Getty ImagesPeople who eat lots of ultra-processed foods (UPF) may be at greater risk of dying early, a study in eight countries including the UK and the US suggests.
Processed meats, biscuits, fizzy drinks, ice cream and some breakfast cereals are examples of UPF, which are becoming increasingly common in diets worldwide.
UPFs tend to contain more than five ingredients, which are not usually found in home cooking, such as additives, sweeteners and chemicals to improve the food's texture or appearance.
Some experts say it's not known why UPFs are linked to poor health - there is little evidence it's down to the processing itself and could be because these foods contain high levels of fat, salt and sugar.
The researchers behind the study, published in the American Journal of Preventive Medicine, looked at previous research to estimate the impact of ultra-processed food intake on mortality.
The study cannot definitively prove that UPFs caused any premature deaths.
This is because the amount of ultra-processed foods in someone's diet is also linked to their overall diet, exercise levels, wider lifestyle and wealth, which can all also affect health.
The studies looked at surveys of people's diets and at data on deaths from eight countries - Australia, Brazil, Canada, Chile, Colombia, Mexico, UK and US.
The report estimates that in the UK and the US, where UPFs account for more than half of calorie intake, 14% of early deaths could be linked to the harms they cause.
In countries such as Colombia and Brazil, where UPF intake is much lower (less than 20% of calorie intake), the study estimated these foods are linked to around 4% of premature deaths.
Lead study author Dr Eduardo Nilson, from Brazil, said UPFs affected health "because of the changes in the foods during industrial processing and the use of artificial ingredients, including colorants, artificial flavours and sweeteners, emulsifiers, and many other additives and processing aids".
By their calculations, in the US in 2018, there were 124,000 premature deaths due to the consumption of ultra-processed food. In the UK, nearly 18,000.
The study says governments should update their dietary advice to urge people to cut back on these foods.
But the UK government's expert panel on nutrition recently said there wasn't any strong evidence of a link between the way food is processed and poor health.
There is no one definition that everyone agrees on, but the NOVA classification is often used. Examples include:
The numbers in the study are based on modelling the impact of ultra-processed foods on people's health.
Prof Kevin McConway, emeritus professor of applied statistics, Open University, said the study makes lots of mathematical assumptions which make him cautious about what the findings mean.
"It's still far from clear whether consumption of just any UPF at all is bad for health, or what aspect of UPFs might be involved.
"This all means that it's impossible for any one study to be sure whether differences in mortality between people who consume different UPF amounts are actually caused by differences in their UPF consumption.
"You still can't be sure from any study of this kind exactly what's causing what."
Dr Nerys Astbury, an expert in diet and obesity at the University of Oxford, also agrees there are limitations to the research.
It's been known for some time that diets high in energy, fat and sugar can increase the risk of diseases, such as type 2 diabetes, obesity, heart conditions and some cancers, which can lead to premature death.
"Many UPF tend to be high in these nutrients," she says, adding that studies to date haven't been able to prove that the effects of UPFs are due to anything more than "diets high in foods which are energy dense and contain large amounts of fat and sugar".
This type of research cannot prove that consumption of ultra-processed foods is harmful, says Dr Stephen Burgess at Cambridge University.
How physically fit someone is may be the main cause of poor health instead. But when numerous studies across many countries and culture suggest UPFs could be a risk to health, Dr Burgess says "ultra-processed foods may be more than a bystander".
The Food and Drink Federation, which represents manufacturers, said the term 'ultra-processed food' "demonises a wide variety of food that can help people achieve a healthy balanced diet, such as yoghurt, pasta sauces or bread".
It said all additives used by food manufacturers are approved by the Food Standards Agency, who ensure they are safe to eat and drink.
