The sharp climb of colon and rectal cancers in young people has overlapped with the consumption of ultra-processed foods in the United States – where the fare now comprises roughly 73% of the American food supply and nearly 60% of adult calorific intake, and where several studies have linked this growing trend with the risk of such cancers.
Now, CNN reports, a first-of-its-kind study has recently added to the growing evidence by suggesting that eating ultra-processed foods may significantly raise the odds of developing early-age non-cancerous colorectal adenomas – growths, or polyps, in the colon and rectum that can lead to these cancers.
In the latest research, ultra-processed food intake was primarily from ultra-processed breads and breakfast foods; sauces, spreads and condiments; and sugar- or artificially-sweetened beverages.
Participants with the highest intake of ultra-processed foods – about 10 servings daily – had a 45% higher risk of developing those growths by age 50 when compared with those with the lowest consumption, a bit more than three servings daily.
The study, which followed more than 29 100 female nurses for a median period of 13 years, was published in JAMA Oncology.
“Our study isn’t cause and effect, so we can’t say that this is definitive,” said senior study author Dr Andrew Chan, a gastroenterologist at the Mass General Brigham Cancer Institute in Boston.
“But it does serve as some clues that what we eat may play a role. So, as we move forward, I think it’s helpful to think about where it is that we can potentially limit our intake and lay the groundwork for future studies for us to be able to identify, more specifically, the mechanisms and the specific foods.”
Non-cancerous colorectal tumours usually don’t have symptoms, but when they grow large enough, they can cause problems worth seeing a doctor about, experts said. These include dark or bloody bowel movements, pain, iron-deficiency anaemia, unintended weight loss in combination with gastrointestinal symptoms, and blockage-induced constipation.
It is also recommended that screening starts at 45 or if people have a family history of colorectal cancer, said Dr Robin Mendelsohn, as the earlier issues are diagnosed, the sooner and more effectively they can be treated.
Mendelsohn is co-director of the Centre for Young Onset Colorectal and Gastrointestinal Cancers at Memorial Sloan Kettering Cancer Centre in New York, and wasn’t involved in the study.
Ultra-processed food consumption over time
Ultra-processed foods are made with industrial techniques and some ingredients “never or rarely used in kitchens”, according to the Food and Agriculture Organisation of the United Nations. They are typically low in fibre and high in calories, added sugar, refined grains and fats, sodium and additives, all of which are designed to help make food more appealing.
Additives often include preservatives to maintain freshness and texture or resist mould and bacteria, and emulsifiers to prevent ingredients from naturally separating. Other common additives include fragrance and flavour enhancers and agents for anti-foaming, bleaching, bulking, gelling and glazing.
The study participants were part of the Nurses Health Study, an ongoing study established in 1989 to follow female nurses born between 1947 and 1964 to learn about risk factors for major chronic diseases in women.
The women answered an initial diet questionnaire in 1991; every four years they were asked to recall their dietary choices over the past 12 months.
As with most nutrition studies, this type of recollection can be limited in accuracy. “I don’t remember what I ate last week, and people may not tell the entire truth,” Mendelsohn said.
Additionally, classification of ultra-processed foods and the determination of which ones are more harmful than others still need work, Chan said, and that ability would help experts more specifically determine health effects and dietary guidance.
However, the researchers contend that the participants may be better than the average person at accurately providing such details, given their background in nursing.
Most of the colorectal tumours were discovered via endoscopy before 2015, “which is before the age for (initial) screening was decreased to 45,” Mendelsohn said. “So if people were getting screening (endoscopies) we have to assume they were at increased risk of colorectal cancer – i.e, from family history – and that’s why they were being screened earlier. And, of course, if done for symptoms, there is an increased rate of finding polyps.” Whether these tumours became cancerous is also unknown.
Chan said the study was prompted by an effort to understand what was driving rising rates of bowel cancer in younger people.
“Most of these polyps do not become bowel cancer. But at the same time, we know the vast majority of bowel cancers we see in young people arise from these precursor lesions,” he said.
“One of the study’s strengths was detailed information about other colorectal cancer risk factors in the participants, such as body mass index, type 2 diabetes, and low fibre intake,” he added. “Even after accounting for all of these other risk factors, the association with ultra-processed foods still held up.”
While the risk for precancerous growths increased the more ultra-processed foods participants ate, the odds for developing serrated lesions – another type of precancerous polyp and the other main pathway for colorectal cancer – did not.
That finding suggests ultra-processed foods may cause biological processes that turn classic adenomas into cancerous tumours, said Dr Ganesh Halade, a member of the Cancer Biology Programme at the Tampa General Hospital Cancer Institute, who wasn’t involved in the research.
Importantly, ultra-processed foods of the 1990s “are not identical to today’s products”, Halade added, “given changes in formulations, the introduction of novel additives, and shifts in the proportion of UPFs in the diet.
“However, one consistent feature across those decades has been the widespread use of omega-6-rich seed oils, which may be a key dietary factor contributing to early-onset colorectal cancer.”
Any potential relationship between ultra-processed foods and colorectal tumours may be explained by the foods possibly altering the gut microbiome and its protective lining, causing chronic inflammation and producing toxic molecules when metabolised, Mendelsohn and Chan said.
“Indirectly, consumption of ultra-processed foods is associated with obesity, which is also a risk factor for colorectal cancer,” Mendelsohn added.
Study details
Ultraprocessed Food Consumption and Risk of Early-Onset Colorectal Cancer Precursors Among Women
Chen Wang, Mengxi Du, Hanseul Kim, et al.
Published in JAMA Oncoloy on 13 November 2025
Abstract
Importance
Early-onset colorectal cancer (EOCRC) (diagnosed age <50 years) incidence is increasing globally, in parallel with increased consumption of ultra-processed foods (UPFs). The role of UPFs in early-onset colorectal neoplasia remains under-explored.
Objective
To evaluate the association between UPF consumption and risk of EOCRC precursors.
Design, Setting, and Participants
This prospective cohort study included participants of the Nurses’ Health Study II, an ongoing US prospective cohort of female registered nurses established in 1989. Participants were followed up from June 1, 1991, through June 1, 2015. Data were analysed from October 2024 to July 2025. UPF intake, derived from food-frequency questionnaires administered every 4 years and classified using the Nova system, was modelled as quintiles of energy-adjusted servings per day. Of the nurses enrolled, those who had completed the baseline 1991 food-frequency questionnaire, undergone at least 1 lower endoscopy before age 50 years after baseline, had no history of cancer (except for non-melanoma skin cancer) before endoscopy, and no colorectal polyp or inflammatory bowel disease were included.
Main Outcomes and Measures
Incidence of EOCRC precursors, including conventional adenomas and serrated lesions, confirmed via medical records and pathology reports. Multivariable logistic regression models with generalised estimating equations for clustered data were used to estimate adjusted odds ratios (AORs) and 95% CIs, accounting for known and putative risk factors.
Results
Among 29 105 female participants (mean [SD] age, 45.2 [4.5] years) over 24 years of follow-up, 1189 cases were documented of early-onset conventional adenomas and 1598 serrated lesions. UPFs provided 34.8% of total daily calories (median, 5.7 [IQR, 4.5-7.4] servings per day). Participants with higher UPF intake had an increased risk of early-onset conventional adenomas (highest vs lowest intake: AOR, 1.45; 95% CI, 1.19-1.77; overall P < .001) but not serrated lesions (AOR, 1.04; 95% CI, 0.89-1.22; P = .48 for trend). Findings were consistent after further adjustment for body mass index, type 2 diabetes, dietary factors (fibre, folate, calcium, and vitamin D), and Alternative Healthy Eating Index–2010 score.
Conclusions and Relevance
In this study, higher UPF intake was associated with increased risk of early-onset colorectal conventional adenomas. These data highlight the important role of UPFs in early-onset colorectal tumourigenesis and support improving dietary quality as a strategy to mitigate the increasing burden of EOCRC.
See more from MedicalBrief archives:
US studies show colorectal cancer link to ultra-processed foods
Heavily processed foods linked to earlier death risk
Why are so many millennials getting cancer?