Chapter 5: Ulcers, Colitis, and the Runs

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Welcome to the Deep Dive, where we plunge into fascinating insights from incredible sources all distilled just for you.

Today we're taking a really deep dive into the remarkable world of your gut and, well, how it responds to stress.

Think for a moment about digestion.

I mean, it's an incredibly complex process, right?

From the moment food hits your stomach, boom, powerful hydrochloric acid, enzymes,

muscles churning, flinging food against the walls.

It's intense.

Then you've got your small intestine doing this rhythmic, almost snake -like dance.

It's called peristalsis.

That moves things along, absorbs nutrients, and all the while these circular muscles, sphincters, they act like locks in a canal, ensuring everything flows smoothly.

This whole thing takes immense energy coordination, precise water management.

It's just a marvel of biological engineering, really.

But here's the critical question, and it's one Robert M.

Sapolsky tackles in chapter 5 of his amazing book, Why Zebras Don't Get Ulcers.

What happens when you're not leisurely digesting?

What if you're that zebra, you know, bolting from a lion?

Or us humans enduring immense sudden stress?

Suddenly, this whole energy -hungry digestive process, it's not just inefficient, it's a liability, a big one.

Exactly, and that's the core of what Sapolsky explores in this chapter.

It's called Ulcers, Colitis, and the Runs, aptly named, I think.

He shows us the often problematics, sometimes really quite paradoxical ways our internal machinery reacts when we're under pressure.

So our mission today is to unpack four key questions Sapolsky raises.

First,

how do ulcers actually start during stress?

Second, why do we sometimes lose bowel control when we're terrified?

Then, what about chronic stuff like colitis and irritable bowel syndrome, IBS?

And finally, maybe the most confusing bit, why do some of us binge on junk food when stressed, while others, you know, can't stomach a thing?

Okay, let's start right there with that fundamental shift.

What actually happens to this incredible digestive system when stress hits?

Well, the first thing to grasp is just how much energy digestion demands.

It's a huge commitment, and in a life or death situation, your body just doesn't have time to

waste energy on your stomach walls doing a rumba, as Sapolsky puts it so well.

Survival takes over, instantly.

And we've all felt those immediate responses, right?

The first sign, your mouth goes bone dry, saliva production just stops.

But internally, wow, it's way more dramatic.

Your stomach, literally, it grinds to a halt.

Contraction stops.

Enzymes, digestive acids, secretion stops.

Your small intestines, they stop that peristalsis dance.

No nutrient absorption happening there.

And on top of all that, your body instantly redirects blood flow and the oxygen and glucose it carries away from your gut, sends it straight to your muscles, other organs needed for fight or flight.

Yeah, it's all part of this elegant biological switch.

You've got the parasympathetic nervous system, that's your rest and digest system, it gets switched off.

And at the exact same time, the sympathetic nervous system, that's your fight or flight gets slammed on, full throttle.

Now, this makes perfect sense for an acute emergency.

Absolutely adaptive.

You need to run, you need to fight, you definitely don't need to be digesting lunch.

But, and this is Sapolsky's crucial point, this system is great for a zebra facing a brief line encounter.

What happens when humans face chronic psychological stress, day after day?

That's when these adaptive responses can become, well, maladaptive.

And that's where diseases like ulcers and IBS start to creep in.

Okay, that leads us straight into our first deep dive question.

How do ulcers actually originate during stress?

So an ulcer is basically just a hole in the wall of an organ.

We're talking peptic ulcers here, stomach,

maybe the duodenum, that first bit of the small intestine.

Right.

And researchers like Hans Saleh saw this decades ago.

He found peptic ulcers in rabs that were under chronic stress.

It really cemented that link in the public mind, too.

We know stress ulcers can form incredibly fast in humans during crises, massive infections, trauma,

and even the slower forming ones.

They often pop up during really stressful life periods.

Now, it's maybe a bit controversial, but while stress isn't always the only cause, genetics, diet, they matter, too.

It's consistently seen as a major contributing factor.

It can definitely worsen things.

Sapolsky outlined several really fascinating mechanisms for how this happens.

And importantly, it's rarely just one single thing going wrong.

Let's walk through some of those.

The first one sounds kind of paradoxical,

Our stomach uses powerful hydrochloric acid, right?

But it protects itself.

Thick walls, mucus, this stuff called bicarbonate to neutralize the acid.

Exactly.

But here's the twist Sapolsky highlights.

During chronic stress, your body tries to conserve energy.

So it dials back acid production.

Makes sense.

But, and this is the key, it also cuts back on those defenses.

The stomach walls get thinner.

There's less mucus, less bicarbonate.

Why waste energy on

less acid?

The problem comes when the stressful period ends.

Maybe you relax, have a big meal, normal acid secretion kicks back in, but oh, your defenses are still down.

That returning acid hits those weakened walls.

Bam, damage occurs.

It helps explain why maybe lots of short intermittent stresses could be more ulcer forming than one long continuous one.

The damage happens in that recovery phase.

Wow.

So it's the shift back to normal that's dangerous when the shields are down.

That's counterintuitive.

What about just plain old too much acid?

Yeah, that's definitely another mechanism.

Some people are just, well, genetically wired for acid overproduction.

Their bodies make too much hydrochloric acid and the system that's supposed to regulate it, it doesn't work properly.

In these cases, stress might not cause the underlying issue, but it absolutely exaggerates it.

It makes a pre -existing vulnerability much worse because the breaks on acid production fail under pressure.

Okay.

So acid rebound, acid overproduction, what about blood flow?

You mentioned the body diverting blood away from the gut.

Sapolsky has that incredible story, right?

The guy with the gunshot wound whose insides literally turned white when he got anxious.

Yes, it's a striking image and that dramatic decrease in blood flow during severe stress.

It can have really serious consequences for the gut lining itself.

Think about it.

Lack of oxygen can cause kind of infarcts basically, many strokes in the stomach walls.

This creates patches of necrotic or dead tissue and those dead patches, they're perfect starting points for ulcers.

This happens for a couple of reasons.

Less blood flow means less acid gets washed away from the stomach lining, but maybe more importantly, it messes with how our body handles oxygen radicals.

These are harmful byproducts of normal metabolism.

We usually have free radical quenchers to clean them up, but during chronic stress to save energy, blood flow reduction also reduces these quenchers.

So the real kicker often happens after the stress passes.

Blood flow returns bringing oxygen back, but now you have fewer defenses against the oxygen radicals produced by that returning oxygen.

They overwhelm the system and kill stomach cells.

So again, similar to the acid rebound, it's a paradox where the recovery phase can actually cause significant damage.

Right, the aftermath again.

It's fascinating how much damage happens after the immediate crisis.

Okay, next up, bacteria are guts full of microbes, and usually our immune system keeps the bad guys in check.

Usually, yes.

But during chronic stress, your immune system function can be suppressed.

It's another energy saving measure, in a way.

But this suppression can allow certain bacteria to run amuck, as Sapolsky puts it.

A key player here is Helicobacter pylori H.

pylori.

Its exact role is still debated, whether it directly causes ulcers or just thrives in a stressed stomach, but it's very often found in ulcerated stomachs.

And interestingly, treating ulcers with antibiotics to kill bacteria like H.

pylori is often more effective long -term than just using antacids to reduce acid.

That strongly suggests bacteria play a significant role, especially when stress weakens our immune defenses.

Okay, and then there's just every day wear and tear, right?

Like micro -ulcers, how does stress fit in there?

That's right, we get tiny bits of damage all the time.

Normally, the body repairs these using chemicals called

prostaglandins.

Prostaglandins help healing, partly by increasing blood flow to the damaged area.

But here's the link to stress.

A key group of stress hormones, the glucocorticoids, actually inhibit the production of these prostaglandins.

So in this case, stress isn't necessarily causing the initial tiny wounds.

Instead, it's directly impairing your body's ability to heal that normal, everyday damage.

The little problems don't get fixed, and they can then grow into bigger ulcers.

It's the same reason aspirin can cause ulcers, by the way.

Aspirin also inhibits prostaglandins.

Stress essentially mimics that effect hormonally.

Wow.

So many different angles.

Acid rebound, too much acid, lack of blood flow, oxygen radicals during recovery, bacteria running wild, impaired healing.

It really drives home Sapolsky's point that ulcers aren't simple.

It's like a perfect storm of vulnerabilities created by the body trying to cope with stress in ways that backfire under chronic conditions.

Okay, let's shift gears.

From the microscopic level of stomach cells to something much more visceral.

And frankly, embarrassing.

That extreme stress response, completely losing bowel control, spontaneous defecation when someone is, as Sapolsky puts it, immensely terrified.

Soldiers, prisoners.

It happens.

Yeah, it sounds awful.

But there's surprisingly cold, hard biological logic to it.

Think about it from a pure survival perspective.

Any dead weight in the large intestine stuff the body's already taken nutrients from is just extra mass.

So jettisoning it.

It makes you lighter, potentially faster.

It's a body prioritizing escape above all else.

Forget dignity, just survive.

And the biology really supports this, doesn't it?

The sympathetic nervous system, fight or flight, it slams the brakes on the small intestine.

But paradoxically, it hits the accelerator on the large intestine.

Exactly.

Sapolsky mentions experiments with rats.

Give them chemicals that activate the sympathetic system.

Small intestine stops moving.

Large intestine starts contracting like crazy.

It's a very specific targeted response.

Okay, so that explains the emptying part.

But why diarrhea specifically?

That's a direct consequence of speeding things up.

See, the large intestine's main job, besides holding waste, is reabsorbing water back into the body.

But when stress makes the large intestine contrive so rapidly, the waste material just rushes through.

It moves too fast for the water to be properly reabsorbed.

And the result,

diarrhea is physics, really.

Efficient emptying, but messy.

Right.

Okay.

So from that extreme terror response, let's pivot to what Sapolsky calls the similar problems, but writ small.

The kind of gut issues many people experience under less life -threatening, but still significant, chronic stress.

Conditions like colitis, spastic colon, and especially irritable bowel syndrome, or IBS.

Precisely.

And IBS is incredibly common.

It's actually the most

gastrointestinal disease out there, affecting maybe 10, even 20 % of us at some point.

Sapolsky even shares his own experiences getting pretty impressive cases of the runs before big life events.

His Bar Mitzvah, college, PhD defense, wedding.

It just shows how even predictable, albeit stressful, events can trigger these responses in susceptible people.

It's not just about unexpected terror.

And the symptoms of IBS sound just awful.

It's not just one thing, is it?

Frequent stomach pain, cramps, diarrhea, but also chronic constipation, problems absorbing nutrients, water loss, bloating.

It's a really debilitating collection of symptoms.

And Sapolsky suggests it often stems from a kind of dual cause.

First, exposure to too many stressors can lead to what he calls desynchronization in the gut.

Ideally, your small and large intestines should respond to stress and then recover in a coordinated rhythm, like a well -rehearsed orchestra.

But with repeated stress, it's like the conductor walks out.

The small intestine and large intestine get out of sync.

So if the small intestine's movement, motility, gets too inhibited by stress, food backs up.

That leads to constipation.

But if the large intestine's motility gets too stimulated, everything rushes through too fast.

That leads to diarrhea.

It's this loss of internal coordination.

So the timing and the coordination between the different parts gets completely messed up.

Exactly.

And the second piece of the puzzle seems to be an abnormal sensitivity to stress in the gut itself.

Studies show that people with IBS have a bigger gastrointestinal reaction to stressors compared to people without IBS, even relatively mild stressors, like putting a hand in ice water or doing a stressful interview.

And interestingly, those prone to diarrhea tend to show the biggest reaction in their large intestine.

Those prone to constipation show the biggest reaction in their small intestine.

So it suggests it's not just that you're stressed, but also how your specific gut physiology happens to react to that stress.

Okay.

This brings us to our final big question.

And it's one that I think confuses a lot of us in daily life.

Stress and appetite.

Because sometimes you're upset and you find yourself just mindlessly eating junk food, right?

Mechanically chewing, as Sapolsky says.

Other times, you're nervous or grieving and the thought of dinner, zero appetite, complete loss.

How can stress cause such totally opposite reactions?

It's a fantastic question because it highlights a real biological paradox.

In the initial picture from the hormones involved, it's just as contradictory.

You've got at least two key stress hormones pulling in opposite directions.

First, there's CRF, corticotropin releasing factor.

CRFs are released very quickly by the hypothalamus at the start of stress and its main job regarding appetite.

It suppresses it strongly.

It also fires up the sympathetic nervous system, makes you vigilant, jumpy, basically preparing you for immediate action, not for eating.

Okay.

But then you have the glucocorticoids like cortisol.

These are released more slowly from the adrenal glands.

And all the evidence suggests these hormones actually stimulate appetite.

Sapolsky mentions rat studies where glucocorticoids make the animals work harder to get food rewards.

They increase motivation to eat.

So yeah, you've got CRF screaming, don't eat, and glucocorticoids whispering maybe a bit later, hey, let's eat.

It seems like a total contradiction.

Right.

So how does the body sort this out?

How do these opposite effects play out in real life?

The key Sapolsky argues is the time course.

It's all about when these hormones peak and how long they stick around.

Think of CRF as the fastest wave.

It hits within seconds of the stressor, does its job including suppressing appetite, and then it's cleared from the bloodstream pretty quickly, also within seconds or minutes.

Glucocorticoids, on the other hand, are the slowest wave.

They take maybe half an hour or so to really surge after the stressor hits, and they take hours to clear out of your system.

So if you map it out, at the very beginning of stress, CRF is high, glucocorticoids are low.

Result, appetite suppression.

Makes sense, shut down digestion for the emergency.

But later during the recovery phase, CRF levels have dropped, but glucocorticoids are still high.

Result, appetite stimulation.

This also makes sense, time to replenish the energy stores you just burned.

Glucocorticoids seem to mediate that recovery appetite.

Ah, okay.

So the timing explains it.

And this could explain those individual differences too, right?

Like if you have lots of short stressful events one after another.

Exactly.

In that case, you get repeated brief spikes of CRF, suppressing appetite, but maybe not enough time for it to dominate.

Meanwhile, the slower acting glucocorticoids build up or stay elevated from their repeated stress recovery phases.

Their appetite stimulating effects might win out overall, leading to overeating or craving comfort foods.

Okay.

And conversely, someone facing one long continuous stressor.

Sustained appetite loss.

Why?

Because CRF levels could remain consistently high throughout that prolonged period.

Its powerful inhibitory effect on appetite might dominate over the glucocorticoids, which might still be high, but perhaps less effective against constant CRF signaling.

Obviously, it's more complicated than just these two hormones.

There are individual differences in how much people secrete, how sensitive their brains are, other hormones involved.

But this time course model of CRF vs.

glucocorticoids provides a really elegant framework for understanding why stress can make one person overeat and another lose their appetite entirely.

It really does tie it together.

And fundamentally, it comes back to that central lesson Sapolsky keeps highlighting in this chapter, doesn't it?

This inherent incompatibility, this biological clash

between planning for the future, like eating, digesting, storing energy, and dealing with an immediate emergency right now.

Our bodies are forced to choose.

And under chronic stress, that choice can lead down some unhealthy paths.

It's a profoundly important insight, I think.

Our bodies are brilliantly adapted for acute, short -term physical stress.

The zebra escaping the lion.

That system works beautifully.

But the chronic psychological stressors that dominate modern human life.

The constant pressure, the deadlines, the worries, the 24 -7 news cycle.

Our stress response system wasn't really designed for that kind of constant low -grade activation.

It puts immense strain on systems like digestion that are meant to be switched off only briefly.

Living in that perpetual state of sprint, as you called it earlier, is likely at the root of so many of these gut issues.

It really makes you think about the long -term cost and perhaps the importance of finding genuine ways to switch off that stress response to allow our bodies and our guts that crucial period of recovery and calm they desperately need.

Thank you so much for joining us on this deep dive into why zebras don't get ulcers, chapter 5.

We hope walking through this has given you a much clearer picture of just how tightly your stress response is linked to your gut health.

From that instant shutdown of digestion through the complex ways ulcers can form the acid rebound, blood flow issues, bacteria, healing problems to those more dramatic bowel responses, and finally untangling that confusing appetite puzzle.

It certainly gives you something to think about regarding your own well -being and maybe finding ways to step off that stress treadmill once in a while.

Our bodies are definitely trying to tell us something and a very warm thank you from the last minute lecture team.