Humans have changed a lot recently.  

We eat differently, work differently and play differently than the people who were here just a couple of generations before us, in environments they might struggle to recognise. And while we tend to live longer, we also face different health risks.

Over the past few years, scientists have uncovered a concerning rise in the number of people developing bowel cancer before they turn 50. It’s a pressing problem, but with so much changing so quickly, working out what’s behind it is a huge challenge.

Now, researchers are calling on the UK public to help find the answers. The PROSPECT-UK study, which Cancer Research UK is funding through Cancer Grand Challenges, aims to recruit 250,000 people aged 18 to 50 to share information that could show how diet, lifestyle and environment might contribute to bowel cancer risk in younger people.

It takes a trial this big to start picking out the patterns and trends that matter. Thankfully, early-onset bowel cancer is still relatively rare, so researchers need to study very large groups of people to spot the crucial details.

“Over just a few generations, our lifestyles, diets and environments have changed dramatically,” says Professor Sarah Berry, PROSPECT-UK’s lead researcher, from King’s College London. “But we don’t know which of these changes are increasing people’s risk of bowel cancer or which ones could help reduce it. We urgently need large-scale, long-term data to uncover the true causes.”

That data will play a key role in the wider Cancer Grand Challenges team PROSPECT’s global effort to understand and ultimately tackle the problem of bowel cancer in under-50s.

Early-onset bowel cancer and PROSPECT-UK

Bowel cancer has long been considered a disease of older adults, and more than 9 in 10 cases still happen in people over 50.

However, recent studies have shown that bowel cancer incidence rates in younger people are rising around the world, even as they stabilise or fall in older age groups. 

In 2024, other researchers from PROSPECT found increasing rates of early-onset bowel cancer in 27 of the 50 countries they looked at. England saw the fourth-fastest rise of any of those countries between 2007 and 2017, faster than any other country in Europe.

Cancer Research UK’s stats tell a similar story: UK-wide, bowel cancer incidence rates in 25 to 49-year-olds have increased by more than 50% since the early 1990s.

PROSPECT-UK is an important step toward understanding what’s behind these increases. It’s an observational study, so it can’t directly prove causes on its own, but people who take part will provide crucial information to help researchers identify some of the likeliest culprits and guide the next phases of research.

It’s important to note that factors PROSPECT-UK isn’t looking at, like genetics and biology, may also be playing a part in the rise. The wider PROSPECT team will keep studying a range of potential contributors and investigating how they might combine to shape someone’s overall risk of early-onset bowel cancer.

Studying diet and lifestyle

The research team will ask PROSPECT-UK participants to complete short online questionnaires on their diet, lifestyle, environment, health and other factors, and to give consent to link their electronic health records. This will help the study spot any associations between the things people are exposed to and their health outcomes. A small subgroup will also be invited to complete more detailed diet diaries and provide blood and poo samples.

“Our food environment has become increasingly complex, and this means we need to look at diet in much greater detail,” explains Dr Rosiered Brownson-Smith, a PROSPECT-UK research associate at King’s College London.

This will involve looking beyond broad categories like ultra-processed foods to understand how specific food items might influence cancer risk.

“In the UK, around 60% of our calorie intake comes from highly processed foods, but these foods are not all the same,” says Brownson-Smith. “They can differ substantially in their ingredients, processing methods and nutritional composition – even within the same food category.

“PROSPECT-UK is innovative because, for the first time, we are collecting detailed, brand-level information about the foods people actually eat. This will allow us to better understand which foods and dietary patterns may be linked to the development of early-onset bowel cancer.  

“Combining detailed dietary information with long-term health data, we hope PROSPECT-UK will help us better understand the complex relationship between what we eat and our risk of disease.” 

A global, interdisciplinary effort to understand early-onset bowel cancer

As big as PROSPECT-UK might be, it’s just one element of PROSPECT’s work. The wider research group is studying both the patterns in people’s lives and risk levels, and the changes that can happen inside our bodies and cells.

We’re still in the early phases, and there’s much more work to do, but the progress so far has been encouraging. Earlier this year, one of the team’s projects at Harvard University in the US found signs that cells’ “memories” of inflammation could influence how bowel cancer develops, which could help lead to new prevention strategies. Other sub-teams have also used pre-existing population data to open up new ways of thinking about early-onset bowel cancer, including by considering how it might be linked to changes in the way younger people are ageing compared to previous generations.

PROSPECT-UK is also joining other aspects of PROSPECT in looking at the gut microbiome – the community of tiny organisms living in our bowels. As other research groups have shown, this remarkable collection of bacteria, fungi and viruses could play a crucial role in raising or lowering cancer risk.

If you’d like to be part of PROSPECT’s work, you can sign up for PROSPECT-UK on King’s College London’s Healthspan Connect site. And if you’d like to find out more about the overall project, you can listen to Professor Andrew Chan, one of the team’s two co-leads, in this episode of That Cancer Conversation: