In this episode, Jen, Chris, and Jamie unpack why Omega-3 is so much more than a vague health recommendation. They cover the critical difference between ALA and the active forms EPA and DHA, why plant sources alone aren't enough, and what a significant body of large scale research says about the effects on heart health, brain function, mood, joints, eye health, and pregnancy outcomes.

They also address the omega-6 to Omega-3 ratio, the signs of deficiency that most people attribute to other causes, and how much EPA and DHA you actually need each day — versus what most people are actually getting.

Timestamps

00:00 Introduction 01:00 The Building Block Your Body Can't Make 01:41 ALA, EPA and DHA — Not All Omega-3 Is Equal 03:39 Why Plant Sources Aren't Enough 04:30 Heart Health and Cardiovascular Evidence 05:38 Brain Function, Mood and Mental Health 07:16 Joints, Eye Health and Pregnancy 09:03 The Omega-6 to Omega-3 Ratio 10:07 Signs You're Not Getting Enough 11:25 How Much Do You Actually Need? 13:39 Finding the Right Source

Key Points

Why the source of your Omega-3 matters more than most people realise

Omega-3 is a family of fatty acids, not a single compound. The three main types are ALA, EPA, and DHA — and they are not interchangeable. ALA is found in plant foods like flaxseed and chia seeds. EPA and DHA are the active forms the body actually needs, found naturally in microalgae.

Microalgae are the original producers of EPA and DHA in the food chain. Fish accumulate it by eating algae. As Jamie puts it: "The algae are doing all the work and the fish have been taking the credit this whole time."

Your body can technically convert ALA into EPA and DHA, but the conversion rate is around 5% to EPA and well under 1% to DHA. Relying on plant foods alone for active Omega-3 isn't a realistic strategy.

The cardiovascular and brain evidence is substantial

A Cochrane review of 86 randomised controlled trials involving over 160,000 participants found that Omega-3 supplementation reduced triglyceride levels by around 15% and decreased rates of death from cardiovascular disease. The VITAL trial, which followed over 25,000 adults for more than five years, found that one gram of Omega-3 daily produced a 28% reduction in total heart attacks — rising to 40% for those who weren't already getting EPA and DHA through their diet.

For the brain, DHA makes up a significant structural portion of grey matter. As Chris explains: "It firmly answers the question of whether a supplement this small can make a measurable difference to health."

Deficiency signs are easy to miss

Dry or irritated skin, joint stiffness without a clear injury, poor concentration, brain fog, mood changes, dry eyes, fatigue, and brittle hair and nails are all signs of low Omega-3. They're also the kinds of things most people put down to being tired or getting older.

As Jen observes in the episode, people often spend time and money chasing individual solutions — a cream for dry skin, painkillers for joints, coffee for concentration — when part of the answer might be addressing one underlying nutritional gap.

Most people are getting far less than they need

Most health organisations recommend 250 to 500mg of combined EPA and DHA daily for healthy adults. The average person is currently getting around 100mg a day. Heavily processed fish products are unlikely to offer meaningful EPA or DHA unless fortified. The most reliable route is a quality EPA and DHA source — whether from oily fish or algae based supplements — taken consistently. As Chris puts it: "Consistency matters more than perfection. The best source is the one you'll actually take daily."

About So That's Why

So That's Why is a weekly podcast where Jen, Chris, and the team unpack the science behind everyday health questions. No jargon, no judgment. Just genuine curiosity and proper research.

In this episode, Jen, Chris, and Jamie unpack the biology of grey hair: the specialised cells that inject pigment into each strand as it grows, why those cells eventually stop working, and what a landmark study published in Nature revealed about stem cells getting physically stuck in the wrong part of the follicle. They also cover the hydrogen peroxide mechanism that bleaches hair from the inside, the Harvard research linking stress to accelerated greying, the genetic factors that set your personal timeline, and the nutritional deficiencies that are often overlooked as a cause of premature greying. And they ask the question most people quietly wonder about: can grey hair actually be reversed?

Timestamps 00:00 - Introduction: why does hair turn grey? 01:03 - Hair grows grey, not turns grey 01:47 - Melanocytes: the cells that colour your hair 02:32 - The stem cell discovery that changed the picture 03:56 - Hydrogen peroxide: your body's internal bleach 05:07 - Stress, genetics and the pace of greying 07:11 - Nutritional deficiencies and premature greying 09:07 - Can grey hair actually be reversed?

Key Points

Your Hair Was Never Actually Coloured to Begin With

[01:03]

Every strand of hair grows out of the follicle completely white. The colour you see is injected into the hair shaft during the growth process by specialised cells called melanocytes — and there are around 100,000 of them on the average head. Two types of pigment are at work: eumelanin (black and brown shades) and pheomelanin (blonde and red tones). Your unique combination of the two determines your natural colour. Greying isn't colour fading — it's the pigment system stopping.

As Chris explains: "Every single strand of hair starts off completely white before pigment gets added. When we say our hair turns grey, what we actually mean is the pigment system has stopped doing its job."

The Stem Cells Aren't Dead — They're Stuck

[02:32]

A study published in Nature revealed that melanocyte stem cells, the parent cells that produce new pigment-making melanocytes, normally shuttle between two compartments inside the hair follicle. In one they sit dormant; in another they receive the signals that tell them to mature and start producing colour. As hair ages through repeated growth cycles, those stem cells start getting physically stuck in the dormant compartment. They stop migrating to where the signals are and never receive the instruction to produce pigment.

Jamie put it plainly: "It's like having all the ingredients for dinner sitting in the cupboard, but nobody's walking to the kitchen to actually start cooking."

The significance is real — stuck cells are potentially fixable in a way that dead cells aren't.

Your Body Is Bleaching Your Hair From the Inside

[03:56]

Hair follicles naturally produce small amounts of hydrogen peroxide as a byproduct of normal cell activity. An enzyme called catalase normally breaks it down into harmless water and oxygen — but catalase levels decline with age. When that happens, hydrogen peroxide builds up and interferes directly with pigment production. Researchers at the University of Bradford confirmed this by analysing pigmented hair versus grey hair: the grey samples contained high levels of hydrogen peroxide; the pigmented samples had none. The hydrogen peroxide also damages the repair mechanisms that would normally fix the problem, creating a compounding effect over time.

Nutrition May Be Playing a Bigger Role Than You Think

[07:11]

For premature greying specifically, nutritional deficiencies are frequently overlooked. Vitamin B12 supports melanocyte function and deficiency is one of the most common nutritional causes of early greying — studies have found significantly lower B12 levels in people experiencing premature greying. Copper is another factor, acting as a co-factor for tyrosinase, the key enzyme in melanin production. Iron, zinc, vitamin D, and calcium have also been flagged in research. Addressing a deficiency may help slow further greying, though reversing existing grey hair through nutrition alone is uncommon. The primary benefit is in prevention, not reversal.

About So That's Why

So That's Why is a weekly podcast where Jen, Chris, and the team unpack the science behind everyday health questions. No jargon, no judgment — just genuine curiosity and proper research.

In this episode, Jen, Chris, and Matt unpack the biology behind one of modern life's most common habits. Specialised cells in your retina contain a protein called melanopsin that is maximally sensitive to blue light wavelengths — the same wavelengths emitted by our screens. When those cells fire, they signal your brain's master clock that it's daytime, suppressing melatonin and delaying your body's natural wind-down process. Your circadian system, it turns out, cannot distinguish your phone from the morning sun.

The team also covers why children are significantly more vulnerable than adults, what the research actually says about blue light blocking glasses (the tint colour matters far more than most people realise), whether night mode on your phone is doing anything useful, and why the widely marketed claim that screens damage your eyes isn't supported by current evidence.

Timestamps 00:00 - Introduction 01:37 - How much does blue light actually matter? 03:14 - The biology: what's happening in your brain 06:55 - Why children are more vulnerable than adults 09:45 - Do blue light blocking glasses work? 11:14 - Night mode, brightness and practical tips 13:04 - Does blue light actually damage your eyes?

Your Phone Is Triggering a Sunrise Response

[03:14]

The reason blue light disrupts sleep isn't a vague sensitivity — it's a specific, hardwired biological pathway. Your retina contains specialised cells called IPRGCs (intrinsically photosensitive retinal ganglion cells) that contain a light-sensitive protein called melanopsin. Melanopsin is most sensitive to blue wavelengths between 460 and 480 nanometres, which overlaps directly with the light emitted by screens.

When these cells detect blue light, they signal the suprachiasmatic nucleus — the brain's master clock — that it's daytime. The SCN responds by suppressing melatonin production in the pineal gland.

As Chris explains: "Your circadian systems can't distinguish between natural daylight and artificial light from screens, because both activate the same pathway."

The Numbers Are More Significant Than Most People Expect

[01:37]

Just two hours of evening screen use can suppress melatonin production by over 50% and delay the normal melatonin rise by an hour and a half. Around a third of people experience reduced sleep duration as a result, and half report feeling less tired at bedtime — which sounds convenient until you realise their natural drowsiness signals are being chemically overridden.

The effects don't stop when you put the phone down, either. Melatonin suppression and the alerting effects persist for some time after the screen goes off. As Chris puts it, the circadian system doesn't have an instant reset button.

Children Are Significantly More Vulnerable — Here's the Biology

[06:55]

A study comparing children (average age nine) to adults (average age 40) found that under blue light-enriched conditions, children experienced over 80% reduction in melatonin levels, compared to a much weaker response in adults.

Two physical factors explain this. Children have larger pupils, which admit more light. Their eye lenses are also clearer — as we age, the lens naturally yellows, filtering out some blue light before it reaches the photosensitive cells. Children don't yet have that filter.

As Matt observes: "The very thing that gives kids those beautiful crystal clear eyes also makes them more vulnerable to the screen."

Blue Light Glasses and Night Mode: What the Research Actually Shows

[09:45]

Not all blue light glasses are equal. Clear lenses filter only 10 to 30% of blue light. Amber or orange lenses can block 90% or more — and studies involving people with insomnia found that amber-tinted lenses worn for two hours before bedtime did lead to measurable improvements in sleep quality and duration.

Night mode alone isn't the full picture, either. A 2024 study found that overall screen brightness may matter as much as, or more than, colour temperature. Night mode combined with reduced brightness performs better than either setting alone.

One important note: current evidence does not support the claim that blue light from screens damages eyes. The American Academy of Ophthalmology has stated there is insufficient evidence for this. The sun delivers up to 1,000 times more blue light than a screen.

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.

In this episode, Jen, Chris, and Matt unpack the truth behind delayed onset muscle soreness (DOMS): what's actually happening inside your muscle fibres, why the pain peaks a day or two after exercise rather than straight away, and why the familiar "no pain, no gain" mantra is more complicated than it sounds.

Along the way they bust one of the most persistent myths in fitness, explain why running downhill causes more soreness than running uphill, and reveal which popular recovery methods are actually backed by evidence — and which aren't. (Stretching fans, brace yourselves.)

In this episode:

1. 00:58 — The lactic acid myth debunked
2. 02:21 — What's actually causing DOMS
3. 05:11 — Individual variation in soreness
4. 06:20 — The no pain, no gain myth
5. 07:43 — Should you exercise when sore?
6. 09:12 — What actually works for recovery

The Lactic Acid Myth Has Been Comprehensively Disproven

(00:58)

For generations, "feel the burn, that's the lactic acid" has been repeated in gyms, by coaches, and in fitness articles. There's one straightforward problem with it: lactic acid clears from your bloodstream within 30 to 60 minutes of stopping exercise. DOMS doesn't even begin until 12 to 24 hours later.

As Chris explains: "The lactic acid explanation has been comprehensively disproven. That timeline alone makes this theory impossible because muscle soreness typically doesn't begin until 12, even 24 hours post-exercise, sometimes longer."

The culprit that fitness culture has blamed for generations couldn't physically be responsible.

Your Body Has Builders In — And They Make a Lot of Noise

(02:21)

The real cause of DOMS is microscopic damage to muscle fibres and the surrounding connective tissue, followed by the inflammatory response your body launches to repair it. Specific hormones called prostaglandins and leukotrienes are released, causing swelling and activating pain receptors. The whole process takes time to develop — which is why soreness peaks one to three days after exercise, not immediately.

Jen adds that DOMS may also involve damage to the deep fascia — the connective tissue wrapping around muscles — which is densely populated with pain-sensitive nerve endings. This explains why even gentle pressure on sore muscles can feel disproportionately uncomfortable.

As Matt puts it: "The soreness is actually a repair job in progress. Like my body's got builders in. And they're making just an awful lot of noise."

Getting Less Sore Over Time Is a Good Sign

(06:20)

One of the most widespread myths in fitness is that soreness equals an effective workout. Research conclusively demonstrates that DOMS is neither necessary nor sufficient for muscle growth. Some muscle groups, like the shoulders, rarely experience significant soreness yet still grow perfectly when trained properly.

Chris explains the repeated bout effect: "Your body adapts to exercise through something called the repeated bout effect. That means you'll experience progressively less soreness for the same workout, even as your strength and muscle mass continues to increase."

Getting less sore over time isn't a sign you're not working hard enough. It's a sign your body is adapting and improving.

What Actually Works for Recovery (And What Doesn't)

(09:12)

An analysis of around 120 studies identified which recovery treatments have real evidence behind them:

1. Active recovery — light movement at 30 to 60% of maximum heart rate — outperforms complete rest for reducing soreness
2. Massage therapy increases blood flow and may stimulate endorphin release
3. Cold water immersion at around 10 to 15 degrees Celsius shows effectiveness, as does contrast therapy (alternating hot and cold)
4. Stretching reduces soreness by less than two millimetres on a 100-millimetre pain scale — effectively undetectable

Beyond specific treatments, the fundamentals matter most: seven to nine hours of sleep (growth hormone released during deep sleep stimulates muscle repair), 20 to 40 grams of protein per meal, and increasing training volume by no more than 10% per week.

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.

Episode Chapters

00:00 Introduction 01:33 Chemophobia and the Appeal to Nature Fallacy 03:15 MSG: Fear Outlasting Evidence 05:20 Sweeteners, Food Dyes and When Concern Is Legitimate 07:02 The Dose Makes the Poison 08:31 Seed Oils and the Influence Machine 09:58 What Actually Matters for Your Health

The "Chemical-Free" Myth That Isn't Possible

Timestamp: 01:33

The word "chemical" has become almost synonymous with "dangerous" in everyday language — but everything is a chemical. Water. Oxygen. Your own body. Chris illustrates this with a simple list: ascorbic acid, sodium chloride, dihydrogen monoxide. Most people would want to avoid all three. They are, of course, vitamin C, table salt, and water.

Underlying this is what researchers call the Appeal to Nature Fallacy — the belief that natural automatically means safe and synthetic automatically means harmful. The evidence doesn't support it. Arsenic is natural. Botulinum toxin, one of the most lethal substances known to science, is completely natural. Meanwhile, synthetic vitamin C made in a laboratory is molecularly identical to vitamin C from an orange. The body cannot tell the difference.

"The idea of something being 'chemical-free' is completely impossible." — Chris

The Principle That Reframes Every Food Fear

Timestamp: 07:02

The dose makes the poison. This is the foundational principle of toxicology, and it reframes almost every ingredient scare story. Any substance, including water, can be harmful in excessive amounts. And many substances considered dangerous are perfectly safe at low quantities.

Regulatory agencies use this principle to set Acceptable Daily Intakes. Scientists identify the highest dose at which no adverse effects occur in studies, then divide that figure by 100 to create a safety margin. When agencies say something is safe at a given level, that level is already a fraction of where concern would begin.

Chris uses caffeine to make the numbers real: the lethal dose for a person weighing around 72 kilograms would require well over 100 cups of coffee. At that point, water poisoning would be a more pressing concern than the caffeine.

"Occasionally exceeding guidelines on a given day isn't cause for alarm. These limits are designed around a lifetime of exposure, not single occasions." — Jen

MSG: One Letter, Decades of Fear

Timestamp: 03:15

The MSG panic didn't start with a clinical trial or a peer-reviewed study. It started when a doctor wrote a letter to a medical journal in the late 1960s, describing how he felt unwell after eating Chinese food. One anecdote. Decades of cultural fear followed.

Since then, multiple well-designed double-blind studies have consistently failed to trigger reactions in people who claim MSG sensitivity, when consumed as part of food. The FDA, the European Food Safety Authority, and regulatory bodies globally all classify MSG as generally safe. And glutamate — the core compound — occurs naturally in tomatoes, mushrooms, parmesan, and breast milk.

"A single poorly evidenced claim gets amplified, creates a cultural fear, and then persists long after the science has moved on." — Chris

What the Evidence Actually Says About Seed Oils

Timestamp: 08:31

Seed oils are a current example of misinformation spreading faster than science can correct it. The claim — that omega-6 fatty acids in seed oils cause inflammation — sounds plausible. The evidence doesn't support it.

Multiple systematic reviews of randomised controlled trials have found virtually no evidence for the inflammation claim. A 2017 meta-analysis found that participants consuming the most linoleic acid, the main omega-6 in seed oils, had the lowest levels of inflammation in many studies. Both the American Heart Foundation and the British Heart Foundation maintain that seed oils are beneficial when used to replace saturated fats.

"Many of the loudest voices against seed oils are influencers with no scientific training, while actual nutrition researchers and cardiologists aren't worried." — 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.

In this episode, Jen, Chris, and Matt unpack the brain science behind food cravings: why they're completely different from hunger, why chocolate tops the craving charts, and why the common idea that cravings signal nutritional deficiencies is largely a myth.

Timestamps

00:00 Introduction 02:02 Cravings vs hunger: what's the difference? 03:04 The brain's reward system and dopamine 04:32 Conditioning, triggers, and the food industry 06:48 Stress, sleep and hormones 09:09 Do cravings signal nutritional deficiencies? 10:21 The gut microbiome connection 12:17 What you can actually do about cravings

Key Points

Cravings and hunger are not the same thing (02:02)

Hunger develops gradually and is regulated by hormones — ghrelin signals it's time to eat, leptin signals fullness — and it can be satisfied by most foods. Cravings are different. They arrive suddenly and intensely, often alongside stress, boredom, or emotion. Researchers describe them as "head hunger": a mental preoccupation with something specific that can persist even after eating to fullness.

As Jen puts it in the episode: "Cravings are your brain demanding something incredibly specific, like it's placed an order at a restaurant and it won't accept substitutes."

What makes this even more striking is that the body begins preparing for a craved food before any conscious decision has been made — heart rate elevates, stomach activity increases — before you've even decided whether you're going to eat.

Dopamine is about wanting, not happiness (03:04)

The mechanism behind cravings centres on the mesolimbic dopaminergic pathway, which uses dopamine to signal motivation and reward. Dopamine is widely described as the "happiness chemical" — but as Jen explains, that's a simplification. It's more accurately the chemical of wanting and anticipation. When cues that predict food appear (the sight of a bakery, the smell of something cooking, even just thinking about a favourite food), dopamine surges — and that surge is what creates the feeling of craving.

This is why walking past a chip shop without being hungry, catching a whiff of vinegar, and suddenly feeling ravenous makes complete physiological sense. The brain is responding to cues that have been paired with reward.

Why restriction makes cravings worse (08:32)

When people label foods as forbidden or actively try to suppress thoughts about them, cravings increase. This is called ironic process theory. As Chris explains: "Deliberately trying not to think about chocolate cake makes it more mentally accessible." Studies confirm that participants on restrictive diets report more food cravings, and those on very restricted diets are more likely to overeat previously banned foods when they stop.

Cravings don't signal nutritional deficiencies (09:09)

The popular idea that craving chocolate means you need magnesium is largely debunked. As Chris explains, if cravings truly reflected nutrient needs, people would crave spinach or nuts when deficient. The chocolate and magnesium link has been directly tested: when chocolate cravers consumed white chocolate, which contains no magnesium, their cravings were reduced just as effectively as with dark chocolate. It's the fat and sugar content driving the craving — not any mineral.

As Jen summarises: "Your reward circuits responding to a lifetime of positive food experiences, amplified by whatever's going on in your life and your body at that moment."

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.

In this episode, Jen, Chris, and Jamie unpack the science of caffeine tolerance: what adenosine is and why it matters, how your brain physically restructures itself in response to daily caffeine use, why the afternoon crash hits harder for habitual drinkers than non-drinkers, what your genetics have to do with it, and what you can actually do to manage it.

Timestamps

00:00 Introduction 01:40 Why caffeine stops working: the research 02:58 Adenosine: your brain's built in brake pedal 04:17 How tolerance builds and how fast 06:48 Why genetics change everything 09:37 How to reset your caffeine tolerance 12:07 Caffeine, exercise, sleep and the bigger picture

Your Brain Is Not Broken — It Is Adapting

Most people assume caffeine tolerance is a minor inconvenience. The science tells a different story. A 2017 trial found that while caffeine still improved mental and physical performance after two weeks of daily use, those benefits completely disappeared after one month. More strikingly, research shows that habitual drinkers are essentially consuming caffeine just to return to the baseline they had before they started. Without it, they feel worse than someone who has never touched it at all.

As Chris explains in the episode: "Your brain is basically hiring extra staff to handle the complaints your coffee keeps ignoring."

The reason is adenosine — a molecule your brain produces throughout the day as a byproduct of burning energy. Caffeine works by blocking adenosine receptors rather than creating energy. With regular use, the brain responds by growing 20 to 30% more receptors, which means you need more caffeine to achieve the same effect. A 2024 review confirmed that measurable receptor changes begin within two weeks at moderate doses.

The Genetics Behind Your Caffeine Tolerance

Not everyone builds tolerance at the same rate or experiences the same effects. Twin studies suggest genetics account for around 36 to 58% of the variation in how people respond to caffeine. Two genes are key: CYP1A2, which controls how fast your body metabolises caffeine, and ADORA2A, which affects the adenosine receptor itself and determines whether caffeine is more likely to keep you awake or make you anxious.

Fast metabolisers break caffeine down around 1.5 to 1.6 times faster than slow metabolisers. About 10% of the population carry a variant linked to higher caffeine tolerance, allowing them to drink espresso in the evening without side effects.

As Jamie puts it: "This explains every argument in every office kitchen ever. How can you drink at 4pm? How can you not? Turns out we're all just having a genetics debate and we didn't know it."

Managing Tolerance: What the Research Actually Suggests

The most effective approach is strategic rather than habitual use. Research shows that using caffeine on two to three days a week prevents the receptor buildup that causes tolerance. For those wanting a full reset, sensitivity typically normalises within around two weeks of stopping, returning to roughly 70 to 80% of its original level — though heavy users may need up to two months.

For a gentler approach, reducing intake by 25% every 10 days produces significantly fewer withdrawal symptoms: around 80% fewer severe effects compared to stopping abruptly. Caffeine withdrawal is clinically recognised, with symptoms including headaches, fatigue, and difficulty concentrating, peaking a few days after stopping and resolving within a couple of weeks.

Keeping daily intake below roughly 200 milligrams — around four cups of tea — appears to slow the rate at which tolerance builds, and may sit in a sweet spot where some benefit is preserved without triggering major receptor changes.

About So That's Why

So That's Why is a weekly podcast where Jen, Chris, and the team unpack the science behind everyday health questions. No jargon, no judgment — just genuine curiosity and proper research.

In this episode of So That's Why, Jen, Chris, and Matt unpack what Vitamin D is actually doing inside the body, why the sunshine route fails so many people, and why deficiency shows up as fatigue, frequent illness, and muscle weakness rather than just weak bones. Along the way, they bust the sunscreen myth, explain why D3 is not the same as D2, and make the case for why Vitamin D supplementation is one of the most cost-effective health decisions available.

Timestamps 00:00 — Introduction 02:14 — Why Vitamin D is also classified as a hormone 05:18 — How the body produces Vitamin D from sunlight 06:07 — Why so many people are deficient despite sunshine 09:32 — Food sources, fortification, and supplementation 11:03 — How much Vitamin D do you actually need? 14:46 — The bigger picture: sleep, immunity, and muscle function

Vitamin D Is a Hormone as Much as a Vitamin

[02:14]

Most people know Vitamin D as a bone health supplement. What fewer people know is that it functions as a hormone — one that regulates over a thousand genes and has receptors in virtually every cell in the body.

"Vitamin D regulates over a thousand genes. It coordinates calcium absorption, it manages immune function, it helps maintain muscle strength and influences cellular processes throughout your body." — Jen

This is why deficiency produces such a varied range of symptoms. It is not one system failing — it is the body's master regulator running below capacity.

Why Sunlight Alone Is Not Enough

[06:07]

The UV radiation needed to produce Vitamin D requires sunlight at the right angle — typically midday sun. Anyone living above around 35 degrees latitude, roughly north of Los Angeles or Southern Spain, cannot produce Vitamin D from winter sunlight at all. For UK listeners specifically, Chris shares a striking statistic: if you live north of Milton Keynes, the average year does not deliver enough UV to consistently maintain Vitamin D production.

But latitude is only part of the picture. The Middle East records a 65% deficiency rate despite abundant sunshine, because staying indoors or covering up to escape heat means the skin never gets adequate exposure. Parts of Australia and some areas of India show similarly high rates. Skin pigmentation matters too — melanin reduces Vitamin D synthesis, meaning people with darker skin need significantly more sun exposure to produce the same amount. As Jen points out, darker skin in a northern climate is a genuine double challenge and a health equity issue that deserves more attention.

"If you live north of Milton Keynes, on the average year, you don't get enough UV for the entirety of the year to consistently produce Vitamin D." — Chris

On sunscreen: Chris is unequivocal — the idea that sunscreen blocks Vitamin D production is a myth. Sunscreens reduce UVB rays but not completely; enough UV still gets through for Vitamin D synthesis. Please do not avoid sunscreen for the sake of Vitamin D.

What Deficiency Actually Does to the Body

[02:23]

The effects of Vitamin D deficiency extend well beyond bone health.

1. Calcium absorption: Without adequate Vitamin D, the body absorbs only around half the dietary calcium it should. Bones do not mineralise properly — structurally present but soft and weak.
2. Immune function: Vitamin D controls antimicrobial peptides — the first line of defence against bacteria and viruses — while simultaneously preventing the immune system from overreacting and attacking the body's own tissues. As Jen puts it: it is about balance, not just strength. This is why deficiency links to both increased infection risk and increased autoimmune disease risk.
3. Muscle strength: Deficiency causes proximal muscle weakness — the large muscles in the thighs and upper arms — affecting everyday activities like stair climbing and standing from a chair. Chris notes this happens regardless of training level.
4. Sleep quality: Vitamin D receptors exist in the brain regions that regulate sleep-wake cycles. Deficiency links to poor sleep quality, difficulty falling asleep, and reduced deep sleep.

"There are multiple systems running below capacity — and understanding the why helps prioritise it." — Matt

D3 vs D2 — Why the Form Matters

[09:32]

Food sources of Vitamin D are limited and unreliable. For most people, supplementation is the most practical and consistent option. When choosing a supplement or fortified food, the form matters: Vitamin D3 is nearly 90% more effective than Vitamin D2, and is the form the body naturally produces from sunlight. Many fortified foods use D2 as a default, often labelled as the vegetarian option — but plant-source D3 is now available, and as Chris confirms, is directly equivalent to animal-derived D3. The body cannot tell the difference.

The European safe upper limit for ongoing daily intake is 4,000 IU per day.

"Consistency beats perfection — daily supplement, weekly high dose, or fortified foods plus supplementation. Whatever you'll actually stick to." — 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.

In this episode: 00:00 — Introduction 01:02 — Why cholesterol has such a confusing reputation 02:09 — The scale of the risk: what elevated LDL actually does 04:13 — LDL vs HDL: how cholesterol travels through your body 05:34 — How arterial plaque forms (and why it takes decades) 07:05 — Why boosting HDL isn't the simple fix it seems 08:27 — Age, genetics and why cholesterol tends to creep up 10:41 — Diet, fibre and the practical changes that work 12:25 — Exercise, statins and how quickly they take effect 13:48 — How cholesterol connects to sleep, weight and diabetes 15:34 — So that's why we need to manage our cholesterol levels

Key Points

Cholesterol Isn't the Enemy — Excess LDL Is

Timestamp: 04:13

Cholesterol is a single molecule that your body uses to build cell membranes, produce hormones and even synthesise vitamin D. Because it's fat-soluble, it can't travel through your bloodstream on its own — so your body packages it into transport vehicles called lipoproteins.

LDL (low-density lipoprotein) delivers cholesterol from the liver to cells around the body. In normal amounts, this is healthy and necessary. The problem starts when there's too much circulating. HDL (high-density lipoprotein) works in the opposite direction, collecting excess cholesterol from tissues and returning it to the liver for excretion.

"When everything's working normally, LDL is doing its job in a normal and healthy way. The problem is when you've got too much LDL cholesterol circulating." — Chris

What Actually Happens Inside Your Arteries

Timestamp: 05:34

When excess LDL infiltrates an artery wall, the immune system sends in white blood cells to clean it up. But those white blood cells get overwhelmed. They keep consuming damaged LDL particles until they're completely stuffed, transforming into what are known as foam cells.

These foam cells trigger inflammation and attract more white blood cells, creating a vicious cycle. The result is arterial plaque — a fatty deposit that builds up inside the artery wall. As it grows, blood clots can form. A clot in a heart artery causes a heart attack. A clot in a brain artery causes a stroke. The whole process can unfold silently over decades.

"Foam cells sound like something you'd find in a posh latte. It's probably not as pleasant when they're accumulating in your arteries." — Jen

80% of Your Cholesterol Comes From Your Liver, Not Your Diet

Timestamp: 07:53

Most people assume cholesterol is primarily a dietary problem. In reality, around 80% of your cholesterol is produced by your own liver, with only 20% coming from food. This is why some people can eat well and exercise regularly and still have elevated LDL — genetics play a significant role.

For those with familial hypercholesterolaemia (FH), an inherited condition affecting approximately one in 200 people, LDL levels are two to three times higher than normal from birth. Without treatment, around 50% of men with FH develop heart disease before the age of 50. It's typically managed with statins from childhood.

"Risk assessment looks at the whole picture. The same cholesterol number carries very different implications depending on context." — Chris

The Good News: Cholesterol Is Highly Manageable

Timestamp: 10:41

Cholesterol is one of the most manageable risk factors in medicine. For many people, lifestyle changes alone can reduce LDL by 20 to 30%. Statins can reduce it by up to 60%. Diet and exercise changes show results within four to eight weeks; statins work within around six weeks.

Key practical steps include reducing saturated fat (red meat, full-fat dairy), replacing it with healthy fats like olive oil and omega-3 rich foods, increasing soluble fibre from oats, beans, lentils and fruit, and aiming for at least 150 minutes of moderate exercise per week. Getting a simple blood test is the essential first step — because without symptoms, it's the only way to know where you stand.

"For most people, lifestyle change alone can reduce LDL cholesterol by 20 to 30%. And taking statins can reduce it by up to 60%." — Chris

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.

In this episode, Jen and Chris are joined by Jamie for a deep dive into why hunger hijacks your mood. The team unpacks four separate biological mechanisms that fire simultaneously when blood sugar drops: stress hormones that can't be distinguished from a genuine threat, a brain molecule that links hunger and aggression through the same neural circuits, a shutdown of the brain's impulse filter, and a drop in serotonin. Then there's a psychological layer on top — and understanding it might be the most practically useful thing you take away from this episode.

Timestamps

00:00 - Introduction: Jamie joins the show 02:16 - How big a deal is hanger? The 21-day study 03:37 - Blood sugar and why your brain panics 04:06 - Why hunger and stress feel chemically identical 05:05 - Neuropeptide Y: hunger and aggression on the same circuit 06:00 - The prefrontal cortex goes offline 06:39 - Serotonin and the fourth mechanism 07:14 - The psychology of hanger: why you blame the wrong thing 09:35 - What actually helps 11:35 - Hanger, sleep, and gut health 13:03 - So that's why we get hangry

Hunger Accounts for More Than a Third of Your Irritability

The first large-scale study to track hanger in real everyday life followed 64 participants over 21 days. Five times a day, they recorded their hunger levels and emotions via smartphone. The results: hunger accounted for 37% of the variation in irritability and 34% of the variation in anger levels — even after controlling for age, sex, BMI, and personality traits.

"More than a third of the time someone's being irritable, they might just need a sandwich. That reframes a lot of workplace disagreements." — Jamie

Your Body Can't Tell the Difference Between No Food and a Bear

When blood sugar drops, the body releases cortisol and adrenaline to mobilise glucose. The problem? Cortisol and adrenaline are also the hormones released under stress. The chemical signal for "I need food" and the signal for "I am under threat" are virtually identical. Research confirmed this by temporarily blocking the brain's ability to use glucose — cortisol rose and stress responses emerged, driven through the brain's stress pathways rather than by physical energy depletion alone.

"So my body literally can't tell the difference between there's no food and there's a bear. That seems like a design flaw." — Jamie

Hunger and Aggression Run on the Same Brain Wiring

Neuropeptide Y (NPY) is one of the brain's most potent appetite-stimulating molecules. But the same NPY pathways that drive hunger also increase aggression, because they operate through shared circuits with serotonin. A study confirmed that NPY released during food deprivation directly reduces activity in brain regions that normally suppress aggression.

"Hunger and anger are literally using the same wiring in the brain. That's like having your heating and your smoke alarm on the same circuit — turn one on and the other starts going off." — Jamie

The Psychology Layer: Why You Blame the Wrong Thing

A series of experiments showed that hunger alone isn't enough to trigger hanger — it requires biology, environment, and self-awareness working together. Hungry participants only interpreted situations negatively when already exposed to negative cues. In neutral environments, hunger didn't trigger hanger. Critically, participants who reflected on their emotions beforehand didn't become hangry even in deliberately frustrating situations — showing that recognising hunger as the source of irritability can short-circuit the whole process.

"Hanger is basically a case of mistaken identity." — Jamie

About So That's Why

So That's Why is a weekly podcast where Jen, Chris, and the team unpack the science behind everyday health questions. No jargon, no judgment — just genuine curiosity and proper research.

About 70% of people experience significant tearing when cutting onions, and no matter how many you've chopped over the years, the reaction doesn't get easier. In this episode, Jen, Chris, and Matt unpack the full chemistry behind one of cooking's most universal frustrations. They explore the two-enzyme system inside every onion, the volatile compound it produces, the sulfuric acid that forms on your cornea, and why some people are hit far harder than others. They also look at what actually reduces the reaction — and what the so-called folk remedies get wrong.

Timestamps

00:00 Introduction 01:42 The Two-Enzyme System Inside Every Onion 03:25 The Second Enzyme Discovered in 2002 05:58 Sulfuric Acid and the Wasabi Receptor 07:55 Why Some People React More Than Others 10:09 What Actually Works to Reduce Tears 12:04 Why Garlic Doesn't Make You Cry

The Science of Onion Tears

The Two Chemicals Inside Every Onion That Only React When You Cut It

Timestamp: 01:42

Every onion stores two chemical components in completely separate cellular compartments, physically prevented from interacting. One compartment holds an enzyme called alliinase; the other holds reactive substances called amino acid sulfoxides. As Jen explains, it's like storing oxidiser and fuel in separate tanks — perfectly stable when apart, but the moment a knife ruptures those cell walls, the compartments break open and the reaction begins. Alliinase reacts with the sulfoxides to produce unstable compounds called sulfenic acids, and from there, a second enzyme takes over.

The Enzyme Nobody Knew About Until 2002

Timestamp: 03:25

For most of human history, nobody could fully explain why onions make us cry. In 2002, Japanese researchers finally identified the missing piece: a second enzyme called lachrymatory factor synthase (LFS). This enzyme intercepts the sulfenic acids produced in the first reaction and converts them into a volatile compound — syn-propanethial-S-oxide — that immediately becomes airborne. High-speed camera studies have clocked the tiny droplets ejected from a cut onion at speeds of up to 40 metres per second, roughly 89 miles per hour. The entire two-step reaction completes within seconds of your knife making contact. This is also why sharper knives genuinely help: cleaner cuts rupture fewer cell walls, producing fewer droplets at lower velocity.

"The stats are enough to make you cry." — Chris

Sulfuric Acid, the Wasabi Receptor, and Why You Can't Build a Tolerance

Timestamp: 05:58

When those airborne droplets reach the eye, the volatile compound dissolves into the moisture on the surface of the cornea and reacts to form dilute sulfuric acid. The cornea is densely packed with nerve endings designed to detect harmful chemicals, and tears are the body's immediate safety response. The specific receptor triggered is TRPA1, better known as the wasabi receptor, because it responds to the same class of pungent compounds found in mustard, horseradish, wasabi, and onions. When sulfuric acid activates this receptor, a signal travels along the nerves to the brainstem, which fires the tear response — all within milliseconds of the compound arriving.

Crucially, this receptor doesn't adapt. Reaction intensity has no correlation with cooking experience. Every cut into a raw onion triggers the same chemical sequence, every time.

Why Some People React Far More Strongly Than Others

Timestamp: 07:55

The same onion can leave one person unaffected while reducing another to tears. Two factors drive the variation: the onion itself, and individual biology. Different onion varieties produce vastly different enzyme concentrations — there can be up to a threefold difference even within a single variety. Beyond that, people vary in their corneal receptor sensitivity, their baseline rate of tear production, and how efficiently their eyes flush out the irritant. None of these factors are within our control, and none change with repeated exposure.

"I have to time my meal prep to when the family aren't around. Otherwise they're just gonna laugh at me the whole time." — Matt

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.

In this episode, Jen, Chris, and Matt unpack the real biological mechanisms behind brain fog — from neuroinflammation and a compromised blood-brain barrier to mitochondrial dysfunction and hormonal shifts. The team explains why your brain's immune cells can get stuck in "emergency mode," how chronic stress physically shrinks the part of your brain responsible for memory, and why up to 95% of serotonin is produced in your gut, not your brain. Most importantly, they explain why brain fog is typically reversible once you address what's causing it.

In this episode:

1. 00:00 — Introduction and what brain fog actually is
2. 01:38 — Your brain's energy demands and neuroinflammation
3. 03:24 — The blood-brain barrier and why it leaks
4. 05:35 — Mitochondria and the vicious cycle
5. 07:04 — Sleep and the brain's rubbish collection
6. 08:15 — How chronic stress shrinks your hippocampus
7. 09:34 — Hormones, menopause, and thyroid
8. 11:30 — Dehydration, gut health, and nutritional deficiencies
9. 14:30 — What you can actually do about brain fog
10. 17:33 — Why everything is connected
11. 19:01 — So that's why we get brain fog

Your Brain's Immune Cells Can Get Stuck in Emergency Mode

(01:38)

One of the major drivers of brain fog is neuroinflammation — when the brain's immune cells, called microglia, become activated and stay activated long after the initial threat has passed. These cells keep releasing inflammatory molecules called cytokines, which disrupt normal brain signalling.

"Studies using brain imaging found that patients with post-COVID brain fog show widespread microglia activation — their brain's immune cells are basically still in this emergency mode, months after the infection." — Chris

The degree of inflammation directly correlates with symptom severity — the more inflamed the brain tissue, the worse the cognitive symptoms. Those cytokines impair memory, attention, and mental clarity.

This connects to the blood-brain barrier — the membrane that controls what enters the brain from the bloodstream. A 2024 study found that in long COVID patients with brain fog, this barrier becomes compromised, allowing inflammatory molecules and cells that should never reach the brain tissue to get in.

"The security gate isn't just ajar — it's actually letting through some suspicious characters that really shouldn't be getting in." — Matt

The barrier disruption was most notable in the temporal lobes and frontal cortex — regions crucial for memory and attention.

Sleep Deprivation Cancels Your Brain's Rubbish Collection

(07:04)

Sleep sits at the top of the brain fog trigger list. Research shows that after just one night without sleep, reaction time slows by 50%, working memory drops by 40%, and the ability to form new memories decreases by nearly 40%.

During sleep, the brain goes into maintenance mode — flushing out waste products, including proteins that can contribute to conditions like Alzheimer's. Brain function doesn't typically return to normal until roughly 72 hours after sleep deprivation.

"Pulling an all-nighter essentially cancels the brain's rubbish collection." — Matt

Chronic stress compounds the problem. Cortisol — the body's main stress hormone — can physically shrink the hippocampus when it stays elevated for too long. Research has shown that people with chronically high cortisol levels often have a smaller hippocampus and perform worse on memory tasks. And because the hippocampus also helps regulate stress, damage to it means the brain can't keep cortisol in check — creating a vicious cycle.

Hormones, Gut Health, and the Triggers Most People Overlook

(09:34)

Oestrogen acts as a neuroprotective hormone in the brain — supporting memory, enhancing blood flow, and protecting cells from damage. During perimenopause and menopause, when oestrogen levels drop, many women experience brain fog for the first time. Studies have documented measurable cognitive changes during these transitions.

"Women aren't just being emotional or stressed. Their brains are actually responding to dramatic shifts in a hormone that's been protecting and supporting their cognitive function for decades." — Jen

Thyroid hormones are equally important. Nearly 80% of people with hypothyroidism report frequent brain fog symptoms — the direct result of brain cells operating at a slowed metabolic rate.

The gut-brain connection adds another layer. The brain and gut communicate bidirectionally through the gut-brain axis, and up to 95% of serotonin — crucial for mood and cognition — is produced in the digestive system. Studies have shown that patients with irritable bowel syndrome often experience brain fog, and treatments that help rebalance the gut microbiome can improve cognitive symptoms.

Brain Fog Is Reversible — Here's What Actually Helps

(14:30)

The encouraging news is that for most people, brain fog is not permanent cognitive decline — it's a reversible state that improves when you address the underlying causes.

1. Sleep — Most adults need seven to nine hours. The brain needs that time for maintenance, waste clearance, and memory consolidation.
2. Hydration — The brain is over 70% water. Even mild dehydration impairs cognitive function, but effects reverse quickly once you rehydrate.
3. Nutrition — Omega-3 fatty acids, B vitamins, vitamin D, and natural antioxidants all support cognitive function. Limiting processed foods that trigger inflammation is also worth considering.
4. Stress management — Chronic stress physically damages the hippocampus. Finding what works for you — mindfulness, breathing exercises, walking outside — helps break the cortisol cycle.
5. Exercise — Physical activity increases cerebral blood flow, supports mitochondrial function, reduces inflammation, and regulates stress hormones.

"Brain fog's telling you that something needs attention. But your brain is incredibly resilient. If you address the underlying cause, give it the support, your cognitive function typically does improve." — Jen

For brain fog that coincides with perimenopause, menopause, or thyroid issues, speaking with a doctor is recommended — there are treatments that can help.

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.

In this episode, Jen, Chris, and Matt tackle one of the most debated topics in the supplement world. With Chris's 30+ years as a formulation scientist, the team explains why supplements physically cannot be made from pure nutrients alone, what common excipients actually do, and where the real concerns in this industry lie. Along the way, they bust myths about magnesium stearate, silicon dioxide, maltodextrin, and carrageenan, and reveal some genuinely questionable practices hiding behind "filler-free" marketing.

In this episode:

1. 00:00 - Introduction
2. 01:32 - Why supplements can't just be pure nutrients
3. 04:01 - Magnesium stearate and why it's safe
4. 06:06 - Silicon dioxide and the nanoparticle question
5. 07:57 - Maltodextrin and the dose that makes the poison
6. 10:12 - Carrageenan and research misinterpretation
7. 13:02 - The salt shaker situation
8. 16:42 - What "filler-free" labels actually mean
9. 18:39 - What to actually look for on a label

Why Supplements Can't Be Pure Nutrients

(01:32)

A typical vitamin B12 dose is around 100 micrograms, a millionth of a gram. That's too small to see with the naked eye, let alone measure consistently or form into a tablet. Without excipients, you'd have a pile of powder too tiny and too clumpy to work with.

Chris uses a beach sand analogy to explain the manufacturing challenge. Fine, dry beach sand flows through your fingers almost like liquid and pours easily into a capsule. Wet sandcastle sand? Great for building, but impossible to get through a machine. Most nutrient powders behave like the wet sand. Excipients give them the flow they need.

"Supplement companies don't actually financially benefit by adding these things. These ingredients add cost. So if we could make a tablet with just pure vitamin D3 powder, we would. But the problem is it's often physically impossible." — Chris

The Safety of Common Excipients

(04:01)

The team works through four of the most questioned ingredients on supplement labels.

Magnesium stearate is a salt of stearic acid, a natural fatty acid found in cooking oil, chocolate, and any oily food. It's used in milligram quantities as a flow agent. The FDA considers it safe at up to 2,500 milligrams per kilogram of body weight daily. For an average person, that's 175,000 milligrams. A typical capsule contains around 50 milligrams, or roughly 0.03% of the safety threshold.

"It's kind of ironic, right? Avoiding supplements with magnesium stearate whilst eating everyday foods like chocolate that contain far more of the ingredient seems a bit odd." — Matt

Silicon dioxide (silica) prevents clumping and absorbs moisture. There is a legitimate conversation around nanoparticles, and the European Food Safety Authority has been reviewing this. But most silica used in supplements is non-nano, meaning the particles are larger and raise no safety concerns.

Maltodextrin is derived from starch (potatoes or maize) and serves as a binder and natural sweetener in chewable tablets. Online concerns about its glycaemic index come from studies using many grams per day, compared to the 100–200 milligrams in a supplement tablet. At these levels, maltodextrin does its structural job without any measurable effect on the body.

Carrageenan is a natural gum from seaweed, used to form plant-based soft gel capsules. The inflammation concerns originate from studies on poligeenan, a completely different compound not even permitted for use in foods.

"It's literally like saying water is dangerous because of studies about hydrogen peroxide." — Chris

The Salt Shaker Situation and Hidden Ingredients

(13:02)

The genuinely concerning practices in the supplement industry aren't about which excipients are present. They're about transparency.

Some companies, when their vitamin mix won't flow into capsules, use what Chris describes as "a big salt shaker" full of a flow agent like magnesium stearate, pouring it over the mix at the machine. Because they classify this as a "processing aid," they don't declare it on the label. Some of these companies are simultaneously marketing their products as "filler-free."

The team tested a set of "clean" capsules from another company. The plant extract was beige, but there were visible white specks and white residue in the bottle. Nothing white was listed on the ingredients.

"To forget to list flow aids or sub-ingredients is one thing, but to then be making a big noise about how clean or filler-free the product is, is completely unacceptable." — Chris

What to Actually Look for on a Label

(18:39)

The team offers three things to check when choosing a supplement:

1. Bioavailable forms of active ingredients. Vitamin D3 rather than D2, folate rather than folic acid, EPA and DHA for omega-3, and chelated mineral forms.
2. Full transparency. Every ingredient should be listed, including sub-ingredients and processing aids. If something seems to be missing, ask the company directly.
3. Formulation expertise. Is the company run by formulation scientists, or by marketers importing cheap multivitamins?

"What ultimately matters is whether the product contains the active ingredients that are in the right forms and effective doses, and that the product's been formulated properly." — Chris

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.

In this episode, Jen, Chris, and Matt unpack the biology behind sweat rate variation, from the hypothalamus acting as your body's built-in thermostat, to the sweat gland architecture determined by your DNA before you were even born. They explore why fitter people often sweat more (not less), how your body learns to cool itself more efficiently over time, and what you can do to work with your sweat response rather than against it. Chris also walks through a simple method for calculating your personal sweat rate — something most people have never thought to do.

Timestamps 00:00 — Introduction 01:41 — How much sweat rates can actually vary 02:56 — Your brain's built-in thermostat: the hypothalamus 03:51 — Sweat gland architecture, genetics, and the factory analogy 06:42 — Does sweating more mean you're fitter? 08:50 — How to calculate your personal sweat rate 11:57 — How sweat connects to sleep, mood, and energy

The Sweat Rate Gap Is Bigger Than You Think

[01:41]

The variation in how much people sweat isn't small. Chris explains that sweat rates can range from half a litre per hour up to two and a half litres per hour in some athletes — more than a five-fold difference for the same exercise intensity. Beyond the curiosity factor, this has real consequences: research shows that even 2% dehydration caused by sweating can decrease performance by around a fifth, and 40 to 50% of athletes consistently underestimate their sweat losses.

"The variation can mean sweating between half a litre per hour and two and a half litres per hour in some athletes. That's more than a five-fold difference for a similar exercise." — Chris

Your Sweat Glands Work Like Tiny Factories — and Everyone's Are Different

[03:51]

The variation in sweat response comes down to what Chris calls your individual sweat gland architecture. Each gland produces a fluid similar to blood plasma, and then a duct reabsorbs sodium chloride before that fluid reaches the surface of your skin — a built-in quality control process Chris describes as "tiny water treatment plants." Individual differences in how efficiently that reabsorption happens explain differences in both sweat volume and saltiness. Critically, the genes governing sweat gland development are active while we're still embryos, meaning our relationship with sweat is written into our DNA.

"My brain decides how much to sweat without me having any say." — Jen

Fitter People Often Sweat More — Not Less

[06:42]

This section busts one of the most common gym-floor assumptions. People at peak fitness typically begin sweating within one to two minutes of exercise, compared to five or more minutes for less trained individuals. A trained body doesn't wait to overheat — it anticipates the heat and starts cooling proactively. After one to two weeks of regular heat exposure during exercise, the system acclimatises further: heat-acclimatised people produce sweat around six times lower in sodium than unacclimatised people, because the body has learned to conserve its electrolytes.

"Being a heavy sweater can actually be a badge of honour. Which changes everything for people who might feel self-conscious about their sweating." — Matt

How to Calculate Your Personal Sweat Rate — and Use It

[08:50]

Chris walks through a simple method: weigh yourself before exercise, exercise for an hour without drinking, then weigh yourself again. The weight difference in kilograms, multiplied by 1,000, gives your sweat rate in millilitres per hour. From there, the team covers practical strategies — including why over-drinking during exercise can deplete electrolyte balance, why timing workouts for the cooler parts of the day can cut sweat losses by 30 to 40%, and why pre-cooling techniques like running cold water over the wrists and forehead are more effective than most people realise.

"There is no universal hydration strategy. It's what's right for you." — Chris

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.

In this episode, Jen, Chris, and Matt explore why some people turn tomato red during a workout while others barely change colour. The answer lies in genetics, specifically in blood vessel density and reactivity. The team breaks down what's really happening under your skin, why people with pronounced flushing often have better thermal regulation, and what you can actually do about it if it bothers you.

In this episode:

1. 00:00 Introduction
2. 01:04 Why fitness has nothing to do with it
3. 02:47 Blood vessel density and reactivity explained
4. 04:06 Why going red might actually be an advantage
5. 05:39 Ethnicity, gender and age differences
6. 08:09 What actually helps reduce flushing
7. 11:41 The human mood ring connection
8. 13:04 So that's why your face turns red

It's Not About Fitness. It's About Your DNA.

[01:04]

The assumption that you'll stop going red when you get fitter is one of the most persistent myths in exercise culture. Research shows that flushing intensity has virtually no correlation with cardiovascular fitness, effort level, or how out of shape someone is.

As Chris puts it: "It's got virtually nothing to do with fitness level and everything to do with how your cooling system is programmed."

Despite this, the myth has real consequences. Studies have shown that people with pronounced exercise flushing are around 40% more likely to avoid group fitness classes, often choosing to exercise alone or during quieter gym times. That's a significant number of people changing their health routines because of something they can't actually control.

"My fitness has improved loads over the past five years especially, and I still turn bright red." — Jen

Blood Vessel Density and Reactivity

[02:47]

So what is actually causing the variation? It comes down to two genetically determined factors: blood vessel density and blood vessel reactivity.

1. Blood vessel density refers to the number of blood vessels packed into the skin of the face. This varies greatly from person to person. More vessels near the surface means more visible blood flow when they dilate.
2. Blood vessel reactivity is how quickly those vessels respond to triggers like heat and rising core temperature. Research conducted in Australia found that some people's facial blood vessels react to increases as small as a third of a degree Celsius.

For context, core body temperature during exercise might rise by one to two degrees overall. For highly reactive individuals, their facial blood vessels are already responding before they've barely warmed up.

"In some people it could be responses that kick in when your body temperature increases by just a third of a degree Celsius." — Chris

Why Going Red Might Be a Superpower

[04:06]

People with high facial vascular reactivity tend to have better overall thermal regulation. Their bodies get ahead of the heat problem before it becomes serious, which means better core temperature maintenance and reduced overheating risk during prolonged activity.

Chris notes that "pronounced facial flushing often correlates with better performance in hot temperatures." Athletes with higher facial vascular reactivity appear to maintain better performance when training in the heat.

The difference comes down to how the body distributes its cooling effort. Some people have distributed thermoregulation, spreading heat dissipation evenly across their body. Others concentrate the response in the face. Same system, same outcome, different display. From a physiological perspective, concentrated facial flushing has no trade offs.

People with this responsive vascular system also tend to blush more easily during emotional stress and react more strongly to spicy foods and temperature changes.

"Those of us who turn red during exercise, basically we're human mood rings." — Matt

The same genetic programming also supports better long term cardiovascular adaptation. People with responsive vascular systems often see resting heart rate and blood pressure reductions faster with training.

"The same genetic programming that's making us look like tomatoes is actually supporting the long-term cardiovascular adaptation." — Jen

What Actually Helps (and What Makes It Worse)

[08:09]

Since flushing is genetic, it can't be eliminated entirely. But the episode covers several evidence backed ways to reduce its intensity:

1. Pre cooling — Applying cool, damp cloths to the wrists and temples for two to three minutes before exercise can reduce facial flushing intensity by about a quarter. These pressure points have blood vessels close to the surface that connect directly to facial capillaries.
2. Hydration timing — A glass of cool water about 20 minutes before exercise helps maintain better temperature regulation. The body needs time to distribute that fluid before heat stress begins.
3. Clothing choices — Light coloured, moisture wicking fabrics reduce overall heat load. The neck area is particularly important, as it contains major blood vessels that supply the face.
4. Avoid alcohol within 24 hours of intense exercise, as it dilates blood vessels and makes flushing more pronounced. Very hot showers immediately after exercise can also prolong the response.

For most people, exercise flushing is completely harmless. If it's accompanied by dizziness, nausea, or confusion, or doesn't resolve within 30 minutes, that's worth checking as it could indicate heat exhaustion.

"It's not a sign of being out of shape. It's a sign that your temperature control system is working exactly as designed." — 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.

A 2025 study published in The Lancet, analysing data from over 160,000 adults globally, found that the real health benefits of walking kick in much earlier than most people think, and that the ideal step count depends on your age, your health, and your lifestyle.

Key points covered in this episode:

1. 00:00 Introduction
2. 01:43 The huge health benefits of walking
3. 03:19 The 1964 Tokyo Olympics marketing origin
4. 05:10 What researchers actually found decades later
5. 06:38 Why age changes your ideal step count
6. 08:42 Why not all steps are created equal
7. 11:06 What your personal target should be
8. 15:29 Weekend warriors and other forms of exercise
9. 16:28 How steps connect to sleep and mental health
10. 18:21 So that's why we chase 10,000 steps

The 10,000-Step Target Was Born From Marketing, Not Medicine

In 1964, a Japanese company developed one of the first commercial pedometers and named it the Manpo-kei, meaning "10,000 step meter." The number was chosen partly because of its cultural significance in Japan as a symbol of long life, and partly because the Japanese character for 10,000 looks like a person walking.

There was some science in the mix. Dr Yoshiro Hatano at Kyushu University calculated that going from 4,000 to 10,000 steps would burn roughly 500 extra calories per day. But as Jen puts it, "It was basically one guy with a calculator being like, yeah, 10,000 sounds good."

"Our entire fitness culture is based on what a Japanese character looked like. It feels a little bit like deciding to eat eight meals a day because that's the shape of a snowman." — Matt

The Science Says You Probably Need Fewer Steps Than You Think

When researchers eventually studied the relationship between step counts and health, they found a more nuanced picture. A major study of 160,000 older women found that just 4,400 steps per day was associated with a 40% reduction in mortality risk compared to 2,000 steps. Benefits plateaued at approximately 7,500 steps.

The Lancet study reinforced this, showing that people walking at least 7,000 steps per day had a 25% reduction in cardiovascular disease risk, 38% lower chance of dementia, and 22% reduction in depression.

The health gains follow a curve that rises steeply at first, then flattens. The biggest improvements come from moving out of a sedentary lifestyle, not from chasing the highest possible number.

"10,000 steps as a daily target's not wrong. It's just not universally right either." — Chris

Your Ideal Step Count Depends on Who You Are

Optimal step counts vary dramatically based on age, health status, height, and lifestyle. For adults under 60, benefits plateau at 8,000 to 10,000 steps. For those over 60, maximum benefits are often reached at 6,000 to 8,000. People with chronic conditions can see meaningful improvements from just 2,000 to 3,000 additional steps per day.

Intensity matters too. A 2024 study found that 15 minutes of brisk walking daily was associated with a nearly 20% decrease in mortality risk. The same number of steps at a slower pace doesn't deliver the same benefit.

"The best exercise you should do is one that you will actually do." — Matt

Steps Connect to Sleep, Mood, and the Bigger Health Picture

Higher daily step counts are directly linked to better sleep quality, less time falling asleep, and more deep sleep. The mental health connection is equally striking, with a 22% reduction in depression risk at 7,000 steps compared to 2,000.

"Your movement affects your sleep and your sleep affects your mood and that affects your motivation. It all works together." — Matt

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 judgement — just genuine curiosity and proper research.

What You'll Learn

1. Why less than 1% of people carry genuine short-sleep genetics
2. What happens to your brain after just one night of poor sleep
3. The waste-removal system your brain runs every night
4. Why you can't train yourself to need less sleep
5. How age, circadian rhythms, and environment shape your sleep needs
6. Practical ways to figure out what your body actually needs

Key Timestamps

00:00 - Introduction

01:08 - Genetic mutations and natural short sleepers

04:09 - Your brain takes out the trash while you sleep

05:25 - Sleep stages and where the real recovery happens

07:21 - The myth of adapting to less sleep

08:20 - Age, teenagers, and biphasic sleep history

11:33 - Warning signs of chronic sleep debt

13:45 - Circadian rhythms and sleep environment

15:06 - Can supplements help with sleep quality?

16:31 - Why sleep connects to everything else

19:19 - So that's why some people need less sleep

The Genetics of Short Sleep

In 2009, researchers at the University of California, San Francisco, discovered the first family with natural short sleep syndrome. A mother and daughter required just 6.25 hours of sleep per night, compared to 8.06 hours for other family members. The difference was a mutation in the DEC2 gene, which affects the molecular clock in the brain.

As Chris explains: "These people with this ability, this mutation, they don't just cope with less sleep, they actually need less while maintaining the same perfect cognitive function."

Since then, scientists have found other gene mutations with similar effects. But these natural short sleepers remain extraordinarily rare.

"They've won the genetic lottery, except instead of millions, they won the ability to function on less sleep." — Matt

What One Night of Bad Sleep Does to Your Brain

Research involving over 5,000 people found that after just one night of four to six hours of sleep, reaction time slows by 50%, working memory drops by 40%, and the ability to form new memories decreases by roughly 40%.

The unsettling part? People don't realise how impaired they are.

"Your brain adapts to feeling tired, so you think you're functioning normally when you are actually functioning like you've had several drinks." — Jen

That adaptation has a name: sleep debt. And it accumulates quietly.

Your Brain's Nightly Maintenance Routine

During deep sleep, brain cells physically shrink by 60%, opening up space to flush out waste products accumulated during the day, including proteins associated with Alzheimer's disease. An all-nighter essentially cancels this process entirely.

"When someone says they're too busy to sleep, they're saying they're too busy to let their brain take out the trash." — Matt

REM sleep transfers information from temporary storage to permanent storage in the cortex. Miss it, and long-term memory formation suffers.

The Myth of Adapting to Less Sleep

Multiple studies show that while you might feel less tired over time, performance continues to deteriorate beneath the surface.

"It's a bit like altitude sickness. You stop feeling nauseous, but your blood oxygen levels are still dangerously low." — Matt

Warning signs of chronic sleep debt include needing caffeine to function, falling asleep within minutes of lying down, sleeping significantly longer on weekends, and feeling groggy upon waking.

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.

In this episode, Jen, Chris, and Matt trace the eight-glasses myth back to a 1945 report that almost everyone misread, examine a landmark study of 5,600 people across 23 countries that revealed individual hydration needs can vary by up to 1,000%, and explain why your body's built-in thirst system is far more reliable than most of us give it credit for. Along the way, the team tackles some surprising findings, including why milk is more hydrating than water, why coffee counts towards your fluid intake, and why over-hydrating can actually do more harm than good.

In this episode:

1. 00:00 — Introduction
2. 01:21 — Where the eight-glasses rule actually came from
3. 05:00 — The isotope tracking study that changed the picture
4. 06:28 — How your body's hydration system really works
5. 08:28 — How needs vary by person, lifestyle, and life stage
6. 11:28 — Electrolytes, milk, and what actually hydrates
7. 12:58 — The simplest way to check your hydration
8. 16:00 — When over-managing hydration backfires

The 1945 Recommendation That Got Lost in Translation

[01:21]

The original "eight glasses a day" idea traces back to a report from the US Food and Nutrition Board in 1945. It recommended around 2.5 litres of total fluid per day, but that included fluids from food, coffee, tea, and all other beverages. Somewhere along the way, the crucial word "total" got dropped, and the recommendation became "drink eight glasses of plain water."

As Chris explains: "It's a multi-decade misunderstanding that became so deeply embedded in everything that we do, it's almost overridden our body's natural programming."

A well-known kidney specialist, Dr Heinz Valtin, spent years trying to find scientific proof for the eight-glasses rule. His conclusion? There was no evidence that every person needs to drink at least eight glasses a day.

The result: many of us have been over-hydrating by 30 to 40% more than our bodies actually need.

Your Body Has a Built-In Hydration System

[06:28]

The body manages hydration through sensors in the brain that effectively taste blood for salt concentration. If the blood is too salty, they trigger the sensation of thirst. If it's too dilute, they send signals to the kidneys to flush out the excess.

"Your body detects when you need food. It detects when you need to sleep, when you need to go to the bathroom. So why would water detection be uniquely unreliable?" — Chris

There's a widely repeated claim that by the time you feel thirsty, you're already dehydrated. Chris addresses this directly: that idea comes from studies on athletes in extreme conditions or elderly people with impaired thirst mechanisms. For most healthy people, thirst is a perfectly reliable indicator.

Hydration Needs Vary By Up to 1,000%

[05:00]

Researchers tracked 5,600 participants across 23 countries using isotope tracking, a technique Chris describes as "giving water molecules little name tags so we can follow them around the body." The findings showed enormous variation: some people need just one litre of water a day, while others need more than ten.

Young adult males needed roughly 1.5 to 1.8 litres of drinking water a day. For females, slightly less, around 1.3 to 1.4 litres. Crucially, that includes all fluids, not just water.

As Jen puts it: "Everyone thinking they need exactly eight glasses of water is like everyone trying to wear the same size shoes."

Factors that shift individual needs include age, activity level, climate, body size, genetics, and even personality traits. People with higher anxiety tend to have higher water turnover, linked to increased breathing and heart rates.

What Actually Counts Towards Hydration

[11:28]

One of the episode's most reassuring findings: coffee, tea, and other beverages all contribute to hydration. Although caffeine has a mild diuretic effect, the water content in coffee more than compensates for it.

The team also reveals that milk is actually more hydrating than water, retaining fluid about 50% better thanks to its sodium and protein content. And food accounts for 20 to 30% of daily fluid intake — cucumbers are 96% water, tomatoes 95%, and oranges around 86%.

"Your body knows how to manage hydration. Trust your thirst, check your urine colour, save that mental energy for something more pressing." — Chris

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.

In this launch episode of So That's Why, hosts Jen, Chris, and Matt introduce the podcast that takes everyday health questions and actually answers them — with real research, proper context, and the kind of curiosity that makes you want to tell someone about it afterwards.

The team behind Vegetology — a science-driven supplement company — explain why they started the show, what listeners can expect from each 20-minute episode, and why understanding the mechanism behind health advice matters more than memorising rules. Plus, a first look at what's coming in Episode 1: the truth about that "eight glasses of water a day" recommendation.

Key Points:

1. 00:00 — Opening and host introductions
2. 01:00 — Why health advice rarely explains the "why"
3. 02:00 — The Vegetology connection
4. 02:30 — What to expect from every episode
5. 03:00 — Teaser for Episode 1 on hydration myths
6. 04:00 — Who the podcast is for
7. 05:00 — How to subscribe and get involved

The Gap Between Health Rules and Understanding Why They Exist

(00:00)

Most health content tells people what to do without explaining why it works. Drink this much water. Walk this many steps. Sleep this many hours. The rules pile up, they often contradict each other, and there's rarely any explanation of the biology underneath.

"When you understand the why behind health advice — whether it's about your body, your nutrition, your fitness, or just the way we live our lives — you can actually make decisions that work for your life, not just follow rules that may or may not apply to you." — Matt

So That's Why was built to fill that gap. Not with more instructions, but with genuine understanding of how the body works and what the research actually says.

Meet the Team Behind the Microphones

(01:00)

The show is hosted by three people who also run Vegetology, a nutritional supplement company built on science rather than marketing trends.

1. Jen holds a PhD in biochemistry and molecular biology. She asks the questions the listener is already thinking — and because she understands the science deeply, her follow-ups go exactly where they need to.
2. Chris is a formulation scientist with over 30 years of experience. He brings the research citations, explains the mechanisms, and reaches for analogies that make complex biology feel intuitive.
3. Matt comes from an e-commerce and nutrition background. He bridges the science to everyday life, checking that the explanations actually make sense for real people.

"Think of us as your science-curious friends who happen to have the backgrounds to dig into research and translate it into something actually useful." — Matt

"You basically mean we are geeks." — Chris

What Makes This Show Different

(02:30)

Every episode runs about 20 minutes and follows a consistent format: one question, usually starting with "Why do we...?", answered with real research, named institutions, and genuine numbers — not vague claims.

The show sits in what Jen describes as "that sweet spot between too technical to understand and so simplified it's not actually true anymore."

Key commitments:

1. Real research with specific studies and institutions named
2. Analogies that make complex biology click
3. Acknowledgement that science applies differently to different people
4. No prescriptions, no guilt, no fear-based messaging
5. Empowerment through understanding, not rules

"We're the people who read the full study, not just the headline." — Matt

Coming Next — The Eight Glasses of Water Myth

(03:00)

The first proper episode tackles a piece of health advice that almost everyone has absorbed as fact: the idea that you need to drink eight glasses of water every day.

"There's an interesting background to where that specific number came from and how research doesn't necessarily agree with it at all." — Chris

The answer involves a misunderstood recommendation from 1945, individual variables most people never consider, and the role of water content from food — all of which got lost somewhere along the way.

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.