This major study compiles and analyses global-level data to assess relationships among diet, environmental sustainability and human health. It evaluates the potential future environmental impacts of the global dietary transition before exploring some possible solutions to the diet–environment–health trilemma.
The study draws upon a large body of data: environmental impacts of foods are based on 120 LCA publications that together contain 555 LCA analyses of 82 types of crops and animal products. This allows them to calculate diet-related GHG emissions per gram protein, per kilocalorie and per serving from ‘cradle to farm gate’. As regards health, 50 years of data for 100 of the world’s more populous nations are used to analyse global dietary trends and their drivers and then to forecast future diets should past trends continue. To quantify effects of alternative diets on mortality and on type II diabetes, cancer and chronic coronary heart disease, the paper compiles and summarizes results of studies encompassing ten million person-years of observations on diet and health. These relationships are then combined with projected increases in global population to forecast global environmental implications of current dietary trajectories and to calculate the environmental benefits of diets associated with lower incidences of chronic non-communicable diseases.
The study finds that changes towards healthier diets can have globally significant GHG benefits. Figures showing the relative impacts of the Mediterranean, vegetarian and pescetarian diets in terms of per capita GHG emissions, global GHG emissions, contribution to changes in cropland, and changes in cropland reduction find these dietary types have much lower impacts than business as usual dietary patterns (Figure 4 in the paper, copied below).
The paper calculates that if the global population consumed an average of the Mediterranean, pescatarian and vegetarian diets combined, there would be no net increase in global food related emissions.
Finally, the paper makes the following points:
a. Healthier diets are not necessarily more sustainable, and more sustainable diets are not necessarily healthier but there are many dietary options that can substantially improve both human and environmental health.
b. To address food related environmental problems action also needs to be taken to reduce food losses and waste and to close the yield gap.
c. And finally the dietary choices that individuals make are influenced by culture, nutritional knowledge, price, availability, taste and convenience, all of which must be considered if the dietary transition that is taking place is to be counteracted.
Diets link environmental and human health. Rising incomes and urbanization are driving a global dietary transition in which traditional diets are replaced by diets higher in refined sugars, refined fats, oils and meats. By 2050 these dietary trends, if unchecked, would be a major contributor to an estimated 80 per cent increase in global agricultural greenhouse gas emissions from food production and to global land clearing. Moreover, these dietary shifts are greatly increasing the incidence of type II diabetes, coronary heart disease and other chronic non-communicable diseases that lower global life expectancies. Alternative diets that offer substantial health benefits could, if widely adopted, reduce global agricultural greenhouse gas emissions, reduce land clearing and resultant species extinctions, and help prevent such diet-related chronic non-communicable diseases. The implementation of dietary solutions to the tightly linked diet–environment–health trilemma is a global challenge, and opportunity, of great environmental and public health importance.
D. Tilman, M. Clark, Global diets link environmental sustainability and human health, Nature, doi:10.1038/nature13959