Bowel Cancer Is Rising in Young Adults. Scientists Want Answers

Bowel cancer used to be thought of as an older person's disease, but the numbers no longer fit that picture. Across the world, cases in people under 50 have been climbing for decades, and now British researchers are launching the biggest study of its kind to find out why. They are asking a quarter million adults to hand over detailed information about their diets, lifestyles and health records in the hope of cracking one of the most worrying trends in modern medicine.

The project, called Prospect-UK, is run by researchers at King's College London together with the health science company ZOE. It is funded by Cancer Research UK through the Cancer Grand Challenges programme, with backing from research bodies in the United States and France. Recruitment opened this month, and the goal is to enrol adults aged 18 to 50 from across the UK. According to Cancer Research UK, participants will fill in short online questionnaires about what they eat, how they live, where they live and their health history, and they will be asked to let the team link their answers to their electronic health records so future diagnoses can be tracked over time.

A smaller subgroup will go further, keeping detailed diet diaries and providing blood and stool samples. That deep-dive data will let scientists look beyond broad food categories and examine specific products. As research associate Dr Rosiered Brownson-Smith explains, the study will gather detailed, brand-level information about the foods people actually eat, a first for research on this scale. The distinction matters because, as reported by Hits Radio, around 60% of calorie intake in the UK now comes from highly processed foods, yet those foods differ substantially in their ingredients and processing methods.

Why bowel cancer in under-50s has researchers so worried

The rise is not small and it is not just a British story. Experts say early-onset bowel cancer has increased substantially around the world since 1990, and the UK has one of the fastest-rising rates anywhere. A 2024 analysis from the wider Prospect team found increasing rates of early-onset bowel cancer in 27 of the 50 countries studied, with England recording the fourth-fastest rise of any of those countries between 2007 and 2017, faster than anywhere else in Europe.

Cancer Research UK's own figures tell the same story at home. Bowel cancer incidence rates among 25 to 49-year-olds have increased by more than 50% since the early 1990s. The charity estimates there are about 48,200 new bowel cancer cases in the UK every year, including around 2,900 in people aged 25 to 49. Those numbers are the reason the study needs to be so large: because the disease is still relatively rare in younger adults, only a giant cohort can reveal the patterns that matter.

What a quarter million diets might reveal about bowel cancer

Food is one of the strongest suspects. Professor Sarah Berry, the study's lead researcher and a professor of nutritional sciences at King's College London, says that over just a few generations our lifestyles, diets and environments have changed dramatically, yet nobody knows which of those changes are pushing risk up or down. Her team "urgently need large-scale, long-term data to uncover the true causes," as she put it in the launch announcement.

It is not only diet under the microscope. The gut microbiome, the community of bacteria, fungi and viruses living in our bowels, is another focus, and other research groups have shown these organisms could play a crucial role in raising or lowering cancer risk. Earlier this year, a Prospect sub-team at Harvard University in the United States found signs that cells' "memories" of inflammation could influence how bowel cancer develops, a finding that could open up new prevention strategies. The wider project is also examining how the way younger people are ageing biologically compares with previous generations.

There are important limits to what the study can show. Prospect-UK is observational, so it can identify associations between exposures and health outcomes but cannot directly prove that any one factor causes the disease. It is also not looking at genetics and biology, which may be playing a part in the rise; other arms of the global Prospect team will keep studying those. And for all the alarm, context matters: more than 9 in 10 bowel cancer cases still happen in people over 50, and researchers stress that the disease remains uncommon in young adults.

What you can actually do with this information

Scientists are clear that there is not yet enough evidence to blame any particular food or habit for the rise. But the charity points to several lifestyle changes that can lower bowel cancer risk generally: eating more fibre alongside plenty of fruit, vegetables and whole foods, eating less processed and red meat, staying active, maintaining a healthy weight, limiting alcohol and not smoking.

For anyone who wants to help answer the question directly, the study is recruiting now. The charity says people can sign up through King's College London's Healthspan Connect site if they are between 18 and 50 and live in the UK. The commitment for most participants is modest: periodic online questionnaires plus consent to link health records, with only a small group asked for samples and diet diaries.

The results will take years to arrive, but the researchers say that wait is the point. Big, long-running studies are how public health puzzles like this one eventually get solved, and this generation's shopping lists and eating habits may hold the answer. For a related look at how infections drive another large share of global cancers, see our coverage of the World Health Organization's finding that infections cause one in eight cancers worldwide, and browse more health reporting on the Health topic page.