When was the last time you checked your country’s dietary guidelines? If the answer is never, then you are probably in the company of many. Despite that, dietary guidelines often form the basis for a range of educational programmes as well as national food and nutrition policies. So even if you don’t quite remember what your national food pyramid, pagoda, or wheel looks like, chances are you have been affected by its content in one way or another.
In a new study, colleagues from the universities of Oxford, Harvard, Tufts, Adelaide and I have gone through all the national food-based dietary guidelines we could get our hands on—85 in total. [1] We were interested in analysing what the recommendations were, how clear they were, and most importantly, how they scored not only on healthiness, but also on environmental sustainability.
The last bit has become increasingly important as the evidence on the immense impacts our dietary choices have on the environment is mounting. Last year, for example, the Intergovernmental Panel on Climate Change put the portion of greenhouse gas emissions attributable to diets and the food system at a third of overall emissions. [2] And it does not look much better for other environmental domains such as land use, water use, and chemical pollution. [3]
What we found early on in our research was that it is surprisingly hard to quantify the healthiness and sustainability of dietary guidelines. For one, many guidelines were vague and rather indirect. We got around that by developing a coding system that would translate the guidance, so to say: “five servings of fruits and veg a day“ became 400 g/d, a “handful of nuts” became 28 g/d, and “eat less meat” became “20% less than baseline intake, with a range of 10-30%”.
We then evaluated the dietary representations with established health and environmental models, and soon were confronted with a new problem: how to judge whether a 10% increase in food-related greenhouse gas emissions in India, for example, is more or less sustainable than a 17% reduction in the UK. After all, baseline diets, and consequently emissions, differ substantially across these countries. So, to have a more objective measure of sustainability, we developed a global sustainability test.
That test asked two questions:
- What would the health and environmental impacts be if everybody in the world followed a specific country’s national dietary guidelines just as that country’s population would do, and
- how do those impacts compare to the food-related aspects of global policy targets, such as the Paris Climate Agreement of keeping global warming to below 2 degrees Celsius, the Action Agenda on Non-Communicable Diseases, and the Sustainable Development Goals for land use, freshwater, and chemical pollution of nitrogen and phosphorus?
The logic is that if dietary guidelines don’t meet that test, then they are not only in conflict with stated policy objectives, but also load the responsibility for meeting these global targets onto other populations and sectors which in turn have to do more. In essence, it’s a global equity test.
What we found when undertaking that test was revealing and shocking at the same time: whilst some guidelines 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, if everybody around the world followed the national dietary guidelines of either the USA or the UK, then food-related emissions would exceed the food-system limits for avoiding dangerous levels of climate change by more than three times.
But it was not only the dietary guidelines of the USA and the UK that performed poorly. 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. And if you are wondering, the various recommendations issued by the World Health Organization didn’t fare much better.
Our top-level recommendation is therefore straight-forward: a reform of national dietary guidelines that takes into account both health and environmental aspects is urgently needed.
We also looked at several examples of how reformed dietary guidelines could look like. 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. Such examples, we found, were both healthier and compatible with the set of global health and environmental targets.
What’s left is that we need a few more people talking about dietary guidelines.
You can read the research here.
Marco Springmann is a senior researcher in the Oxford Martin Programme on the Future of Food and the Nuffield Department of Population Health at the University of Oxford. He leads the department’s research domain on Healthy and Sustainable Food Systems.
Competing interests: see research paper
References:
1 Springmann M, Spajic L, Clark MA, et al. The healthiness and sustainability of national and global food based dietary guidelines: modelling study. BMJ 2020;370:m2322.
2 Mbow, C., C. Rosenzweig, L.G. Barioni, T.G. Benton, M. Herrero, M. Krishnapillai, E. Liwenga, P. Pradhan MGR-F, T. Sapkota, F.N. Tubiello YX. Food Security. In: P.R. Shukla, J. Skea, E. Calvo Buendia, V. Masson-Delmotte, H.-O. Pörtner, D.C. Roberts PZ, R. Slade, S. Connors, R. van Diemen, M. Ferrat, E. Haughey, S. Luz, S. Neogi, M. Pathak, J. Petzold JPP, P. Vyas, E. Huntley, K. Kissick, M. Belkacemi JM, eds. Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems. 2019.
3 Springmann M, Clark M, Mason-D’Croz D, et al. Options for keeping the food system within environmental limits. Nature 2018;562:519–25. doi:10.1038/s41586-018-0594-0