Linking diets to planetary and human health​

The impact our diets can have on human health is recognised across the board.  ‘Imbalanced diets’, which may be low in fruit and vegetables yet high in red and processed meats, as well as those that provide excessive energy intake ‘represent one of the greatest health burdens globally’, noted the study authors.

Further, chronic diseases related to unhealthy diets, such as cardiovascular diseases, cancer, and type 2 diabetes, require expensive medical treatment.

Associations between the food system and environmental impacts is also increasingly acknowledged. Without dietary changes towards more plant-based diets, the study authors say key environmental limits related to climate change, land use, and freshwater extraction risk being exceeded.

How dietary recommendations score on environmental sustainability has become increasingly important, noted Springmann, as evidence on the ‘immense impacts’ our diet choice have on the environment is continues to build.

“Last year, for example, the Intergovernmental Panel on Climate Change put the portion of greenhouse gas emissions attributable to diets and the food system as a third of overall emissions. And it does not look much better for other environmental domains such as land use, water use, and chemical pollution.”​

What if everyone followed a specific country’s guidelines?​

The researchers analysed the impacts of 85 FBDGs – at both country level and when adopted globally – on health and sustainability. Specifically, the team looked at global challenges and policy targets, including climate change and the Paris Agreement, and mortality from chronic diseases.

The FBDGs were also compared with those of the World Health Organization (WHO) and the EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems.

A global sustainability test focusing on two questions was developed by the researchers.

Firstly, they asked what the health and environmental impacts would be if everybody in the world followed a specific country’s national dietary guidelines just as that country’s population would do.

And secondly, how do these impacts compare to food-related aspects of global policy targets, such as the Paris Climate Agreement of keeping global warming to below 2°C, the Action Agenda on Non-Communicable Diseases, and the Sustainable Development Goals for land use, freshwater, and chemical pollution of nitrogen and phosphorous?

‘Shocking’ findings​

The researchers were very surprised by their findings, Springmann recalled, as some countries’ FBDGs were found wanting.

“What we found when undertaking that test was revealing and shocking at the same time: whilst some quidelines seemed to reduce environmental resource use and pollution at the national level (i.e. compared to their high baseline (yes, I am looking at you, USA and UK), when evaluated globally, they were often woefully inadequate.”​

For example, he continued, if the global population followed either the US or UK’s FBDGs, then food-related emissions would exceed the food-system limits for avoiding dangerous levels of climate change by more than three times.

Yet it was not only the dietary guidelines of these two countries that performed poorly. China’s guidelines were also incompatible with climate change, land use, freshwater, and nitrogen targets.

“In fact, 98% of dietary guidelines failed at least at one of the global health and environmental targets, and two thirds were compatible with only one or two of the global targets,” ​said Springmann.

“And if you were wondering, the various recommendations issued by the WHO didn’t fare much better.” ​

In comparison, adoption of the EAT-Lancet recommendations was associated with 34% greater reductions in premature mortality. More than three times greater reductions in greenhouse gas emissions, and generational attainment of the global health and environment targets, could also be achieved by following this diet.

From a human health perspective, adoption of national FBDGs was associated with reductions in premature mortality of 15% on average. About one-third were incompatible with the agenda on non-communicable diseases.

‘National guidelines could be both healthier and more sustainable’​

Ultimately, the analysis suggests that countries’ guidelines could be improved – both in terms of planetary and human health.

“​​Our top-level recommendation is…straight-forward: a reform of national dietary guidelines that takes into account both health and environmental aspects is urgently needed,”​ noted Springmann. 

The researches also looked at several examples of how reformed dietary guidelines could look alike. “In short, they involved much stricter limits for meat and dairy, both for health and environmental reasons, and to be specific but not overly prescriptive, they included different dietary patterns based around plenty of whole grains, vegetables, fruits, nuts, and legumes,”​ he explained.

“Such examples, we found, were both healthier and compatible with the set of global health and environmental targets.” ​