Over the past decade and a half, doctors have noticed a troubling rise in colorectal cancer among adults under 50. In a NY Times article  highlighting a new study led by Dr. Andrew T. Chan and published in JAMA Oncology suggests that ultra-processed foods may contribute to this trend. Following more than 29,000 women in their 20s to 40s over two decades, researchers found that those who consumed the most ultra-processed foods were 45 percent more likely to develop conventional adenomas—common precancerous polyps—before age 50. These foods included processed breads and cereals, packaged sauces and condiments, and sugary or artificially sweetened drinks. While the study is the first of its kind in younger adults and aligns with other recent research, experts emphasize that it shows correlation, not proof of causation, and that the findings may not apply to all populations because the participants were mostly white female nurses.

Researchers are exploring several potential biological explanations, such as the impact of ultra-processed foods on obesity, Type 2 diabetes, gut microbes, and the intestinal lining. Still, experts note that not all ultra-processed foods are harmful—some, like certain yogurts and whole grain products, can offer protective nutrients. Other factors, including antibiotic use, micro-plastics, and environmental chemicals, may also contribute to rising cancer rates in younger people. While limiting ultra-processed foods may help lower risk, lifestyle habits like exercising, avoiding smoking, moderating alcohol and processed meats, and eating plenty of produce are also important. Because genetics play a role and even healthy individuals can develop colorectal cancer, doctors stress the importance of screening starting at age 45, or earlier with a family history, so precancerous polyps can be detected and removed before they turn into cancer.