Colorectal cancer is currently the second leading cause of cancer-related deaths in the United States, according to the American Cancer Society (ACS). Traditionally, this type of cancer has affected older adults, but recent trends indicate a troubling shift. Rates of colorectal cancer among individuals under the age of 50 have risen sharply, with those born in the 1990s being twice as likely to develop the disease compared to those born in the 1950s, as reported by the American College of Surgeons. In response to these alarming statistics, the ACS lowered its recommended screening age from 50 to 45 in 2018.
A new study published in JAMA Oncology has identified a potential contributor to this trend: a diet high in ultra-processed foods (UPFs). Researchers analyzed data from over 29,000 female participants in the long-term Nurses’ Health Study II. They found that women who consumed the highest amounts of UPFs had a 45% increased risk of developing adenomas, which are pre-cancerous polyps, compared to those who consumed the least.
Dr. Andrew T. Chan, a gastroenterologist at the Mass General Brigham Cancer Institute and a professor at Harvard University, emphasizes the correlation between the rising prevalence of UPFs in the American diet and the increasing rates of early-onset colorectal cancer. “Given the increasing evidence that ultra-processed food might have some detrimental health effects, we wanted to know if these things were related,” Dr. Chan stated.
Study Insights and Methodology
The researchers utilized 24 years of data from the Nurses’ Health Study II, which included 29,105 women under the age of 50, all of whom had no history of cancer (except for nonmelanoma skin cancer), colorectal polyps, or inflammatory bowel disease. Participants completed self-reported food-frequency questionnaires every four years and underwent two lower endoscopies before reaching age 50 to screen for any precursors to colorectal cancer.
On average, the women in the study consumed 5.7 servings of UPFs daily, accounting for 35% of their total caloric intake. The results indicated that those with the highest consumption of UPFs, averaging 10 servings per day, had a significantly higher likelihood of developing pre-cancerous polyps than those with the lowest intake, who averaged just three servings per day. Notably, the study found no association between UPF consumption and serrated lesions, another type of precancerous growth.
Understanding Ultra-Processed Foods
The classification of UPFs is based on the NOVA food classification system, which categorizes foods according to their level of processing. UPFs are described as industrially manufactured food products that often contain numerous artificial additives. Common ingredients in these foods include high fructose corn syrup, hydrolyzed proteins, and various artificial flavors and colors, as well as elevated levels of salt, sugar, and unhealthy fats.
Dr. Chan points out that approximately 70% of the U.S. food supply consists of ultra-processed products, as noted by the U.S. Food and Drug Administration (FDA). Examples of UPFs include packaged snacks, sugary beverages, and convenience meals such as frozen pizzas. Additionally, many seasoning products and condiments also fall into the UPF category.
The potential impact of UPFs on colorectal cancer risk is concerning. Dr. Chan notes that these foods may contribute to chronic inflammation and metabolic syndrome, both of which are recognized risk factors for colorectal cancer. Furthermore, UPFs can disrupt the balance of beneficial gut bacteria, which may lead to damage to the intestinal lining.
“UPFs can upset the healthy balance of your microbiome,” Dr. Chan explained. “If the microbes in our intestines get disrupted, it’s possible this could lead to some damage to the intestinal lining.” An imbalance in gut microbes can promote inflammation and interfere with normal cellular functions, as highlighted by research published in the journal Cancers.
Conclusions and Recommendations
While dietary factors alone do not fully explain the increase in colorectal cancer rates among those under 50, the findings underscore the importance of diet in cancer prevention. Dr. Chan encourages individuals to consider lifestyle modifications that can help reduce cancer risk.
He advises focusing on a diet rich in plant-based, fiber-rich foods such as fruits, vegetables, legumes, nuts, and whole grains, while limiting the intake of red and processed meats. Maintaining a healthy body weight and engaging in regular physical activity are also essential preventive measures. For those at average risk of colorectal cancer, the ACS recommends beginning screening at age 45.
As research continues, understanding the links between diet, particularly the consumption of ultra-processed foods, and colorectal cancer will be crucial for developing effective prevention strategies.
