Colorectal cancer is currently the second leading cause of cancer-related deaths in the United States, according to the American Cancer Society (ACS). Traditionally associated with older adults, the incidence of this cancer has shifted, showing a decline among those aged 65 and older while rising sharply in individuals under 50. Notably, people born in the 1990s are now twice as likely to develop colorectal cancer compared to those born in the 1950s, as reported by the American College of Surgeons. In response to this alarming trend, the ACS revised its guidelines in 2018, lowering the recommended age for colorectal cancer screening from 50 to 45.
A new study published in JAMA Oncology highlights a potential factor contributing to this rise: a diet high in ultra-processed foods (UPFs). Researchers analyzed data from over 29,000 women participating in the long-term Nurse’s II study, revealing that those who consumed the highest amounts of UPFs had a 45% increased risk of developing adenomas, pre-cancerous polyps, compared to those with lower intake.
Dr. Andrew T. Chan, a gastroenterologist at the Mass General Brigham Cancer Institute and a professor at Harvard University, emphasized the significance of the findings. He noted, “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.”
What the Study Revealed
The research team examined 24 years’ worth of data from female nurses under the age of 50, all of whom had no prior history of cancer—except for nonmelanoma skin cancer—no colorectal polyps, and no evidence of inflammatory bowel disease. Participants completed food-frequency questionnaires every four years and underwent two lower endoscopies before age 50 to identify any precursors to colorectal cancer.
On average, the women consumed approximately 5.7 servings of UPFs daily, which constituted about 35% of their total caloric intake. The analysis showed that those with the highest consumption of UPFs, averaging 10 servings a day, had a 45% greater likelihood of developing pre-cancerous polyps linked to early-onset colorectal cancer compared to those eating an average of three servings daily. Interestingly, researchers found no connection between UPF intake and serrated lesions, another type of precancerous growth.
Understanding Ultra-Processed Foods
The classification of UPFs stems from the NOVA food classification system, designed to categorize foods based on their processing levels. UPFs are industrially manufactured food products laden with various additives, including high fructose corn syrup, artificial flavors, and elevated levels of salt or sugar. According to the Food and Drug Administration (FDA), an estimated 70% of the U.S. food supply consists of UPFs.
Dr. Chan describes these foods as being engineered for shelf stability and ease of preparation. Common examples include packaged snacks, sugar-sweetened beverages, and frozen meals. Certain condiments and sauces also fall into the UPF category due to their high additive content.
Impact of Ultra-Processed Foods on Cancer Risk
The consumption of ultra-processed foods may promote chronic inflammation, metabolic syndrome, and obesity, all recognized risk factors for colorectal cancer. Dr. Chan explains that UPFs can disrupt the balance of beneficial gut bacteria, potentially leading to damage in the intestinal lining. One study published in the journal Cancers indicates that microbial imbalances can foster inflammation and interfere with normal cell functions, increasing cancer risk.
Although the exact mechanisms require further investigation, these findings suggest a possible connection between UPFs and the rising incidence of colorectal cancer in younger populations.
Moving Forward
While dietary habits alone do not fully account for the increasing rates of colorectal cancer among those under 50, they play a crucial role. Dr. Chan advises individuals to consider lifestyle changes that can mitigate cancer risk, such as reducing the intake of pre-packaged and processed foods. Instead, he encourages consumption of plant-based, fiber-rich options, including fruits, vegetables, legumes, nuts, and whole grains, while limiting red and processed meats.
Additionally, maintaining a healthy body weight and staying physically active are vital. For those at average risk, screening for colorectal cancer is recommended starting at age 45, as early detection can significantly improve outcomes.
