, water use, nitrogen application, phosphorus application, and the species extinction rate. It then applied a global food systems modeling framework to analyze which combinations of measures are needed to stay within planetary boundaries while still delivering healthy diets by 2050.
On the basis of this analysis, the commission concluded that feeding 10 billion people a healthy diet while boosting the sustainability of food systems is well within today’s capabilities. The Planetary Health Diet developed by the commission calls for substantial increases in the consumption of fish, vegetables, legumes, whole grains, and nuts (see Figure 3-1). The diet would allow the equivalent of one glass of milk per day and one hamburger per week. Such a diet would have substantial health benefits, with a reduction of about 11 million premature diet-related adult deaths per year. It also would reduce greenhouse gas emissions caused by food consumption below today’s level, as compared with almost a doubling by 2050 under the business-as-usual scenario. Further improvements in food production and a decrease in food waste could drive greenhouse gas emissions below today’s levels. However, increases above the Planetary Health Diet in such areas as dairy and meat consumption, especially beef, would increase emissions substantially.
An estimated 25 to 30 percent of all food produced is lost or wasted, as defined by discarding food or an alternative (non-food) use of food along the entire supply chain.5 Reduction of this loss could mitigate environmental harms while enhancing food security and health.
Much food waste occurs with perishable foods, which could be reduced through shorter supply chains and the consumption of more local and seasonal foods.6 Better formulations and understanding of expiration dates on packaging could also reduce the amount of food that is wasted. Research and development could focus on extending the shelf life of nutritious foods and on changes to food systems that would lower food losses from production to consumption.
5 Ishangulyyev, R., S. Kim, and S. H. Lee. 2019. Understanding food loss and waste—Why are we losing and wasting food? Foods 8(8):297.
6 NASEM (National Academies of Sciences, Engineering, and Medicine). 2019. Reducing Impacts of Food Loss and Waste: Proceedings of a Workshop. Washington, DC: The National Academies Press.
The patterns of food waste tend to differ from one part of the world to another, which argues for the study of the particular factors that cause food to be lost. For example, more food is wasted where food is relatively abundant and cheap compared with places where it is less abundant and more expensive, and levels of food waste tend to track levels of obesity.7
Many other national and international bodies have issued recommendations that would result in healthier diets that have fewer harmful consequences. However, relatively few address sustainable agriculture, especially because incremental gains will not be enough to resolve the underlying environmental and health issues.
7 Toti, E., C. Di Mattia, and M. Serafini. 2019. Metabolic food waste and ecological impact of obesity in FAO world’s region. Frontiers in Nutrition 6:126.
More diverse diets and more diverse agriculture could be healthier and more sustainable in many ways. Although there are around 30,000 edible plant species around the world, only three—rice, wheat, and maize—provide more than 50 percent of the world’s plant-derived calories.8 This minimal diversity of modern agriculture has led to excessive homogeneity and oversimplification of both farming and food systems, disrupting the ecological, biological, and social drivers of sustainable, resilient, and healthy agriculture. It also has pushed many traditional crops to the margins, both in terms of their consumption and the amount of research and development devoted to their improvement.
Increasing the diversity of diets will require a greater recognition of the values, beyond price, associated with food. Different diets could drive a more diversified agriculture, creating more mixed farms, multifunctional and resilient landscapes, and rural employment. At the same time, a greater focus on overall system efficiency could lower waste, reduce greenhouse gas emissions, and make space for land-based climate mitigation.
Research and development could explore the nutritional profiles of a wider variety of plants as well as the bioavailability of nutrients at different points in the supply chain. (Box 3-1 provides an example of the need for research and development on the major nutrients as well as on a broader range of foods.) Greater knowledge of phenotype–genotype associations could help breeders improve nutritional qualities. As a specific example, foods like brussels sprouts and quinoa have seen large increases in demand in recent years, in part because of advances in breeding that have improved their quality. If a market potential for a healthy food was identified, crops could be developed to meet that demand.
Demand side changes in diets could reduce environmental harms by altering the kinds of foods eaten. Examples range from purely vegan diets that include no animal-source foods to pescatarian and Mediterranean diets that include seafood and moderate meat consumption. Better understanding of the food system as a whole, including its dependencies, opportunities, and change levers, could foster the structural changes that are needed all the way from farms to consumers. Creating a sustainable agriculture will require a focus on food systems, not just farms; farming systems, not just crops; and landscapes, not just fields.