So That's Why

About So That's Why

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.

Publisher

Vegetology

Category

education · science · science

Language

en

Explicit

No

First episode

25 Feb 2026

Latest episode

29 Oct 2026

Latest episodes

40 episodes in the feed.

1. 

   29 Oct 2026

   Why Does Your Gut Affect Your Mood?

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

2. 

   22 Oct 2026

   Why Do We Dream?

   Your brain builds a convincing world every night, then clears nearly all of it before you wake. So why do we dream? Most of us have between four and seven separate dreams a night and forget up to 95% of them within minutes. Jen, Chris and Matt work through what is actually happening in the brain during REM sleep, why the forgetting is a consequence of the mechanism rather than a memory failure, and what the best current evidence says dreaming is for. The episode covers the four regions that swing out of balance during REM, the 2024 Scientific Reports study on dreaming and emotional memory, why babies spend so much more time in REM than adults, the simple line that separates a bad dream from a nightmare, and whether what you eat can genuinely change what you dream about. By the end you should be able to explain the whole thing in one sentence. Chapters 00:00 Why do we dream 01:34 How much we actually dream and why we forget it 02:26 What is happening in the brain during REM sleep 07:37 Dreaming as emotional processing 10:44 How dreaming changes with age and how you wake 12:46 What separates a bad dream from a nightmare 15:15 Can food actually change your dreams 17:22 The verdict on why we dream Four Regions Swing Out of Balance During REM Sleep (02:26) Most vivid dreams happen during rapid eye movement sleep, and what makes REM unusual is not simply that the brain is busy. Several regions shift at once. The prefrontal cortex, which handles logic and self awareness, powers down. That is why nothing in a dream seems questionable while it is happening. The amygdala, involved in processing emotions, becomes more active, which helps explain the emotional intensity. The visual cortex fires with no real input coming in, generating the images fresh rather than replaying old footage. The hippocampus keeps feeding the dream real material from recent memory. Underneath it all, the brainstem fires bursts of signals and the rest of the brain builds a story around them, which is why a dream lurches from your kitchen to a beach with no join. "My brain's improvising over random noise and pretty much hoping that I don't notice." Matt The Same Switch Explains the Strangeness and the Forgetting (06:46) The prefrontal cortex is not only the region that would normally question a dream. It is also the part that bookmarks a memory as worth keeping. With it turned down, dreams barely get flagged, so they are hardly stored. "The one night your brain does its most vivid work, it keeps no receipts." Chris Dreaming Looks Like Emotional Sorting (07:37) The leading theory is that dreaming is emotional and memory processing. The brain holds onto the memory of something that upset you while turning down the emotional charge attached to it. A 2024 study published in Scientific Reports found people who dreamed kept their emotionally charged memories, let neutral material fade, and rated the charged memories as less upsetting by morning. Older work from sleep researcher Rosalind Cartwright found people going through a painful breakup who dreamed about it recovered their mood noticeably faster. The hosts are careful with the limits here. This is still open science, and much of it shows a link rather than a nailed down cause. A Nightmare Is the Same Process Running Hot (12:46) The dividing line is simple. A nightmare wakes you. A bad dream is unpleasant and you sleep through it, whereas a nightmare pulls you out of REM with the fear still running. Roughly two thirds of dreams carry sadness, worry or anger, and only about a fifth are clearly happy. "A nightmare isn't your mind failing. It's that same system working on something heavy and getting stuck partway through." Chris Stress is the biggest trigger, and lost sleep does it too, because the brain packs in extra REM to catch up. Frequent nightmares are common after trauma, affecting up to 70% of those living with it. If nightmares become frequent and start wearing you down, it is worth speaking to a GP, as treatments such as imagery rehearsal therapy genuinely work. About So That's Why So That's Why is a weekly podcast where Jen, Chris and Matt unpack the science behind everyday health questions. No jargon, no judgment, just genuine curiosity and proper research. Website:

3. 

   15 Oct 2026

   Why Do We Develop Pre-Diabetes?

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

Reach and audience

Public platform figures. Ratings count people who left a rating, not total listeners.

Apple Podcasts (US)

5.0 / 5

1 ratings

Spotify

5.0 / 5

6 ratings

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Guest appearances

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