Ultra processed foods dramatically raise risk of abnormal growths in the bowel linked to cancer

Women under 50 who regularly eat ultra-processed foods are significantly more likely to develop bowel polyps which have been linked to cancer, concerning new research suggested today. 

The latest global analysis found that colon cancer is the only form of the disease to have solely surged in this age group—leading researchers to look more closely and potential environmental triggers. 

Ultra-processed foods, typically low in fibre and packed full of emulsifiers, have long been linked to bowel cancer, but until now data on UPFs and early-onset growths in the bowel have been largely overlooked.   

In the study, leading cancer experts from PROSPECT, funded by Cancer Grand Challenges—a global research initiative founded by Cancer Research UK and the National Cancer Institute—studied endoscopy results from over 29,100 women. 

The researchers found that those who ate the most UPFs were at a 45 per cent increased risk of developing growths on their large intestine or rectum.

Whilst polyps are usually harmless and are not always a cause for concern, in a small number of cases a polyp can become cancerous over time. 

Dr Andrew Chan, an expert in clinical and translational epidemiology at Massachusetts General Hospital and study lead author, said: ‘We’re seeing more cases of bowel cancer in younger adults and we still don’t understand why. 

‘Our research is exploring possible factors such as diet, lack of exercise and disruption to the gut microbiome, which may all play a role.’

Publishing their findings in the journal JAMA Oncology, the researchers analysed whether eating more UPFs was associated with an increased risk of non-cancerous tumours and serrated lesions in the bowel—the two main drivers of colorectal cancers. 

They compared lower-endoscopy results of 29,105 female nurses aged 25 to 42, enrolled on the Nurses’ Health Study II to gain an early insight into diet-related cancer progression. 

Colonoscopies are routinely carried out to check what’s causing bowel symptoms such as rectal bleeding, diarrhoea, constipation and unexplained weight loss. They can also detect bowel polyps.  

Lifestyle factors, family and medical history were collected through questionnaires sent out every other year starting from 1989 and dietary habits through food frequency questionnaires conducted every four years beginning in 1991. 

Those who had a history of irritable bowel disease (IBS), colorectal polyps or who had been diagnosed with cancer before endoscopy were excluded.

The remaining participants were followed up until June 1 2015, by which time all had reached 50-year-old. 

UPF intake was assessed using the foods questionnaires which were split into four groups according to the Nova classification system—unprocessed or minimally processed, processed ingredients, processed foods and ultra-processed foods—and featured over 130 items. 

Within the UPFs category, foods were further categorised to reflect their health benefits. For example, wholegrain bread and sugary cakes were ranked differently. 

Overall, UPF consumption was assessed as how many servings of UPFs the nurses ate a day, in relation to total calorie intake. 

Over the 24-year study periods, researchers found that those who are the most UPFs had a higher BMI, smoked more and had a higher prevalence of type 2 diabetes than those who ate less. 

These women also tended to take more anti-inflammatory painkillers, like aspirin, and were more likely to be on hormone replacement therapy. They were also less likely to take supplements and were less active than their peers. 

On average, UPF intake made up around 35 per cent of total daily calories—equating to around 5.7 servings a day, primarily from breads and breakfast foods, sauces, spreads, condiments and sugary drinks. 

By the end of the study 1,189 cases of early-onset tumours and 1,598 serrated lesions were recorded. 

Those who ate the most UPFs were more likely to develop early-onset tumours, but not lesions—with artificially sweetened drinks driving the trend.

The researchers concluded: ‘This suggest the combined exposure to multiple food additives may exert a cocktail effect on gut health by impairing barrier function and altering the microbiome.

‘Our findings highlight the importance of diet in early-onset colorectal carcinogenesis and support dietary quality improvements as a strategy to mitigate the increasing burden of early-onset colorectal cancers.’ 

Professor Charles Swanton, Cancer Grand Challenges Scientific Committee Chair and Cancer Research UK’s Chief Clinician, added: ‘This study sheds light on how diet and other factors are associated with gut health and changes in the bowel linked to cancer risk. 

‘While causation has not yet been demonstrated, researchers around the world in the PROSPECT team are combining large-salce population studies with cutting-edge lab science to build a clearer picture of the factors that may be contributing to this trend, and how we might help reduce it in future generations.’ 

There are around 44,000 cases of bowel cancer every year in the UK and 142,000 in the US, making it the fourth most common cancer in both countries.

Previous research has also suggested that in England, diagnoses in 25 to 49-year-olds have increased by more than 50 per cent since the early 1990s. 

In the US, meanwhile, the disease has already been projected to become the most common cancer in people under 50 by the year 2030. 

Symptoms often include changes in bowel movements such as consistent and new diarrhoea or constipation, needing or feeling the need to go more or less frequently and blood in the stool.

Abdominal pain, a lump in the stomach, bloating, unexplained weight-loss and fatigue are among other signs.

Anyone experiencing these symptoms should contact their GP for advice.

Cancer Research UK estimates that over half (54 per cent) of bowel cancer cases in the UK are preventable. The charity is now calling for braider changes to make healthier lifestyles more accessible to slash soaring cancer rates. 

Fiona Osgun, head of health information at the charity, said: ‘Whilst this study doesn’t directly measure cancer risk, it offers useful insight into how diet might influence early changes in the bowel that sometimes lead to cancer.

‘Our diets are shaped by the world around us, from food prices, marketing and local availability. 

‘This can make healthy choices harder. We need broader changes – from food policy to public health initiatives – to make healthier diets more accessible for everyone. Our overall diet matters more for cancer risk than any single food type.’