So That's Why

Why do we get heart palpitations when a heart monitor so often shows a perfectly normal rhythm? Jen, Chris and Matt unpack the science behind one of the most unsettling sensations a healthy person can have.A palpitation isn’t a diagnosis. It’s simply the word for becoming aware of your own heartbeat, and it can come from two very different places: a genuine change in what the heart is doing, or a change in how much attention you’re paying to it. In this episode, the team explores how adrenaline turns up both the speed and the force of each beat, why a “skipped” beat is usually an early one, and why sodium, potassium and magnesium matter for the heart’s electrical signals. They also look at Harvard Health figures on palpitations during perimenopause and after menopause, everyday triggers from caffeine to decongestants, the warning signs that need prompt medical attention, and what the evidence actually supports, from vagal manoeuvres to a two-week trigger diary.In this episode00:00 Why do we get heart palpitations?01:20 Two causes, your heart or your awareness02:38 How adrenaline changes your heartbeat04:58 The skipped beat that arrives early07:28 When the rhythm is normal but you still feel it09:29 Hormones, stimulants and medications13:04 When to get palpitations checked15:45 What the evidence actually supports18:41 So that’s whyWhy Adrenaline Makes Your Heartbeat Feel Louder (02:38)The most frequent driver of palpitations is the sympathetic nervous system, better known as fight or flight. Anxiety, fear, excitement and fever all trigger the release of stress hormones such as adrenaline.Adrenaline speeds the heart up and increases the force of each contraction, which are two separate effectsYour heart rate climbs normally when you jog for a bus, yet almost nobody calls that a palpitationIt’s the stronger beat, not the faster one, that people tend to noticeChris: “If you think of your heartbeat as music that’s been playing quietly all day, adrenaline turns up the tempo and the volume at the same time.”The Skipped Beat That Actually Arrives Early (04:58)The skipped beat is the sensation that frightens people most, but there often isn’t a gap at all.Many “skipped” beats are premature contractions, where an early electrical impulse fires ahead of the normal rhythmThese are called ectopic beats (“ectopic” means out of place) and they’re extremely common in structurally normal heartsEvery heartbeat starts as an electrical signal that relies on minerals such as sodium, potassium and magnesium moving across cell membranes, which is why electrolyte imbalances can set early beats offChris: “Your heart is basically an overachiever, Matt.”Why a Normal Heart Rhythm Can Still Feel Wrong (07:28)When people wear an ambulatory ECG (a wearable device that records the heart’s electrical activity over hours or days), clinicians frequently find a completely normal rhythm, even during a reported episode.Johns Hopkins University is clear that the sensation is real, even when there’s no rhythm disturbancePerceiving your own heartbeat is a genuine sensory process, and how much attention it receives varies enormouslyNoticing the beat can trigger alarm, which feeds the very response that makes the beat strongerJen: “You notice the beat. Noticing it is alarming. Alarm triggers a sympathetic response, and the sympathetic response makes the beat stronger and easier to notice.”When Heart Palpitations Are Worth Getting Checked (13:04)Most palpitations settle on their own, but occasionally they signal an arrhythmia, a genuine electrical malfunction such as atrial fibrillation.Palpitations with chest pain or pressure, breathlessness, dizziness, fainting or unusual sweating need emergency assessmentPalpitations that are frequent, getting worse or persistent through the day should prompt an ECG or extended wearable monitoringMonitoring is non-invasive, widely available, and replaces guessing with an answerMatt: “So it’s the company that it keeps rather than the palpitation on its own, and do go.”About So That’s WhySo That’s Why is a weekly podcast where Jen, Chris and Matt unpack the science behind everyday health questions. No jargon, no judgment. Just genuine curiosity and proper research.Website: https://www.vegetology.com/so-thats-why-podcast

Ever been in a foul mood for no obvious reason and blamed your brain? A surprising amount of that feeling starts a good deal further south. This week Jen, Chris and Jamie unpack why your gut has more say over your mood than you'd think, and why the gut, not the brain, does most of the talking.Your gut houses around 500 million neurons and 100 trillion microorganisms, and that community is chemically busy all the time. It makes over 90% of your body's serotonin, produces calming signals like GABA, and reports back to your brain along the vagus nerve in seconds. The team explores the gut-brain connection, the two-way stress loop that links anxiety and IBS, and the genuinely encouraging news that your microbiome, and your mood, can start shifting in as little as 72 hours.No jargon, no judgment, just the science behind why trusting your gut turns out to be more literal than it sounds.In this episode: 00:04 - Your gut has a direct line to your brain 01:30 - 500 million neurons and 100 trillion microorganisms 03:02 - The vagus nerve and why the gut does most of the talking 04:16 - Where your serotonin is actually made 06:11 - The stress loop and how anxiety damages your gut 07:15 - What you eat changes your microbiome in 72 hours 09:53 - What to actually do about it 13:39 - The takeawayTimestamps are based on transcript section markers and should be checked against the final edit.Your Gut Does 80% of the TalkingThe gut and brain are wired together by the vagus nerve, a direct line with no switchboard in between. Around 80% of the traffic on that line travels upwards, from gut to brain, which means the brain spends most of its time listening rather than instructing.The gut contains around 500 million neurons, more than your entire spinal cordRoughly 100 trillion microorganisms make up the gut microbiomeA 2023 study found gut dysbiosis in around 75% of people diagnosed with major depression"It's not a conversation. The gut keeps leaving voicemails for the brain." JamieOver 90% of Your Serotonin Is Made in Your GutSerotonin is the chemical we all associate with mood, and the overwhelming majority of it is manufactured in the gut. But there's a subtlety: gut serotonin can't cross the blood-brain barrier, so it doesn't travel to the brain directly. Instead it stimulates the vagus nerve, and the nerve carries the message.Gut bacteria also produce GABA, your main calming signalShort-chain fatty acids lower inflammation and protect the gut liningA 2025 Duke University study identified a "neurobiotic sense" that detects specific bacteria within seconds"So the gut rings ahead and tells the brain what to do, and the brain just does it." JamieThe Stress Loop Runs Both WaysSustained pressure raises cortisol, which weakens the gut lining and increases intestinal permeability, commonly known as leaky gut. Bacterial byproducts then slip into the bloodstream, triggering inflammation that feeds straight back into low mood. Stress damages the gut, and the damaged gut worsens the stress.This is why the link between IBS and anxiety isn't a coincidenceDiets high in ultra-processed foods reduce lactobacillus and bifidobacterium speciesA 2022 study found measurable microbiome shifts after just 72 hours of dietary changeThe People With the Most to Gain, Gain the MostFermented foods and specific probiotic strains have real evidence behind them. A 2020 study of over 1,000 adults found regular fermented food eaters had measurably lower stress scores across all ages, and the benefit was strongest in those whose microbiome diversity started off lower."Rules on their own don't stick, but the reasons do." ChrisAbout So That's WhySo That's Why is a weekly podcast where Jen, Chris and Matt unpack the science behind everyday health questions. No jargon, no judgment, just genuine curiosity and proper research.Website: https://www.vegetology.com/so-thats-why-podcast

Your brain builds a convincing world every night, then clears nearly all of it before you wake. So why do we dream?Most of us have between four and seven separate dreams a night and forget up to 95% of them within minutes. Jen, Chris and Matt work through what is actually happening in the brain during REM sleep, why the forgetting is a consequence of the mechanism rather than a memory failure, and what the best current evidence says dreaming is for. The episode covers the four regions that swing out of balance during REM, the 2024 Scientific Reports study on dreaming and emotional memory, why babies spend so much more time in REM than adults, the simple line that separates a bad dream from a nightmare, and whether what you eat can genuinely change what you dream about. By the end you should be able to explain the whole thing in one sentence.Chapters00:00 Why do we dream01:34 How much we actually dream and why we forget it02:26 What is happening in the brain during REM sleep07:37 Dreaming as emotional processing10:44 How dreaming changes with age and how you wake12:46 What separates a bad dream from a nightmare15:15 Can food actually change your dreams17:22 The verdict on why we dreamFour Regions Swing Out of Balance During REM Sleep (02:26)Most vivid dreams happen during rapid eye movement sleep, and what makes REM unusual is not simply that the brain is busy. Several regions shift at once.The prefrontal cortex, which handles logic and self awareness, powers down. That is why nothing in a dream seems questionable while it is happening.The amygdala, involved in processing emotions, becomes more active, which helps explain the emotional intensity.The visual cortex fires with no real input coming in, generating the images fresh rather than replaying old footage.The hippocampus keeps feeding the dream real material from recent memory.Underneath it all, the brainstem fires bursts of signals and the rest of the brain builds a story around them, which is why a dream lurches from your kitchen to a beach with no join."My brain's improvising over random noise and pretty much hoping that I don't notice." MattThe Same Switch Explains the Strangeness and the Forgetting (06:46)The prefrontal cortex is not only the region that would normally question a dream. It is also the part that bookmarks a memory as worth keeping. With it turned down, dreams barely get flagged, so they are hardly stored."The one night your brain does its most vivid work, it keeps no receipts." ChrisDreaming Looks Like Emotional Sorting (07:37)The leading theory is that dreaming is emotional and memory processing. The brain holds onto the memory of something that upset you while turning down the emotional charge attached to it. A 2024 study published in Scientific Reports found people who dreamed kept their emotionally charged memories, let neutral material fade, and rated the charged memories as less upsetting by morning. Older work from sleep researcher Rosalind Cartwright found people going through a painful breakup who dreamed about it recovered their mood noticeably faster.The hosts are careful with the limits here. This is still open science, and much of it shows a link rather than a nailed down cause.A Nightmare Is the Same Process Running Hot (12:46)The dividing line is simple. A nightmare wakes you. A bad dream is unpleasant and you sleep through it, whereas a nightmare pulls you out of REM with the fear still running. Roughly two thirds of dreams carry sadness, worry or anger, and only about a fifth are clearly happy."A nightmare isn't your mind failing. It's that same system working on something heavy and getting stuck partway through." ChrisStress is the biggest trigger, and lost sleep does it too, because the brain packs in extra REM to catch up. Frequent nightmares are common after trauma, affecting up to 70% of those living with it. If nightmares become frequent and start wearing you down, it is worth speaking to a GP, as treatments such as imagery rehearsal therapy genuinely work.About So That's WhySo That's Why is a weekly podcast where Jen, Chris and Matt unpack the science behind everyday health questions. No jargon, no judgment, just genuine curiosity and proper research.Website:

Pre-diabetes might be the only common diagnosis experts can't agree on, and a quarter of the people told they have it quietly recover on their own. In this episode, Jen, Chris and Jamie unpack why we develop pre-diabetes, why it builds in near silence for a decade or more, and why a warning that lands while you feel perfectly fine is still genuinely good news.The team dig into the two changes at the heart of it: muscles that stop listening to insulin, and insulin-making cells that go quiet rather than die off. They explain the "fat in the wrong place" idea that pulls it all together, why even slim people can be affected, and why three different tests can disagree so wildly that the experts still argue about the word itself. Then comes the hopeful part, which is the unusually deep evidence that modest, sustainable changes can shift the whole picture. As Chris puts it, pre-diabetes is best thought of as a stage, not a disease.In this episodeTwo Quiet Changes Drive Pre-Diabetes (03:14)It's Fat in the Wrong Place, Not Just How Much (05:41)Why Experts Still Argue Over the Diagnosis (07:01)What the Evidence Says Actually Works (10:12)(Timestamps are based on the transcript's section markers. Please verify against the final edit before publishing.)Two Quiet Changes Drive Pre-Diabetes03:14Pre-diabetes comes down to two things drifting slightly out of step over years, each making the other worse. The first is insulin resistance, where your cells stop listening to insulin as well as they used to. The cells that go deaf first are your muscles, the biggest customer for blood sugar, taking up about three-quarters of it after a meal. The second is in the pancreas, where the insulin-making beta cells gradually stop keeping up.Insulin tells your cells to take sugar in and use it. When they stop listening, sugar hangs around in the bloodstream.This can build for ten or even twenty years before anything shows on a test. It's a drift, not a breakdown.The reassuring twist: the beta cells largely don't die. They seem to change job and go quiet, so there is a route back.Chris: "Pre-diabetes is a stage, not a disease."Jamie: "They've downed tools. They're still in the building, they're just not doing the skilled bit."It's Fat in the Wrong Place, Not Just How Much05:41The idea that pulls everything together is a domestic one. Picture your body's fat as something you store in a cupboard. Most of it is meant to live there, under the skin, safely. But every cupboard has a size, and that size is different for everyone. The trouble starts when it overflows into places it was never meant to go.This explains why you can be fairly slim and still develop pre-diabetes. Your personal storage cupboard might just be a small one.It's part of why people of South Asian heritage can be affected at lower body weights, and why screening thresholds are set lower for some groups.The cupboard hasn't shrunk. Many of us are simply filling it faster and emptying it less than a couple of generations ago.Jamie: "So the bathroom scales are never really telling the interesting story."Why Experts Still Argue Over the Diagnosis07:01Whether you count as having pre-diabetes depends heavily on which test you happen to get, and that is where the debate comes from. There are three common ways to diagnose it, and the share of people who count swings wildly between them. The most common, the HbA1c test, adds a further wrinkle, because it reads a touch higher in Black patients for the very same blood sugar.One analysis found the proportion of a group counted as pre-diabetic ranged from about 4% to over 40%. Same people, different test.Over a few years, very roughly a quarter of people progress, half stay put, and a quarter drift back to normal.This busts the biggest myth, that pre-diabetes means diabetes is definitely coming and nothing can be done. It's a real signal, just drawn with a slightly blunt pencil.What the Evidence Says Actually Works10:12After all the uncertainty, this is one of the most changeable situations in medicine, and the evidence is unusually deep. In a landmark prevention trial, people making modest changes cut their chance of developing diabetes by getting on for 60% over about three years, which was clearly better than the medication group in the same trial.The levers are reassuringly dull: roughly 7% weight loss and about 150 minutes of movement a week, the equivalent of a brisk 20 to 25-minute walk a day.Movement helps on its own. People who missed the weight target but kept moving still cut their risk by over 40%.A Mediterranean-style diet of veg, beans, whole grains and olive oil meaningfully cut new diabetes in one big trial, even when people barely lost weight.A responsible note from the team: the pre-diabetic range is typically an HbA1c of 42 to 47. If it's on your radar, that's a good reason for a chat with your doctor, not a cue to panic or self-diagnose.Jamie: "So the walking and eating group beat the drug? That's not how these stories usually go."About So That's WhySo That's Why is a weekly podcast where Jen, Chris and Matt unpack the science behind everyday health questions. No jargon, no judgment, just genuine curiosity and proper research.Website: https://www.vegetology.com/so-thats-why-podcast

Ask anyone what makes us cry and they'll say sadness. When researchers track real crying episodes, they find something else entirely.Jen, Chris and Matt unpack why we cry when we're sad, and discover the answer isn't the sadness at all. It's powerlessness. The triggers people actually report are far smaller than anyone assumes, turning up as conflict, criticism, rejection and minor personal failures rather than bereavement and tragedy.The team follows the signal from the limbic system to the brainstem to the tear glands, explains why tears spill over your eyelid at all, and looks honestly at the evidence behind the popular idea that crying flushes stress toxins out of the body. They also tackle the biggest contradiction in this research. Over 70% of people say crying makes them feel better, while controlled lab studies found the opposite. The resolution comes down to timing, and to who else is in the room.Chapters00:00 Why do we cry when we're sad 00:51 Powerlessness, not sadness 04:20 What happens in the brain and body 08:33 What emotional tears are made of 10:51 Why crying varies so much between people 16:02 Does crying actually make you feel better 19:03 When crying isn't good for you 21:29 The verdict on why we cryThe Real Trigger Isn't Sadness, It's Powerlessness (00:51)Sadness is almost always present when we cry, but rarely on its own. It turns up blended with anger, fear, frustration or disappointment, and the common denominator underneath is not being able to do anything about the situation.One psychologist frames the tipping point as the moment psychological demands exceed your sensory effective threshold. In other words, the emotion has outpaced whatever coping mechanism was available at the time."So it isn't then about how bad the thing is, it's the gap, I guess, between that and what you've got left in the tank." MattThis is also why the same event can floor you one week and barely register the next. Sleep deprivation, alcohol, stress and mental health all lower the threshold.Why Tears Actually Run Down Your Face (04:20)The sequence starts in the limbic system. The amygdala helps determine how intense an emotion feels, while the anterior cingulate cortex helps you recognise and respond to it. From there the signal travels to the pons in the brainstem, which activates the tear glands through a facial nerve.The overflow itself is simpler than most people expect. The glands produce fluid faster than the tear ducts can drain it, so the drainage isn't failing, it has just been outpaced."So think about it like a sink with the tap on harder than the plug hole can cope with." JenThe team also covers the three tear types (basal, reflex and emotional), and why there's no rigorous evidence that any other species produces the third kind.The Stress Toxin Idea Doesn't Hold Up (08:33)Some studies have reported higher levels of prolactin and adrenocorticotropic hormone in emotional tears, alongside compounds including leucine enkephalin, potassium and manganese. Chris and Jen are careful to flag that these findings still need stronger replication.That matters, because they're the foundation of the popular idea that tears flush stress toxins out of the body. One of the influential early studies supporting it was not successfully repeated by later researchers. The chemistry that is present, including oxytocin, vasopressin and endogenous opioids, points at stress regulation and social connection rather than detox.Whether a Cry Helps Depends on Who's in the Room (16:02)Over 70% of people say crying makes them feel better. Controlled lab studies found criers felt worse immediately afterwards. The resolution appears to be timing. One study tracked mood after a sad film and found criers felt worse straight away, recovered within 20 minutes, and by 90 minutes were better than before the film began.Context does the rest. Social support is the biggest single factor. There's also a finding about numbers that will be familiar to anyone who has cried at work, because people tend to feel better crying alone or with one other person, and worse with two or more."There's a real permission in that, isn't there? You're not actually then doing crying the wrong way." MattThe episode closes on what tears are actually for. Researchers photographed faces and digitally removed the tears, and the same faces with tears visible were judged as sadder and more in need of help."So a good cry isn't a system failing, it's a message going out, and whether you feel better depends far more on who's around to answer it." JenAbout So That's WhySo That's Why is a weekly podcast where Jen, Chris and Matt unpack the science behind everyday health questions. No jargon, no judgment, just genuine curiosity and proper research.Website: https://www.vegetology.com/so-thats-why-podcast