Colon Cancer: Should Young People Worry?

Summary

Science Vs – "Colon Cancer: Should Young People Worry?"

Host: Michelle Dang (with Rose Rimler)
Date: March 19, 2026
Podcast: Science Vs (Spotify Studios)

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Episode Overview

In this episode, guest host Michelle Dang investigates the alarming rise in colon and rectal cancer diagnoses among young adults. Through personal stories, expert interviews, and the latest scientific research, the team explores why more young people are being affected, what symptoms to watch for, the potential causes behind this uptick, and what we still don’t understand about early-onset colorectal cancer.

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Key Discussion Points & Insights

Becca’s Story: A Young, Active Patient Diagnosed With Colon Cancer

• [00:00–05:50]
  • Introduction to Becca Lynch, who was 28 when she began experiencing abnormal bowel habits, including frequent stools, blood, and "pencil-thin" shape.
  • Initial hesitation to seek medical care, eventually prompted by social media content about colon cancer symptoms.
  • Upon colonoscopy, she learns she has a 5cm (lemon-sized) tumor. Diagnosed with stage 3 colon cancer at 29, despite lacking risk factors or family history.
  • Notable Quote:
    • “If it is cancer, which I’m certain that it is, you’ll be the youngest person I’ve ever seen with it.” — Becca's doctor ([04:09])
  • Emotional shock and rapid transition to coping and treatment.

The Broader Trend: Colon Cancer Rising in Young Adults

• [06:58–10:55]

  • Statistical rise: 1 in 5 colorectal cancer diagnoses now occur in people under 55; previously, it was 1 in 10.
  • High-profile cases noted, e.g., Chadwick Boseman (died at 43) and James Van Der Beek (died at 48).
  • The disease is still uncommon in the young (under 1% risk if <50), but the increase is real.
  • Millennials (now 40) have 2–3 times the risk of colon cancer as 40-year-olds from earlier generations.

• [10:00–13:00]

  • Colorectal cancer recently became the leading cause of cancer death in Americans under 50.
  • Young adults are often diagnosed at later, more dangerous stages (stage 3 or 4), making it harder to treat.
  • Quote:
    • "Your chance of dying within five years with colorectal cancer at stage four is about 80%." — Michelle Dang ([10:54])
  • Late diagnoses are not because tumors are more aggressive, but because they’re often caught later in younger people.

Why the Late Diagnoses in Young Adults?

• [13:00–17:00]
  • Young adults typically aren't screened (colonoscopies are generally offered starting at age 45).
  • Symptoms (like back pain, blood in stool, thin stools) can be missed or attributed to less serious conditions.
  • Expert Input:
    • "Once they're diagnosed, the tumor behaves pretty similarly to a dozen adults... Not their fault, but they've had a longer amount of time before they were diagnosed to catch this." — Dr. Michael Foote ([11:33], [11:59])
  • Many young patients are initially told they're too young to have cancer; diagnosis is often delayed by 40% compared to older adults.
  • Studies show young adults’ first symptoms are frequently mistaken for IBS, hemorrhoids, etc.

What Symptoms Should Young People Watch For?

• [15:43–17:03]
  • Don’t panic over short-term changes in bowel movements, but persistent symptoms (>2 weeks) are cause for concern:
    • Changes in stool frequency/shape (especially “pencil-thin” stools)
    • Blood in stool (especially dark, tarry, or mucusy blood)
    • Persistent abdominal pain
    • Unexplained back pain (rare, but can be a sign if cancer metastasized)
  • Quote:
    • "If there's a tumor there, it starts to press on the colon... Like a little cylinder squeezes the stool into a thinner shape." — Dr. Michael Foote ([16:07])

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What's Driving the Rise? Investigating the Causes

[21:48–35:04]

The Usual Suspects: Environment and Diet

• Ultra-Processed Foods:

  • Large study of nurses found 45% higher rates of polyps (which can become cancerous) in those who ate the most ultra-processed foods. ([22:26])
  • Red and processed meats, preservatives, and lack of fiber are also implicated.

• Other Risk Factors:

  • Obesity, inactivity, smoking, and alcohol are known contributors.

• But: Even very healthy young adults sometimes get the disease, suggesting more factors are at play.

  • Expert Input:
    • "Most of the people that we see are actually pretty healthy... that’s kind of the scary thing, I think, for all of us." — Dr. Michael Foote ([24:51])
    • Personal story: Patient who was vegan, nonsmoker, and rarely drank alcohol still got colon cancer.

New Lead: The Colibactin Hypothesis

[25:58–35:04]

• Genetic Detective Work:

  • Prof. Lyudmil Alexandrov analyzed genetic "fingerprints" (mutational signatures) in tumors of young and old patients.
  • Found 50%+ of young patients' tumors showed a unique pattern linked to bacterial toxins, particularly colibactin (produced by some E. coli).
  • Quote:
    • "Essentially, the difference was striking. If you look at individuals who are younger than 40, more than 50% of them had these very specific patterns of mutations." — Prof. Lyudmil Alexandrov ([28:12])
  • Colibactin is a bacterial toxin (produced by certain gut bacteria) that can mutate gut cells' DNA.

• When Does Exposure Happen?

  • Most colibactin-linked mutations occurred very early in life — often before age 10, possibly in the first two years. ([32:05])

  • The gut microbiome and immune system are especially vulnerable in young children.

  • Possibilities: changes in antibiotic use, birth practices (C-section rates), exposure to certain bacteria in early childhood.

  • Quote:

    • “We think it’s happening something in very, very early life...when you have a young child...their microbiome and their immune system are getting formed...and if they get this infection, they get many, many mutations.” — Prof. Lyudmil Alexandrov ([32:05])

• Caveats:

  • The link is “correlation, not causation”—it can’t be proven directly in humans.
  • Other suspects may include other microbes, viruses, antibiotics, or environmental exposures ([34:44]).

---

Becca’s Prognosis and Reflections on Healing

[35:03–37:39]

• Becca underwent surgery (removal of tumor, lymph nodes, 1 foot of colon) and chemotherapy.
• Celebrated the end of chemo with friends—with, humorously, lots of cheese on advice from her treatment dietitian.
• Ongoing surveillance: scans and bloodwork every 3 months for 2 years with a 25% recurrence risk.
• Notable Quote:
  • “I think I would tell myself, it’s going to be okay and, you know, your friends are going to show up in ways that you would never have expected. And like, that’s what’s really going to get you through it is the people in your life.” — Becca Lynch ([37:35])

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Memorable Quotes & Moments

• “We found a mass. It's 5 cm, about the size of a lemon.” — Becca Lynch recounting her doctor’s diagnosis ([04:03])
• “Colorectal cancer was just declared the leading cause of cancer death in people under 50.” — Michelle Dang ([10:00])
• “Your chance of dying within five years with colorectal cancer at stage four is about 80%.” — Michelle Dang ([10:54])
• “If you see changes or feel pain that lasts for weeks, then get it checked out.” — Dr. Michael Foote ([15:45])
• "It's sneaking up on people and their doctors too, and getting found after it's had a lot of time to get dangerous." — Michelle Dang ([17:52])
• “What we think happens is that when you have a young child... their microbiome and immune system are getting formed... if they get this infection, they get many, many mutations...” — Prof. Lyudmil Alexandrov ([32:05])
• "You have to learn how to let the love in... you can’t do this by yourself... your friends are going to show up in ways that you would never have expected." — Becca Lynch ([37:35])

---

Timestamps of Important Segments

• [00:00–05:50] — Becca’s personal journey and diagnosis story
• [06:58–10:55] — Exploring the trend: colon cancer increasing in the young
• [13:00–17:00] — Why are young adults diagnosed so late? Symptoms and screenings
• [21:48–25:14] — Environmental factors, diet, and “standard” risks
• [25:58–35:04] — New genetic and microbiome evidence (colibactin hypothesis)
• [35:03–37:39] — Becca’s treatment, recovery, and life lessons

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Final Thoughts

This episode makes clear that while lifestyle factors like diet and exercise do matter, they don't explain the entire increase in young-onset colorectal cancer. There is emerging evidence that early-life exposures to certain gut bacteria (and their DNA-damaging toxins) could set the stage for cancer decades later. But much remains uncertain—and researchers are urgently seeking answers.

Through Becca’s powerful story and the voices of scientists, "Science Vs" gives listeners a nuanced, science-driven understanding of this worrying – but still rare – trend.

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For more information and citations, see the transcript in the show notes.

Transcript

[Michelle Dang]

Hi, I'm Michelle Dang, and I'm filling in for Wendy Zuckerman this week. And to start off today's episode, I want you to meet Becca Lynch. Becca lives in Colorado with her dog. She's 30 years old now, but throughout her 20s, she was leading a pretty hectic life.

[Becca Lynch]

Kind of have always been pretty, like, full steam ahead. I've never been, like, comfortable not being busy, just.

[Michelle Dang]

She was getting her master's, growing her career, and being super active.

[Becca Lynch]

I go, like, climbing. I go to the gym. I was running a lot. I did a Half Marathon in 2024, playing live music. Yeah, I have a little duo with a friend of mine that we play around town sometimes.

[Michelle Dang]

But a couple of years ago, when Becca was 28, she noticed a change in her body. Specifically in one area, the poo department. She noticed she was going number two more often, like, five to six times a day. And it wasn't just that. There were a couple weird things she saw in these frequent poos. And fair warning, we're about to get a bit detailed here. So for one thing, there was blood.

[Becca Lynch]

It was like a dark, almost mucusy kind of thicker, bloody substance that was everywhere, like, when I was going to the bathroom, and it was every single time.

[Michelle Dang]

And the other thing she noticed is that her poo started to take on a different shape than usual.

[Becca Lynch]

Like, thinner. Size wise, like, pencil thin. I did the thing that everybody does. Like, I googled it, obviously. I googled all my symptoms.

[Michelle Dang]

The results spit out quite a list of things it could be. Ulcerative colitis, ibs, Crohn's disease. Becca thought she should get it checked out, but didn't go in right away. And then one day, she was scrolling on social media.

[Becca Lynch]

Someone's video came across my feed. I think it was on Instagram, of someone talking about the exact same symptoms. She had said, like, for years she thought she just had hemorrhoids, right?

[Michelle Dang]

But this woman didn't have hemorrhoids. She had something a lot. Colon cancer. It was really advanced, stage four. And she was making these videos to tell people what to watch out for. And this was the push that Becca needed.

[Becca Lynch]

I think it definitely solidified. Like, okay, I should go to the doctor.

[Michelle Dang]

Her doctor ordered a colonoscopy. So Becca eventually went through the prep where you have to drink this gross liquid and poo a whole lot. And then she went in.

[Becca Lynch]

I went there first thing in the morning. They just took me back. And I met the doctor who was gonna be doing it. You know, he was Very, like, chipper. And just like, yeah, we're gonna figure out what's going on. He's like, could be a bunch of things. Like, it might just be hemorrhoids. Like, don't worry about it. You're gonna be in and out of here. In, like, I'll see you in there. And then they rolled me back, and that was it. I took a. Took a lovely nap.

[Michelle Dang]

When Becca woke up, there was a nurse there. And immediately Becca could tell something wasn't good. The nurse told her she was going to go out to the waiting room to get Becca's friend, who had come to pick her up.

[Becca Lynch]

And she was just like, we're bringing your friend back because the doctor has to tell you something. And I was like, something bad. And she was like, yeah. And then she left. I waited there for 10 minutes. She left me with a bag of Goldfish and a Sprite. I sat there and waited, and eventually my friend came back, and I was. I was trying to keep it light, but at that point, I think I kind of knew, like, I knew it wasn't going to be good. Obviously, the doctor came back in, and I just remember, like, it was more so his body language and, like, facial expressions that were more upsetting than, like, what he was saying, because he had been this very, like, chipper, bubbly person before. Like, the last time I'd see him, when he came back in, he was very sad, and he, like, sat at the foot of my bed, and he just was like. We found a mass. It's 5 cm, about the size of a lemon.

[Michelle Dang]

For Becca to officially get a diagnosis, the doctor told her she would need more scans and surgery.

[Becca Lynch]

And he kind of ended it with being like, if it is cancer, which I'm certain that it is, you'll be the youngest person that I've ever seen with it.

[Michelle Dang]

Becca was eventually diagnosed with stage three colon cancer at age 29. And this was really weird. She didn't have any of the usual risk factors. They ran genetic tests and didn't find any explanation. It all felt very strange.

[Becca Lynch]

I knew that it was happening, but it really felt like I was, like, watching it happen to someone else. But from that moment on, time kind of split. And I just went into this kind of numb headspace of, all right, well, we have to deal with this. So, you know, we're going to deal with it, and we'll figure it out.

[Michelle Dang]

And Becca isn't the only person having to deal with this and figure it out. Around the world, more and more young adults are getting diagnosed with colorectal cancer in the U.S. one in five people diagnosed with it are now younger than 55. That's a big increase from just a few decades ago when only one in 10 colorectal cancers were being diagnosed in younger people. And that's not the only concerning thing. We're hearing that young adults are more likely to get diagnosed with a cancer that has already progressed pretty far despite being otherwise healthy. So today on the show, we're going to talk about what exactly is going on here. Why are so many young people suddenly turning up with this type of cancer? And we'll hear more about what this has looked like for Becca. All that is coming up.

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[Michelle Dang]

Welcome back. I'm producer Michelle Dang. Today on the show, we're looking at colorectal cancer. And with me is senior producer Rose Rimler. Hey, Rose. Hi, Michelle. You know, Rose, I wanted to make this episode cause I kept seeing scary headlines about this about colorectal cancer increasing in young people. Have you been seeing these headlines, too?

[Rose Rimler]

Yes, I have. I've been seeing headlines about people getting colorectal cancer really young. And there's been some really high profile people that have gotten it and unfortunately actually died from it. So I'm thinking of the guys from Black Panther. That was a little while ago.

[Michelle Dang]

Yeah. Chadwick Boseman.

[Rose Rimler]

Yes.

[Michelle Dang]

Yeah. He died from it in 2020 and he was only 43.

[Rose Rimler]

That's awful.

[Michelle Dang]

Yeah. And then just last month, the actor James Van Der Beek, he also died from colorectal cancer. And he was 48, right? Yeah. And by the way, this term, colorectal cancer it includes both colon cancer and rectal cancer, and sometimes also called bowel cancer.

[Rose Rimler]

Okay, got it.

[Michelle Dang]

And for years, doctors have thought of these cancers as cancers that older people get. In fact, Becca ran into this too.

[Becca Lynch]

The hospital that I went to, they put me in this support group. It was like a zoom support group for other people with GI cancers. And I joined it once, and it was like, me and then four women, all in their, like 70s and 80s, and they were all so kind and so lovely and they were very sweet to me. And like, I think one of them told me she was pissed off at God on my behalf, which I thought was very sweet.

[Michelle Dang]

And the thing is, like, these cancers are still more common in older people. If you are under 50, the risk of getting this cancer is actually very low. Way less than 1%. But this increase is real and it's freaking doctors out.

[Rose Rimler]

So it's not. Cause sometimes you hear about a disease going up and it turns out what's really happening is that doctors are getting better at catching it or diagnosing it or something. But in this case, it sounds like what you're saying, Michelle, is that, no, it's actually going up in young people.

[Michelle Dang]

It's simply going up. There's more cases and there's more deaths.

[Rose Rimler]

Okay.

[Michelle Dang]

And doctors really caught onto this in the 90s, but the risk keeps increasing with each generation. Like take a 40 year old who's part of the millennial generation.

[Rose Rimler]

My generation.

[Michelle Dang]

Oh, your generation.

[Rose Rimler]

Yep.

[Michelle Dang]

And compare it to a 40 year old who's part of the boomer generation.

[Rose Rimler]

My generation spiritually.

[Becca Lynch]

No, I'm just kidding.

[Michelle Dang]

Yeah. So that the 40 year old millennial compared to a 40 year old boomer, the millennial has a two to three times greater risk of developing colorectal cancer.

[Rose Rimler]

So if you're 40 now, basically your risk of colon cancer or colorectal cancer is higher than someone who was 40, you know, in the 80s or 90s.

[Michelle Dang]

Yes, exactly. Geez.

[Rose Rimler]

Wow. That's real.

[Michelle Dang]

Yeah.

[Rose Rimler]

Yeah.

[Michelle Dang]

And in the us, Colorectal cancer was just declared the leading cause of cancer death in people under 50. It's led to nearly 4,000 deaths a year.

[Rose Rimler]

Wow.

[Michelle Dang]

So the thing I want to talk about next is the fact that when young people are diagnosed with this cancer, a lot of the time it's really serious. You hear about people turning up with stage three or stage four cancer upon diagnosis. And studies have found that more than half of cases in early onset colorectal cancer are caught at these later stages.

[Rose Rimler]

That sucks.

[Michelle Dang]

Yeah. This makes this cancer sound really scary, because stage four, for example, is when the cancer has already start to spread to different organs and other parts of the body. And if this is the case, it can be incredibly hard to cure. Your chance of dying within five years with colorectal cancer at stage four is about 80%.

[Rose Rimler]

Wow.

[Becca Lynch]

Okay.

[Michelle Dang]

So I wanted to find out, like, why is this.

[Rose Rimler]

Yeah. What's going on here?

[Michelle Dang]

So I called up Dr. Michael Foot. He's a gastrointestinal oncologist from Memorial Sloan Kettering Cancer center, and he's been watching what's going on here.

[Dr. Michael Foote]

We've been worried about this for a while, you know, over 10, 15 years. But it has reached a critical point in the last few years.

[Michelle Dang]

And I wanted to know, is there something weird or creepy about the colorectal cancer that young people are getting? Like, is it moving faster or is it more aggressive? And Michael told me, no. Based on the studies we have, it

[Dr. Michael Foote]

looks like once they're diagnosed, the tumor behaves pretty similarly to a dozen adults. It responds to treatments in the same way. It can be just as aggressive.

[Michelle Dang]

So why are young people showing up sicker? Michael says that young people's symptoms tend to be worse and the cancer spread further, not because of this, you know, idea that cancer is more aggressive, but because it's often getting caught a lot later than it is in older people.

[Dr. Michael Foote]

Not their fault, but they've had a longer amount of time before they were diagnosed to catch this.

[Rose Rimler]

Well, that makes sense to me, Michelle, because they're not routinely getting screened because they're too young to start getting screened with colonoscopies. So if there was a really young cancer, a really new cancer that wasn't causing any symptoms, there would be no way for them to know. But an older person who is getting screened, that would get. That would get picked up.

[Michelle Dang]

Yeah, exactly. Like, the main reason that we find this cancer is with a colonoscopy, and we're just not usually giving those to young people unless something is wrong. And what is interesting is that in older people in the US Rates of this kind of cancer have actually been decreasing. Like, fewer people are getting it, Fewer people are dying from it. And we think that's partly because we've gotten, like, pretty good at getting older people to go get colonoscopies regularly where they can catch polyps in your gut that might turn into cancer.

[Rose Rimler]

So the rates in older people are going down, but the rates in younger people are going up?

[Michelle Dang]

Yeah, it's this dichotomy or discrepancy of, like, why. Why Is it going down for most of the people who are getting this, but going up, particularly for young people. And because of that, several years ago, doctors did decide to lower the recommended age for your first colonoscopy for most people from 50 to 45. There's actually people who say it should be even lower.

[Rose Rimler]

Okay.

[Michelle Dang]

Another piece of all of this is that for a lot of these young people, the symptoms can be easily confused for other things. Here's Michael again.

[Dr. Michael Foote]

I have a young person right now who's in their 30s, in their mid-30s, who has an extremely aggressive cancer type that is very, very sick with metastases all over his bones.

[Michelle Dang]

So this patient of Michael's has stage four colon cancer. And what's weird is that Michael told me that their main symptom was back pain.

[Rose Rimler]

Wow. Okay. I mean, that could be anything. Like, who doesn't have back pain? I could imagine you wouldn't go and get seen for that, you know, certainly not by an oncologist who would think you'd have cancer just because your back hurts.

[Michelle Dang]

Yeah, exactly. Here's Michael.

[Dr. Michael Foote]

Why are you having so much back pain? Why is this going on? No one would ever think about colon cancer. And then we found it. You know, we found it on a colonoscopy, and he's been ongoing with treatment.

[Michelle Dang]

How did that patient react when they heard the news?

[Dr. Michael Foote]

They were absolutely terrified.

[Michelle Dang]

Yeah. And the real reason this patient had the back pain was because a cancer had spread to his spine.

[Rose Rimler]

Are they still with us?

[Michelle Dang]

They are, yeah. And, you know, it's not great. They're treating the cancer, but it's aggressive. So basically, Michael and his team are just trying to make him feel better and give him as much time as they can.

[Rose Rimler]

Less pain, at least.

[Michelle Dang]

Mm. Yeah. Now, Michael says that back pain as the only symptom is extremely rare.

[Rose Rimler]

Yeah. We're really freaking everyone out, Michelle, with that one, with that story.

[Michelle Dang]

I'm sorry. Yeah. But, you know, changes in your stool are much more common. Okay. Like, blood in your. Your stool and even abdominal pain. But even. Even those symptoms are something that you could mistake for something else.

[Rose Rimler]

Okay. Actually, Michelle, I have a question for you. I have seen, like, a lot of chatter about this online, and people talking about, like, symptoms to watch out for, but mostly they just say, like, look for any change in your bowel movements. It's like, get that checked out. And I find that really broad, like, not very helpful.

[Michelle Dang]

I've seen those kinds of videos, too, and I'm curious, too. Like, what. What exactly should you look for in Your.

[Rose Rimler]

Yeah.

[Michelle Dang]

And so I asked Michael for you.

[Rose Rimler]

Thank you.

[Michelle Dang]

He told us that you shouldn't panic over a few weird poo days. But it's more like if you see changes or feel pain that lasts for weeks, then get it checked out. This includes things like diarrhea, constipation, and dark tarry stools or blood, like what Becca saw. And Michael has some more particular advice here too.

[Dr. Michael Foote]

What we typically say with the stool is the stools become thinner, meaning, you know, if there's a tumor there, it starts to press on the colon and, like a little. Like a little cylinder squeezes the stool into thinner shape. Right. Cause if there's less space in the tunnel, you have a smaller diameter there for the stool to go through, so it starts to get thinner.

[Michelle Dang]

And while Becca, she had a lemon sized tumor in her colon.

[Rose Rimler]

Right. And she was talking about the skinny stools as well.

[Michelle Dang]

Mm.

[Becca Lynch]

Like, the mass was putting a lot of pressure on my colon, which was obviously making me having to go to the bathroom a lot more often. And the mass was also what was bleeding. So that's where the blood was coming from. That makes sense.

[Michelle Dang]

But Becca's experience with her cancer speaks to another huge problem that doctors are seeing. Because some of this stuff, like some of these poo symptoms, they often don't show up until the cancer is already pretty far along, when the tumor is already there and has had a chance to grow and cause problems.

[Becca Lynch]

Which is still so crazy to me because when I think about how long I was having symptoms, really, it was, like, noticeable symptoms were only a few months, and it was still stage three. Yikes.

[Michelle Dang]

And that, plus the fact that some of the symptoms can be vague, means that sometimes young people get misdiagnosed by doctors or even told they're too young to have colorectal cancer. So, you know, they don't get the tests that they need. Like, in a big survey, four in 10 young people with colorectal cancer were initially told that they were too young to have it.

[Rose Rimler]

Oh, wow.

[Michelle Dang]

Okay. Overall, it can take, like, a really long time for young people to get diagnosed. And one study found that compared to older people, young people waited 40% longer to get a diagnosis from an oncologist.

[Dr. Michael Foote]

So by the time they get to us, it's further along in their disease course.

[Michelle Dang]

So bottom line, it's not the disease itself that's doing something weird. It seems to be more like it's sneaking up on people and their doctors, too, and getting found after it's had a lot of time to get dangerous So I guess that answers the question

[Rose Rimler]

of why is it more likely to be caught at a later stage in younger people. But it doesn't answer the question of why are younger people getting it at all in such increasing numbers?

[Michelle Dang]

Yes, that is the big question. And actually we'll be looking at that next. Why is this all happening?

[Rose Rimler]

Because I'm very impatient. I want to know now.

[Michelle Dang]

Yes. So after the break, we'll take a look and talk to a scientist who's trying to find out.

[Rose Rimler]

Okay, I can't wait till after the break.

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[Michelle Dang]

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[Michelle Dang]

Welcome back, I'm Michelle. Dang. We just learned that colorectal cancer is on the rise in young people and the question now is why? So we're on the trail trying to figure it out. Like what the hell is going on here? And I'm here with senior producer Rose Wermiller.

[Rose Rimler]

Hello.

[Michelle Dang]

Hey Rose. So yeah, one thing that comes up a lot is diet. People are eating a lot more ultra processed food than they were before. And a big study just came out on this. It looked at this big data set of almost 30,000 nurses and their health. I don't know if you're familiar, like the nurses.

[Rose Rimler]

The nurses health study. Yeah, yeah.

[Michelle Dang]

It's a group of nurses that have been followed for a long time and used in a bunch of studies. And what they found in this study is that people who ate the most ultra processed food had a 45% higher chance of having polyps in their gut. Which polyps can be harmless, but sometimes they do lead to cancer.

[Rose Rimler]

Okay. So people who ate more ultra processed food had more polyps. Very suspicious. It's not super surprising because as we know from the ultra processed foods episode, they tend to be associated with a lot of bad health outcomes. As we know from the fiber episode, if you're not eating a lot of vegetables, you need the fiber and vegetables. So that all makes sense that that would be bad for your gut and probably create an environment that could be helpful for growing cancer.

[Michelle Dang]

Yeah, it's like, we always come to that conclusion in science versus Episodes.

[Rose Rimler]

We do. It's like, eat vegetable.

[Becca Lynch]

Okay.

[Rose Rimler]

Over and over and over and over.

[Michelle Dang]

Yeah. And that is because we do think there's some stuff that could be causing problems in ultra processed foods, like preservatives. And then we also know that eating a lot of red meat, especially charred meat and processed meats, are linked to some cancers, too.

[Rose Rimler]

Yeah. Actually, working on the ultra processed food episode, I stopped buying, like, lunch meat.

[Michelle Dang]

Oh, really?

[Rose Rimler]

Sometimes I'd have, like, turkey. Sliced turkey meat. Yeah, I don't. I don't eat that anymore.

[Michelle Dang]

Sliced turkey meat?

[Rose Rimler]

Yes, because it has nitrates and nitrites in it, and that has been associated with cancer.

[Michelle Dang]

What about cheese boards?

[Rose Rimler]

Cheese boards? Does that count?

[Michelle Dang]

Oh, sorry, I meant, like, prosciutto and salami.

[Rose Rimler]

Oh, like charcuterie boards.

[Michelle Dang]

Yeah, yeah, yeah, Charcuterie boards.

[Rose Rimler]

Once in a blue moon. I don't set out my spread of, you know, peeled grapes and charcuterie boards every night anymore.

[Michelle Dang]

Yeah. Overall, it's probably a good idea to eat less of this stuff. And there are a few other risk factors that might be at play here too. Things like obesity, lack of exercise, smoking, and alcohol. But I kept thinking, like, there's got to be something else going on here, because I keep seeing and hearing stories of people with very healthy lives that eat great, exercise a bunch, yet still getting colorectal cancer at a very young age. Here's Dr. Michael Foote, who we heard from earlier.

[Dr. Michael Foote]

Most of the people that we see are actually pretty healthy. I have a patient who was a vegan, you know, who came in, and she was, like, astounded. She had an early stage colon cancer, so we were able to remove it with surgery and then. And then treat her. And she's doing well, but, you know, she didn't really drink very much. She didn't smoke at all. So, you know, that's kind of the scary thing, I think, for all of us.

[Michelle Dang]

Yeah.

[Rose Rimler]

I'm thinking about Becca, who we met earlier. She seemed very healthy. I don't know what she was eating, but it didn't sound like she was sitting down at McDonald's for every meal.

[Michelle Dang]

Yeah. Similarly, Becca told me she wasn't big on processed foods or alcohol.

[Becca Lynch]

I don't know. Like I said, I was 28. I was healthy. Like, I had just run a half marathon. I really wasn't thinking I might have cancer. My energy levels were fine. I was still go, go, go.

[Michelle Dang]

So what could be going on here? Lots of scientists are wondering if there's something else weird in the environment that people were exposed to that's maybe contributing to this or perhaps changed up the gut microbiome. They're on the hunt for explanations. And so I want to talk about one of these ideas.

[Rose Rimler]

Okay, great.

[Michelle Dang]

One scientist we talked to is looking for clues inside the cancers themselves, like the actual DNA of these tumors. And his name is professor Lyudmil Alexandrov, and he's a cancer biologist at the University of California, San Diego.

[Professor Lyudmil Alexandrov]

I actually specialize in cancer genetics and cancer genomics, and my focus is on understanding the processes that cause cancer.

[Michelle Dang]

Several years ago, Ludmil and several colleagues started this big study looking at the genetics of colorectal cancer tumors. So what they did is they collected a bunch of tumors from people who had this kind of cancer, and they ended up with almost 1000 tumors from across 11 different countries. Then they brought these samples back to the lab to test their genetic profiles. So Ludmil says, inside a tumor, you can see these molecular fingerprints. These are made up of unique patterns of genetic mutations that can actually tell you a lot about that person's life.

[Professor Lyudmil Alexandrov]

Molecular fingerprints, which we call mutational signatures. A phot cause the tumor. So, for example, if you smoke tobacco, cigarettes, you're going to mutate in a very specific way many cells of your body. For example, the lung. And we can say, oh, this person smokes cigarettes. If you drink alcohol, you can see exactly the same thing.

[Michelle Dang]

Wow.

[Rose Rimler]

I didn't know scientists could do that. That's kind of cool.

[Michelle Dang]

Yeah, I didn't either. I don't know what my cells could tell about me.

[Rose Rimler]

I know. I was just thinking that.

[Michelle Dang]

And a good chunk of these samples were tumors that came from younger people.

[Professor Lyudmil Alexandrov]

About 15% of all the samples we collected were early onset cases, which is a very large number. You wouldn't expect that number. When we were designing the study, we would expect less than 5%.

[Michelle Dang]

Oh, so you weren't looking for that at the time?

[Professor Lyudmil Alexandrov]

No, not at all.

[Michelle Dang]

Now that he had this data with all these younger people in it, he could compare the tumors to see if there were genetic differences between the tumors and the younger and older People to try and see, like, was there anything different that might help explain why the cancer is showing up more and more in young people? And he found that, yes, there was something different between these two groups. There was actually this particular set of fingerprints that stood out.

[Professor Lyudmil Alexandrov]

And essentially, the difference was striking. If you look at individuals who are younger than 40, more than 50% of them had these very specific patterns of mutations.

[Michelle Dang]

And when they looked into this specific pattern, it turned out that this type of mutation is often caused by certain bacteria that find their way into the gut. Okay. And what can happen is that bacteria that get into our gut can release a toxin called colibactin. Rose, what do you know about colibactin?

[Rose Rimler]

Colibactin? I don't know anything about it. Does it have something to do with cauliflower?

[Michelle Dang]

Like cauliflower?

[Unidentified Advertiser Voice]

Yeah.

[Michelle Dang]

No, it does not have anything to do with cauliflower.

[Rose Rimler]

Okay, well, that was my best guess.

[Michelle Dang]

But it's something that gets made by some bacteria. Like, for example, some types of E. Coli make it.

[Rose Rimler]

Oh, that's.

[Michelle Dang]

Yeah, it's more like cholibactin than a coli. Coliflower. Bactin.

[Rose Rimler]

Coli. Bactin.

[Michelle Dang]

Yeah.

[Becca Lynch]

Yeah.

[Michelle Dang]

And one thing that colibactin does is it can damage our DNA because of how it works as a toxin.

[Professor Lyudmil Alexandrov]

I think of it as a weapon system. A weapon system that certain bacteria have, and they use it to protect themselves from other bacteria.

[Michelle Dang]

This is like a weapon that the bacteria create for themselves.

[Professor Lyudmil Alexandrov]

Yes, exactly.

[Rose Rimler]

So there's this bacteria scooting around in our guts, pooting out this toxic substance.

[Michelle Dang]

Yeah, I like that phrase. Pooting. Yeah. If a bunch of these bacteria get into your gut that make colibactin, when the bacteria encounter other bacteria, they'll start pooting or shooting this stuff out in all directions. It's like a little bacteria war.

[Rose Rimler]

Chemical warfare.

[Michelle Dang]

Yeah, exactly. That's the theory. And some of that colibactin could be slamming into cells in the wall of your gut, and that's where it can mess with your DNA.

[Rose Rimler]

Oh, so the. That colobactin chemical warfare stuff damages the cells of the gut, and somehow that damages your DNA as well?

[Michelle Dang]

Mm, yeah. To break it down a bit more, what happens is colibactin can hit a cell and then cause damage to the DNA in that cell. The cell will try to repair that damage, but sometimes it doesn't work, so you get mutations, and when that cell replicates, of course, those mutations replicate too. And so sometimes mutations do nothing. Same thing with these colibacting mutations, but other times, they Might be the first step toward a cancerous tumor.

[Becca Lynch]

Right.

[Michelle Dang]

But what's really interesting here is that Ludmil and his team were actually able to track down when these fingerprints were left behind because they could put together this genetic tree and track mutations over time. At a basic level, how it works is the trunk of the tree shows you the DNA's original state, and then it hits a mutation, grows a new branch, then another mutation, another branch. This sort of thing allowed Lude Mill's team to put together an estimate of how old the person was when this mutation happened. Wow. Yeah.

[Rose Rimler]

This detective work is fascinating.

[Michelle Dang]

Here's Ludmil again.

[Professor Lyudmil Alexandrov]

We always saw that molecular fingerprint in the trunk of the tree, and what that means is that happens very early.

[Michelle Dang]

So studies have estimated that these colibacting mutations happened when people were kids, before they were 10 years old. Oh.

[Rose Rimler]

Before they even had the chance to start drinking or smoking or.

[Michelle Dang]

Yeah, yeah. Wow.

[Rose Rimler]

So it's. The seed is planted very early, which

[Michelle Dang]

is, you know, super surprising. And even more surprising, Ludmil says more recent work that's unpublished points to an even narrower window that it might have

[Professor Lyudmil Alexandrov]

happened, that the more proper estimate is probably within the first two years of life.

[Michelle Dang]

Oh, wow.

[Professor Lyudmil Alexandrov]

So. So we think it's happening something in very, very early life. What we think happens is that when you have a young child, a year old, two years old, their microbiome and their immune system are getting formed, the microbiome in the colon. And if they get this infection, they get many, many mutations. And if you get many, many mutations at an early age, including some of the driving mutations that cause cancer, then if you get it at age two. Well, now you're on the fast track for cancer. You get cancer in 20 or 30 years when you're a young adult.

[Rose Rimler]

Two.

[Michelle Dang]

Yeah, two. Oh, my God. This little baby.

[Rose Rimler]

That's interesting. He says infection. Does he mean this bacteria that poots out the.

[Becca Lynch]

What was it?

[Rose Rimler]

Colibactin? Is that the infection he's talking about?

[Michelle Dang]

Yeah. When Lyudmil says infection, he's talking about this idea that some kind of bacteria ended up in these people's guts as little kids.

[Rose Rimler]

Okay.

[Michelle Dang]

Maybe E. Coli, which is pretty common in our guts, maybe something else. And they pooted out a bunch of this Colibactin, and maybe that contributed to colorectal cancer developing years and years later.

[Becca Lynch]

Wow.

[Michelle Dang]

Yeah. Now, we do have to mention here that it's correlation, not causation. We can't test this by putting this bacteria into a bunch of babies, you know?

[Rose Rimler]

Yeah.

[Michelle Dang]

But we do have studies in some mice showing that when you put colibacting making bacteria in their guts, they do get more tumors. So that's some more evidence of a potential link here.

[Rose Rimler]

But let's assume that this is a real link. Do we have any idea, like, where this infection came from in the first place?

[Michelle Dang]

So we don't exactly know, but Ludmil was like, the things that babies are exposed to that can affect the microbiome does change a lot from one generation to another. Like, younger people might have been exposed to more or different antibiotics. Maybe it's related to C section rates or breastfeeding versus formula. Or maybe it's as simple as, like, a lot of us. Like, everybody got exposed to a particular bacteria and it caused an infection and it just happened to do more damage if it happened to you as a baby.

[Professor Lyudmil Alexandrov]

And I suspect that these microbes, some microbes that may be very harmless for us when we're adults, are not that harmless for a one year old that's forming its immune system.

[Rose Rimler]

Huh?

[Michelle Dang]

Yeah.

[Rose Rimler]

Like it could have been a pandemic, a very quiet pandemic that some people are feeling the repercussions of now. Wow, that's fascinating.

[Michelle Dang]

Yeah. And now this is just one possible contributor. Scientists are going full steam ahead to try to solve this mystery. Other suspects include other types of bacteria, maybe viruses, also chemicals in the environment or medications like the antibiotics.

[Rose Rimler]

That makes sense.

[Michelle Dang]

So overall, we're getting a bunch of hints here, but no clear smoking gun. And this means that people like Becca don't have answers about where their cancer might have come from. But the good news is that Becca's doctors got her into treatment fast after she was diagnosed. So Becca had surgery. They took out the tumor, some lymph nodes, and more than a foot of her colon.

[Rose Rimler]

Oh, man.

[Michelle Dang]

And they got rid of all the cancer that they could find. But doctors also had her do chemotherapy last year. And after her last treatment, she celebrated with friends like they had a picnic in the park. I asked her what they had.

[Becca Lynch]

Oh, gosh, I think we just had a lot of cheese. It was really funny. I met with a dietitian early on during chemo, and they actually told me to, like, eat a lot of cheese.

[Michelle Dang]

That's a nice blessing.

[Becca Lynch]

Yeah. Say less. Like, I'll have no problem eating a lot of cheese.

[Michelle Dang]

But she's not totally out of the woods.

[Becca Lynch]

I finished in quotes end of August. And so now people will ask, like, so you're done now, right? And it's like, yes and no.

[Michelle Dang]

So Becca has to Go back every three months for scans and blood work. And this part will last two years. There's a 25% chance of her cancer coming back during this time. Hmm.

[Becca Lynch]

So every three months I get to be like a ball of anxiety and not know what's going to happen. But other than that, I'm just trying to, I don't know, focus on being here and feeling good right now.

[Michelle Dang]

What do you wish you had known?

[Becca Lynch]

I wish I had a good answer for this. I don't know. I think the biggest hurdle for me was like, getting over this fear of being thought of a certain way. Right. Like, my life was kind of always going 100 miles an hour. And I feel like I had built a big part of my personality around being this very independent person. And nothing will humble you faster than this experience. And so I think it was, it was actually that first support group I went to with all of the, like 70 year old women. And one of them just told me, like, you have to learn how to let the love in. Like, you have to, like, you can't do this by yourself. And so I think, I think I would tell myself, like, it's going to be okay and, you know, your friends are going to show up in ways that you would never have expected. And like, that's what's, that's what's really going to get you through it is the people in your life.

[Michelle Dang]

That's Science Versus.

[Rose Rimler]

All right, thanks, Michelle.

[Michelle Dang]

Thanks, Rose. Before we get to the citations, we've got a special sponsored segment for you with a very fun fact from the team. You're going to Hear from Science vs. Producer Akedi Foster Keys. Here it is.

[Ikedi Foster Keys]

This segment is brought to you by the all new Audi Q3. Here's an impressive fact. The Q3 features a roomy, comfortable, refreshed interior with a 12.8-inch touchscreen. Now let's get to dinner Party Genius. I'm Ikedi Foster Keys and this is our segment, Dinner Party Genius, sponsored by Audi. I'm here with senior producer Meryl Horne. Hi, Meryl.

[Michelle Dang]

Hey, Eketi.

[Ikedi Foster Keys]

We're here to give you a fun science fact that will help you charm the crowd at your next party. Okay, Meryl. So the fact that I want to talk to you about comes from research that I've been doing about running for an episode coming out soon. And it's about really long distance running, like ultramarathons. Science is still figuring out what happens to our body when we run for super long periods of time. And it turns out there might be Something strange going on in our brains when we do this. Huh? So there was a small study that looked at runners who competed in a really long race. Like they went all the way from Italy to Norway.

[Professor Lyudmil Alexandrov]

Whoa.

[Unidentified Advertiser Voice]

How long is that?

[Ikedi Foster Keys]

It's close to 2,800 miles and more than 4,000 kilometers.

[Michelle Dang]

Oh, my God.

[Unidentified Advertiser Voice]

Okay, so this is like forest gump level running.

[Becca Lynch]

Yeah, exactly.

[Michelle Dang]

Geez.

[Ikedi Foster Keys]

And of course, they got their brain scan along the way.

[Unidentified Advertiser Voice]

Oh, so they popped into a brain scan during the run. Got it.

[Ikedi Foster Keys]

Right. And so when scientists looked at the the scans, they found something that they weren't expecting to see. They saw that during the race, these runners, their brains shrank a little.

[Unidentified Advertiser Voice]

Ooh, that sounds bad.

[Ikedi Foster Keys]

Yeah, it does sound pretty bad, right?

[Unidentified Advertiser Voice]

Yeah, their brains shrank.

[Michelle Dang]

Okay.

[Ikedi Foster Keys]

Yeah, they lost on average about 6% of their gray matter. But the good news is it wasn't permanent.

[Unidentified Advertiser Voice]

Oh, okay. Well, that's good.

[Ikedi Foster Keys]

The scientists also scanned people's brains after the race, about eight months afterwards, and their brains had gone back to normal like nothing had ever happened.

[Unidentified Advertiser Voice]

So if you ever run over 2,000 miles, your brain might shrink a little bit. But don't worry, it'll all bounce back when it's over. That's the fun fact.

[Ikedi Foster Keys]

Yeah, it might shrink, but it might come back too. It will come back.

[Unidentified Advertiser Voice]

Okay.

[Ikedi Foster Keys]

Do you feel prepared for your next dinner party?

[Unidentified Advertiser Voice]

Oh, yes, yes. I am so prepared with this just fun fact. Yeah, I am ready for the party.

[Becca Lynch]

Okay.

[Ikedi Foster Keys]

Thanks, Meryl.

[Unidentified Advertiser Voice]

Thanks, Ikede.

[Ikedi Foster Keys]

That segment was brought to you by the all new Audi Q3. Here are a few more fun facts. The all new Audi Q3 features more power and more space than ever before. Plus, Quattro All Wheel drive gets you there with confidence. It's built to impress. Kind of like you at your next dinner party. Say yes to the all new Audi Q3. Made for the yes.

[Becca Lynch]

Life.

[Ikedi Foster Keys]

Learn [e-mail]

[Michelle Dang]

okay, Rose, we're back. Time for citations. Can I tell you how many we have in this week's episode?

[Rose Rimler]

You sure can.

[Michelle Dang]

There are 72 citations. And where can people find them? Rose?

[Rose Rimler]

You can find them in the transcript of the episode, and you can find that by clicking a link in the show notes.

[Becca Lynch]

Cool.

[Michelle Dang]

Thanks, Rose.

[Rose Rimler]

Thanks, Michelle.

[Michelle Dang]

This episode was produced by me, Michelle Deng, with help from Rose Rimler, Meryl Horne and Ekedi Foster. Keys Wendy Zuckerman is our executive producer. War Edited by Blythe Terrell Fact checking by Erica Akiko Howard Mix and sound design by Bobby Lord and Bumi Hidaka Music written by Bobby Lord Bumi Hidaka so Wiley, Emma Munger and Peter Leonard. And thank you to Professor Caitlin Murphy. Science Versus is a Spotify Studios original. Listen for free on Spotify or wherever you get your podcasts. Follow us and tap the bell for episode notifications. We'll factor soon.

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[Becca Lynch]

How quick?

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