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Jen Oliver: Welcome to the, so That's
Why Podcast where we unpack the

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science behind everyday questions.

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I'm Jen.

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Chris Smith: I'm Chris.

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Matt Edmundson: And I'm Matt.

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Jen Oliver: Okay, so today's question
is something that every single person

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listening will be able to relate to.

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Why do we get pins and needles?

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Matt Edmundson: Good question.

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Uh, we all know that sensation, I
dunno if you like me, where your

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foot completely stops working.

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And you're just sat there hoping no
one gets to see you try and walk,

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uh, in the next 30 seconds, right?

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Chris Smith: And that,
uh, foot won't work.

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Situation is the perfect illustration
because that distinctive buzz doesn't

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happen when something goes wrong.

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It's happening when things
are actually being corrected,

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Jen Oliver: Which goes against
actually what we've all thought.

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But by the end of this episode, you'll
understand exactly what's happening at an

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nerve level, why getting pins and needles
feels the way it does, and crucially

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why they are worth paying attention
to rather than just shaking them off.

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Matt Edmundson: Yeah, and also
why your arm can go completely

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dead from sleeping on it.

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But then be entirely fine.

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I dunno if you found this within just
a few minutes, which always seems like

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a disproportionately quick recovery
for something that felt quite dramatic.

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I wish the common cold was,
uh, as fast to recover.

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Jen Oliver: Yeah, imagine.

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Chris Smith: I know.

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That'd be good.

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But yeah, the, the speed of recovery,
um, is actually one of the most telling

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things about what's going on, and
it's a clue that we'll come back to

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once we've unpacked the mechanism.

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Jen Oliver: So how do they actually start?

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It's got a fancy name.

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As do a lot of things paraesthesia,
which is an umbrella term for

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any abnormal skin sensation
without an obvious external cause.

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But the everyday kind of pins and
needles we get from being in certain

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positions is really a circulation
story as much as it is a nerve story.

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Matt Edmundson: That's
quite interesting, isn't it?

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I, I, I'd always thought
this was a nerve thing.

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Mm. Um, so the circulation angle.

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Uh, it's gonna help me
reframe it, I guess.

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Chris Smith: Yeah.

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And they are genuinely, um, inseparable.

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So nerves are extraordinarily
demanding structures and they rely

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on a continuous, uninterrupted
blood flow to function properly.

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So the everyday positional kind
of pins and needles comes down.

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Two things happening simultaneously.

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We've got mechanical compression of a
nerve and a reduction in its blood supply.

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Jen Oliver: Exactly.

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So they basically make
things worse for each other.

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So the blood vessels that feed
the nerve run right alongside it.

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So when you squeeze the nerve,
you're actually pinching its

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fuel line at the same time.

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Matt Edmundson: So a nerve under
pressure then isn't just physically

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squashed, it's also being cut off
from what it needs to function.

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Chris Smith: That's exactly it.

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And a nerve being deprived
doesn't simply go quiet.

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It starts sending these kind of
chaotic, unpredictable signals

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rather than the orderly ones that
your brain is used to receiving.

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Jen Oliver: And that chaotic firing
is what the brain interprets as

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something strange and unfamiliar.

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It can't make sense of the signal.

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So rather than recognizing it
as an nerve under pressure, it

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registers, uh, registers it as
something that needs attention.

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Matt Edmundson: Right.

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So when your leg falls asleep,
then it's not actually asleep.

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It's not actually silent.

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It's more like a radio that's
kind of picked up interference

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instead of the actual station.

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Chris Smith: Yeah, that
interference analogy is a good one.

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In fact, we should call
you captain analogy.

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Sure,

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Matt Edmundson: yeah, yeah, yeah.

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Chris Smith: If I'm captain, kind
of sensible or Captain MythBuster

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Matt Edmundson: MythBuster,

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Jen Oliver: I,

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I still need one.

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I still need a title.

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Matt Edmundson: Madam
MythBuster, wasn't it?

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I can't

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Jen Oliver: remember.

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Yeah, I wasn't keyed on

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Matt Edmundson: that.

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Oh, yeah.

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We need a better one.

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Chris Smith: Um, so
I've, I've lost my train.

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We, we'll talk about Oh yeah.

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Your analogy of, um, interference.

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And it is a good one because, um, what
determines the specific character of

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that buzz that you get comes down to
which nerve fibers are affected and

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in what order, because not all fibers
respond to compression the same.

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Jen Oliver: So to add to that, so
the big myelinated ones, they're

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called the AB to fibers and they
handle regular light touches.

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They're the most sensitive to being
squeeze because they need the most energy.

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So they're the first to shut down
essentially when the blood flow drops.

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Matt Edmundson: So the fibers whose
entire job is to tell your brain

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everything is fine, or the first
ones to check out under pressure.

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So is this a bit of a design flaw?

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Chris Smith: Well, yeah, I
think, I think it's a fair point.

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And when, um, when those large fibers
go offline, the brain stops receiving

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the usual reassuring touch signals
and in the absence of that normal

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input, its interpretation of what's
happening to that limb shifts entirely.

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Jen Oliver: So you then left with the
smaller fibers, the A delta and the C

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fibers that carry pain and temperature
signals, and they're more resilient,

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so they keep firing even when the
larger fibers have already dropped out.

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Matt Edmundson: Yeah, so your brain
is getting the something run signals.

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Without the, actually it's fine
signals to balance them out.

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It's like the alarm is going
off, uh, without the all clear.

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Chris Smith: Yep.

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Captain analogy.

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Thank you very much.

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But yeah, that alarm without the all clear
framing explains why there's kind of often

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a distinct sequence of the experience.

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So many people notice the area goes
numb first before that tingling begins.

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And that numbness is the.

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A B to fibers that gem
mentioned going quiet.

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The tingling that follows is what
happens when those smaller fibers

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are left broadcasting on their own.

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Jen Oliver: And that's a really, it's
a really useful distinction 'cause

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many people assume that the numbness
and tingling are the same thing, but

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that actually two stages of the same
process just happening in sequence.

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Matt Edmundson: Yeah.

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So you go through the numbness on the
way in and then the tingling on the

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way back out and those two feelings.

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Are basically the backends
of the whole event, right?

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Mm-hmm.

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Chris Smith: Exactly right.

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And, and here's the find that
I find genuinely fascinating.

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Okay?

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Make of that what you will
geek the tingling itself,

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Matt Edmundson: captain geek,

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Chris Smith: the tingling doesn't
happen while the nerve is compressed.

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It happens when the pressure is released.

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And the blood flow is rushing back in,

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Jen Oliver: and that's the key part.

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As the circulation returns, the NA
near fibers, they start coming back

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online, but it's not all at once
and it's not in a coordinated way.

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So different fibers recover at
different speeds, which causes them to

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fire chaotically as they reactivate.

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Matt Edmundson: So the pins
and needles are not, then the

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injury is what I'm hearing.

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They're the recovery.

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So you feel the worst of it when
you are actually getting better.

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Which kind of reframes the experience.

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Chris Smith: Yeah, absolutely.

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And picking up on that recovery idea,
the reason the tingling seems to travel

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that kind of crawling feeling, moving up
your foot or along your arm is because

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it's following the actual nerve path as
sections progressively come back online

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Jen Oliver: and different fibers also
have different recovery thresholds,

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which is why the sensation shifts from
like a burning to a buzzing to something

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more normal over the course of a few
minutes, it's staged and it's sequential.

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Matt Edmundson: So your nervous system is
doing a staged restart section by section,

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and those uncomfortable feelings are just.

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In my terminology, the loading screen.

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Chris Smith: Absolutely.

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And it explains that kind of quick, I
think you said few minute or two minute

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recovery that you, Matt mentioned
right at the top, the nerve was never

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damaged, it was just temporarily offline.

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And once that blood supply
is restored, the hardware is

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intact and recovery is rapid.

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Jen Oliver: And that distinction
between positional, parathesia and

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nerve damage is key because like a
brief compression that resolves cleanly,

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but a prolonged or repeated pressure.

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That can cause structural
changes over time.

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Matt Edmundson: Yeah.

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So there's a meaningful difference,
isn't there, between sitting awkwardly

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for 20 minutes, which I do do, and
then doing the same thing every

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day for years, which I may do.

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Um, and I guess the body can
handle the occasional mistake.

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It's that sustained habit
that changes things.

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Mm,

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Chris Smith: it is.

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But to look at.

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From another angle, this is all fine
unless the cause isn't positional at all.

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So pins and needles can also be
one of the first signals of an

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underlying health condition, and
it's worth knowing what to look for.

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Jen Oliver: Yeah, so diabetes is probably
the most clinically significant cause,

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um, having persistently high blood sugar
that damages the small vessels that

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supply peripheral nerves, the same ones
that we've been chatting about and that

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eventually causes peripheral neuropathy.

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You know, chronic tingling
and numbness, and that usually

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starts in the hands and the feet.

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Matt Edmundson: Yeah.

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So it's the same mechanism, right?

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Nerves not getting enough blood.

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But this time it's chronic
rather than temporary.

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Chris Smith: It is.

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And um, the scale of it is striking.

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So research from diabetes uk um, estimates
that around 50% of people with diabetes

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develop some degree of peripheral
neuropathy, making it one of the most

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common causes of, uh, complications
of the condition of diabetes.

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Jen Oliver: And that statistical alone
is a good reason to take persistent,

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unprovoked tingling seriously.

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Um, another cause vitamin B12 deficiency.

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Um, is a co a cause that's often
underdiagnosed, so B12 that maintains

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the myelin sheath, the protective coating
around your nerve fibers that lets

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signals travel quickly and accurately,

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Matt Edmundson: which is particularly
relevant for anyone who's on a plant-based

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diet because B12 is entirely, uh,
well, almost entirely absent, isn't

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it, from, um, non-animal food sources.

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So it's not a deficiency that's
gonna correct itself without

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kind of deliberate action.

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Chris Smith: Exactly.

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It's so important.

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And, um, without adequate B12, that
myelin progressively degrades with one

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of the earliest symptoms typically being
tingling or numbness in the extremity.

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So the hands and the feet,
but it becomes more serious,

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neurological issues can develop.

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Jen Oliver: But what makes B12 tricky
is that the body stores a large

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reserve of it, and the depletion
happens gradually over months or years.

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So by the time someone's symptoms appear,
they may actually be really deficient.

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Matt Edmundson: Yeah, so persistent pins
and needles then in your hands could

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be your body's first clear, noticeable
signal of a nutritional gap that's been

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quietly building up for a long time, and
it's probably worth taking seriously.

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Yeah.

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Chris Smith: Yeah, it really is.

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And that's why regular B12 monitoring
for all of us is, uh, so important.

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And it's particularly for those
on long-term, um, diabetes

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medications like metformin, which
interferes with B12 absorption.

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Jen Oliver: And magnesium.

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That's another one that's probably worth
us flagging that directly affects nerve

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signal transmission and low magnesium.

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It makes the nerves more excitable,
which produces spontaneous tingling,

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especially again in the hands and feet.

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Matt Edmundson: And magnesium is one
of the most consistently under consume

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minerals in our modern day diet, isn't it?

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Mm-hmm.

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So it's another case where the nutritional
gap might be showing up as a symptom.

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Um, that seems to be
completely unrelated to food.

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Chris Smith: Uh, it's a really good point.

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And um, carpal tunnel syndrome is another
very common cause, and it follows the same

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compression logic we've already laid out.

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So in this case, the median nerve
gets compressed as it passes

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through a narrow channel in the
wrist producing this kind of.

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Tingling, uh, specifically in the thumb,
the index finger and the middle fingers.

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Jen Oliver: But what's worth adding to
that is that carpal tunnel, it isn't just

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a risk problem 'cause it's a nerve pathway
problem, and the median nerve that you

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mentioned that runs from the neck all the
way to the fingertips, and compression

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anywhere along that root can contribute
to symptoms that you feel in your hand,

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Matt Edmundson: which explains why
it's, I guess, so widespread now.

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Right?

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Um, if you're at a keyboard, six
to eight hours a day, or 10 to 12

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hours a day, depending on your job.

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Um, if you've got your wrist sort of
bent, slightly out position, the nerve is

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sort of under this low level compression,
isn't it, for most of your working life.

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And I, I figure it's eventually
gonna stop tolerating that.

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Mm-hmm.

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Chris Smith: And with this whole topic of
pins and needles, there's one more cause

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that genuinely catches people off guard.

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And that's anxiety.

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So when we're anxious, we tend to
over breathe often, quite subtly,

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you know, without even noticing.

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But this lowers the CO2
levels in our blood.

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Jen Oliver: Yeah.

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And that CO2 drop, it's got direct
physiological consequence, so it

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changes the blood pH, it lowers
blood calcium, and that increases

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the peripheral nerve excitability.

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So that means the nerves start
firing more spontaneously, producing

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tingling, particularly in the
hands and around your mouth.

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Matt Edmundson: Mm-hmm.

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So the tingling you get during
an anxious moment that isn't

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imagined, it's a real measurable.

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Um, physiological response
to a breathing change, right?

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Jen Oliver: Mm.

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Chris Smith: Yeah.

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And, and the evidence for it
is, um, surprisingly direct.

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So studies using controlled
hyperventilation.

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Can reliably reproduce pins and needles
in healthy subject within two to three

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minutes, which shows exactly how quickly
CO2 changes affect that nerve function.

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Jen Oliver: But the good news is
that, you know, slow control breathing

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during an anxious episode, it doesn't
just calm you psychologically, it

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actively corrects that CO2 imbalance.

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So that's triggering the nerves,
which is why the tingling fades as you

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breathe more slowly and gain control.

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Matt Edmundson: Yeah, so there's
a specific physiological loop

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at play here, isn't there?

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That we can see.

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You've got anxiety, which
triggers shallow breathing.

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Mm-hmm.

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Um, which then drops the CO2
levels, which then makes.

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Um, nerves, fire spontaneously,
which feels alarming, which

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can then deepen the anxiety.

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Mm-hmm.

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Uh, and knowing what's happening I think
is a good way to help break that loop.

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Jen Oliver: Yeah, yeah,

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Chris Smith: totally.

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And, um, building on that, so brief
pins and needles that go away as

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soon as you move are totally normal.

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So the good news is that's exactly
what most people experience rather than

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something kind of more serious behind it.

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Matt Edmundson: Yeah.

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Fascinating.

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I mean, the practical rule
I'm taking from all of this.

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If change in position fixes it,
it's almost certainly mechanical.

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Mm-hmm.

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If movement makes no difference
at all, um, that's the signal

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probably to go get it looked at.

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Jen Oliver: Exactly.

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And the patterns worth flagging
to a doctor are persistent,

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tingling in the same location
without a positional explanation.

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You know, tingling that comes alongside
muscle weakness or symptoms that are

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consistently worse at night when you
haven't even been in an unusual position.

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Chris Smith: Yeah, and beyond
those, I think any sudden onset

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of numbness or tingling in.

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You know, one side of the body.

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Yeah.

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Especially alongside the, um, like facial
drooping, slurred speech or arm weakness

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that needs emergency attention because
it can indicate a stroke or a TIA.

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Mm-hmm.

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Matt Edmundson: Yeah.

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And that presentation is clearly
different right from gradual,

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uh, from the gradual bilateral.

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I've been sitting on the floor
in a weird position way too long.

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Mm. Um, it's sudden it's one-sided and
accompanied by other things that feel.

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Unmistakably wrong.

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Jen Oliver: Yeah.

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So as Matt says, the vast majority of
pins and needles is your body doing

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exactly what it should be, but it's a
sensation worth staying curious about

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rather than always dismissing it.

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Chris Smith: Yep, it is.

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And so for everyday positional kind
of pins and needles, gentle movement

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is the most effective response
because it encourages that blood flow.

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It speeds up that nerve recovery
process that we described earlier.

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Jen Oliver: So here's a fun fact for you.

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There is

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Matt Edmundson: F I've
figured out your name.

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Jen Oliver: Go on.

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Matt Edmundson: Fun fact, Jenny.

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Jen Oliver: So you two get
capped in something and I get you

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Matt Edmundson: can be captain in.

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Fun fact.

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Fun fact.

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Jen Oliver: Okay.

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Okay.

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I thought I was just gonna get fun.

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Fact, Jenny.

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Okay, so yeah, so here's a fun fact.

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There is no evident.

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For the vigorous shaking is more
effective than gentle movement

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to get rid of pins and needles.

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So the nerve just needs circulation
restored and a bit of time to resequence

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its firing, which happens naturally.

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Matt Edmundson: Well, thank you, uh,
captain from fact because I am the

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person that violently flex my hands
trying to get, you know, like I'm

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trying to launch it off my wrist.

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Uh, and I figure I'm not the only
one that's, uh, that's done that.

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Jen Oliver: No, no, no,

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Chris Smith: Yeah, there's genuinely no
need for the kind of vigorous action.

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Um, gentle is enough, but for
recurrent carpal tunnel symptoms,

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specifically wrist splints worn at
night have solid clinical evidence.

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They prevent the risk from flexing
during sleep, which is when

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compression tends to be at its worst.

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Jen Oliver: And for the anxiety related
kind, slow diaphragmatic breathing is

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probably the most direct intervention.

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So you are actively restoring
CO2 levels and reducing the nerve

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excitability, not just managing
how you feel about the situation.

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Matt Edmundson: So the box breathing
that gets recommended for anxiety is

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a direct physiological reason why it
works specifically for the tingling.

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Jen Oliver: Mm-hmm.

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Chris Smith: Yeah.

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And for a lot of people.

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If you think of kind of office workers,
the most useful long-term habit is

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actually about posture and screen setup.

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00:17:06,200 --> 00:17:10,430
So keeping your wrists in a neutral
position during keyboard work.

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Taking regular breaks from
sustained positions that removes

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the low level compression that
accumulates across that working day.

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Jen Oliver: Well, if you get chronic or
recurring pins and needles, try and focus

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on root causes like posture, nutrients,
blood sugar, rather than quick fixes.

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Matt Edmundson: Yeah, so the long term
answer isn't what you do when it happens.

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It's the conditions you're creating
day in, day out that determine how

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often it shows up in the first place.

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Jen Oliver: And that connects back to
a lot of ground we've covered before,

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like B12, vitamin D, Omega-3, magnesium.

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These all affect neurological function
in different ways, and pins and

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needles is just another place where
those gaps surface as physical signals

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before anything more serious develops.

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Chris Smith: Yeah, that's a really
important thread and blood flow.

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Quality runs through all of it.

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So whether it's cardiovascular
health, uh, brain function, or

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peripheral nerve health, the quality
of circulation fundamentally shapes

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how the whole system performs.

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Matt Edmundson: Yeah, and it also ties
back to the brain fog episode where nerves

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under sustained stress and nutrients
aren't reaching where they need to go.

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The body uses these sort of sensations
like pins and needles to flag something.

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It can't communicate in any other way.

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Jen Oliver: And I keep coming right
back to what Chris said at the start,

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that the pins and needles themselves
are the recovery, not the damage.

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So the uncomfortable sensation
is actually proof that your

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00:18:40,355 --> 00:18:42,575
nervous system is doing its job.

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Chris Smith: Yeah, and it's a good
reminder that the body's warning

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systems, uh, signals are often
the same as its repair signals.

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So the discomfort and the correction are
the same event happening at the same time.

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Matt Edmundson: Your nervous system,
your nervous system, staging a full.

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Uh, protest turns out to be
working exactly as intended,

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which makes it considerably easier
to live with that knowledge.

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Jen Oliver: So that's why the next
time that familiar buzz starts

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working it's way up your foot,
you'll know exactly what's happening.

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That's not a problem.

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That's the recovery already underway.

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Yeah.

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Matt Edmundson: Your nervous system is
doing a full-time reboot in real time.

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Jen Oliver: So that's it for this week.

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Hit subscribe and drop as a
comment with whatever question

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00:19:29,270 --> 00:19:30,980
you'd like us to explore next.

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00:19:31,340 --> 00:19:34,730
Thanks for geeking out with us,
but for now, that's it from me.

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00:19:35,210 --> 00:19:36,020
Matt Edmundson: That's it from me.

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00:19:36,290 --> 00:19:37,040
Chris Smith: And that's it from me.

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Jen Oliver: Bye for now.