Earlier this month, US health secretary Robert F. Kennedy Jr released new dietary guidelines urging Americans to “eat real food”. Rather than consuming highly processed and sugary foods, the guidance recommends that people eat more protein, fruits and vegetables.
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The guidelines have reignited a long-standing debate over what the best evidence says about healthy diets. Yet the broader environmental footprint of food remains mostly absent from discussions about national nutrition recommendations.
As an Earth-systems scientist, I have spent years developing the Planetary Boundaries framework, which identifies nine biophysical thresholds that governments must respect to avoid destabilizing the planet. From a planetary perspective, what we choose to eat is not merely a lifestyle choice but a systemic driver of both human and Earth’s health. Your lunch matters — because the question of which diets public authorities must prioritize is inextricably linked to the conditions necessary for Earth’s stability.
How food is currently produced and consumed accounts for roughly 30% of global greenhouse-gas emissions, and about 70% of the world’s yearly freshwater use is for agricultural purposes. Agriculture is also a leading driver of nutrient pollution and biodiversity loss.
Current diets undermine human health. Each year, around 15 million adults die prematurely owing to unhealthy diets. This toll exceeds the annual number of deaths caused by air pollution worldwide.
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Only 1% of the world’s population is currently in a ‘safe and just space’, in which people’s rights and food needs are met within planetary boundaries.
Changes are urgently needed. Last year, I co-chaired the 2025 EAT–Lancet Commission — comprising specialists in nutrition, climate, economics, health and agriculture originally from some 35 countries. The commission published a state-of-the-art scientific assessment of what constitutes a healthy diet and proposed an updated planetary health diet (PHD) last October (J. Rockström et al. Lancet 406, 1625–1700; 2025). This diet is rich in fruit, vegetables, nuts, legumes and whole grains, which together supply some 65% of people’s daily caloric intake. It recommends roughly one portion of red meat a week and two modest servings of poultry and fish or shellfish. The PHD offers a high degree of flexibility, and many traditional cuisines — such as those in the Mediterranean, South and East Asia, Africa and Latin America — already align with its principles.
This healthy, plant-rich way of eating helps to prevent conditions such as heart disease, diabetes and some types of cancer. The PHD provides all essential nutrients and derives about 14% of daily energy from protein.
Currently, most people’s diets deviate substantially from the PHD. In many countries, people overconsume foods from animal sources and don’t eat enough vegetables, fruit, legumes and nuts. Moreover, diets that rely heavily on ultra-processed foods are becoming increasingly embedded in cultures globally. The commission highlighted the excessive and rising intake of added sugars, saturated fats and salt — particularly through ultra-processed foods.
