A new global study has found that women under 50 who regularly consume ultra-processed foods (UPFs) are significantly more likely to develop bowel polyps, which can sometimes progress to cancer.
Researchers from PROSPECT, a project funded by Cancer Grand Challenges, analysed endoscopy results from 29,105 female nurses aged 25 to 42, enrolled in the Nurses’ Health Study II. The team examined links between UPF consumption—foods low in fibre and high in additives such as emulsifiers—and early-onset bowel growths.
The study found that women who consumed the most UPFs had a 45% higher risk of developing polyps in the colon or rectum. While polyps are generally harmless, some may eventually become cancerous if left untreated.
Dr. Andrew Chan, lead author and expert in clinical and translational epidemiology at Massachusetts General Hospital, said:
“We are seeing more cases of bowel cancer in younger adults, and diet may play an important role. Factors like lack of exercise and disruption to the gut microbiome are also under investigation.”
The researchers tracked dietary habits using detailed food frequency questionnaires over 24 years, categorising foods into four groups according to the Nova classification system. Ultra-processed foods—including breads, breakfast foods, sauces, sugary drinks, and snacks—made up around 35% of participants’ daily calories, averaging 5.7 servings per day.
By the end of the study, 1,189 early-onset tumours and 1,598 serrated lesions were recorded. The analysis suggested that artificially sweetened drinks in particular were associated with an increased risk of tumours.
The researchers concluded that additives in UPFs may collectively harm gut health, affecting the intestinal barrier and microbiome. They emphasised the importance of improving dietary quality as a preventive measure against early-onset colorectal cancers.
Professor Charles Swanton, Chair of Cancer Grand Challenges Scientific Committee, added:
“This study highlights how diet and lifestyle can impact gut health and may contribute to changes in the bowel linked to cancer.”
Colon cancer is the only type of cancer rising sharply among younger adults. In the UK, there are approximately 44,000 cases annually, and in the US 142,000, making it the fourth most common cancer in both countries. Projections indicate that in the US, it may become the most common cancer in people under 50 by 2030.
Symptoms include changes in bowel habits, blood in stool, abdominal pain, bloating, unexplained weight loss, and fatigue. Cancer Research UK stresses that over half of bowel cancer cases are preventable and is calling for broader public health and policy measures to promote healthier diets.
Fiona Osgun, head of health information at Cancer Research UK, said:
“Our diets are shaped by the world around us—from food prices to marketing—which can make healthy choices harder. Overall diet quality matters more for cancer risk than any single food type.”
