Colorectal cancer is now the second leading cause of cancer-related deaths in the United States, according to the American Cancer Society (ACS). While traditionally more common among older adults, the incidence among individuals under 50 has alarmingly increased. In fact, those born in the 1990s are twice as likely to develop colorectal cancer compared to those born in the 1950s, as noted by the American College of Surgeons. This shift prompted the ACS to lower its recommended screening age from 50 to 45 in 2018.
Recent findings published in JAMA Oncology provide insight into one potential contributor to this trend: a diet high in ultra-processed foods (UPFs). Researchers analyzed data from over 29,000 women and discovered that those with the highest consumption of UPFs faced a 45% greater risk of developing adenomas, which are pre-cancerous polyps, compared to those with the lowest intake.
Dr. Andrew T. Chan, a gastroenterologist at the Mass General Brigham Cancer Institute and a professor at Harvard University, emphasized the concerning correlation, stating, “The American diet has increasingly been comprised of ultra-processed foods, such that more than 50% of calories now consumed by Americans are those that are ultra-processed. This mirrors the trends we’re seeing of early onset colorectal cancer.”
Study Overview and Findings
The study utilized data from the long-running Nurse’s II study, which tracked the health of 29,105 female nurses under 50 with no prior history of cancer (excluding nonmelanoma skin cancer), colorectal polyps, or inflammatory bowel disease. Participants completed food-frequency questionnaires every four years and underwent two lower endoscopies before their 50th birthday to screen for precursors to colorectal cancer.
On average, participants consumed 5.7 servings of UPFs daily, which constituted 35% of their total caloric intake. The analysis revealed that those consuming the most UPFs—averaging 10 servings per day—had a significantly increased risk of developing pre-cancerous polyps associated with early-onset colorectal cancer compared to those eating the least (three servings per day).
Interestingly, the study did not find a correlation between UPF consumption and serrated lesions, another type of precancerous growth.
Understanding Ultra-Processed Foods
The NOVA food classification system identifies UPFs as industrially produced items containing multiple synthetic additives. Common ingredients include high fructose corn syrup, hydrolyzed proteins, artificial flavors, and excessive levels of salt, sugar, and unhealthy fats. An estimated 70% of the U.S. food supply consists of these products, according to the Food and Drug Administration (FDA).
Dr. Chan describes UPFs as foods designed for convenience and shelf stability. Examples include packaged snacks, sugar-sweetened beverages, and pre-made meals. Additionally, many bottled seasonings, sauces, and dressings also fall under the UPF category.
The potential health implications of UPFs are significant. Dr. Chan suggests they may contribute to chronic inflammation, metabolic syndrome—which encompasses conditions like diabetes—and obesity, all of which are risk factors for colorectal cancer. Furthermore, they can disrupt the gut microbiome, leading to an imbalance that might promote inflammation and interfere with normal cellular functions, potentially paving the way for cancer.
While the specific mechanisms remain to be fully explored, these factors provide insight into how UPFs may be linked to the rising rates of colorectal cancer among younger populations.
The takeaway from this study underscores the importance of dietary choices. Although diet alone does not account for the increase in colorectal cancer in those under 50, it plays a crucial role. Dr. Chan advises individuals to consider practical lifestyle modifications to reduce cancer risk, such as minimizing the consumption of packaged and processed foods.
Instead, focusing on a diet rich in plant-based, fiber-filled foods—such as fruits, vegetables, beans, legumes, nuts, and whole grains—is recommended. He also emphasizes the importance of maintaining a healthy body weight, staying active, and ensuring screenings begin at age 45 for those at average risk of colorectal cancer.
