Colorectal cancer is now the second leading cause of cancer deaths in the United States, as highlighted by the American Cancer Society (ACS). Although traditionally associated with older adults, recent trends indicate a troubling rise in colorectal cancer rates among individuals under 50. According to the American College of Surgeons, those born in the 1990s are twice as likely to develop this disease compared to those born in the 1950s. In response to this alarming shift, the ACS lowered its recommended screening age from 50 to 45 in 2018.
A new study published in JAMA Oncology provides insights into a potential factor contributing to this increase: a diet high in ultra-processed foods (UPFs). The research, which analyzed data from over 29,000 women, found that participants with the highest consumption of UPFs had a 45% greater risk of developing adenomas, a type of pre-cancerous polyp, compared to those with the lowest intake.
Andrew T. Chan, MD, MPH, a gastroenterologist at the Mass General Brigham Cancer Institute and a professor of medicine at Harvard University, emphasizes the correlation between the American diet’s reliance on ultra-processed foods and the rising incidence of colorectal cancer. “The American diet has increasingly been comprised of ultra-processed foods, such that more than 50% of calories now consumed by Americans are ultra-processed,” he noted. “This trend mirrors the early onset of colorectal cancer.”
Research Details and Diet Analysis
The study involved participants from the long-running Nurse’s II study, consisting of 29,105 female nurses under the age of 50, all of whom had no prior cancer history (except for nonmelanoma skin cancer) or indications of inflammatory bowel disease. Throughout the study, participants completed food-frequency questionnaires every four years and underwent two lower endoscopies before turning 50 to check for precursors to colorectal cancer.
On average, the women reported consuming 5.7 servings of UPFs daily, which accounted for 35% of their total caloric intake. The findings revealed that those with the highest UPF consumption—approximately 10 servings a day—faced a 45% increased likelihood of developing precursors to colorectal cancer compared to women consuming an average of three servings a day.
Interestingly, the study did not find a significant link between UPF intake and serrated lesions, another form of precancerous growth less commonly associated with early-onset colorectal cancer.
Understanding Ultra-Processed Foods
Ultra-processed foods are defined using the NOVA food classification system, which categorizes foods based on their processing levels. These foods typically include industrially manufactured products with numerous unnatural additives such as high fructose corn syrup, artificial flavors, and preservatives. The Food and Drug Administration (FDA) estimates that around 70% of the U.S. food supply comprises UPFs.
Dr. Chan describes these foods as designed for long shelf life and easy preparation. Common examples include packaged snacks, sugary beverages, and frozen meals. Additionally, many bottled seasonings and condiments contain ultra-processed ingredients.
Dr. Chan explains the potential health implications of a diet high in UPFs. These foods may contribute to chronic inflammation, metabolic syndrome, and obesity—all of which are known risk factors for colorectal cancer. Moreover, they can disrupt the balance of beneficial bacteria in the gut.
“UPFs can upset the healthy balance of your microbiome, and if the microbes in our intestines get disrupted, it’s possible this could lead to damage to the intestinal lining,” he explained. Research published in the journal Cancers suggests that an imbalance in gut bacteria can promote inflammation and produce harmful substances, potentially leading to cancer.
These mechanisms require further investigation, but they offer possible explanations for the growing colorectal cancer risk among individuals under 50.
Implications and Recommendations
While diet alone cannot fully explain the rising rates of colorectal cancer in younger populations, it plays a critical role. Dr. Chan advises that individuals looking to reduce their cancer risk should consider simplifying their diets. “We should focus on eating foods that are less pre-packaged, prepared, and processed,” he said.
He encourages an emphasis on plant-based, fiber-rich foods, including fruits, vegetables, beans, legumes, nuts, and whole grains. Limiting or avoiding red and processed meats, such as bacon and cold cuts, is also recommended.
For those at average risk, Dr. Chan highlights the importance of maintaining a healthy body weight, engaging in regular physical activity, and starting colorectal cancer screenings at age 45. These lifestyle modifications can collectively contribute to a lower risk of developing colorectal cancer.
