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Ultra-processed foods – such as chicken nuggets, ice cream and breakfast cereals – have been linked to early death and poor health, scientists say.

Researchers in France and Spain say the amount of such food being eaten has soared.

Their studies are not definite proof of harm but do come hot on the heels of trials suggesting ultra-processed foods lead to overeating.

Experts expressed caution but called for further investigation.

What are ultra-processed foods?

The term comes from a way of classifying food by how much industrial processing it has been through.

The lowest category is “unprocessed or minimally processed foods”, which include: • fruit • vegetables • milk • meat • legumes such as lentils • seeds • grains such as rice • eggs

“Processed foods” have been altered to make them last longer or taste better – generally using salt, oil, sugar or fermentation.

This category includes: • cheese • bacon • home-made bread • tinned fruit and vegetables • smoked fish • beer

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Then come “ultra-processed foods”, which have been through more substantial industrial processing and often have long ingredient lists on the packet, including added preservatives, sweeteners or colour enhancers.

Prof Maira Bes-Rastrollo, from the University of Navarra, told BBC News: “It is said that if a product contains more than five ingredients, it is probably ultra-processed.”

Examples include: • processed meat such as sausages and hamburgers • breakfast cereals or cereal bars • instant soups • sugary fizzy drinks • chicken nuggets • cake • chocolate • ice cream • mass-produced bread • many “ready to heat” meals such as pies and pizza | meal-replacement shakes

How bad were the findings?

The first study, by the University of Navarra, in Spain, followed 19,899 people for a decade and assessed their diet every other year.

There were 335 deaths during the study.

But for every 10 deaths among those eating the least ultra-processed food, there were 16 deaths among those eating the most (more than four portions a day).

The second study, by the University of Paris, followed 105,159 people for five years and assessed their diet twice a year.

It showed those eating more ultra-processed food had worse heart health.

Rates of cardiovascular disease were 277 per 100,000 people per year among those eating the most ultra-processed food, compared with 242 per 100,000 among those eating the least.

Dr Mathilde Touvier, from the University of Paris, told BBC News: “The rapid and worldwide increasing consumption of ultra-processed foods, to the detriment of less processed foods, may drive a substantial burden of cardiovascular diseases in the next decades.”

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So do these foods damage health?

Dr Mathilde Touvier, from the University of Paris, told BBC News: “[The] evidence is accumulating.

“Increasing numbers of independent studies observe associations between ultra-processed foods and adverse health effects.”

Last year, a link was made with an increased risk of cancer.

Prof Bes-Rastrollo, from the University of Navarra, told BBC News she was “very certain” they were bad for health.

The challenge is being 100% sure.

The studies have spotted a pattern between highly processed food and poor health but they cannot prove that one causes the other.

Those who ate the most ultra-processed food were also more likely to have other unhealthy behaviours, such as smoking, which the researchers tried to account for.

But Kevin McConway, a professor of statistics at The Open University, said: “One can’t be sure that everything relevant was allowed for.

“These studies do increase my confidence that there’s something real behind these associations – but I’m still far from sure.”

Why might ultra-processed foods be bad?

The first trial of ultra-processed foods showed they led people to eat more and put on weight.

Researchers at the US National Institutes of Health monitored every morsel of food that volunteers ate for a month.

And when given ultra-processed food, they ate 500 calories a day more than when they were given unprocessed meals.

Other suggestions include:

• They are energy dense but lacking in nutrients and fibre
• While the additives in food have been safety tested, it may be unhealthy to consume lots of additives from different foods
• People eat more because they’re easy to eat
• They push healthier foods such as fruit and vegetables out of diets – who wants a banana when you can have ice cream?

These ideas still need researching.

Is there any useful advice?

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While the term ultra-processed food may be new, the health advice coming out of the study will be very familiar.

Victoria Taylor, senior dietician at the British Heart Foundation, said: “We already recommend people adopt a Mediterranean-style diet, which also happens to include plenty of minimally or unprocessed foods, such as fruit, vegetables, fish, nuts and seeds, beans, lentils and wholegrains.

“This, along with exercising regularly and not smoking, has been shown to be beneficial for lowering risk of heart and circulatory disease.”

Prof Bes-Rastrollo thinks there is already enough evidence for governments to start acting too.

She said: “Measures like taxation and marketing restrictions on ultra-processed foods to discourage consumption [should be considered].

“At the same time, promotion of fresh and minimally processed food is a requirement.”

Is the ultra-processed label a load of nonsense?

Describing foods as ultra-processed has a lot of critics.

Dr Gunter Kuhnle, an associate professor in nutrition and health at the University of Reading, said the studies were important and warranted further investigation.

But the labelling of food as ultra-processed could be inconsistent.

He said: “It is also not obvious why salami is considered to be ultra-processed, yet cheese, which often requires considerably more processing steps and additives, is not.

“The classification combines a wide range of foods with very different potential impacts on health, which limits its usefulness as a basis for recommendations.”

The studies were published in the British Medical Journal.

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