Why Colon Cancer Is Rising in Millennials — Risks, Diet, and What You Can Do

Why Colon Cancer Is Rising in Millennials — Risks, Diet, and What You Can Do

Recent data have shown a worrying trend: colorectal cancer rates are increasing among people under 50. The American Cancer Society's 2024 report found that what was once the fourth-leading cause of cancer death for women under 50 is now the second-leading cause in that group. Experts at an SXSW SHE Media Co-Lab panel — including Katie Couric, Dr. Nancy You, Dr. Susan Bullman, and Julie Smolyansky — discussed potential drivers and practical steps to lower risk and catch disease earlier.

What the numbers show

The ACS observed a rise in colorectal cancers among younger adults, and TIME-reported statistics quoted by Katie Couric note that people born in recent generations are about twice as likely to be diagnosed with colon cancer and four times as likely to be diagnosed with rectal cancer compared with those born around 1950. Many younger patients are diagnosed at advanced stages: Dr. Nancy You noted that, unfortunately, most young patients presenting with colorectal cancer are already at stage three or four.

Multiple factors — not a single cause

“Cancer is a complex disease,” Dr. You emphasized. The ACS suggests lifestyle exposures that began with cohorts born around 1950 may play a role. Known contributors include sedentary behavior, alcohol use, smoking, and diet; researchers and clinicians also point to environmental factors that are still being studied (for example, microplastics have been proposed as a possible contributor). Most people diagnosed with early-onset colorectal cancer do not have a hereditary predisposition: the ACS found only about one in three cases had a family history or known genetic risk, and clinicians report many patients lack identifiable predispositions.

Diet, ultraprocessed foods, and the microbiome

A JAMA Oncology study that followed more than 29,000 women from their mid-20s to early 40s (1991–2015) found that women who consumed the most ultra-processed foods — roughly 10 servings a day — had a 45% higher likelihood of having a precancerous polyp associated with the most common type of colorectal cancer than women who ate about three servings daily. While polyps do not always become cancer, they increase risk and are an important warning sign.

Diet shapes the gut microbiome, and the colon harbors the vast majority of our microbial community. Dr. Susan Bullman explained that beneficial microbes help with digestion, vitamin production, immune priming, and maintaining the gut barrier. Diets high in ultra-processed foods — which often include long ingredient lists of emulsifiers, stabilizers, artificial flavors, sweeteners and other additives — can promote inflammation and increased intestinal permeability, sometimes called "leaky gut." These changes may contribute to disease processes and to the development of polyps.

Fermented foods, probiotics and traditional approaches

Fermented foods are one accessible way to support a diverse gut microbiome. Julie Smolyansky described kefir, a fermented dairy drink her family makes and sells through Lifeway, and cited traditional uses and recent research. A February 2025 Mass General Brigham study followed people who regularly consumed fermented dairy and reported a lower incidence of colon cancer over a 30-year period. Dr. Bullman noted that a more diverse microbiome is associated with better outcomes for chronic disease and improved responses to some cancer therapies.

Food-based probiotics (fermented dairy, yogurt, kimchi, kombucha, sauerkraut) are generally preferred by experts to supplements because they provide live cultures in the context of whole foods. As Dr. Bullman said, "The beauty of the microbiome is that it's modifiable" — through diet, fiber, exercise and limiting heavily processed foods.

Screening and acting on symptoms

Screening is a critical tool. Although many guidelines now recommend beginning routine colorectal cancer screening at age 45, uptake is low: only about 20% of people aged 45–49 are currently getting screened. Experts continue to debate whether screening should start earlier, but clinicians stress that screening differs from diagnostic evaluation. If you have symptoms — rectal bleeding, persistent change in bowel habits, unexplained weight loss, or persistent abdominal pain — you should seek evaluation at any age.

Dr. Nancy You: "If you have a symptom, we’re not talking about screening. We’re talking about diagnosis, at whatever age that comes. Don’t delay, don’t wait… be your own advocate and really push for the diagnostic test."

Practical steps to lower risk

• Follow screening guidelines and discuss family history with your clinician; don’t hesitate to request diagnostic evaluation if you have symptoms.
• Reduce intake of ultra-processed foods and prioritize whole foods rich in fiber (fruits, vegetables, whole grains, legumes).
• Include fermented foods (kefir, yogurt, kimchi, sauerkraut, kombucha) as part of a varied diet to support microbial diversity.
• Stay physically active, limit smoking and excessive alcohol, and maintain a healthy weight.
• Avoid unnecessary overuse of antibiotics and antimicrobial products that can disrupt the microbiome; discuss antibiotic use with your doctor.

Takeaway

Rising early-onset colorectal cancer appears linked to multiple, interacting factors — from diet and lifestyle to environmental exposures and microbiome disruption. Screening and prompt diagnostic evaluation of symptoms are essential. Small, sustainable changes to diet and lifestyle can help support gut health, but anyone concerned about their risk should consult a healthcare provider for personalized guidance.