A more ambitious shift in diets around the world will be needed to meet both sustainability and dietary health goals, according to a new study published last month in Global Environmental Change (1).
Food and agriculture systems are the underlying drivers of undernutrition, obesity, climate change, and freshwater scarcity, the authors write. Moreover, the latest comprehensive high-level report from the UN’s Intergovernmental Panel on Climate Change (IPCC) emphasises a need for drastic dietary changes in order to meet goals set out in the Paris Agreement of keeping the global temperature rise to with 1.5–2 degrees Celcius above pre-industrial levels. The IPCC report suggested that eating less meat — especially red meat — would be beneficial for both climate and human health.
In light of this increasing emphasis on adopting plant-based diets for both health and the planet, the researchers from Johns Hopkins Bloomberg School of Public Health examined how plant-forward diets could affect food production and greenhouse gas emissions, as well as the health of both undernourished and overnourished populations.
In their study, they modelled the greenhouse gas and water footprints of nine increasingly plant-forward diets to determine how they align with criteria for a healthy diet specific to 139 countries. To do this, they integrated country-specific data such as current food availability and trade and import patterns with greenhouse gas emissions and water use data. In addition, they estimated the carbon emissions associated with land-use changes for food production purposes. And this data-driven approach allowed the researchers to compare countries.
Unsurprisingly, the authors note the huge variation in the so-called ‘dietary footprint’ across countries. Importantly, a food’s country of origin can have enormous consequences for the climate. For instance, one pound of beef produced in Paraguay contributes nearly 17 times more greenhouse gases than the same amount produced in Denmark mainly owing to deforestation to make room for grazing lands.
Interestingly, diets that only include animal products for one meal per day were linked to less greenhouse gas emissions than lacto-ovo vegetarian diets (excludes meat but includes dairy products and eggs) in 95 per cent of countries – partly due to intensity of greenhouse gas emissions associated with dairy foods.
Notwithstanding, plant-based diets could indeed help mitigate some of the impacts of climate change. However, as senior author Dr Keeve Nachman points out, there is no one-size-fits-all diet to address the climate and nutrition crises and dietary recommendations must balance health and nutrition needs, cultural preferences, and planetary boundaries. The findings reiterate previous reports that high-income countries should accelerate adapting plant-forward diets to help mitigate climate change.
Complex and global problems like nutrition, climate change, freshwater depletion, and economic development will always require tradeoffs, says Dr Martin Bloem, a professor at John Hopkins University and one of the authors. “Environmental impact alone cannot be a guide for what people eat; countries need to consider the totality of the nutritional needs, access, and cultural preferences of their residents.”
Nonetheless, Bloem says the new data will provide policymakers with “a tool to develop nationally appropriate strategies, including dietary guidelines, that help meet multiple goals”.
(1) Kim, B.F. et al. Country-specific dietary shifts to mitigate climate and water crises. Global Environmental Change (2019). DOI: 10.1016/j.gloenvcha.2019.05.010