25 July 2023 – There was a lot of talk in the media recently about how changing to a planet-friendly diet could help our environment. But now research has found a sustainable diet could also cut our risk of dying from a chronic illness by 25%.
Scientists at Harvard University have undertaken a research project, in which they studied the diet of 100,000 American people over 30 years.
They found that those with a sustainable diet, which includes more plant-based foods, had a 25% lower chance of dying over the three decades compared to those who ate food that was less environmentally friendly.
Planetary Health Diet Index (PHDI)
The scientists from the Department of Nutrition at Harvard University’s T.H. Chan School of Public Health devised a new diet score to show the effects of foods on human health and the environment.
The index is based on existing evidence and gives foods a score, and the scientists hope that it can be used as an effective tool to develop policies. The higher the PHDI score, the lower the risk of dying from a chronic illness.
We proposed a new diet score that incorporates the best current scientific evidence of food effects on both health and the environment. The results confirmed our hypothesis that a higher Planetary Health Diet score was associated with a lower risk of mortality.
Linh Bui, PhD Student in the Department of Nutrition at Harvard University’s T.H. Chan School of Public Health
The PHDI index looks at what effect foods have on the development of chronic illnesses, such as heart disease, bowl cancer, diabetes and stroke. But it also takes into account the environmental impact of the food. This includes water use, land use, greenhouse gas emissions and nutrient pollution.
Using their new scoring system, the scientists looked at the diets of 100,000 Americans over a thirty-year period, between 1986 and 2018. Over 47,000 died during that time.
The researchers then scored their diets using their index and compared the outcomes. And results show that people with diets with higher PHDI scores, which means a more sustainable diet, had a 15% lower risk of dying from cancer or heart diseases.
They also had a 20% lower risk of dying from neurodegenerative diseases and a 50% lower risk of dying from respiratory diseases.
Over all, people with diets that score higher on the index were 25% less likely to die from such chronic illnesses.
This shows that adopting a more plant-based diet, that is also better for our environment, can help us to live longer and reduces the risk of developing fatal chronic illnesses.
Eating Less Meat Would Cut Carbon Emissions By Almost 50%
Researchers from Oxford University meanwhile, have looked at what impact meat consumption has on our environment. The study divides diets into high meat, low meat, fish, vegetarian and vegan. It’s the first time that researchers distinguish between high and low meat consumption.
The researchers class people who eat more than 100g of meat a day as having a high meat diet. Low meat eaters consume 50g or less per day.
To determine how each of these diets impact on our environment, the scientists looked at factors such as greenhouse gas emissions, land and water use, water pollution and loss of species for each diet.
It’s no surprise that a vegan diet has come out as the most sustainable diet. It only produces 2.47kg of carbon dioxide per person per day.
A vegetarian diet produces 4.16kg and fish-eaters are responsible for 4.74kg of carbon emissions per person per day.
A high meat diet creates 10.24kg of carbon dioxide per person every day. Low meat eaters produce 5.37kg of greenhouse gases a day.
This is good news for meat lovers, because it means that they don’t have to stop eating meat completely; reducing the amounts they eat can make a big difference.
Our results show that if everyone in the UK who is a big meat-eater reduced the amount of meat they ate, it would make a really big difference. You don’t need to completely eradicate meat from your diet.
Prof Peter Scarborough, University of Oxford
The researchers have calculated that if everyone with a high meat diet would change to a low meat diet, it would have the same effect as removing 8 million cars from UK roads.
It was the same picture for all the environmental factors the study looked at: high meat diets had the biggest impact.
It’s not the first study that has shown that meat consumption has a negative impact on our environment. Even an independent review for the Department for the Environment, Food and Rural Affairs (Defra) has called for a 30% reduction in meat consumption to help the UK to achieve its net zero targets.
But this latest study has studied the effects of various diets in much more detail, and it has shown that a sustainable diet doesn’t mean meat free. A reduction in meat consumption will have a big impact.
