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Why Do We Need Cortisol? · So That's Why

0:05
Jen: Welcome to the So That's Why podcast, where we unpack the
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science behind everyday questions.
0:09
I'm Jen.
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Chris: I'm Chris.
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Matt: And I'm Matt.
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Jen: Okay.
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So cortisol has suddenly become the hormone everyone wants to get rid of.
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But here's the thing worth saying at the start, it's one of the reasons you
0:22
can get out of bed and function at all.
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So why do we need cortisol?
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Matt: Which is a great question, 'cause if I'm honest, the only thing
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I know about cortisol is that it is, like, the main stress hormone
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that I'm supposed to be lowering.
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Mm-hmm.
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Right?
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Um, I couldn't actually tell you what it's supposed to do though, to be fair.
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Chris: And that is the thing we want to clear up, because- Woo.
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Because far from it just being the enemy, as we're constantly told by, like, social
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media ads, cortisol is doing essential work for you all around the clock.
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Jen: It really is, and it's a bit humbling actually.
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So your body was handling this perfectly well before any of us
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learned the word or made it a baddie.
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Matt: A baddie.
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So now I'm mildly stressed about how stressed I've apparently
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been, I'm sensing, though that's probably not the fix.
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Chris: Well, hopefully our little chat today, Matt, will help you- … and
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take a bit of the pressure off.
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Yeah, hopefully.
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Um, so let's start with what it is.
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So cortisol is a glucocorticoid.
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Of course it
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Matt: is.
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Chris: Yep.
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Go on.
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What is it, Matt?
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Matt: Glucocorticoid.
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Corti-
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Chris: See, it's not that easy, is it?
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Matt: No, it's not.
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It's why you get all the posh words.
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Chris: Um, so a glucocorticoid i- it's a steroid hormone that your
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adrenal glands, the glands located at the top of your kidneys, produce,
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and they build it from cholesterol.
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And cortisol's day job is keeping your energy, your blood pressure,
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and your body clock in check.
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Jen: And its reach is actually enormous across the body.
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So nearly every tissue you own carries or has glucocorticoid receptors, which
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are the sites that cortisol locks onto to pass on instructions to the cell
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Matt: So it's not tucked away doing one small job then, it's talking to more
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or less all of me at the same time.
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Chris: It certainly is.
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And, um, because cortisol's fat soluble, it slips straight into your
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cells and into the nucleus, where it changes which genes are switched on.
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And the last part is called gene transcription, and it's why
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cortisol's effects reach so far.
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Jen: Which is really the answer to why getting it wrong matters so much.
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So when one thing touches every system, a problem anywhere
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tends to show up everywhere.
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Matt: Okay.
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So, uh, so who's then actually deciding how much of it I've
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got at any given moment?
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Chris: So the thing that decides this is called the HPA axis, which
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consists of your hypothalamus, your pituitary, and your adrenal glands.
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And the hypothalamus sends a signal called
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CRH
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Jen: Which is?
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Chris: I knew you'd do that.
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So CRH is the corticotropin-releasing hormone that tells the pituitary
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to send the signal ACTH.
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Jen: Which is?
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Chris: I knew you'd do that as well.
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So ACTH is the adrenocorticotropic hormone, and that ACTH tells the
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adrenals to release cortisol.
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Matt: Can I just say, well done.
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Jen: I feel like we need to pause and give Chris a moment of well
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done- There's no way I'm saying those letters … on explaining that science.
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Chris: Yeah.
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I'm, I'm sweating now.
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But let's be honest, my Scrabble score is through the
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Matt: roof at the moment.
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Well done.
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Yeah, yeah, yeah.
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And of course, if you're still listening, well done to you too if
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you're keeping up with all of this.
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Jen: Yeah, it's full-on science today.
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And the clever part of the whole system is that it's self-limiting.
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So once cortisol rises, it signals back up that chain and tells the top
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to, to slow down and ease off so the, the system keeps correcting itself.
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Matt: So in my language then, it's not a tap left running.
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It turns itself down once the messages seem to have landed.
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Chris: Yep, that's fair enough, and that restraint keeps it s- to a
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strict daily timetable rather than your tap trickling out nonstop.
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Jen: And that timetable is one of the most reliable rhythms in human biology.
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So cortisol is highest in the early morning and lowest amound around midnight.
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So in a sense, it clocks on before you do and clocks off at night.
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Matt: Which could explain a great deal, like when I ask my teenage
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daughter anything before 9:00
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Jen: in the morning.
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Oh, don't do that.
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Don't do that.
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Matt: Don't do what?
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Jen: Don't ask her before 9:00.
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Matt: I know.
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This is- … uh, I'm obviously not aware of the hormone situation.
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I don't- That's the problem
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… Chris: I don't dare ask my teenage daughter anything at all.
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Jen: Yeah.
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Ever.
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Matt: Ever.
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Jen: But there's a, there's a lovely extra layer, too, and this one's
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well-established, and it, you know, the Endocrine Society puts a name
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to it, which is the lovely layer, the cortisol awakening response.
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Matt: So that's what she needs.
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Jen: That's what she needs.
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So in the first half an hour after waking, cortisol jumps again between,
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somewhere between, like, 38 and 75% on top of the level it's already
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climbing to, in roughly 77% of people.
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Maybe your daughter's the other, other percentage.
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Chris: Maybe.
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I mean, no offense to my daughter in case she's listening- No
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which she won't.
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Jen: We love you.
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You're great.
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Chris: She won't be.
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She'll be on Snapchat or TokTik or whatever those- TokTik … TikTok or
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whatever, whatever these kids use.
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Jen: Check us out on TokTik.
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Chris: Yeah.
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Matt: And this is why Chris is in charge of all the technology
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here- Absolutely … at Vegetology.
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Chris: Uh, right.
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I've completely lost my train of thought.
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Um, but we-
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Jen: Talking about the cortisol awakening response.
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Chris: Yes, we were.
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And, um, so the current thinking on this is that it's anticipatory.
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So your brain is priming you for the day ahead, before the day's even started,
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which is why the jump is bigger before a workday, and it goes flat in burnout.
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Matt: So a rough can't face it morning then that we experience
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isn't being lazy, it's just the ramp-up running late perhaps.
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Jen: I've got to admit, I am quietly smug about being a morning person,
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but it turns out that it's just a healthy awakening response and
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nothing to do with virtue at all.
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Chris: What a surprise.
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Well, I take it.
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Take the smugness all you can, yeah.
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Um, so that morning rise isn't just a side effect of waking up.
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It's part of the signal that actually wakes you.
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So without it, the jump from asleep to properly alert would be way rougher.
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Matt: Okay, so the snooze button then is me arguing with my own
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biology, and it seems losing.
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Mm.
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Chris: Yeah, that's fair enough.
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And, um, while that rise in cortisol's happening, it's making sure your
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brain never runs short of fuel.
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So cortisol is telling the liver to release stored sugar to make…
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And also to make fresh sugar, which is gluconeogenesis, and to free up fats
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for energy, which is called lipolysis.
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Jen: And it deliberately holds some of the fuel back from your muscles,
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so your brain gets the first pick, which is part of why a morning, like
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a normal morning rise, leaves you feeling sharp and able to think.
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Maybe I'm missing it some days.
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Don't always feel sharp and able to think, but hey.
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Matt: Well, apparently the gap be- then between a clear morning and a foggy one is
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partly just this hormone doing its rounds.
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Mm.
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Chris: Yeah, largely.
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And, um, it also props up your blood pressure by making your vessels respond
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properly to adrenaline, and it helps lock in your memory of emotional moments,
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which happens in the hippocampus, which is the brain's memory hub.
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So
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Jen: it's doing loads of jobs here.
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Yeah.
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It's doing tons.
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But you know, on top of that, it's your body's main built-in anti-inflammatory.
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So it actually turns your immune response up when you're first injured
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or infected, and then it calms it back down so it doesn't like
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overshoot and cause harm of its own.
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It's really a clever system.
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Matt: It really is magical.
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And it's less of a on switch for inflammation and more of a thing deciding,
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uh, how loud it's allowed to get.
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Jen: Mm.
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Chris: Yeah, that's the job, and that's exactly why steroid medicines
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like, um, hydrocortisone exist.
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They're lab-made versions of that same hormone.
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They're borrowing that calming effect on purpose.
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Jen: So a huge amount of what makes you feel like a steady, functioning
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human, I can't say I always feel like a steady- … functioning human, but hey.
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So-
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Matt: I'm like, can I get this to put in someone's tea?
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I'm not saying who.
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Can, can we buy it to put, put in the cup of tea, please?
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Jen: So a huge amount of what makes me feel like a steady, functioning
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human is quiet, is cortisol just, like, quietly getting on with its work.
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Matt: Right.
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So, uh, if this is really useful and magical, like we've been
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talking about, where does its frightening reputation come from?
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Chris: Okay.
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So this all comes down to what happens when cortisol stays too high for too
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long Uh, which is really a problem.
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So over years, it can actually shrink the hippocampus and leave
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the amygdala, which is your brain's fear center, more reactive.
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Matt: Mm. And there's the cortisol belly idea, isn't there?
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The, the, the one that's sort of online everywhere.
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Is there anything real behind this?
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Chris: There is, and I'd say more than you expect.
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So the deep fat that ar- around your organs, which is known as visceral fat,
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carries far more of the glucocorticoid receptors than the fat under your skin.
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And high cortisol also drives insulin resistance, which
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results in storing even more fat.
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Jen: And it even nudges up your appetite for calorie-dense food,
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which can switch on brand-new fat cells, and I'm jumping on Chris's
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bandwagon, that is called adipogenesis.
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Um, and so it changes how much you store, not just where you store it.
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Chris: I think, can someone in the comments put what adipogenesis
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would get you on Scrabble?
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That's, that's probably a decent
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Jen: score.
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Oh, could you imagine a triple word score with that?
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I know.
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Matt: With your A-C-T-H.
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Chris: Yeah.
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Jen: You'd just need somebody else to have genesis, and then you could
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swoop in with your adipo and be like,
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" Chris: Oh."
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Yeah.
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There's always someone gets, like, xylophone anyway- Yeah, yeah … and,
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like, ruins it for everyone else.
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Matt: I'm never playing Scrabble with you two ever.
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It's just not gonna do.
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Um, so anyway, there's a real effect, isn't there, rather than
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a myth, I suppose, but it's the same story as the rest of this.
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It should settle when the rhythm does, and we shouldn't really need anything exotic.
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Jen: No.
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But, you know, with everything, there's also, like, clinical
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extremes, isn't there?
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So we've talked about what happens when it stays high.
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So you've got something called Cushing syndrome, where really high cortisol,
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it ends up doing things like thinning the skin, um, it wastes muscle,
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and it pushes up your blood sugars.
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But that's, like, the far end of the spectrum, and we're talking, you
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know, most of us, for most of us, we're talking about milder versions
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from, like, ordinary longterm stress, where it's just slightly raised.
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Matt: So, I mean, we're both, we're all inside the industry
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right now, and cortisol is having a real moment, isn't it?
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Yeah.
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It's, um-
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Jen: Holding hands with magnesium.
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Matt: It's just like what a beautiful couple they make.
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Mm-hmm.
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Um, get an invite to the wedding and everything.
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Uh, but it's, it is one of those things that's a word on everyone's lips.
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It's behind half the questions that we seem to be getting asked at the moment.
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Jen: Mm.
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Chris: It is, but this is where the science and the supplement aisles can
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start to part ways because a lot of the marketing messages that ride on the
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word cortisol don't actually stack up.
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Jen: They don't.
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You
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Matt: surprise me.
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Chris: Yeah.
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Jen: But there's also this idea, I mean, I'm targeted with ads about
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cortisol all the time on Instagram, and also you get targeted with ads
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about adrenal fatigue, and this is the notion that your glands get exhausted
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and simply stop making cortisol, but that isn't a recognized diagnosis, and
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evidence doesn't support it either.
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Chris: No, but the internet doesn't let science get in the way of a good
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marketing message- … sometimes, does it?
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Yeah.
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Uh, but what is real is, um, the HPA axis dysregulation, and this is where
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the signaling between the brain and the glands drifts out of its normal rhythm.
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So the glands aren't worn out, the timing's off, and that's a
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very different thing to put right.
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Jen: Yeah.
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Matt: Okay, so when someone asks me for an adrenal support pill,
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whatever one of those is- … the honest answer is, is not that.
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It, the, the, it's not really the problem to solve, right?
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Chris: Mm-hmm.
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I'd agree with that, and I'm just hoping our marketing colleagues
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aren't writing, "Yeah, adrenal support pill, that's for the next, next-
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research program." You heard it here first.
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Yeah.
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Um, my obligatory Captain Sensible moment here-
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Matt: Go for it, Captain
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Chris: Sensible … is that identifying and addressing a genuine
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cortisol problem is a blood test and a conversation for your doctor,
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not a hunch from an internet forum.
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And actually, do people still use internet forums or- I was about to say
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is that down there with Tictoc
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Jen: and- Yeah.
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… Snap, Crackle, and Pop, whatever it's called?
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There's, there's always an internet forum for everything, Chris.
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Oh, yeah.
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There is.
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Oh, yeah.
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Even if the comments are six years old, there's
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Chris: always an internet forum.
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That's good.
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I mean, I'm still using Windows XP.
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I, is that still- I, I don't know.
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Matt: Wow, yeah, I thought you were on Windows 95.
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You've gone up.
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Jen: So it's also worth saying that, you know, we talked about when cortisol
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is high, um, there's the opposite problem does exist as well, and that's
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called Addison's disease, where your adrenal glands can't make enough.
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Um, and because cortisol, you know, helps to maintain your blood pressure,
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that can be genuinely dangerous, which kinda proves that the goal
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was never to have zero cortisol.
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Matt: Yeah, so the, the very hormone then, half the internet seems to want
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gone, some people would actually give anything to be able to make more of it.
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Jen: Yeah, they would, because in short bursts, cortisol is clever
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about things like your immune system as well, which is obviously vital.
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So it shifts- Yeah … immune cells out into your skin, and
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you got ready in case there's, like, an injury or illness coming.
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Chris: Yeah, it's so true.
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And to come back to what we said earlier, the trouble only comes
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when cortisol never switches off.
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So when cortisol stays high, the immune cells stop responding to
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it properly, which is called, uh, glucocorticoid resistance.
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So you get more background inflammation and weaker defenses at the same time.
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That's when the problems really arise.
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Mm.
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Jen: Yeah, and it's the real paradox of chronic stress.
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So the hormone that should be calming inflammation, it kinda
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loses its grip, so you're inflamed and under-defended all at once.
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Matt: So run down, then, isn't just, like, a turn of phrase, is it?
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There's an actual mechanism, it seems, sitting behind this.
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Jen: Mm.
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Chris: Yeah, definitely.
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Um, and there's a third way it goes wrong that can be easy to miss as well, and this
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is where your total cortisol levels can look normal, but the rhythm flattens out.
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And what I mean by that is it could be high in the evening and
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low in the morning, which is that kind of tired but wired feeling.
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Matt: Mm. Yeah, that sorta shift work, jet-lagged, staring at the ceiling at
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2:00 in the morning version, right?
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Jen: Oh, yeah.
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Chris: It is.
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And, um, a flattened rhythm like that is one of the most consistent
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biological findings in depression, which is why sleep and routine get
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treated as real levers, not just nice ideas, when it comes to depression.
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Matt: Mm.
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Jen: But the genuinely good news is that the things which keeps the whole system
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healthy are ordinary and mostly free.
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Chris: They are, and it's sleep first by- Well, a very wide margin.
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So sleep, it's the single strongest regulator of the rhythm, and short sleep
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pushes cortisol up in the evening exactly when we want it to be falling away.
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Matt: So the most powerful fix, then, is a decent night's sleep, which is wonderful,
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I suppose, except, if I'm honest, it's the one thing I can't put into a bottle.
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Yet.
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Jen: Yet.
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Matt: Yeah.
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Everyone's trying.
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Jen: Yeah.
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But movement helps, too.
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So, but the intensity of the movement matters more than people think.
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So easy and moderate exercises nudges your baseline, your
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cortisol baseline, down over time.
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But a really, like a really hard gym session can cause
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a sharp spike on that day.
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Matt: Ah.
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So my ongoing case then for a gentle walk over a brutal workout has, in fact, just
16:00
picked up some proper scientific backing.
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Chris: Although, to be fair- … the, uh, the hard session spike is short-lived
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if you're well-trained, like yourself.
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Matt: Oh, obviously, yeah.
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Chris: It's only the, it's the kind of constant over-training that
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keeps cortisol kind of stuck high.
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So gentle to moderate movement and consistent movement is a sweet spot.
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That, that's the truth.
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Jen: Which is probably a relief for anyone who dreads the gym.
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Matt: Yeah.
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But I do like the advice, you know, keep coming back to move a bit.
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Don't overdo it.
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Jen: Oh, don't overdo it.
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Don't
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Matt: overdo it.
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Don't
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Jen: overdo-
16:33
Matt: don't, don't overdo it.
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Uh, rather than, you know, this, uh, this keep pushing, uh, through
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the, which is the sort of regime I normally abandon by week two.
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Chris: Yeah, a gentle walk and a nice sit-down, you know?
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You think that's a long way out.
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Cup of tea.
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Yeah, why not?
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Cup of tea, yeah.
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Uh, so jumping around to another point is, um, blood sugar.
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So blood sugar matters as well when it comes to cortisol because a sharp sugar
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crash, so a real dip in blood glucose, is one of the strongest triggers actually,
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um, that there is for a cortisol spike.
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So regular meals with a bit of protein help keep that steadier, and going easy
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on the old, um, afternoon big cup of coffee and the caffeine, and easing back
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on the late alcohol, they're both things that can help reduce that kind of evening
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dip and make sure it happens on time.
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Jen: That sounds fun.
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Yeah, I'm with
17:25
Chris: this.
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Matt: I'm just thinking back to all the episodes that we've done, and it's
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like they're all saying the same thing.
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Yeah.
17:29
Yeah.
17:29
I'm the fun
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Chris: police, basically.
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Matt: That's you,
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Chris: Captain Sensible.
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Yeah, ditch the coffee, ditch the glass of wine.
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Uh, all I'll say, don't have it too late.
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Yeah.
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Jen: Yeah.
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In moderation, at the right time.
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Matt: The dose is the poison.
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Jen: But there's- All the
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Matt: cliches.
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Jen: There's also, um, calming practices, isn't there, that people are
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often quite cynical about, like slow breathing, meditation, but they've got
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some real evidence behind them as well.
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Matt: So, I, you know, me and my I'm too busy and perhaps wound up to meditate
18:01
is really me being too stressed to do the thing that lowers the stress.
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Jen: Yeah.
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Chris: That is the unfortunate loop, I'm afraid.
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And, um, feeling connected and in control of your day matters more than
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people expect, actually, and 'cause it's tied to a steadier baseline.
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Jen: So another thing that's worth mentioning is supplements, and on
18:21
an honest note, we, since we do sell some supplements, did you know that?
18:25
We sell supplements.
18:25
I, I, I did, yes.
18:26
Thank you for
18:28
Chris: pointing that out.
18:28
Um-
18:29
Jen: I,
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Chris: I was meant to wear my Vegetology T-shirt.
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Yeah.
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We're, we're not advertising products, but, you know.
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Matt: Yeah, yeah.
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Jen: Okay, so for cortisol specifically, though, the evidence is thin.
18:38
Um, omega-3, that we sell, has a modest signal at best, and so we'd more
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steer you to, like, healthy sleep and routine first, and treat anything else
18:50
as a minor extra, not the main event.
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Matt: Yeah, when you line it all up, cortisol is tangled into
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my sleep, my energy, my mood, and my appetite all at once.
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Jen: Mm.
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Chris: Which is exactly why you can't treat it in isolation.
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So cortisol isn't just something to push down, which is what we
19:09
constantly see as the message.
19:11
It's all about the timing that has to line up with everything else.
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Jen: And that flips the whole panic on its head, doesn't it?
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So you were never meant to have low cortisol, you're meant
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to have well-timed cortisol.
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Matt: Love that.
19:25
Well-timed cortisol.
19:26
So the goal changes completely, I think, when you understand that.
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Jen: Yeah.
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So why do we need cortisol?
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Because it fuels your brain, it holds up your blood pressure, it keeps your
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immune system in balance, and lifts you into the morning all on a daily rhythm.
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So the aim was never less of it, it's the right amount at the right time.
19:50
Matt: And the way there isn't a detox or a gadget, which I appreciate is a
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bit of a shame to you gadget lovers.
19:56
It's sleep, it's a bit of movement, it's regular meals, and people hanging
20:01
around with people you actually like.
20:04
Yeah,
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Chris: and get those things roughly right, and the body handles the rest beautifully.
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Although maybe the hanging around people you like, the body
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doesn't really have a say in
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Jen: that.
20:14
Okay, so if that has cleared a few things up for you, follow or
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subscribe wherever you're listening.
20:21
It genuinely helps us out.
20:23
That's it for this week.
20:25
Thanks so much for geeking out with us, but for now, that's it from me.
20:28
Chris: That's it from me.
20:30
Matt: And that's it from me.
20:31
Jen: Bye for now