Physical hobby loved by millions shockingly linked to colon cancer in young people for first time
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It's an activity loved by the health-conscious, but long distance running might raise the risk of colon cancer in young people.
A study has found that 35 to 50 years old who regularly run marathons are more likely to develop precancerous tumors in their colon, precursors of the disease.
Out of the 100 patients studied by DC-based scientists, 41 percent were found to have at least one adenoma - a benign tumor that could develop into the cancer.
Fifteen percent had advanced adenomas, or more advanced growths. Of these people, more than half reported suffering from rectal bleeding, a warning sign of cancer.
Dr Timothy Cannon, the medical oncologist who led the research, told DailyMail.com that the results were higher than what doctors would expect in the general population and warranted further investigation.
He said that any long-distance runners experiencing warning signs of colon cancer, such as rectal bleeding, should get tested for the disease, regardless of age.
The study was observational so it is not clear if distance running raises the risk of if other lifestyle factors like diet play a role.
But Dr Cannon suggested it could be because running long periods causes blood to be directed away from the colon to the legs, raising the risk of cell death and damaging mutations.
Shown above is colon cancer patient Phil Decker in January 2025, pictured running a marathon with Alecia Allen. He was getting ready to run a marathon when he was diagnosed with stage four colon cancer
Radwah Oda never thought she could get cancer as we was in 'excellent health' at the time of her diagnosis at age 33. She was working out five times a week
He said: 'As a colon cancer oncologist, I had seen several patients die of colon cancer that were in their 30s that ran ultramarathons, which were 50km or higher runs.
'We did this study because we were concerned that these runners were/are diverting all their blood flow to their legs during runs.
'And [then are having] infarcts in their colon, and a lot of cell turnover; the cells die and then turn over very quickly [meaning] there may be more risk of cancer causing mutations.'
Infarcts are area of dead tissue caused by a loss of blood supply. When blood flow is blocked or severely reduced —usually by a clot, embolism, or narrowed vessels — the affected tissue doesn't get the oxygen and nutrients it needs, and it dies.
It is just the latest explanation being put forward by scientists to explain the surge in colon cancer cases among those under 50 years old, with those born in the 1980s now having double the risk of being diagnosed with the cancer compared to their parents.
It is not clear whether long-distance running may also be linked to a higher risk of other cancers that are rising in young people, like in the pancreas.
Many young colon cancer patients have been shocked by their diagnosis, saying they are young, healthy and - they thought - were doing everything right.
Patients include Laurie Koshers, a vegetarian who ran every day, but was diagnosed with colon cancer at age 44 years, and marathon runner John B. Johnson, who was diagnosed at 35 years old.
The latest study was carried out in memory of two patients - Josh Wadlington and Spencer 'Trigg' Robbins - who both battled colon cancer despite running marathons.
The research was presented at ASCO 2025 in Chicago, Illinois, the world's largest gathering of cancer researchers.
Lee Rawlinson, who previously ran marathons, learned that his grandfather had pancreatic cancer and he carries a 'dodgy gene'. It is not clear whether there is a link between long-distance running and other early-onset cancers
Holly Shawyer, 35, was diagnosed with pancreatic cancer last year despite being in peak shape and training for a marathon. It is not clear whether there is a link between long-distance running and other early-onset cancers
'I have always been pretty health conscious – watching what I eat and regularly exercising. I rarely got sick, maybe once every few years I would get a stomach bug,' Ms Shawyer said
Patients aged 35 to 50 years old who were ultramarathon runners were recruited for the study.
This was defined as people who had completed at least two marathons of 50 kilometers (31 miles) or more, or five marathons of at least 42km (26.2miles) or longer.
People who had inflammatory bowel disease or other conditions linked to colon cancer were excluded from the analysis.
Overall, participants had an average age of 42 years, 55 percent were female and they reported running around 32 to 64km (20 to 40 miles) every week.
Between October 2022 and December 2024, patients underwent a colonoscopy - a screening for colon cancer where a flexible tube with a small camera on the end is placed into the colon.
Dr Cannon said they were still investigating other factors that may have put them at risk of developing pre-cancerous polyps.
Preliminary results had shown that runners ate at least five energy bars and also consumed gels daily - which are highly processed foods, with foods in this category previously being linked to a higher risk of colon cancer.
Laurie Koshers (left) was diagnosed with colon cancer after 'doing everything right'. She is a vegetarian and also would run every day
Colon cancer cases are rising among under 50 year olds, even as they fall in older age groups
Dr Cannon added: 'I think that i would get a colonoscopy if you have blood from your stool, even if you are not at the age yet where colonoscopies are approved - or at least i would ask your doctor for one.
'I think bleeding from the rectum in runners is dismissed because it is a known entity, runners colitis is known, and it hasn't been known to be associated with cancer, so it is often dismissed by doctors.
'But my hope is that, with more awareness, people who run long distance and have bleeding will go get a colonoscopy.
'In our study, most of the people who were having advanced adenomas were having blood in their stools.'
The American Cancer Society estimates over 154,000 Americans will be stuck by colorectal cancer this year, including about 20,000 under 50.
While this is roughly in line with two decades ago, the disease is rising sharply in younger groups.
According to the latest data, early-onset colon cancer diagnoses in the US are expected to rise by 90 percent in people 20 to 34 years old between 2010 and 2030.
In teens, rates have surged 500 percent since the early 2000s.
Daily Mail
