The more ultraprocessed foods you eat, the more potential for colon polyps.
Over more than two decades, nearly 30,000 women quietly filled out questionnaires about what they ate, not knowing their answers would one day illuminate a quiet crisis: colorectal cancer arriving earlier in life than it once did. Researchers at Mass General Brigham have now drawn a measurable line between the ultraprocessed foods that define so much of modern eating and the precancerous growths that can precede that disease, finding that women consuming the most such foods faced a 45 percent greater risk than those consuming the least. The finding, published in JAMA Oncology, does not indict any single food or explain the whole of a rising trend — but it places the everyday act of eating within the longer story of how we are shaping our own health across generations.
- Early-onset colorectal cancer is rising in people under 50, and researchers are racing to understand why before the trend deepens further.
- Women eating roughly 10 servings of ultraprocessed foods daily faced a 45 percent higher risk of precancerous colon polyps compared to those eating just 3 — a gap wide enough to demand attention.
- Even after accounting for obesity, diabetes, and low fiber intake, the risk association held firm, suggesting ultraprocessed foods carry independent danger beyond simply marking an unhealthy lifestyle.
- This is the first study to link ultraprocessed food consumption specifically to early-onset colorectal cancer risk, not just the disease in older populations — a distinction that shifts the conversation toward younger patients.
- Researchers are careful to note that diet alone does not explain the full picture, and work is already underway to identify the additional factors driving this troubling pattern in younger adults.
A study tracking nearly 30,000 women over more than two decades has found a significant connection between ultraprocessed food consumption and the development of precancerous colon growths before age 50. Conducted by researchers at Mass General Brigham, the work drew on data from the Nurses' Health Study II, in which participants underwent repeated colonoscopies and reported their diets every four years.
The findings were striking in their consistency: women eating around 10 daily servings of ultraprocessed foods — the sugar-laden, additive-heavy staples of modern convenience eating — faced a 45 percent higher risk of developing adenomas compared to those eating roughly 3 servings. Adenomas are benign but precancerous growths in the colon or rectum, and their presence is considered an early warning sign for colorectal cancer. The relationship appeared dose-dependent, with risk climbing incrementally alongside consumption.
Critically, the association persisted even after researchers controlled for obesity, Type 2 diabetes, and low fiber intake, pointing to ultraprocessed foods as an independent risk factor rather than merely a proxy for broader unhealthy habits. Published in JAMA Oncology, the study marks the first time such a link has been drawn specifically to early-onset colorectal cancer.
Still, the researchers urge caution. Diet does not fully account for the rising incidence of colorectal cancer in younger people — some who eat well still develop the disease, and not all ultraprocessed foods appear equally harmful. With colorectal cancer expected to claim roughly 52,900 lives in the United States in 2025 alone, the team at Mass General Brigham continues investigating what other forces are driving this disease's increasingly early arrival.
Researchers at Mass General Brigham have found a troubling connection between the foods many people eat every day and a cancer that is striking younger women with increasing frequency. The study, which tracked the diets and health outcomes of nearly 30,000 women over more than two decades, reveals that those who consumed the most ultraprocessed foods faced a substantially elevated risk of developing precancerous growths in the colon and rectum before age 50.
The women in the study, all born between 1947 and 1964, participated in the Nurses' Health Study II. Each underwent at least two colonoscopies before turning 50, and every four years they filled out detailed questionnaires about what they ate. The researchers were looking specifically at ultraprocessed foods—the ready-to-eat items loaded with added sugars, salt, saturated fats, and chemical additives that line supermarket shelves and fill convenience stores. The difference in consumption was stark: women eating roughly 10 servings of these foods daily had a 45 percent higher risk of developing adenomas compared to those consuming about 3 servings a day.
Adenomas are benign growths that form in the lining of the colon or rectum, but they matter because they are considered precancerous. They can be early warning signs that colorectal cancer may develop later. The relationship between ultraprocessed food consumption and adenoma risk appeared to be dose-dependent—the more of these foods a woman ate, the higher her risk climbed. This pattern held even after researchers accounted for other known risk factors like obesity, Type 2 diabetes, and low fiber intake, suggesting that ultraprocessed foods themselves carry independent risk, not merely as a marker for other unhealthy behaviors.
The findings, published in JAMA Oncology, represent the first time researchers have specifically linked ultraprocessed food consumption to early-onset colorectal cancer rather than the disease in general. Andrew Chan, the study's senior author and chief of the Clinical and Translational Epidemiology Unit at Mass General Brigham, emphasized that the association remained significant even when controlling for multiple other factors. He noted that the increased risk appears to follow a fairly linear pattern—each additional serving of ultraprocessed food incrementally raises the likelihood of developing these precancerous polyps.
Yet Chan and his colleagues are careful not to overstate their findings. Diet, they acknowledge, is not the complete explanation for why early-onset colorectal cancer is rising. Some people who eat very healthy diets still develop the disease, and some who consume ultraprocessed foods never do. The researchers also note that not all ultraprocessed foods carry equal risk. The work at Mass General Brigham Cancer Institute is now focused on identifying what other factors might be driving this troubling trend in younger patients.
In the United States, colorectal cancer ranks as the third most common cancer overall and the second leading cause of cancer death. For 2025 alone, an estimated 154,000 new cases are expected, along with roughly 52,900 deaths. The rising incidence in people under 50 has become a particular concern for public health officials and clinicians. This new research adds weight to the argument that reducing ultraprocessed food consumption should be part of any strategy to slow the disease's advance, particularly among younger women. But it also underscores how much remains unknown about what drives this cancer's increasing prevalence in younger populations.
Notable Quotes
Our findings support the importance of reducing the intake of ultraprocessed foods as a strategy to mitigate the rising burden of early-onset colorectal cancer.— Andrew Chan, Mass General Brigham Cancer Institute
Diet isn't a complete explanation for why we're seeing this trend—we see many individuals in our clinic with early onset colon cancer who eat very healthy diets.— Andrew Chan
The Hearth Conversation Another angle on the story
Why does it matter that this study focused specifically on women under 50, rather than colorectal cancer in general?
Because early-onset colorectal cancer is a relatively new and growing problem. We used to think of this as a disease of older people. Now we're seeing it in people in their 30s and 40s, and we don't fully understand why. This study helps narrow down one piece of that puzzle.
The 45 percent increase sounds significant, but how do we know that's not just noise in the data?
The study tracked nearly 30,000 women over 20 years with detailed dietary records every four years. That's a lot of data, and the researchers controlled for other major risk factors. The pattern was also dose-dependent—more ultraprocessed food, more risk—which suggests a real relationship rather than coincidence.
But you said diet doesn't fully explain the trend. So what else could be happening?
That's the honest answer nobody has yet. Environmental exposures, changes in the microbiome, infections, stress, sleep patterns—there are many possibilities. The researchers are saying diet is part of the story, but not the whole story.
If someone eats three servings of ultraprocessed food a day instead of ten, are they safe?
Safer, probably. But the study doesn't tell us there's a safe threshold. It just shows that the risk increases as consumption increases. The researchers would likely say the safest approach is to minimize these foods as much as possible.
What counts as ultraprocessed, exactly?
Things like packaged snacks, sugary cereals, instant noodles, mass-produced baked goods, energy drinks—foods engineered to be shelf-stable and convenient, usually high in added sugars, salt, and industrial additives. Not just junk food in the obvious sense, but a lot of what people grab because it's quick.
Does this change how doctors should screen younger people?
It's one more piece of evidence that screening guidelines might need to shift. If you're under 50 and eating a lot of ultraprocessed foods, this study suggests you might want to talk to your doctor about whether screening makes sense for you.