Reforming national dietary guidelines to help people eat healthier and more sustainably could prevent deaths from chronic diseases and cut greenhouse gas emissions—but, according toan analysis published by The BMJ,most dietary guidelines are not compatible with these targets.

An international research team set out to compare the health and environmental impacts of adopting global and national food-based dietary guidelines, according to a press release on the topic. The collated and scored measurable recommendations from 85 national guidelines along with global guidelines from the World Health Organization and theEAT-Lancet Commission. They then estimated how these recommendations would reduce early death from chronic diseases like heart disease, type 2 diabetes, and cancer, and how the recommendations would help meet environmental targets related to greenhouse gas emissions, use of land, and fresh water resources.

The findings: Adoption of national guidelines was associated with an average 15% reduction in early death from chronic disease and an average 13% reduction in greenhouse gas emissions from the food system—but 83 of the guidelines analyzed, or 98%, were incompatible with at least one of the global health and environmental targets. 29 of the guidelines were incompatible with the agenda on non-communicable diseases, and 57 to 74 of the guidelines were incompatible with the Paris Climate Agreement and other environmental targets.

Adoption of the WHO recommendations was associated with similar health and environmental changes; adoption of the EAT-Lancet recommendations was associated with 34% greater reductions in early death, and more than three times greater reductions in greenhouse gas emissions. In the US, adoption of the EAT-Lancet recommendation could increase the number of avoided deaths from 480,000 to 585,000.
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The study’s conclusions: “Providing clearer advice on limiting in most contexts the consumption of animal source foods, in particular beef and dairy, was found to have the greatest potential for increasing the environmental sustainability of dietary guidelines, whereas increasing the intake of whole grains, fruits and vegetables, nuts and seeds, and legumes… were associated with most of the additional health benefits.”

The researchers note that while the study has several strengths—the large number of countries, the rigorous assessment of guidelines—it also has several weaknesses, such as the qualitative nature of many national guidelines.

An editorialby researchers in Germany, too, advised interpreting the findings with caution. The first issue the editorial notes: The modelling the analysis used assumed that the effects of diet on health are causal, but the studies the models were based on were observational—which cannot determine cause and effect—rather than randomized controlled trials. Another issue the editorial raised is that, while the analysis graded the certainty of evidence for associations between risk and disease, the researchers did not use a particular comprehensive approach which “could have improved both transparency and trustworthiness.” And finally, the editorial notes that the health impact of a food group is not determined solely by its associations with disease, but by how many essential nutrients it provides.

The editorial summarizes the findings as: “Perhaps the most important finding from this study is the uncertainty that it highlights, not least about plant-based foods. In overall terms the EAT-Lancet Commission proposals seem superior… However, adopting the EAT-Lancet recommendations globally would not be affordable for many in low-income countries without concomitant economic growth, improved local food production and supply, and expansion of the range of lower-cost animal products, fruits, and vegetables." It may be worth noting that theWHO withdrew support for the EAT-Lancet recommendationsfor precisely that reason.

"We still have some way to go before diets can become healthier and more sustainable worldwide," concludes the editorial.