High Intake Of Ultra-Processed Foods Linked To Greater Risk Of Colon Polyps In Younger Women

A major new long-term analysis of nearly 30,000 women under age 50 has found that consuming large amounts of ultra-processed foods is linked to a significantly higher risk of developing colon polyps that can precede early-onset colorectal cancer, adding weight to concerns about the role modern diets may play in rising cancer rates among younger adults.

The research, led by Mass General Brigham as part of the Cancer Grand Challenges PROSPECT team, examined 24 years worth of dietary surveys and endoscopy records from participants in the long-running Nurses Health Study II, which follows female nurses born between 1947 and 1964. 

The results, published in JAMA Oncology, showed that women who consumed the highest levels of ultra-processed foods had a 45% higher risk of developing adenomas — colorectal cancer precursors — compared with women who ate the least.

“Our findings support the importance of reducing the intake of ultra-processed foods as a strategy to mitigate the rising burden of early-onset colorectal cancer,” said senior author Andrew Chan, MD, MPH, chief of the Clinical and Translational Epidemiology Unit and a gastroenterologist in the Mass General Brigham Cancer Institute. “The increased risk seems to be fairly linear, meaning that the more ultra-processed foods you eat, the more potential that it could lead to colon polyps.”

The rise in early-onset colorectal cancer, once considered a disease of older age, has puzzled researchers, especially in high-income countries like the United States. Ultra-processed foods — typically ready-to-eat items high in sugars, salt, saturated fat and additives — have grown increasingly common during the same period. Chans group had previously linked these foods to colorectal cancer more broadly, but this study is the first to show a specific connection to early-onset disease.

All of the study participants had undergone at least two lower endoscopies before turning 50. Participants completed detailed food surveys every four years, enabling researchers to estimate average daily intake of ultra-processed foods. Although self-reported, these surveys have been validated for accurately reflecting eating patterns.

On average, women in the study consumed 5.7 servings of ultra-processed foods per day, accounting for 35% of daily calories — slightly below the U.S. national average.

Endoscopy results identified 2,787 cases of precursor polyps. Women consuming the highest amounts of ultra-processed foods — about 10 servings a day — had a 45% higher risk of conventional adenomas, the type most strongly linked to early-onset colorectal cancer. No similar association was found for serrated lesions, which tend to develop more slowly and are less commonly tied to early-onset cases.

“One of the strengths of our study was that we had detailed information about other colorectal cancer risk factors in the participants, such as such as body mass index, type 2 diabetes, and low fiber intake,” said Chan. “Even after accounting for all these other risk factors, the association with ultra-processed foods still held up.”

While the findings reinforce concerns about modern diets, the researchers say diet alone cannot explain the rise in early-onset colorectal cancer. Their work continues to examine additional risk factors and refine how ultra-processed foods themselves are categorized, acknowledging that not all items in the category carry the same potential harms.

“Diet isn’t a complete explanation for why we’re seeing this trend — we see many individuals in our clinic with early onset colon cancer who eat very healthy diets,” said Chan, who conducted this work as part of the Cancer Grand Challenges PROSPECT team. “Identifying other risk factors for early onset colorectal cancer is one of the focuses of the work that we’re leading here at the Mass General Brigham Cancer Institute.”