So That's Why

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.

Chapters

00:00 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 cry

The 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." Matt

This 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." Jen

The 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." Matt

The 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 Why

So 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

Nearly all of us blame the calendar for wrinkles, but the science says the calendar is mostly innocent.

Estimates put at least 80% of visible facial ageing down to sun exposure, not birthdays. In this episode, Jen, Chris and Matt go one layer beneath the surface of the skin to find out what a wrinkle actually is. They cover the slow collagen decline that starts in the late twenties, the fibroblasts that build the skin's scaffolding, and the MMP enzymes that break it down again. They explain how UV light manages to speed up demolition and quieten repair in a single move, why not all wrinkles are the same thing, and the sharp collagen drop that arrives around menopause. There is also a straight answer on collagen drinks, and the cheap, unglamorous product that outperformed everything else in a four-year controlled trial.

Key Point Timestamps

• 00:04 The question and the 80% figure
• 01:51 The collagen timeline, decade by decade
• 03:15 Collagen, elastin, fibroblasts and MMPs
• 08:18 How sunlight causes most of what we see
• 10:06 Dynamic, static and sleep wrinkles
• 12:22 What the evidence says about collagen supplements
• 14:28 SPF, retinoids and vitamin C
• 18:02 Injectables, lasers and the lifestyle stuff

Wrinkles Form in a Layer You Cannot See (03:15)

Wrinkles do not start in the visible surface of the skin. They form in the dermis underneath, where three things do the structural work. Collagen provides firmness and tensile strength, elastin lets skin stretch and spring back, and hyaluronic acid holds water and keeps the layers plump.

All three are made and maintained by one type of cell, the fibroblast. In young skin, fibroblasts lay down fresh collagen and elastin about as fast as the old material wears out.

Two things change that with age. A growing share of fibroblasts become senescent, meaning they largely stop producing and start giving off low-level inflammatory signals. At the same time, a family of enzymes called MMPs becomes more active. Their normal job is useful, clearing out worn collagen so fresh collagen can replace it, but the balance tips.

"Collagen and elastin get broken down and disorganised faster than the fibroblasts rebuild them." — ChrisSunlight Speeds Up Breakdown and Slows Repair (08:18)

When ultraviolet light hits the skin, it generates a burst of unstable molecules called free radicals. Within minutes, those free radicals switch on the MMPs, the very enzymes that break collagen down. Each unprotected sunny hour becomes a small spike of collagen loss.

Then it does a second thing simultaneously. It quietens the signal that tells fibroblasts to make new collagen.

That is why sunlight accounts for so much of what shows up on skin. It is not vague damage. It drives both ends of the same process, and the effect is cumulative rather than dramatic.

"The sun isn't ageing our skin in some vague way, it seems to be driving the two exact processes you've both just described at both ends, which kind of makes it feel less like fate and something that we can actually deal with." — MattThe Collagen Drop Nobody Talks About Enough (10:06)

Individual variation matters enormously here. How much protective pigment skin produces is largely down to genetics, and that pigment strongly affects how much UV gets through in the first place.

Hormones matter too, and this part is badly under-discussed. Around menopause, as oestrogen falls, women can lose up to about 30% of their skin's collagen in roughly the first five years. By the age of 50, nearly 50% can be gone. Set against the background rate of one to 1.5% a year, that is a very different order of change arriving in a very short window.

The Cheapest Bottle in the Shop Wins (14:28)

For collagen drinks and powders, a recent pooled analysis of 23 peer-reviewed trials found the strongest independent studies do not show a clear effect on wrinkles or elasticity. The gut cannot absorb collagen whole, so it breaks it into amino acids first.

What does have strong evidence is considerably less exciting. In a well-known controlled trial, people using a daily broad-spectrum sunscreen showed no measurable increase in skin ageing over four years, while the comparison group aged visibly. Retinoids and topical vitamin C form the next tier down.

"The cheapest and most ignored bottle in the shop beats the 40 quid miracle serum sitting right next to it." — Matt"It's never too late to start, because you're always preventing the next decade of damage even if you can't undo the last one." — JenAbout So That's Why

So 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 metabolism has an alibi. A study of over 6,000 people found metabolic rate is essentially flat from 20 to 60.

Most of us start blaming our metabolism somewhere in our thirties. The largest study ever done on human energy expenditure suggests we have been accusing the wrong party. Using doubly labelled water, the gold standard for measuring energy expenditure in real life, researchers tracked over 6,000 people aged from eight days old to 95 across 29 countries. Between 20 and 60, metabolic rate holds steady. No dip in the thirties, no crash in the forties, and no measurable effect of pregnancy or menopause once size and body composition are accounted for.

A real decline does arrive after 60, at around 0.7% a year, and Jen, Chris and Matt unpack the five things driving it. They also cover what actually holds it off, from resistance training and protein targets to where creatine, caffeine and green tea genuinely sit in the evidence.

Chapters

00:00 Why we all blame our metabolism 00:54 What the biggest study on energy expenditure found 04:58 So why do we gain weight in midlife 07:03 The five things that change after 60 13:07 Resistance training at any age 14:14 The protein numbers that have shifted 16:55 Creatine, aerobic activity, caffeine and green tea 22:07 The verdict on metabolism and age

Metabolic Rate Is Flat From 20 to 60 (00:54)

The doubly labelled water technique tracks heavy forms of hydrogen and oxygen as they leave the body, which tells researchers how much CO2 someone is producing and therefore how much energy they are burning. Crucially, it measures ordinary life rather than a treadmill test.

• Over 6,000 participants, aged eight days to 95, across 29 countries
• Energy expenditure peaks at around eight or nine months old, when babies burn roughly 50% faster than an adult relative to body size
• The rate settles at around 20 and then stays flat for four decades

"You've been blaming an innocent party, so it's like accusing a housemate who moved out years ago of finishing all the biscuits."JenWhy Midlife Weight Gain Happens Anyway (04:58)

If the rate is flat, the weight gain needs another explanation. Tom Sanders, professor of nutrition at King's College London, said findings like these support the view that rising obesity is driven by excess energy intake rather than falling energy expenditure. Alongside that, muscle mass tends to fall, and a body with less muscle burns less energy in total.

"So your machinery isn't getting worse with age. There may simply be less of the expensive machinery in your body."JenThe Five Things That Change After 60 (07:03)

After 60, total energy expenditure falls by around 0.7% a year, which reaches roughly 26% lower by the age of 90. Five mechanisms run at once.

1. Sarcopenia. Inactive adults can lose 3 to 5% of their muscle per decade from their thirties. Muscle is metabolically active tissue, so it costs energy even at rest. Jen compares it to the standing charge on an energy bill, the bit you pay whether or not you switch anything on.
2. Mitochondria. Mitochondrial DNA accumulates mutations and oxidative damage, so ATP production becomes less efficient. Mitophagy, the process that clears out damaged mitochondria, also slows.
3. Hormones. Growth hormone, IGF-1 and testosterone decline alongside changes in thyroid function and insulin sensitivity.
4. Reduced output per kilo. The remaining tissue does less per kilogram than it used to.
5. Anabolic resistance. Ageing muscle responds less strongly to protein and to being used.

"So it's wear and tear, plus the maintenance team that's also slowing down."MattWhat Actually Holds It Off (13:07)

Resistance training is the single most evidence-backed intervention because it targets the biggest modifiable driver. Muscle protein synthesis machinery stays responsive to training into very old age, so there is no point at which starting stops being worthwhile.

• Protein targets for older adults now sit at roughly 1 to 1.2 grams per kilogram of body weight, rising to 1.2 to 1.5 for those training
• Around 25 to 40 grams of good quality protein per sitting, spread across three meals, does more than one large evening portion
• A 2025 systematic review and meta-analysis found creatine plus resistance training improved lower limb strength and lean muscle mass more than training alone
• Caffeine and green tea have real but small and short-lived effects
• If you have kidney disease or are on a medically restricted diet, protein targets are a conversation for your doctor

"Keep the muscle you've got and feed it properly. Your body stays responsive to training and diet far longer into life than people assume."ChrisAbout So That's Why

So 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

Two people, the same beach, the same sun. One turns golden, the other turns red. Why?

That is the question Jen, Chris and Jamie set out to answer this week, and the answer surprises almost everyone. Tanning isn't a skill you build over a summer. Whether you can tan at all is settled by your genes, and it was decided before you were born. The team unpack what a tan really is (a repair job, not a sign of health), why everyone has roughly the same number of pigment cells but wildly different results, and the two pigments that decide whether you go bronze or go pink. Along the way they bust the base tan myth, put sunbeds firmly in their place, and explain why the person who moves abroad and looks "permanently tanned" is actually showing years of damage. Chris, a formulation scientist who has spent decades working in sun protection, also lays out what genuinely protects your skin.

Key Point timestamps:

• 00:34 What a tan actually is
• 06:59 Why some people tan and others only burn
• 10:50 The Fitzpatrick scale and what it means
• 13:18 What actually protects you (and the truth about sunbeds)

(Timestamps are based on the transcript section markers and should be verified against the final edit.)

A Tan Is a Repair Job, Not a Sign of Health

(02:34)

Whatever your skin tone, you carry roughly the same density of pigment-making cells, about 1,200 per square millimetre. The pigment they make is melanin, the skin's own sunscreen. The catch is that skin doesn't make more melanin because the sun is good for it. It makes more because ultraviolet light has already caused damage. UVB harms a skin cell, a protein called p53 (nicknamed the guardian of the genome) raises the alarm, and that signal tells your pigment cells to start producing melanin. The damage always comes first.

"A tan is a repair job. It's not a glow of good health." (Chris)Why Some People Tan and Others Only Burn

(06:59)

There isn't one melanin; there are two. Eumelanin is the dark, more protective pigment that absorbs and safely disperses UV. Pheomelanin is the reddish one that offers little protection and can even trigger oxidative stress. Chris compares your pigment cells to little printing shops. The question was never how many you have, since everyone has about the same number. It's which melanin cartridges are loaded inside them, and that is largely genetic. Around 1 in 20 people, the classic redheads, make almost entirely pheomelanin and barely any eumelanin, so they burn and freckle however careful they are.

The Fitzpatrick Scale and What It Means

(10:50)

Dermatologists grade skin from 1 to 6 on how readily it burns and tans, using the Fitzpatrick scale, developed in the 1970s. Even the darkest, type 6 skin offers natural protection roughly equivalent to an SPF of only 10 to 13, and that is a rough comparison. Every skin type can still burn and be damaged. An older version of the scale wrongly suggested darker skin was safe, and that myth causes real harm because skin cancers can get spotted later.

"So it's protection that turns up late and leaves early." (Jamie)What Actually Protects You (and the Truth About Sunbeds)

(13:18)

If the tan isn't doing the protecting, something else has to. Chris recommends a broad-spectrum sunscreen (covering UVA and UVB) at SPF 25 or higher, reapplied through the day, plus clothing, shade and avoiding the midday sun. Sunbeds are not a gentler option. They deliver very concentrated UV, most of the damage is invisible, and starting young sharply raises the risk of serious skin cancer. And the pale person who moves somewhere sunny and looks bronzed years later? That is accumulated UV injury, not a built-up tan.

"There's no such thing as a safe tan, and you sadly can't train your skin into making one either." (Jen)About So That's Why

So 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

Cortisol has become the hormone everyone wants to get rid of. It is also one of the reasons you can get out of bed at all.

Jen, Chris and Matt unpack what cortisol is actually doing while you go about your day. They cover how the HPA axis works as a self-correcting chain rather than a tap left running, why cortisol climbs before you wake and jumps again in the first half hour after you open your eyes, and how one hormone reaches nearly every tissue in the body by slipping into the nucleus of your cells and changing which genes are switched on.

They also look at where the frightening reputation genuinely comes from. Chronic elevation is a real problem, the cortisol belly has more behind it than you might expect, and a flattened daily rhythm is one of the most consistent biological findings in depression. Adrenal fatigue, on the other hand, is not a recognised diagnosis.

In this episode

• 00:00 Introduction
• 01:13 What cortisol actually is
• 02:49 How your body decides how much you get
• 04:10 The daily rhythm and the cortisol awakening response
• 08:46 When cortisol goes wrong
• 11:09 Adrenal fatigue and the myths the internet loves
• 14:54 What actually helps
• 19:03 Well-timed cortisol, not low cortisol

Cortisol Is Talking to Almost Every Cell You Own (01:13)

Cortisol is a glucocorticoid, a steroid hormone built from cholesterol by the adrenal glands that sit on top of your kidneys. Nearly every tissue in the body carries glucocorticoid receptors, the docking sites cortisol uses to pass instructions into a cell.

The reason its reach is so wide comes down to one property. Cortisol is fat soluble, so it slips straight through the cell membrane and into the nucleus, where it changes which genes are switched on.

"So it's not tucked away doing one small job then, it's talking to more or less all of me at the same time." MattThe System Was Built to Turn Itself Down (02:49)

The HPA axis is a three-part chain. The hypothalamus releases CRH, which tells the pituitary to release ACTH, which tells the adrenals to release cortisol. Once cortisol rises, it signals back up the chain and tells the top to ease off.

"It's not a tap left running. It turns itself down once the messages seem to have landed." Matt

Almost everything that goes wrong with cortisol is a version of that tap failing to turn itself down.

Cortisol Clocks On Before You Do (04:10)

Cortisol runs highest in the early morning and lowest around midnight. On top of that sits the cortisol awakening response, named by the Endocrine Society. In the first half hour after waking, cortisol jumps a further 38 to 75 per cent on top of the level it was already climbing to, in roughly 77 per cent of people.

That rise is not a side effect of waking up. It is part of the signal that wakes you, and current thinking is that it is anticipatory. The jump tends to be bigger before a workday and it goes flat in burnout.

"So the snooze button then is me arguing with my own biology, and it seems losing." MattAdrenal Fatigue Is Not the Problem to Solve (11:09)

Adrenal fatigue, the idea that the glands get exhausted and stop making cortisol, is not a recognised diagnosis and the evidence does not support it. What is real is HPA axis dysregulation, where the signalling between brain and glands drifts out of rhythm.

"The glands aren't worn out, the timing's off, and that's a very different thing to put right." Chris

The team are also clear that a genuine cortisol problem is a blood test and a conversation with a doctor, not a hunch from an internet forum. And on supplements, they are upfront. Vegetology sells them, and for cortisol specifically the evidence is thin.

What Actually Helps (14:54)

Sleep is the single strongest regulator of the rhythm, by a wide margin. Gentle to moderate movement nudges the baseline down over time, while constant over-training keeps cortisol stuck high. A sharp blood sugar crash is one of the strongest triggers there is for a cortisol spike, so regular meals with a bit of protein help. Easing back on the big afternoon coffee and late alcohol helps the evening dip arrive on time.

"You were never meant to have low cortisol, you're meant to have well-timed cortisol." JenAbout So That's Why

So 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

A cold shower, a jump scare and your favourite song all trigger the same reflex. Here's why we get goosebumps, and what they really mean.

This week, Jen, Chris and Jamie unpack one of the body's quietest mysteries. Why does a freezing shower, a fright in a dark room and the best moment of a song you love all produce the exact same reaction? The answer starts with a single nervous-system circuit and a tiny muscle at the base of every hair. Along the way, the team explores why goosebumps are far more common than most people assume, the surprising 2020 finding that links the reflex to hair growth, why some people get musical chills and others never do, and a neat myth-bust: most of the goosebumps you think you feel never actually reach your skin. There's a rare superpower, a gentle wellbeing footnote, and Chris's obligatory Captain Sensible moment.

In this episode:

• (01:44) How common goosebumps really are
• (03:42) The biology behind the bumps
• (05:52) Where the reflex comes from
• (08:20) Frisson and why music gives you chills
• (10:17) Why the shiver and the bump are not the same thing
• (12:21) What goosebumps say about you

Goosebumps Are a Whole-Body Reaction, Not Just Your Hair (03:42)

Almost every hair on your body has a tiny muscle at its base called the arrector pili muscle. When it contracts, it tugs the hair upright and pulls the skin into a little dome. Across a whole patch of skin, that gives you the pebbled look named after a plucked goose. The trigger is the sympathetic nervous system, the same side of you that runs fight-or-flight, with noradrenaline carrying the message. For almost everyone, it is completely involuntary.

"Picture it less like an alarm and more like an orchestra following the same conductor." (Chris)"Goosebumps are simply the part of the performance that you actually see." (Jen)The Reflex Has a Surprising Second Job (06:55)

Goosebumps are not the do-nothing quirk people assume. A 2020 study found that the nerves setting off goosebumps sit right next to the stem cells in your hair follicles. A brief burst of cold gives you the bumps. Prolonged cold can nudge those same nerves into helping the follicle grow new hair. It is still fresh research, but it suggests the reflex is doing quiet maintenance work most of us never knew about.

Frisson Explains Why Music Gives You Chills (08:20)

The musical version of goosebumps has its own name: frisson. Your emotional brain flags a sudden swell in the music as a possible big event and fires the response. Then the rest of your brain catches up, confirms you are safe, and rewards you with a hit of dopamine. Estimates suggest anywhere from 45% to 85% of people get musical chills, and it turns out to be less about being emotional and more about how actively you engage with what you are hearing.

"So it's basically a jump scare with a happy ending." (Jamie)The Shiver and the Bump Are Not the Same Thing (10:17)

Here's the myth-bust. When researchers use skin sensors to measure the real muscle response, only about a third of the goosebumps people report actually show up on the skin. The shivery chill you feel and the physical contraction are two separate events. They often travel together, but they don't have to.

"So most of the time that I think I've got goosebumps, I haven't actually got goosebumps. It's my brain telling me I've got goosebumps." (Jamie)About So That's Why

So 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 body will copy three billion letters of DNA today, tens of billions of times over, and get almost every one right.

So the real puzzle is not why cells occasionally go wrong. It is why they so rarely do.

Jen, Chris and Matt take on one of the biggest questions the show has tackled, and they take it on strictly as biology. This episode is about what physically changes inside a single cell to turn it cancerous. It does not cover causes, risk or anyone's diagnosis, and the hosts say so plainly at the top.

What follows is the mechanism, step by step. The three rules a healthy cell lives by, including the one most people never think about. What a mutation actually is, and why inserting or deleting a letter does more damage than swapping one. The two families of genes that decide whether any of it matters. P53, the Guardian of the Genome, faulty in more than half of all cancers. And why a process that creeps along quietly for years can appear to arrive all at once.

The takeaway is not the one you might expect going in. Given the sheer number of cell divisions happening every day, cancer is genuinely rare, and it is rare precisely because the body is so good at catching it.

Timestamps

00:00 Introduction and a note before we start 01:00 The scale of what the body gets right 02:36 The rules a normal cell lives by 03:46 DNA, mutations and how errors slip through 06:44 Oncogenes, tumour suppressors and the Guardian of the Genome 09:33 How it accelerates and the epigenetics layer 11:34 The hallmarks of cancer 15:41 So that's why

Why the Real Puzzle Is How Rarely Cells Go Wrong

01:00

Over a lifetime the body performs tens of trillions of cell divisions, each one copying what is effectively a three billion letter instruction manual. Errors do happen. What is remarkable is the amount of proofreading and repair sitting on top of the process, catching them before they ever matter.

Chris reframes the whole topic in one line early on.

"Cancer isn't one dramatic event. It's what happens on the very rare occasions where a series of those safeguards fail in the same cell one after another." (Chris)

Jen also sets out the three rules a healthy cell lives by. It divides only when signalled to, it does its specific job, and it dies on a schedule. That last one is called apoptosis, a controlled self shutdown the body uses to clear out cells that are old, damaged or no longer needed. Matt's response is the one most listeners will share.

"So my cells are programmed to die. Sounds a little bit like a fault, not a feature." (Matt)What a Mutation Actually Is

03:46

DNA is a long instruction written in a four letter alphabet, and the letters pair up in a fixed way. A with T, C with G. When a cell divides the double helix unzips and each strand is used as a template to rebuild its partner, which makes the pairing rule a built in check.

Errors that slip through come in three kinds. A letter substituted, a letter inserted, or a letter deleted. The reason the last two matter more comes down to how the code is read, in three letter blocks that each code for one amino acid. Insert or delete one and every block after it shifts along, which is called a frame shift.

"A substitution is a typo in one word, but an insertion or deletion knocks the whole sentence out of step from that point on." (Matt)

Most mutations still never amount to anything. They land in stretches of DNA that do not code for anything, or they get repaired within minutes, or the cell triggers apoptosis.

The Two Families of Genes That Decide Whether It Matters

06:44

Proto-oncogenes normally drive healthy growth, telling cells to divide when there is a real signal. Mutate one and it becomes an oncogene, locked permanently on, so cells divide nonstop with nothing asking them to.

Tumour suppressor genes do the opposite job. They hold growth back, repair DNA and call for apoptosis when a cell is too far gone. The most important is P53, nicknamed the Guardian of the Genome, and Chris notes that it is faulty in more than half of all cancers.

"So losing P53 doesn't just allow damage, it removes the very thing that would have caught the damage." (Matt)

Jen adds the detail that explains why some cancers appear to run in families. You inherit two copies of each tumour suppressor, so both have to be knocked out before the safeguard is gone. That is the two hit rule, first worked out in 1971 by Alfred Knudson. Being born missing one copy changes where the count starts, and as Chris is careful to say, it does not mean anyone's fate is sealed.

Why Cancer Can Look Sudden When It Has Been Building for Years

09:33

A cancer cell can carry hundreds of mutations, but most are passengers doing nothing. It is the handful of drivers that matter, and it usually takes six or more of them stacking up in the same cell line.

Things change pace when some of the genes knocked out are the DNA repair genes themselves. The genome becomes unstable, a state called a mutator phenotype, and a process that crept along quietly can appear to accelerate.

"What looks sudden is usually the visible end of a long, quiet process." (Jen)

The episode closes on the hallmarks of cancer, including how a cancer cell becomes effectively immortal by switching the enzyme telomerase back on, and how it learns to hide from the immune system using checkpoint signals such as PD-L1. A 2025 study published in Nature found it can go further still, physically passing its own faulty mitochondria into the immune cells sent to destroy it.

And then the reassurance, which is where the hosts deliberately land.

"Given the sheer number of cell divisions every day, cancer is genuinely rare." (Jen)About So That's Why

So 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

Stress gets blamed for everything, yet a little of it is genuinely good for you. So why does stress make us ill?

In this episode, Jen, Chris and Jamie unpack one of the most misunderstood ideas in health. Stress on its own isn't the problem. The problem is a system that's brilliant in short bursts but never gets switched off. The team walks through the two systems that fire when your brain senses a threat, why chronic stress is now ranked alongside smoking as a heart risk, and how the same chemistry that saves you in a five-minute scramble starts wearing down your heart, immune system, brain, muscles and gut when it runs for months. Along the way there's a kitchen full of guests who never leave, a healthy dose of Captain Sensible, and a clear, evidence-based look at what actually helps. The goal was never a stress-free life. It's an off switch that works as well as the on switch.

In this episode:

• 00:04 When stress is actually on your side
• 01:22 How big is the problem
• 03:48 What stress actually does to your body
• 06:29 Stress, your heart and your immune system
• 09:22 Brain fog, gut knots and the ageing effect
• 12:47 What actually moves the needle
• 17:22 The goal was never a stress-free life

The Good Kind of Stress Has a Name

(00:04)

Not all stress is the enemy. The nerves before a big presentation or the push before a deadline can sharpen you up, and there's even a word for the helpful kind: eustress. The trouble is that most of us aren't living in short bursts anymore. We're living in the chronic version that never lets go.

"I spent years blaming stress for everything, bad mood, lost keys, the lot. Now you're telling me it was on my side the whole time?"Jamie

• A survey of more than 145,000 adults across 144 countries found more than one in three had felt significant stress on an ordinary day
• The World Health Organisation counts over a billion people living with a mental health condition
• In the UK, around 964,000 workers were dealing with work-related stress, anxiety or depression across 2024 and 2025, the sharpest single-year jump on record

Your Body Reacts Like a Kitchen Before Guests Arrive

(03:48)

When your brain senses a threat, two systems fire. A fast one floods you with adrenaline, raising your heart rate and blood pressure. A slower one releases cortisol, which keeps your energy topped up by quietly turning down anything non-essential, including digestion, repair and part of your immune system.

"You get a text that guests are arriving at the door in five minutes. Everything urgent gets done immediately. The gas goes on, the hob's on full. That's the adrenaline."Jamie

For a short scramble, your body is brilliant at this. The problem is the version where the guests never leave, the hob stays on full day after day, and the upkeep never happens.

Chronic Stress Wears the Body Down System by System

(06:29)

Run that emergency chemistry for months instead of minutes, and the damage shows up everywhere. Chronic stress is now treated as an independent risk factor for cardiovascular disease.

• Heart: A 2023 study found depression and anxiety raised the risk of a major heart event by about 35% and brought warning signs forward by roughly six months. It doesn't hand you a heart attack on the spot; it moves the timeline forward
• Immune system: Short bursts sharpen your defences, but sustained cortisol suppresses them, which is why you often fall ill the first day of the holiday
• Brain, muscles and gut: The hippocampus can shrink under a long soak in cortisol, muscles brace into tension headaches and a tight neck, and digestion drops out, leaving that knotted feeling

"Walking into a room and forgetting why you went there isn't you being hopeless. It's just chemistry."JamieWhat Actually Moves the Needle

(12:47)

The strongest evidence is for movement, and the dose is gentler than most people think. Around 20 minutes of something moderate on most days lowers cortisol and improves sleep. Consistency beats intensity, breathing helps in the moment, sleep and social contact both steady the system, and if stress is genuinely affecting your health, that's a conversation with a doctor rather than a podcast.

"The best exercise is one that you will actually do."JamieAbout So That's Why

So 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 wondered why your energy nosedives at almost exactly the same time every afternoon? Surveys put the average moment at a suspiciously precise 2:36 PM. The twist is that it happens whether you eat lunch or not.

In this episode, Jen, Chris and Matt unpack the real reason behind the afternoon slump. It isn't one thing breaking down. It's four biological systems reaching their low point at the same time and amplifying each other into a measurable dip in focus, accuracy and motivation. They walk through circadian rhythm, sleep pressure, cortisol and food, explain why some people crash much harder than others, and finish with the small, realistic things that actually move the needle. No burpees required.

In this episode:

• 00:00 The suspiciously precise 2:36 PM crash
• 02:29 The real cost at work
• 04:42 The four biological forces
• 10:20 Why it hits some people harder
• 14:00 What actually helps
• 17:30 Working with your biology, not against it

The Afternoon Crash Has Almost Nothing to Do With Lunch (02:29)

Most people blame the post-lunch dip on the food itself. The episode busts that assumption early. Lunch can make the dip sharper, but it isn't the cause, because the crash shows up even on days you skip it.

The stakes are real and measurable. A report from the American Academy of Sleep Medicine concluded that afternoon cognitive performance drops noticeably, and a Slack survey of over 10,000 desk workers found only one in four people felt productive between 3:00 and 6:00 PM.

"So the crash isn't one thing breaking. It's four things showing up at exactly the same time when you don't want it to." — Matt"Cognitive performance drops by about 15 to 25% in the afternoon." — ChrisThe Four Forces That Stack Up (04:42)

The dip is really four systems converging. Your circadian rhythm dips twice a day, and the afternoon one drops your core body temperature by around half a degree to a degree. Sleep pressure, driven by a chemical called adenosine, has been building since you woke. Cortisol, one of your main alertness hormones, can be 50 to 70% lower by mid-afternoon than it was in the morning. And food sets the gradient of the slope.

The key point is that these forces don't simply add together. They amplify one another, which is why a single afternoon coffee rarely fixes things on its own.

"It just decides whether the slope is gentle or steep." — Matt

• Circadian dip: lower temperature, quieter motivation circuits (research from Swinburne University)
• Sleep pressure: adenosine, the same molecule caffeine blocks
• Cortisol: falls steadily across the day, flattened further by chronic stress
• Food: a balanced lunch smooths the dip but doesn't remove it

Why Some People Crash Harder (10:20)

If everyone has these four forces, why does the dip floor some people and barely touch others? Amplifiers. Around 45% of people point to poor sleep as the main reason their crash feels worse, because it lowers your baseline before the dip even starts. Even mild dehydration, a loss of just 1 to 2% of body water, affects attention and fatigue, backed by a meta-analysis of 33 studies. And caffeine, with a half-life of five to seven hours, can still be active at bedtime, quietly shaping tomorrow's slump too.

It also varies from person to person. Early risers dip earlier, night owls dip later, and older adults metabolise caffeine more slowly, so the same coffee lingers longer.

What Actually Helps (14:00)

The fixes are refreshingly ordinary. Drink water early, before you fall behind. Build a balanced lunch with protein, fibre and fats. Get a few minutes of movement and some natural light. And if your day allows, a short nap before 3:00 PM, kept under 30 minutes, can reset things without the grogginess. The things to skip are the big sugary hit and the giant afternoon coffee, both of which borrow energy from later.

"It's not a failure, it's a normal rhythm, and the goal isn't to eliminate it, it's to understand it and work with it." — JenAbout So That's Why

So 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.

Your brain has 86 billion neurons and zero pain receptors, so why does a headache feel like it's happening inside your skull?

It's one of the strangest facts in human biology, and it changes how you think about every headache you've ever had. In this episode, Jen, Chris, and Matt unpack where head pain actually comes from, why migraines arrive with nausea and light sensitivity, why caffeine both helps and hurts, and why reaching for painkillers too often can quietly make things worse. With over 200 classified types of headache and more than 400 potential migraine triggers, generic advice rarely works. Understanding the mechanism does. By the end, you'll see headaches not as random bad luck but as signals worth paying attention to.

In this episode:

• (00:00) Can your brain feel pain?
• (01:50) How common headaches really are
• (03:34) Where head pain actually comes from
• (05:13) Serotonin, CGRP, and hormones
• (07:51) Tension, migraine, and cluster headaches
• (10:07) Triggers, caffeine, and medication overuse
• (12:34) What actually helps, and when to see a doctor

Where Headache Pain Really Comes From (00:03:34)

The brain itself can't feel pain, but the structures around it can. The blood vessels, the meninges (the membranes around the brain), and the muscles of the scalp, face, and neck are full of pain receptors called nociceptors. These all feed into the trigeminal nerve, the head's main communication hub, which carries the signal up to the brainstem to be felt as pain.

"So the brain isn't actually feeling the pain, it's more like it's being told about the pain from somewhere else." — Matt

Because the brainstem also links to systems handling balance, digestion, and light and sound, a bad headache often brings nausea, dizziness, and the urge to shut everything out. That instinct to lie down in a dark room is your nervous system asking for less input.

The Chemicals That Turn Headaches Up and Down (00:05:13)

A few key chemicals control how loud the pain signal gets:

• Serotonin affects blood vessels as well as mood. When levels drop, vessels can expand and amplify pain.
• CGRP (calcitonin gene-related peptide) is released during migraine attacks and dilates blood vessels. It's so central that a whole class of modern migraine drugs is designed to block it.
• Oestrogen drops before menstruation can trigger migraines, one reason migraines are around three times more common in women than men.

In migraine specifically, a process called cortical spreading depression sends a slow wave of altered electrical activity across the brain. It's visible on brain imaging, and it's likely what causes auras. A migraine is a real, measurable biological event, not "just a headache."

Tension, Migraine, and Cluster Headaches Explained (00:07:51)

The three main types differ in location, severity, duration, and the symptoms they bring:

• Tension headaches are the most common, affecting around 80% of adults at least once a year (roughly two billion people). They feel like a tight band, are usually mild to moderate, and rarely bring nausea or light sensitivity.
• Migraines are a neurological condition affecting around 12% of adults. The pain is throbbing and often one-sided, commonly with nausea, light and sound sensitivity, and sometimes aura. They can last from four to 72 hours.
• Cluster headaches affect about 0.1% of people but are among the most intense pain in medicine. They come in cycles and focus around one eye.

Caffeine, Painkillers, and What Actually Helps (00:10:07)

Caffeine confuses everyone because it works both ways. Small amounts can help by constricting blood vessels and boosting painkillers, but 400mg or more a day was linked with over a 40% higher prevalence of headache or migraine. Withdrawal can trigger one too.

The surprising one is medication overuse. Taking painkillers on more than 10 to 15 days a month can flip the system so the medication itself maintains the headache. The encouraging part is that breaking the cycle often brings real improvement (worth a GP conversation rather than stopping everything overnight).

What helps most is reassuringly simple: regular sleep with a fixed wake-up time, steady hydration, regular meals, and stress management. One trial found that drinking about 1.5 litres more water a day improved headaches in almost half of participants.

"Headaches are almost a bit like a pressure gauge for everything else going on inside your body." — JenAbout So That's Why

So 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.