The #1 Food Category Linked To Colon Cancer In Women Under 50

Cancer cases in young adults have surged nearly 80% worldwide over the past three decades. And while population growth accounts for some of that increase, the trend is undeniable: more people in their 20s, 30s, and 40s are developing diseases we once thought of as problems for our parents' and grandparents' generations.

Gastrointestinal cancers, which include colorectal cancer, are growing faster than any other type of cancer in young people. One in 24 men and one in 26 women worldwide will develop colorectal cancer during their lifetime. But what's particularly alarming is who's getting diagnosed. 

According to a recent report from the American Cancer Society, one in five people diagnosed with colorectal cancer are now under the age of 55. And with routine colorectal screening not beginning until age 45, many of these cancers are being caught late, when they're harder to treat.

For years, researchers have been scrambling to understand why. They've pointed to obesity, sedentary lifestyles, and smoking, but none of these factors fully explain the sharp uptick. Now, a first-of-its-kind study published in JAMA Oncology1 is zeroing in on a dietary culprit that's hiding in plain sight: ultra-processed foods.

To examine whether diet quality might influence colorectal cancer risk before age 50, researchers turned to the well-known Nurses’ Health Study II, which has been tracking the health and lifestyle habits of tens of thousands of women since 1989.

Every four years, the women reported how often they ate various foods. Researchers then categorized foods based on the level of industrial processing. 

Women consuming the highest amounts of ultra-processed foods (about 5.7 servings per day, or roughly one-third of their daily calories) had a 45% higher risk of developing precancerous polyps compared to those eating the least. And this wasn't a borderline finding. The relationship was clear and consistent: the more ultra-processed foods women ate, the higher their polyp risk climbed.

What's particularly interesting is that the link was specific to conventional adenomas, the type of polyp most likely to turn into colorectal cancer over time. Researchers didn't see the same association with serrated lesions, another type of polyp. This suggests ultra-processed foods may be triggering specific biological changes that set the stage for cancer development down the line.

The foods most strongly associated with increased risk included the usual suspects, sugar-sweetened beverages, ready-to-eat meals, processed meats like hot dogs and deli slices, but also breakfast cereals, packaged breads, and bottled condiments. You know, the stuff that fills most shopping carts every week. 

These are the convenience foods we've built our routines around—the granola bars in the pantry for busy mornings, the frozen dinners that save us on exhausting nights, the deli turkey we genuinely thought was a decent protein choice.

Scientists still can't say with certainty that ultra-processed foods directly cause colorectal cancer, but they have strong hypotheses about the mechanisms involved. Ultra-processed foods are known to trigger chronic low-grade inflammation throughout the body, including in the gastrointestinal tract. Inflammation creates an environment where cells are more likely to accumulate DNA damage and mutations, aka the first steps toward cancer.

These foods also disrupt the gut microbiome. Ultra-processed foods tend to be low in fiber and high in additives like emulsifiers and artificial sweeteners, which can reduce microbial diversity and promote the growth of harmful bacterial species. 

This study focused exclusively on white female nurses, which means we need more diverse research to understand how these findings apply across different racial, ethnic, and socioeconomic groups. The relationship between diet and disease doesn't affect everyone equally: genetics, access to healthcare, environmental factors, and cultural food traditions all play roles.

But the core message transcends demographics: what we're eating is changing our cancer risk, potentially decades before symptoms appear. The rise in early-onset colorectal cancer isn't happening in a vacuum. It's unfolding alongside dramatic shifts in how we produce, process, and consume food.