The planetary health diet: a food plan to save the world?

A diet that can save the planet and lengthen life expectancy might sound too good to be true, but a growing body of evidence suggests the "planetary health diet" could be the holy grail of ethical living.

Although the planetary health diet was first outlined in 2019, researchers at Harvard University's T.H. Chan School of Public Health were able to assess its long-term impact by examining data from 200,000 subjects whose dietary habits were tracked for more than 30 years.

Their report this month found that "people whose eating habits most closely adhered to the planetary health diet were 30% less likely to die prematurely" compared to those least aligned with the lifestyle, said The Washington Post.

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What is the planetary health diet?

The planetary health diet was devised by the EAT-Lancet Commission, made up of 37 scientists, doctors, and experts in agriculture, sustainability and public health. Not a diet in the sense of an itemised meal plan, it instead sets out a broader rethinking of our eating habits to ensure food production remains sustainable for future generations.

Under the planetary health diet, around half of total food consumed, by volume, would be made up of vegetables and fruits, supplemented with whole grains, plant-based proteins like nuts and legumes, and unsaturated plant oils.

Dairy, meat and refined sugars would account for only a small proportion of caloric intake. For instance, the suggested daily limit for red meat is 14g – a portion which would weigh "little more than a AAA battery", said the Daily Mail.

 The Commission's report also stresses the importance of a mindful attitude, encouraging consumers to cut down on food waste and buy from producers who support sustainable farming practices.

How does it benefit the planet?

Without a significant transformation in global eating habits, "today's children will inherit a planet that has been severely degraded and where much of the population will increasingly suffer from malnutrition and preventable disease", the Commission warned in its report.

The planetary health diet is designed to lower the impact of food production on the environment to sustainable levels. The Commission estimates that global adoption of the diet would "cut land use by 51%, greenhouse gas emissions by 29% and fertiliser use by 21%", said CNN.

Notably, the diet includes only very modest consumption of animal products, in particular red meat, as these have "relatively high environmental footprints per serving compared to other food groups", according to the Commission. Food production accounts for 30% of greenhouse gas emissions, and much of that comes from methane produced by livestock.

How does it benefit health?

Those identified in the Harvard study as adhering to a planetary health diet were significantly less likely to die prematurely from cardiovascular disease, cancer, lung disease and infectious diseases. They also exhibited a "28% lower likelihood of dying of Alzheimer's disease and other neurodegenerative disorders" compared to those identified as least adherent, said The Washington Post.

Dr David Katz, a specialist in preventative medicine, told CNN the study was further evidence that "adhering to a dietary pattern conducive to the health of the planet and sustainability is associated with meaningful reductions in all-cause mortality".

Isn't this just the Mediterranean diet?

The emphasis on grains, vegetables, legumes and olive oil invites immediate comparisons with the "Mediterranean diet" lionised by nutritionists for decades.

But while it shares some surface-level similarities, the planetary health diet differs in its fundamental purpose. While other diets might help adherents lose weight, reduce their risk factor for various diseases, or simply reflect a specific cultural eating pattern, the planetary health diet is about the practical maths of ensuring continued food security on a global level. 

The diet is also not prescriptive in terms of specific foodstuffs, as it is designed to be flexible enough to be relevant on a global scale. By focussing on food groups more broadly, the Commission said, it can be adapted to accommodate "local geography, culinary traditions and personal preferences".