What is ultra processed food? Can it increase the risk of cancer - what have researchers said?

Higher consumption of ultra-processed foods, such as ice cream, ham, crisps, mass-produced bread and breakfast cereal, may increase the risk of developing cancer, experts have said.

Research from Imperial College London suggests there may be some link between very processed food and an increasing risk of cancer. However, the study said the link could not be proven owing to the fact it is based on observations - where people remember what they eat.

The researchers said people in the UK eat far too many ultra-processed foods (called UPFs) and called for front of pack warning labels.

Dr Eszter Vamos, lead author on the study, said: “This study adds to the growing evidence that ultra-processed foods are likely to negatively impact our health including our risk for cancer.

“Given the high levels of consumption in UK adults and children, this has important implications for future health outcomes.

“Although our study cannot prove causation, other available evidence shows that reducing ultra-processed foods in our diet could provide important health benefits.

“Further research is needed to confirm these findings and understand the best public health strategies to reduce the widespread presence and harms of ultra-processed foods in our diet.”

Previous studies have suggested a link between ultra-processed foods and heart disease, as well as obesity and type 2 diabetes.

What is ultra-processed food?

Ultra-processed foods usually contain ingredients such as chemicals, colourings, sweeteners and preservatives to extend shelf-life and is not something people would not add when they are cooking homemade food.

The most commonly eaten ultra-processed foods in the UK are shop-bought mass-produced bread, ready meals, various breakfast cereals, reconstituted meat products such as ham, sweets, and shop-bought biscuits, buns and cakes.

However, not all processed food is bad. For example, the NHS says some foods need processing to make them safe, such as milk, which needs to be pasteurised to remove bacteria.

The Nova food classification separates the foods we buy into four groups:

Group one: Unprocessed and minimally processed

These contain fruit, vegetables, nuts, seeds, grains, beans, pulses and natural animal products such as eggs, fish, milk and unprocessed meat.

Minimally processed foods may have been dried, crushed, roasted, frozen, boiled or pasteurised, but contain no added ingredients. They include frozen fruits and vegetables, frozen fish, pasteurised milk, 100% fruit juice, no-added-sugar yoghurt, spices and dried herbs.

Group two: Processed culinary ingredients

These include oils, fats such as butter, vinegars, sugars and salt.

Group three: Processed

Processed food includes smoked and cured whole meats (like Parma ham), cheeses, fresh bread, bacon, salted or sugared nuts, tinned fruit in syrup, beer and wine.

Group four: Ultra-processed

These include industrialised bread, pre-packaged meals, breakfast cereals, sausages and other reconstituted meat products. Confectionery, biscuits, pasties, buns and cakes, soft and fruit drinks, crisps and salty snacks are also included.

What did the study find? 

In the new study, published in eClinicalMedicine, the team used UK Biobank data to examine the diets of 197,426 people aged 40 to 69. The study was funded by Cancer Research UK and the World Cancer Research Fund.

Their health was tracked over a decade and their risk of developing cancer or dying from it, was also analysed.

The study found higher consumption of ultra-processed foods was associated with a greater risk of developing cancer overall - specifically ovarian and brain cancers.

It was also associated with an increased risk of dying from cancer, most notably with ovarian and breast cancers.

The researchers found for every 10% increase in ultra-processed food in a person’s diet, there was a 2% increased risk of cancer overall, and a 19% increased risk for ovarian cancer specifically.

As an example, if somebody had zero UPFs in their diet, their risk went up for every 10% increase.

Each 10% rise was also associated with a 6% increased risk of dying from cancer, with a 16% increased risk for breast cancer and a 30% increased risk for ovarian cancer.

These links held true even after adjusting for factors that may alter the results, such as exercise, body mass index (BMI) and deprivation.

The researchers also found people who had the highest (typically 41%) UPF level in their diet had a 7% higher risk of cancer overall than those with the lowest intake of UPFs (9%).

Dr Kiara Chang, who also worked on the study, said: “The average person in the UK consumes more than half of their daily energy intake from ultra-processed foods.

“This is exceptionally high and concerning as ultra-processed foods are produced with industrially derived ingredients.

She added: “Our bodies may not react the same way to these ultra-processed ingredients and additives as they do to fresh and nutritious minimally processed foods. However, ultra-processed foods are everywhere and highly marketed with cheap price and attractive packaging to promote consumption.

“This shows our food environment needs urgent reform to protect the population from ultra-processed foods."

Dr Chang called for clear front of pack warning labels to help with customer choices. She said: "Our sugar tax should be extended to cover ultra-processed fizzy drinks, fruit-based and milk-based drinks, as well as other ultra-processed products.”

She said lower income households are “particularly vulnerable” to cheap and unhealthy UPFs, saying minimally processed and freshly prepared meals should be subsidised.

However, Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London, suggested it was difficult to draw conclusions from the study and said some of the claims were unsound.

He added: “The association with ultra-processed food and risk of ovarian cancer in this study is novel but given the relatively small number of cases (291) of ovarian cancer, the finding needs replication in other prospective cohorts before taking the claim that ultra-processed foods increase the risk of cancer seriously.”

What did Cancer Research UK and World Cancer Research Fund say?

Dr Panagiota Mitrou, director of research and innovation at the World Cancer Research Fund, said: “The findings in this first UK study of its kind are significant as this is the most comprehensive assessment of ultra-processed foods and cancer risk. This adds to the growing evidence linking these foods to cancer and other health conditions.”

Dr Mitrou said people should limit the consumption of “fast foods” and other processed foods high in fat, starches or sugars, adding: “For maximum benefit, we also recommend that you make wholegrains, vegetables, fruit and pulses a major part of your usual diet.”

Cancer Research UK’s senior prevention policy manager, Malcolm Clark, said the jury on whether ultra-processed foods cause cancer was still out, but high-calorie and sugary food can cause weight gain.

“Around 22,800 cancer cases are linked to excess weight and obesity each year in the UK,” he said.

“We urge the UK Government to take more action to help people make healthy changes – this is not the time to delay restrictions on junk food advertising and multi-buy deals.”