PHD diet – eat well and feel virtuous

Sustainable, primarily plant-based diets may confer benefits to the planet and human health simultaneously according to Harvard research.

According to scientists from the Harvard T.H. Chan School of Public Health, the ‘Planetary Health Diet’, or PHD, is associated with a halving of land use and 29% reduction in greenhouse gases for those who stick to it.  Greenhouse-gas-emitting fertiliser use is also cut by around 20%.

It’s not a meat-free diet, though consumption of animal products is substantially reduced, with only small amounts of fish and poultry considered in the PHD mix.

The diet was developed jointly by the food system not-for-profit EAT and The Lancet journal’s Commission on Food, Planet and Health.  developed the PHD to prescribe what a standard meal plate should look like if a person wants to reduce their environmental impact.

It includes a half-plate of fruits and vegetables, and a third of wholegrains, plant-sourced proteins (such as tofu) and unsaturated plant oils.

The remainder comprises dairy, starchy vegetables, animal protein and added sugars.

Analysing more than 200,000 Americans over 34 years who were free of chronic disease when they entered one of two long-term health studies, the Harvard team found the top 10% of participants whose diets were most similar to the PHD had 30% lower rates of cancer, heart and lung diseases compared to the 10% whose diets were least similar.

The researchers say theirs is an important study because it highlights the role of human diets on the environment.

“Our study is noteworthy given that the U.S. Department of Agriculture has refused to consider the environmental impacts of dietary choices and any reference to the environmental effects of diet will not be allowed in the upcoming revision of the U.S. Dietary Guidelines,” says Walter Willet, an epidemiologist and nutritionist at Harvard.

“The findings show just how linked human and planetary health are. Eating healthfully boosts environmental sustainability—which in turn is essential for the health and wellbeing of every person on earth.”

Willet and his colleagues argue that halving the land required for agriculture could be harnessed by revegetation measures, effectively a double-win that replaces carbon-intensive agriculture with carbon-capturing plant life.

“Climate change has our planet on track for ecological disaster, and our food system plays a major role. Shifting how we eat can help slow the process of climate change. And what’s healthiest for the planet is also healthiest for humans,” says Willet.

The study is published in the American Journal of Clinical Nutrition.