Processed food has higher emissions, study finds

Healthy diets have lower greenhouse gas emissions and a lower impact on the environment than food that is highly processed, according to a new study.

The research, by the University of Leeds and published in science journal PLOS One, adds to a growing awareness that there is a close link between food that is both healthy for people and healthy for the planet.

Overall, people who consumed more than the exceeded recommended allowances for saturated fats, carbohydrates and salt had higher greenhouse gas emissions than those that didn’t, the study found.

Analysis of over 40,000 food items found that unhealthy foods account for nearly a quarter of diet-related greenhouse gas emissions.

A third of diet-related emissions came from meat items, 15 per cent from drinks, 14 per cent from dairy and eight per cent from cakes, biscuits and confectionery. Non-vegetarian diets had 59 per cent high emissions than vegetarian, researchers found.

Professor Janet Cade from the university’s School of Food Science and Nutrition, said: “This detailed study confirms that diets that are better for the planet’s health are better for our own personal health too.”

To reach their results, researchers overlapped diet diaries of 212 adults with advice on nutrient intake from the World Health Organisation, and data from previous studies looking at greenhouse gas emissions of specific food items.

They said that previously studies into diet look in detail at nutrient intake, but take broader averages of environmental impact. This means the nuances in how food is produced, including how and where it is farmed, would not be taken into account.

Instead, they calculated emissions from food items using tools from multiple studies, including a detailed algorithm that accounts for things like production method, animal feed, soil and climate, and the processing and transport of both the product and inputs, like fertiliser and feed.

This was able to identify emissions to very specific levels, such as separate values for almonds, peanuts and hazelnuts rather than a single value for all nuts. This tool also accounted for life cycles of food produced in the UK, where raising livestock is often done on grass for example, compared to more intensive systems overseas.

Healthy food for people and planet

It comes as speakers at the annual conference by the British Nutrition Foundation held this week also discussed how the multiple problems with food today, including unhealthy diets and diet-related deaths and disease, ‘just in time’ global supply chains where food is vulnerable to volatility, and the climate and nature crises often fuelled by intensive agriculture, should be tackled as a whole.

“The issues in the food system are all interconnected, whether marine plastic outweighing fish in the sea, the volume of food we waste, or the extraction of fresh water for agriculture.

The system we have today is not fit for the future,” said Judith Batchelar, a food supply chain expert and former director of brand at Sainsbury’s.

“Is the answer buying local? It’s not as simple as that because by far the biggest impact on emissions in the supply chain, comes from the agricultural production.

“And it’s not just in food, that is also in other commodities like rubber or leather, which all started out as agriculture,” said Batchelar, pointing out the gaps between who produces, owns and consumes different parts of the food chain.

“The food system is both highly fragmented and highly consolidated. 35 per cent of what we consume comes from small producers, who are also disproportionately affected by climate change. Something they did little to create,” she said.

Guy Poppy, former chief scientific advisor to the Food Standards Agency (FSA), said: “Politics, health and the environment all affect the food system: pulling one lever affects multiple things. To just address the health issues would be very foolish.”

As a result, Poppy leads a joint fund of £47.5m as a partnership between FSA, Defra and the department of health to support projects including access to healthy food in deprived areas, and training new PhD students working on food from a health, policy and environment perspective, rather than in isolation.

Speakers also pointed to the government’s Eatwell Guide as a sensible starting point for people to eat a healthy, but also sustainable, diet. Described as ‘plant-rich’, the diet recommends eating mainly fruit, veg and whole foods, with small amounts of animal-derived foods like meat, fish and dairy, and would reduce dietary emissions by 30 per cent, according to a study.   

While fruit and veg are the “cornerstone” of a healthy diet, speakers also pointed out the complexity of the issue as horticulture also tends to be more water intensive as a crop.

Speaking about the solution to healthy and sustainable diets, nutrition scientist, Simon Steenson, said “there is no one size fits all”.

“Healthy and sustainable diets do need to consider environmental impact, but also nutrition,” he added.