Dear Laura... are ultra-processed foods to blame for the increase in colorectal cancer in younger people?

Welcome to ‘Dear Laura’ - a monthly column where I fashion myself as an agony aunt and answer the questions that readers submit. If you’d like to send in a question for me to answer next month, you can submit it here.

I’m happy to answer Qs about anti-diet nutrition, developing a more peaceful relationship to food and weight-inclusive health, annoying diet trends and news stories, body image challenges, and, of course, challenges with feeding your kiddos. Please give as much detail as you’re comfortable with and let me know if you’d like me to include your name or keep it anon.

Please remember that these answers are for educational purposes only and are not a substitute for medical or nutritional advice; please speak to your GP or a qualified nutrition professional if you need further support.

If you need 1-1 support, I am currently taking on new clients. I can support with a range of nutrition-related issues through a weight-inclusive and mindbody-affirming lens. I especially enjoy working with parents around their children's eating difficulties and how that might intersect with the parent's own relationship with food and their body. If you'd like to find out how I might be able to help, contact hello@laurathomasphd.co.uk to arrange a complimentary 15 minute call.

Dear Laura,

Is there actually any real data to explain the rise in colorectal cancer among younger people? My best friend just got diagnosed at the age of 41 and it is very scary. In conversations and online everyone seems to know it is increasing and feel very confident about why but it's the usual culprits.... "CHEMICALS!", ob*sity, processed foods, etc. Is there any actual data I can cite in these conversations??

Thank you! 

C

Hi C,

Thanks for this question; it’s something I’ve been meaning to look into so I appreciate the nudge. First of all, I’m really sorry to hear about your friend, it sounds really frightening and I hope they are getting the care they need.

Let’s begin by looking at what exactly colorectal cancer is, then look at if there has been a change in rates among younger people, and, if so, why this might be.

To help me, I’ve tapped in CIHAS medical correspondent, Dr. Hammad, a bonafide GP, not an Instagram ~Lyf3sTyl3~ doctor. 

Anyway.

Let’s talk about poop!

The colon and rectum are the bottom length of tube that forms your digestive tract. The colon is known as the large intestine, which is somewhat deceptive as it’s much shorter in length than the small intestine - about 1.5m compared to about 3m of the small intestine. The ‘large’ part refers to the diameter of the tube; the small intestine is much narrower than the large intestine, but overall has much more surface area for absorbing nutrients.  

The colon has three main functions: it absorbs water and electrolytes; it’s where bacteria produce vitamins and these vitamins get absorbed; and it’s where poop is formed and propelled towards the rectum for elimination. 

When we talk about the gut microbiome, we often mean the trillions of bacteria that live in the colon. Complex fibres, from plant-based foods like wholegrains, nuts, seeds, beans and legumes, don’t get fully digested in the small intestine so pass into the colon relatively intact. This becomes a food source for bacteria who break them down through the process of fermentation. This process is generally helpful for the colon and overall health. Bacteria produce B vitamins and vitamin K, which can help make up for some deficiencies in the diet. They also produce short-chain fatty acids which help keep the cells of the colon healthy. 

However some parts of our diet – like cured and red meat – also get fermented by gut bacteria and sometimes produce harmful end products, for example N-nitroso-compounds (NOCs) can form from nitrates in cured meats, which have been identified as carcinogenic and associated with increased colorectal cancer risk.

The colon is one long tube, but can be divided into four parts: the cecum and ascending colon, the transverse colon, the distal colon and sigmoid colon. The sigmoid colon connects to the rectum (which is slightly different in structure compared to the colon) which then leads to the anal passage. 

Colorectal cancer (CRC) is cancer that develops anywhere along the colon and/or the rectum. The severity depends on the size of the cancer and whether or not it has spread to other parts of the body.

I asked Dr. Hammad what we know about the rise in colorectal cancer:

'There is good evidence that CRC incidence has been increasing in younger people in many countries around the world, including in the UK and Europe. Studies use the term ‘early-onset colorectal cancer’ (EO-CRC) to describe a diagnosis in someone under 50 years old. Early-onset colorectal cancer is more likely to be diagnosed at an advanced stage, and with symptoms such as rectal bleeding and weight loss.’

Colorectal cancer is one of the most common types of cancer in the UK. However, Dr. Hammad also made the point that ‘in the UK, more than 90% of all colorectal cancer is diagnosed after the age of 50, and the national bowel cancer screening programme covers those aged between 50-74’. 

So EO-CRC is increasing. Let’s put that into context. The Lancet Oncology published data for 50 countries around the world in 2025. Here I will focus on the four countries that make up the UK (but you can check yours here).

These data are presented as incidence per 100,000 person-years. That is a fancy way of saying that in a single year, per 100,000 people the number of new cases in England has gone from 9 in 1975 to about 12 or 13 in 2020 (ish). 

For NI it has gone from about 10 to 11. Scotland about 9 to 10. And for Wales around 9 to 11/12.

Now these aren’t huge numbers, even when you multiply them by the number of young adults between 18-50 in the UK. 

‘I’ve certainly noticed an increase in younger patients consulting with a concern that their bowel symptoms may be a sign of cancer, so it seems that people are becoming aware of this phenomenon’ Dr. Hammad tells me. ‘However it’s worth remembering that the overall risk of colorectal cancer in this age group, while rising, is still low.’

So, while this phenomenon is real and concerning, it’s helpful to keep in perspective that overall, the chance of developing EO-CRC is low. And the good news is that the number of new cases in the over 50s is going down. 

So, to your question Carynne, what’s behind this (concerning, but small) uptick in EO-CRC? I asked Dr. Hammad his thoughts.