[318] - What Are IPRGCs and Why They Matter for Shift Workers

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Light is the most powerful signal for your body clock—but most shift workers never train it on purpose. In this episode, I explain how your eye’s light-sensing cells set circadian timing and show you exactly how to use morning light, controlled darkness, and smart lighting habits to stabilise sleep, mood, digestion, and energy across any roster.

What You’ll Learn:

• What IPRGCs are and how they differ from rods and cones
• How light signals reach the SCN and set circadian timing
• Why morning light anchors alertness and rhythms
• How evening blue light suppresses melatonin
• How shift work disrupts the body’s clocks
• Practical light strategies for day, afternoon, and night shifts
• When to use blue-blocking glasses after nights
• Home lighting swaps and screen hygiene that protect sleep
• How light timing affects appetite, metabolism, and gut rhythms
• Simple consistency habits to stabilise your clock long term

If you want help building the right light routine for your roster, reach out through the link in the show notes.

Subscribe so you never miss an episode, and please leave a rating and review—it helps more shift workers find the podcast.

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ANNOUNCING

"The Shift Workers Collective"

https://join.ahealthyshift.com/the-shift-workers-collective

Click the link to learn all about it
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YOU CAN FIND ME AT

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• Shift Work Health and Wellbeing Seminars
• One2One Coaching

_____________________

Disclaimer: Roger Sutherland is not a doctor or a medical professional. Always consult a physician before implementing any strategies mentioned in this podcast. Use of this information is strictly at your own risk. Roger Sutherland will not assume any liability for direct or indirect losses or damages that may result from the use of the information contained in this podcast including but not limited to economic loss, injury, illness, or death.

_______________________

Episode Transcript

SPEAKER_00 (03:17):
Shift work can be brutal, but it doesn't have to
be.
Welcome to a healthy shift.
My name is Roger Sutherland,certified nutritionist, veteran
law enforcement officer, and24-7 shift worker for almost
four decades.
Through this podcast, I aim toeducate shift workers using
evidence-based methods to notonly survive the rigors of shift

(03:40):
work, but thrive.
My goal is to empower shiftworkers to improve their health
and well-being so they have moreenergy to do the things they
love.
Enjoy today's show.
And welcome back to a healthyshift podcast.
My name is Roger Sutherland, andI am your guide on this shift

(04:00):
working journey that you haveundertaking.
And I'm here to help you tothrive, not just survive in your
shift working life.
If there's one thing that Ireally want to do, and that is
to give shift workers moreenergy to do the things that
they love outside of their shiftworking life.
Because when we are absolutelythriving outside of our shift

(04:21):
working life, we turn up as amuch better person at work.
And that is something that'sreally important.
Now, today I talk aboutcircumstances rhythms and I talk
about light, but I want to talkabout something that I've never
spoken about yet.
And I think it's somethingthat's really important.
Today, I want to explainsomething that most people have

(04:42):
never heard of.
But it literally drives a hugepart of your health as a shift
worker.
And they are calledintrinsically photosensitive
retinal ganglion cells.
And what I'm going to do is I'mactually going to call them
IPRGCs from here on in.
But that's what they are.
I'll say that again.

(05:03):
Intrinsically photosensitiveretinal ganglion cells.
Don't panic, I will explaineverything.
These cells actually decide howyour body reads light.
That's right.
And if you don't understandthem, your sleep, your mood,
your energy, and even yourdigestion can seriously drift

(05:26):
out of rhythm and cause allsorts of complications for you.
So let's break it down intovery, very simple terms.
Let's start off with what areIPRGCs?
Well, most people know that theeyes have rod and cones, right?
The rods they help you to see inlow light, and the cones

(05:48):
actually help you to see colorand detail.
That's what the rods and conesare.
Now, IPRGCs are not like rodsand cones, they are actually a
completely separate group ofcells that sit in the eye that
do not help you to see picturesat all.
They don't even make an image.

(06:09):
What they are is a light sensor.
Now these cells contain apigment which is called
melanopsin.
And melanopsin reacts to light.
And guess what?
Blue light, especially to brightmorning blue light.
What I want you to do is I wantyou to think of your IPRGCs as

(06:34):
your body's light meter.
Now they're based in the eye,they are not in the rods and
cones, they are not in thecornea, uh the cornea.
Yep, they are literally on theeyeball, but at the back of the
eyeball next to where the opticnerve goes through.
What they do is they actuallytell your brain what time of the

(06:57):
day it is based on theparticular light hitting your
eyes, that blue light.
So how do they differ from theresonar?
Well, the resonant actuallyhelps you to see.
What it does is it sendsdetailed images to the visual
part of your brain.
Now the IPRGCs don't do that.
What they do is they sendinformation directly to a small

(07:22):
part of the brain, which iscalled the suprachiosmatic
nucleus or the SCN, which I willcall it from here on in.
Now the SCN is your body'smaster clock.
It literally is running yourcircadian rhythm.
So while those rods and conesare actually telling you what

(07:43):
you're looking at, the IPRGCsare telling your body what time
it is.
And for shift workers, knowingthe time is everything.
Now, why are they actuallyimportant?
It's clear, your body is runningon light, it is its main key

(08:04):
zekeeper, it's its maintimekeeper.
Every hormone rhythm depends onthe signals from these cells.
Everything, every clock in yourbody, and we now know that every
single cell in your body has atime clock in it, every single
one of them.

(08:25):
And those IPRGCs in your eyeballare actually signaling to the
body clock, the master clock,what time it is.
So when the IPRGCs get brightlight at the right times, things
run smoothly.
So think about yournine-to-fiver, they get up in
the morning, they get outside,they go for their walk, they do

(08:48):
their thing during the day,they're out in the light, things
are running smoothly.
But when you, hello shiftworkers, get light at the wrong
times, everything shifts out ofplace.
And here's what these cellscontrol when you feel alert,
when you feel sleepy, whenmelatonin rises in your body,

(09:10):
when cortisol drops, whencortisol rises, when your
melatonin drops, how yourmetabolism runs, how stable your
mood feels, whether you feeldepressed, whether you feel
happy.
These cells help set the entirecircadian rhythm.
And as a shift worker, yourrhythm is already seriously

(09:32):
challenged.
So you have to be even moreaware of how these IPRGC cells
work because they are superimportant.
So let's look at the light anddark hormone releases.
Let's walk through what wouldhappen in a normal day.
In the morning, and you've heardme say this over and over again,

(09:55):
sky before screen, sky beforescreen, and there's a reason.
The sky that you're looking atoutside, when you go out and you
get daylight, even on anovercast and a rainy day, it's
running at around about 10,000lux of light.
That is the daylight that oureye needs, the blue light.
And the reason why I say skybefore screen is because the

(10:18):
light in your phone isinsufficient.
Now, while it's too much lightat night, it's insufficient blue
light during the day to actuallyreset that circonium rhythm.
Weird, I know, but that's how itworks.
So in the morning, when brightlight, as we do, and you've seen
me, I lie in bed and I look outthe window, open the blinds,

(10:39):
look out the window, getoutside, take your coffee
outside.
What happens then is melatoninis actually switched off because
those IPRGCs in your eyeregister, oop, there's blue
light as part of the spectrum ofwhite light.
There's blue light, it turns offthe melatonin, cortisol rises,

(11:00):
which helps you to wait to getyou going.
Your core body temperature thenstarts to lift, and your brain
and body goes, Okay, it's nowdaytime.
Daytime started, and it startsto alert the rest of the body.
That's why getting that earlylight is so important.
Your body needs to anchor itselfevery single day.

(11:21):
And the way that it does this isit gets a daytime signal.
And the way it gets that daytimesignal, when you open your eyes
and that light hits thoseIPRGCs, they deliver that signal
to the body's master clock.
It's go time.
But if morning light is weak oryou stay inside, like if you

(11:43):
crawl out of bed to the couchand just put on Netflix, your
internal body clock just can'tstart.
It does not start properly.
And this is when people start tofeel really sluggish, you get
brain fog, and you end up out ofsync.
Now, at night, the oppositehappens.
When it gets dark and thosecells stop seeing that blue

(12:05):
light, and I want you to hang onto this one.
When your those cells, theIPRGC, stop seeing that bright
blue light, melatonin starts torise, cortisol falls, your brain
shifts into that night mode,your body goes into rest and
digest, and your body gets readyfor sleep and to repair itself.

(12:27):
And this is the catch.
If you expose those IPRGCs tobright light at night, hello
mobile phones, tablets, overheadLED lights, TVs in your bedroom,
your brain actually getsconfused.
It's actually thinking it'sdaytime and melatonin drops.

(12:48):
Sleep becomes a lot harder.
You don't stay asleep, and yourrhythm slides further away from
where you actually want it.
Now you've got to remember, evenif you're lying in bed in the
dark and you're watching thatscreen, that light is hitting
those IPRGCs.
Anything that's blue is tellingyour body it is still daytime.
And where do we hold our phone?

(13:08):
About six inches from our face,we've got blue light going
straight into our eye.
Now, while it might not inhibitgoing to sleep, it is certainly
having an impact on yourcircadian rhythm.
And I've done a podcast on whatthe difference is between sleep
pressure and regular normalsleep, right?
Circadian aligned sleep.

(13:29):
Now, why does this matter evenmore for you, the shift worker?
Let's talk about that.
Because shift workers live withflipped or irregular light
exposure and irregular lightexposure.
And these cells, they don'tunderstand your roster.
They don't look at the rosterand go, okay, we're on nights.
Oh, we're on days.
Okay.
All they do is they understandlight and they are just

(13:50):
signaling to your body light.
So if you're on nights andyou're blasting your IPRGCs with
bright light at 3 a.m.
or looking at screens, yourbrain thinks the day has
started.
What that does is it makes itharder to sleep later because
your circadian rhythm iscompletely out of sync.
Remember, it's indicatingstraight to the SCN.
It's telling your body's masterclock, daytime, daytime.

(14:14):
And it completely throws youout.
Now, when you walk out intostrong morning light on the way
home, those cells switch offmelatonin at exactly the wrong
time.
This is why many shift workersfeel so wired when they actually
want to sleep.
Now you might go to sleep whenyou get home, but that's sleep
pressure because you've beenawake for so long.

(14:37):
But will you stay asleep?
No.
How many people have troublesleeping when you're on night
shift?
You're not designed to sleep atthat time.
The trick is not to fight yourbiology.
The trick is to work with theseIPRGCs.
Very important.
Those cells in your eye, let'swork with them.

(14:58):
So how can we use them to ouradvantage?
And here are simple andpractical rules.
On a day shift or an earlystart, get bright outdoor light
as soon as you can.
Aim to get at least 10 to 15minutes.
What this does is it anchorsyour circadian rhythm.
As I explained earlier, here'sthe blue light.

(15:19):
Okay, it's daytime.
Suppress it all the night stuff.
Let's get the day stuff going.
When you're on afternoon shift,I still want you to get that
morning light because what itdoes is it keeps your rhythm
stable and it won't hurt yournight sleep once you get home
from work.
And when you're on night shift,get light during the night only

(15:40):
when you need to stay alert.
But avoid blasting your eyeswith very bright light.
And on the drive home, you needto block that morning blue light
with blue light blockingglasses.
You want that melatonin to stayhigh until you get home and can
fall asleep.
If you're driving home and youhaven't got glasses on at all,

(16:04):
and that or normal sunglasses,and that blue light is actually
hitting your eye, what it'sdoing is it's suppressing the
melatonin and telling your bodyyou don't need to sleep now.
It's daytime.
Let's go.
Now, in the evenings on yourdays off, you need to dim your
lights.
You need to use zero blue lightbulbs, you need to reduce that

(16:27):
screen brightness or not look atscreens at all for up to two
hours before you go to sleep.
You need to give those cells inyour eye a clear night signal.
Now we've actually swapped allthe lights in our house to zero
blue lights from block bluelight.
And anybody that's interested inhaving a look at those lights,

(16:48):
you can go to my website.
And at the top, you'll see thatthere's a link to resources, and
underneath that there will beone that says recommended
products.
And have a look on there, andyou'll see the link to the
products that I recommend withBlock Blue Light.
We've gone through our wholehouse and changed all of the LED
down lights to bio lights.
And what that means is they areEMF and flicker-free during the

(17:11):
day and have the full spectrumof blue in them, and then at
night they have zero blue inthem at all.
And it makes an amazingdifference to mood, you're ready
for sleep, you sleep so muchbetter.
It's incredible the differencethat it makes.
Those lights in your house areimpacting on your health, and

(17:33):
it's important that youunderstand that.
And what I also need you to dois to stay consistent where you
can.
Even small patterns will helpthese cells to guide your
hormones.
Literally, anchor your circadianrhythm.
When you're on night shift, it'salmost impossible to anchor it
with daylight.
I get that.
But every other time you can,and this is why I talk about

(17:55):
that regular wake-up time.
Now, why isn't this just aboutsleep?
Because people think this isjust a sleep issue.
But the IPRGCs influence so muchmore, and I mean so much more.
Let's see if you can relate toany of this.
They actually affect moodstability.
Your appetite.

(18:16):
Blue light means daytime meanshunger.
It helps with the appetitetiming, it helps with
metabolism.
We are not designed to actuallyeat overnight.
Blood sugar control, cognitivefunction, brain health, brain
fog, heart health, the rhythmsin your gut.

(18:38):
Is it any wonder that you sufferfrom digestive issues, gas,
bloating when you're on nightshift?
So if your IPRGCs fire at thewrong time, your whole system
becomes disordered.
And that is why many shiftworkers feel like their body is
constantly guessing.
And you know why?
It's because it is.
Because when you give thesecells the right signals, your

(19:01):
body feels a lot steadier.
And it won't take long toactually feel the difference.
I challenge you for one week totry getting up at roughly the
same time every morning.
And this is why I say getting upat the same time every day.
Bonus points for getting to bedat the same time.

(19:22):
But even after a late night,getting up at the same time and
anchoring that circadian rhythmwith light is what will get you
thriving.
And you now know why.
It's because of those IPRGCs.
You need to get that light intoyour eye early and anchor that
circadian rhythm to improveeverything.
And as I said, mood stability,appetite timing, your

(19:43):
metabolism, your blood sugarcontrol, cognitive function,
brain fog, heart health,cardiovascular health, gut
rhythms.
All of this makes a hugedifference by just anchoring
that circadian rhythm.
Understanding these IPRGCs, oneof the most powerful things that
you can actually do as a shiftworker, you have very, very

(20:05):
limited control over yourroster.
I get that.
But the one thing that you dohave control over, and I always
say control the controllables,is you control your light
exposure.
Now, these cells do not careabout your job.
What they do care about islight.
So give them the right signals,and your body will actually

(20:25):
respond so much better.
So thanks for listening to ahealthy shift podcast today.
I really hope you got a lot outof that one.
And if you want support withgetting your light routine
right, you can reach out to methrough the show notes.
There's a link there.
Let's have a chat.
I can help you.
So take care and I'll talk toyou again on the next one.

(20:52):
Thank you for listening.
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If you want to know more aboutme or work with me, you can go
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I'll catch you on the next one.