Diet and colon cancer risk: New ZOE study

ZOE scientists are currently working in partnership with researchers at King’s College London, Massachusetts General Hospital, Harvard Medical School, and other institutions. 

Collectively known as team PROSPECT, they are focusing on early-onset colon cancer and why it is becoming more common in people under the age of 50.

If you’d like to read more about the steady increase in early-onset cancer in younger people and how PROSPECT started, read this next.

The team's first study was published in JAMA Oncology in November 2025. Here, we explain what they found.

The crunch your gut’s* been craving.

Support gut health* and energy* and enhance the flavor and crunch of your meals.

Try Daily30+

Ultraprocessed food and colon cancer

The latest study investigated links between the consumption of ultra-processed foods (UPFs) and the precursors of early-age onset colorectal cancer. 

These precursors are called conventional adenomas and serrated lesions, which are small growths, or polyps, that line the gut. 

While they are not cancerous themselves, they are a sign of increased risk of bowel cancer.

For instance, it might be that developing the early stages of colon cancer changes your food preferences, making you desire more UPFs. This seems unlikely, but epidemiological studies can’t rule it out.

The latest study from PROSPECT, however, is “prospective,” meaning that a group of people is followed over time — starting before the polyps form. This allows scientists to determine which came first: the UPF or the polyp. 

This study is the first prospective investigation to investigate UPFs and their association with early-onset colon cancer precursors.

Taking a long view

The researchers used data from the Nurses’ Health Study II, a large-scale, long-term study involving female registered nurses. In particular, they focused on those who had: 

• Completed a food frequency questionnaire (FFQ) in 1991.

• At least one lower endoscopy before reaching 50 years of age (a procedure where a camera is inserted into the bowel to look for problems).

• No history of cancer (except skin cancer) before the endoscopy. 

• No colorectal polyp or inflammatory bowel disease (both of which increase bowel cancer risk).

In total, this included data from 29,105 participants who were followed for 24 years.

Soda and savory snacks

In this group, they found that UPFs accounted for 34.8% of their total daily calories, on average. 

This is lower than the average consumption across the UK, which might reflect the fact that the participants are medical professionals.

Even after the scientists adjusted their analysis to account for factors that might influence these results, such as type 2 diabetes, BMI, and nutrient intake, the effect remained significant.

When the PROSPECT team analyzed subcategories of UPFs, they found that artificially sweetened beverages and packaged savory snacks had the strongest associations with cancer precursors.

However, no single category of UPFs could account for the overall effect, suggesting that exposure to a wide range of additives might produce a “cocktail effect.” 

Our new app gives you the power to see beyond the marketing

Make smarter, science-backed food choices in seconds. Scan. Score. Reveal the truth.

Download

Mechanisms and limitations

Although this study wasn’t designed to explore why UPF intake is associated with the risk of developing polyps, the authors offer some potential explanations, including:

• Microbiome disruption: Some additives, like emulsifiers, can disrupt the gut microbiome’s composition.

• Driving inflammation: Increased inflammation is associated with an increased risk of cancer and quicker disease progression.

• Diet-related genotoxins: Compounds that can damage DNA and contribute to cancer risk.

This study adds to our understanding of the links between highly processed foods and colon cancer risk. However, like all studies, it has its limitations. 

For instance, dietary information was collected through FFQs, which are designed to capture how participants ate over the previous year. 

So, it asks questions like “How often do you eat pizza?” And you can respond using a 9-point scale that runs from “Never or less than once per month” to “6+ times per day.” FFQs give a general overview of someone’s long-term diet, but they lack detail. 

As an example, a pizza could be a meat-packed deep pan with a thick layer of highly processed cheese. Or, it could be an olive oil-topped thin crust packed with vegetables and just a little mozzarella. 

We don't buy the hype — and neither should you

Our new app reveals what the food labels won't, using data from the world's largest nutrition study run by ZOE.

Download

What should you do?

It’s important to note that, while this study adds to the evidence, it’s not the type of study that can precisely prescribe how an individual should modify their diet: Nutrition needs to be personalized. 

Also, it’s impossible to cut all UPFs out of your diet, and it’s probably not necessary. Research shows that not all highly processed foods are bad for you.

Instead, focus on following a plant-based, whole-food diet, with an emphasis on colorful fruits and vegetables, nuts and seeds, and fermented foods.

If you’d like to learn more about early-onset colon cancer, watch this episode of the ZOE Science & Nutrition podcast with Dr. Andy Chan, the lead author of this PROSPECT study. 

Andy is also a professor of medicine at Harvard Medical School and program director for gastroenterology training at Massachusetts General Hospital.