So That's Why

Vegetology

You've been told to drink eight glasses of water a day. You've chased 10,000 steps like it's some kind of biological law. You've checked your cholesterol without being entirely sure what you're actually checking for. Most health content tells you what to do. Nobody explains why. That's the gap So That's Why was made to fill. Each week, Jen, Chris, and Matt take one everyday health question — the kind that's been nagging at the back of your mind, or that you've just accepted without thinking — and unpack the actual science behind it. Where did this idea come from? What's really happening inside your body? And does the evidence actually hold up? What they find is often surprising. The 10,000-steps rule was invented by a Japanese marketing team in 1964. The eight-glasses-of-water recommendation came from a misread document. The reason some people turn tomato-red when they exercise has nothing to do with fitness — it's about blood vessel density. The thing that makes you cry when you chop onions was only properly understood in 2002. Cholesterol is in every single cell of your body — so why the terrible reputation? The science is real, the research is specific, and the conversations are genuinely fascinating. And the three people having them have the backgrounds to get it right. Jen holds a PhD in biochemistry and molecular biology. She asks the questions you're thinking — informed ones, not naive ones — and keeps the conversation grounded in the human experience of all this biology. Chris is a formulation scientist with over 30 years of experience. He's read the studies, knows the mechanisms, and has the analogies that make complex biology actually click. Matt looks at the science and asks what it means for real people, with real lives, real schedules, and no time for perfectionism. Together they hit that sweet spot between too technical to understand and so simplified it's not actually true anymore. Getting there, it turns out, is harder than it sounds. So That's Why doesn't give you a list of rules to follow. It doesn't shame you for the things you haven't been doing. It explains the mechanism — the actual biology — so you can make decisions that fit your life, rather than just following advice that might not apply to you at all. Episodes run about 20 minutes. They're built for commutes, workouts, or cooking dinner. By the end of each one, you'll be able to explain the answer to someone else — which is the whole point. New episodes every week. Subscribe and find out why.

  1. 6 DAYS AGO

    Why Do We Get Food Cravings?

    You're completely full. And yet twenty minutes after dinner you're standing in front of the fridge, staring down a slice of cake. Sound familiar? Up to 97% of people experience food cravings — but almost nobody understands what's actually driving them. 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 PointsCravings 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 WhySo That's Why is a weekly podcast where Jen, Chris, and Matt unpack the science behind everyday health questions. No jargon, no judgment. Just genuine curiosity and proper research.

    17 min

  2. 23 APR

    Why Does Caffeine Stop Working Over Time?

    Nearly 90% of adults consume caffeine daily — yet most have no idea why it gradually loses its punch. If your morning coffee used to change your day and now just stops you feeling terrible, there is a biological reason for that. And it happens faster than you would expect. 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 AdaptingMost 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 ToleranceNot 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 SuggestsThe 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 WhySo 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.

    16 min

  3. 16 APR

    Why Do We Need Vitamin D?

    Your body can make Vitamin D from sunlight — so why is nearly half the global population still deficient in it? 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." — JenThis 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." — ChrisOn 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. 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.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.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.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." — MattD3 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." — JenAbout So That's WhySo That's Why is a weekly podcast where Jen, Chris, and Matt unpack the science behind everyday health questions. No jargon, no judgment — just genuine curiosity and proper research.

    18 min

  4. 9 APR

    Why Do We Need to Manage Our Cholesterol Levels?

    Cholesterol is in every single cell in your body — yet it's also called "the Silent Killer." In this episode, Jen, Chris and Matt unpack why the same molecule that keeps you alive can silently damage your arteries for decades before you feel a thing, and what you can actually do about it. 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 PointsCholesterol Isn't the Enemy — Excess LDL IsTimestamp: 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." — ChrisWhat Actually Happens Inside Your ArteriesTimestamp: 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." — Jen80% of Your Cholesterol Comes From Your Liver, Not Your DietTimestamp: 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." — ChrisThe Good News: Cholesterol Is Highly ManageableTimestamp: 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%." — ChrisAbout So That's WhySo That's Why is a weekly podcast where Jen, Chris and Matt unpack the science behind everyday health questions. No jargon, no judgment — just genuine curiosity and proper research.

    17 min

  5. 2 APR

    Why Do We Get Hangry?

    That irritable, short-fused feeling when you've missed a meal has a name — and it turns out "hangry" is backed by serious science, not just a lack of willpower. 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. Timestamps00:00 - 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 IrritabilityThe 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." — JamieYour Body Can't Tell the Difference Between No Food and a BearWhen 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." — JamieHunger and Aggression Run on the Same Brain WiringNeuropeptide 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." — JamieThe Psychology Layer: Why You Blame the Wrong ThingA 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." — JamieAbout So That's WhySo 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.

    15 min

  6. 26 MAR

    Why Do Onions Make Us Cry?

    Why do onions make us cry every time we cut them — and why does cooking them make the problem disappear completely? 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. Timestamps00:00 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 TearsThe Two Chemicals Inside Every Onion That Only React When You Cut ItTimestamp: 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 2002Timestamp: 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." — ChrisSulfuric Acid, the Wasabi Receptor, and Why You Can't Build a ToleranceTimestamp: 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 OthersTimestamp: 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." — MattAbout So That's WhySo That's Why is a weekly podcast where Jen, Chris, and Matt unpack the science behind everyday health questions. No jargon, no judgment — just genuine curiosity and proper research.

    15 min

  7. 19 MAR

    Why Do We Get Brain Fog?

    Brain fog affects over a quarter of us — yet it isn't actually a medical diagnosis. So what's really happening inside your brain when thinking feels like wading through treacle? 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: 00:00 — Introduction and what brain fog actually is01:38 — Your brain's energy demands and neuroinflammation03:24 — The blood-brain barrier and why it leaks05:35 — Mitochondria and the vicious cycle07:04 — Sleep and the brain's rubbish collection08:15 — How chronic stress shrinks your hippocampus09:34 — Hormones, menopause, and thyroid11:30 — Dehydration, gut health, and nutritional deficiencies14:30 — What you can actually do about brain fog17:33 — Why everything is connected19:01 — 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." — ChrisThe 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." — MattThe 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." — MattChronic 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." — JenThyroid 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. Sleep — Most adults need seven to nine hours. The brain needs that time for maintenance, waste clearance, and memory consolidation.Hydration — The brain is over 70% water. Even mild dehydration impairs cognitive function, but effects reverse quickly once you rehydrate.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.Stress management — Chronic stress physically damages the hippocampus. Finding what works for you — mindfulness, breathing exercises, walking outside — helps break the cortisol cycle.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." — JenFor 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 WhySo That's Why is a weekly podcast where Jen, Chris, and Matt unpack the science behind everyday health questions. No jargon, no judgment — just genuine curiosity and proper research.

    21 min

  8. 12 MAR

    Why Do Supplements Have So Many Extra Ingredients?

    The ingredients on your supplement label that aren't the vitamin? They're not "fillers" and they're not there to cut corners. Most people don't know what these extra ingredients actually do, or why they're necessary. 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: 00:00 - Introduction01:32 - Why supplements can't just be pure nutrients04:01 - Magnesium stearate and why it's safe06:06 - Silicon dioxide and the nanoparticle question07:57 - Maltodextrin and the dose that makes the poison10:12 - Carrageenan and research misinterpretation13:02 - The salt shaker situation16:42 - What "filler-free" labels actually mean18:39 - 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." — ChrisThe 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." — MattSilicon 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." — ChrisThe 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." — ChrisWhat to Actually Look for on a Label(18:39) The team offers three things to check when choosing a supplement: 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.Full transparency. Every ingredient should be listed, including sub-ingredients and processing aids. If something seems to be missing, ask the company directly.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." — ChrisAbout So That's WhySo That's Why is a weekly podcast where Jen, Chris, and Matt unpack the science behind everyday health questions. No jargon, no judgment — just genuine curiosity and proper research.

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You've been told to drink eight glasses of water a day. You've chased 10,000 steps like it's some kind of biological law. You've checked your cholesterol without being entirely sure what you're actually checking for. Most health content tells you what to do. Nobody explains why. That's the gap So That's Why was made to fill. Each week, Jen, Chris, and Matt take one everyday health question — the kind that's been nagging at the back of your mind, or that you've just accepted without thinking — and unpack the actual science behind it. Where did this idea come from? What's really happening inside your body? And does the evidence actually hold up? What they find is often surprising. The 10,000-steps rule was invented by a Japanese marketing team in 1964. The eight-glasses-of-water recommendation came from a misread document. The reason some people turn tomato-red when they exercise has nothing to do with fitness — it's about blood vessel density. The thing that makes you cry when you chop onions was only properly understood in 2002. Cholesterol is in every single cell of your body — so why the terrible reputation? The science is real, the research is specific, and the conversations are genuinely fascinating. And the three people having them have the backgrounds to get it right. Jen holds a PhD in biochemistry and molecular biology. She asks the questions you're thinking — informed ones, not naive ones — and keeps the conversation grounded in the human experience of all this biology. Chris is a formulation scientist with over 30 years of experience. He's read the studies, knows the mechanisms, and has the analogies that make complex biology actually click. Matt looks at the science and asks what it means for real people, with real lives, real schedules, and no time for perfectionism. Together they hit that sweet spot between too technical to understand and so simplified it's not actually true anymore. Getting there, it turns out, is harder than it sounds. So That's Why doesn't give you a list of rules to follow. It doesn't shame you for the things you haven't been doing. It explains the mechanism — the actual biology — so you can make decisions that fit your life, rather than just following advice that might not apply to you at all. Episodes run about 20 minutes. They're built for commutes, workouts, or cooking dinner. By the end of each one, you'll be able to explain the answer to someone else — which is the whole point. New episodes every week. Subscribe and find out why.

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