Cancer cases among young adults have increased nearly 80 percent worldwide over the past three decades. Gastrointestinal cancers, including colorectal cancer, are rising faster than any other type in younger people. One in 24 men and one in 26 women will develop colorectal cancer at some point in their lives. According to a recent report from the American Cancer Society, one in five people diagnosed with colorectal cancer is now under age 55. Because routine screening does not start until age 45, many of these cancers are caught late, when treatment is more difficult.
A new study published in JAMA Oncology examined a dietary factor that may help explain the trend: ultra-processed foods. Researchers used data from the Nurses’ Health Study II, which has tracked the health and lifestyle of tens of thousands of women since 1989. For this analysis, they focused on 29,105 female participants under 50 who had completed detailed food questionnaires, undergone at least one lower endoscopy, and had no prior history of cancer, inflammatory bowel disease, or colorectal polyps at the start of the study.
Every four years, the women reported how often they ate various foods. The researchers grouped foods according to their level of industrial processing. Ultra-processed foods include packaged breads, sweetened beverages, flavored yogurts, breakfast cereals, snack foods, and ready-to-eat meals. These items are often high in calories but low in nutrients and contain additives to improve taste, texture, or shelf life.
Women who consumed the most ultra-processed foods, about 5.7 servings per day or roughly one-third of their daily calories, had a 45 percent higher risk of developing precancerous polyps compared to those who ate the least. The link was strongest for conventional adenomas, the type of polyp most likely to turn into colorectal cancer over time. The study did not find the same association with serrated lesions, another type of polyp. This suggests ultra-processed foods may trigger specific biological changes that set the stage for cancer development.
The foods most strongly linked to higher risk included sugar-sweetened beverages, ready-to-eat meals, processed meats such as hot dogs and deli slices, as well as breakfast cereals, packaged breads, and bottled condiments. These are common convenience foods that many people eat regularly.
Possible reasons for the link
Scientists have several hypotheses about how ultra-processed foods might drive precancerous changes. These foods are known to cause chronic low-grade inflammation throughout the body, including the gastrointestinal tract. Inflammation can create an environment where cells are more likely to accumulate DNA damage and mutations, which are early steps toward cancer. Ultra-processed foods also disrupt the gut microbiome. They tend to be low in fiber and high in additives such as emulsifiers and artificial sweeteners, which can reduce microbial diversity and promote the growth of harmful bacteria. In addition, many ultra-processed foods contain advanced glycation end products, or AGEs, which form when proteins or fats combine with sugars during high-heat processing. AGEs build up in body tissues and are linked to oxidative stress and inflammation.
Implications for women’s health
With early-onset colorectal cancer rising and screenings still recommended to start at age 45, prevention becomes especially important. The study authors note that reducing ultra-processed staples such as packaged breads, sweetened yogurts, cereals, flavored coffee creamers, and bottled sauces can help. Prioritizing fiber-rich whole foods, aiming for 25 to 35 grams of fiber daily from vegetables, beans, whole grains, berries, nuts, and seeds supports the gut microbiome. Keeping sugary drinks to a minimum is also advised. Choosing foods with shorter ingredient lists can help avoid ultra-processed items. People should know the warning signs of colorectal cancer: persistent changes in bowel habits, blood in the stool, unexplained weight loss, ongoing abdominal cramping, or unusual fatigue. When caught early, the survival rate for colorectal cancer is above 90 percent.
The study focused on white female nurses, so more research is needed in diverse populations. Genetics, access to healthcare, environmental factors, and cultural food traditions all influence the relationship between diet and disease. The core message, however, is that dietary choices made today can affect cancer risk decades later. Unlike genetic risk factors, diet is something people can change.
