New Harvard-led study finds diets high in ultra-processed foods linked to greater risk of early-onset colorectal cancer, raising concern among experts.
Study links ultra-processed foods to higher cancer risk
New research connects diet and rising cancer rates
A large U.S. study suggests that eating more ultra-processed foods is associated with an increased risk of early-onset colorectal cancer, a disease rising rapidly among adults under 50. The findings add weight to growing concern that modern eating habits may be driving preventable health crises.
What researchers uncovered
The 24-year study, led by Harvard researchers and published Thursday in JAMA Oncology, followed nearly 30,000 female participants from the ongoing Nurses’ Health Study II. It found that those who consumed the highest amounts of ultra-processed foods had a 1.45 times greater risk of developing colorectal polyps — growths that can become cancerous — compared to those who ate the least.
Participants completed detailed food questionnaires every four years, tracking items like mass-produced bread, sugary cereals, and instant soups — staples often high in salt, sugar, and preservatives.
Why the results matter
Colorectal cancer rates in people in their 20s, 30s, and 40s have surged in Canada and other developed countries over the past two decades — a trend scientists say cannot be explained by genetics alone. Experts believe diet, sedentary lifestyles, and excess weight are key contributors.
Dr. Andrew Chan, gastroenterologist at Mass General Brigham and co-author of the study, said the risk increase linked to ultra-processed foods mirrors that seen with obesity or physical inactivity.
“There’s growing evidence to limit one’s intake of ultra-processed food,” Chan said, noting that the results add urgency to efforts promoting healthier diets.
Impact on Canadian health experts and policy
Canadian specialists say the findings should spark a public health response.
Dr. Shady Ashamalla, surgical oncologist at Sunnybrook’s Odette Cancer Centre in Toronto, said he increasingly treats younger patients with colorectal cancer.
“My advice is simple: do what you can to reduce ultra-processed foods,” he said.
He urged earlier and broader screening in Canada, recommending that the current age threshold of 50 for at-home kits and colonoscopies be reconsidered. “By the time younger patients are diagnosed, cancers are often advanced,” Ashamalla warned.
How dietary changes could help
Registered dietitian Russell de Souza of McMaster University’s Population Health Research Institute echoed the call for moderation.
“Try to limit ultra-processed foods — they’re often high in sugar, salt, and unhealthy fats but short on nutrients,” he said.
“These foods can increase risk for obesity, diabetes, and cancer, and they’re designed to make you eat more. Whenever possible, choose fresh, whole foods.”
De Souza noted that the study’s findings remained significant even after accounting for body weight and diabetes, suggesting the link goes beyond known risk factors.
Broader implications for food regulation
Chan said further research is needed to determine whether ultra-processed foods directly cause cancer or simply correlate with unhealthy habits. Still, he argues the evidence supports stronger regulation.
“We need to ask whether society should limit exposure to ultra-processed foods through clearer labelling or changes in how we regulate what ends up on shelves,” he said.
Experts say the consistency of findings across studies — connecting these foods to heart, brain, and gut diseases — indicates a growing health concern.
What comes next
Modeling published earlier this year predicts colorectal cancer rates in young adults could double every 15 years across Canada, the U.S., Australia, and the U.K. Without dietary shifts or improved screening, that trajectory is expected to continue.
Health professionals say Canadians can take control through everyday food choices — replacing processed options with fresh produce, whole grains, and lean proteins — while policymakers consider systemic action.
