40. Health Myths | Things We Got Spectacularly Wrong

In this episode of Mohivate, Dr Mohi Sarawgee explores some of the most confidently repeated health and science myths of the last century. Ideas that were taught in schools, printed on food labels, and handed down through generations as absolute truth, only for the evidence to tell a far more interesting story.

Why did an entire generation grow up being told to eat carrots for better eyesight? Why did low-fat yoghurt end up with more sugar than a dessert? And why did one doctor drink a petri dish to prove a point , and later win a Nobel Prize for it?

From wartime propaganda and the low-fat era that made an entire population less healthy, to the brain myth beloved by every self-help book ever written, and the man who spent sixty years cracking only one hand’s knuckles : this is a lighter episode about curiosity, evidence, and the remarkable ability of science to change its mind when better answers emerge.

Because being wrong is where learning begins.

REFERENCES

1.Ancel Keys, saturated fat, and the dietary guidelines controversy — Newport & Dayrit, Nutrients 2024:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11123895/

2.Barry Marshall, H. pylori, and the Nobel Prize — Nobel Prize official:

https://www.nobelprize.org/prizes/medicine/2005/press-release/

3.Carrots, night vision, and RAF wartime propaganda — World Carrot Museum:

http://www.carrotmuseum.co.uk/ww2seeinthedark.html

4.We only use 10% of our brain — Scientific American debunk:

https://www.scientificamerican.com/article/do-people-only-use-10-percent-of-their-brains/

5.Dr Donald Unger, knuckle cracking, Ig Nobel Prize 2009:

https://pubmed.ncbi.nlm.nih.gov/19922237/

Just a gentle reminder: this episode is for information, education, and inspiration only. It’s not a substitute for your doctor’s advice. For any personal health concerns, always seek guidance from your doctor.

Transcript

SPEAKER_00 0:05

Hi everyone, welcome back to Mohivate. I'm Dr. Mohi Saraugi, a GP by profession, but here I'm swapping prescriptions for perspective. It is absolutely scorching across most of the world right now, and somewhere between melting in the heat and trying to decide what to talk about on today's episode, I thought, you know what, let's just do something fun. Because sometimes it's enough to just sit with something interesting, laugh a little, and feel slightly better about the world. I have truly enjoyed putting together this episode because we are talking about things we got spectacularly wrong. Things that have been confidently repeated for decades by parents, teachers, grandparents, doctors, and at least one Hollywood scriptwriter that turned out to have no basis in reality whatsoever. There are some wonderful stories in here today. Some of it is medically important, some deeply satisfying, and one of them involves a man who dedicated 60 years of his life to proving his mother wrong. I hope by the end of this episode you feel slightly more forgiving of yourself the next time you believe something that turns out to be wrong. Because as it turns out, absolutely everyone does it, including the scientists. So let's begin. Let's start with the one that affected an entire generation's relationship with food, a supermarket aisle, and frankly, toast. In the 1970s and 80s, a scientist named Ansel Keys put forward an influential and later heavily debated idea that dietary fat, particularly saturated fat, the kind found in butter, cheese and meat, was responsible for rising rates of heart disease. Governments listened, guidelines were issued, and the world was told, collectively, to eat less fat. The food industry responded with immense enthusiasm. Low fat labeling became the marketing opportunity of a generation. Supermarket shelves filled with products carrying low-fat banners on the front. And if you stood there reading the label, feeling quietly virtuous about your choices, you were not alone. An entire generation did this. The problem was that when you remove fat from food, it tastes like cardboard. So the food industry replaced it with something else: sugar, refined carbohydrates, artificial thickness. The low-fat yogurt that felt like a responsible choice often had more sugar than a small dessert. And the result? Obesity rates rose, type 2 diabetes increased. The very things the low-fat movement was supposed to prevent got worse over the same decades it was being promoted. But it gets better or worse, depending on how you look at it. At the same time, as everyone was being told to avoid butter, they were being actively encouraged to switch to margarine made from vegetable oils, so clearly labeled healthier, except that many margarines were produced through a process called partial hydrogenation, which created trans fats. These trans fats produced through that hardening process turned out to be significantly more damaging to the heart than the natural saturated fat they were meant to replace. Trans fats are now banned or strictly limited in many countries. So to summarize, we replaced butter with something worse, replaced fat with sugar, made the population less healthy, and it took roughly 40 years to fully acknowledge what had happened. The good news, fat is back. What we now know is that fat quality matters far more than fat quantity. The Mediterranean diet consistently comes out as one of the most heart protective eating patterns in the world. Not low fat, just the right fat. Avocado, olive oil, nuts, fish, whole foods, full fat yogurt eaten without guilt. So if you grew up in the low-fat era and spent decades feeling vaguely anxious about butter, you're now free. The science has moved on. The toast deserves proper butter. And on that note, a small personal confession. Since childhood, we ate toast with butter, a pinch of salt, and black pepper every single day. It was simply how toast was eaten. Years later, I watched Nigella Lawson do exactly this on one of her series, and she said it changed her life. And I thought we've been doing this my entire life. I was genuinely surprised that so many people hadn't. I actually wrote to her on Twitter now X, wondering how she and so many others commenting had only just discovered it. So if you have never tried it, butter, salt, black pepper, toast the toast, you're welcome. As a doctor, I will always say moderation, but I will also say that some of life's most genuinely underrated pleasures are hiding in very ordinary places, and life is too short for cardboard. Now, this next one is interesting because it turns out we were wrong about the cause, but not entirely wrong about the connection. How many times have you heard this said to someone in the middle of a hard week, a hard year, or simply a life that felt like too much? You will give yourself an ulcer, said with absolute confidence across cultures, across generations, from worried relatives, from doctors, from the medical establishment itself, usually to someone with a demanding job, a strained relationship, or the kind of life that felt like it was running at full speed without breaks. For most of the 20th century, stress, spicy food, and too much coffee were understood to be the causes of peptic ulcers. The treatment was antiacids, bland diets, and stress reduction. Rest, calm down, eat less curry. And then in the early 1980s, an Australian physician named Barry Marshall became convinced that ulcers were actually caused by a bacteria, specifically a spiral-shaped organism called Helicobacter pylori, named for its shape, helico meaning spiral, and the region of the stomach, pylorus, where it lives. Helicobacter pylori burrows into the stomach's mucus lining, causes inflammation, and over time creates the conditions for ulcers to develop. He had been studying the organism with his colleague Robin Warren. The evidence to him was overwhelming. Nobody believed him. His research was rejected. His presentations were met with skepticism. The idea that any bacteria could survive in the highly acidic environment of the human stomach was considered by most of the medical community simply implausible. So, Barry Marshall did something that is either the most committed act of scientific self-belief in modern medicine or the most alarming thing a doctor has ever voluntarily done, depending on how you look at it. He drank a petri dish of Helicopactor pylori. He developed gastritis within days. He took a combination of antibiotics and bismuth to clear the infection. He recovered. He had demonstrated in his own body the mechanism he had been trying to prove for years. In 2005, Barry Marshall and Robin Warren were awarded the Nobel Prize in Physiology or Medicine. Now here is where I want to be honest with you because the story is not quite as simple as stress has nothing to do with ulcers. That would be the satisfying version. The accurate version is slightly more nuanced. Stress does not cause ulcers on its own, but it is not entirely innocent either. Here is what we now understand. Chronic stress activates the vagus nerve, the long nerve that connects the brain directly to the gut, part of what we now call the brain gut axis. This vagus nerve activation can stimulate the stomach to produce more acid and making it more reactive over time. There are records of increased bleeding gastric ulcers in cities bombed during the Second World War, and studies confirm that psychological stress can worsen existing ulcers, particularly in someone who already has Helicobacter pylori present. So the honest picture is this Helicobacter pylori is the primary cause of most peptic ulcers. NS, non-steroidal anti-inflammatory medications like neproxin are the second most common cause, which is exactly why we always prescribe an anti acid alongside them. Stress on its own does not cause ulcers, but through the vagus nerve and the brain gut axis, it can make the stomach more vulnerable. Most peptic ulcers are now treated with what we call triple therapy. Two antibiotics combined with a proton pump inhibitor and acid suppressing medication taken for 7 or 14 days. A condition that once meant a lifetime of antiacids, and dietary restriction is in most cases curable. And to every worried relative who has ever told someone they were giving themselves an ulcer, you were trying to be kind. The science has updated the ulcer in almost every case had far more to do with a bacterium than with the stress, though perhaps suggest they manage the stress anyway. The vagus nerve, it turns out, is paying attention. Now my personal favorite because this one is more than just a myth. It is a government-constructed, wartime propaganda myth, which makes it significantly more interesting. We all know carrots are a perfectly good vegetable. They contain beta-carotene, which the body converts into vitamin A. And vitamin A deficiency can cause night blindness, a genuine medical condition called nicilopia, where the eyes struggle to adapt to low light. In parts of the world where vitamin A deficiency remains common, this is still a public health concern, and the incidence has fallen with improved nutrition and supplementation programs. But we have all heard that we must eat carrots because they actively improve eyesight, that extra carrots will give a well-nourished person better vision. And it is a myth, it did not arise organically, it was invented deliberately by a government. During the Second World War, the Royal Air Force developed a remarkable new technology, airborne interception radar, which allowed their pilots to detect enemy aircraft at night with extraordinary precision. A RAF pilot named John Cunningham shot down the first enemy aircraft using this technology in 1940 and went on to record 20 aerial victories, 14 of them at night. The British government needed to explain this unusual success without revealing they had radar. So the Ministry of Food with the RAF, happy to go along, told newspapers that pilots like Cunningham had exceptional night vision because they ate enormous quantities of carrots. The story ran everywhere. Posters appeared, radio broadcasts promoted it. Cunningham was dubbed Cat's Eyes, a nickname that stuck for the rest of his life. The myth was constructed at government level, distributed through respectable channels, and the British public absorbed it as fact. And there was a second reason the campaign suited the Ministry of Food perfectly. Britain had a significant surplus of carrots in 1942 and they needed people to eat more of them. The propaganda served two purposes simultaneously: hide the radar and shift the vegetables. Whether the Germans actually believed it is disputed by historians. Some think the story may have had partial effect since the link between carrots and eyesight was already present in German folk belief. Others note that German intelligence was well aware of British radar technology and would not have been surprised by an airborne version. What is not disputed is that the British public believed it entirely and it spread worldwide. And so the instruction to eat your carrots for better eyesight passed from wartime propaganda into parenting, into school dinners, and has been sitting there unchallenged ever since. Generations of children eating carrots they did not particularly want, told it was good for their eyes because the RAF needed to keep a secret in 1940. To be clear, eat your carrots. They are nutritious, genuinely good for you, and support overall eye health as part of a balanced diet. Your eyesight, assuming you are not vitamin A deficient, will remain entirely unchanged by them. The night vision of a fighter pilot, they will not give you. That was Reda. It always was. The next one is perhaps the most persistent myth in popular neuroscience, and almost everyone has heard it. That we only use 10% of our brain. This has been repeated in motivational speeches, self-help books, films, including Lucy, and almost certainly in at least one TED Talk you have seen. It is usually delivered with a tone suggesting that if you could only unlock the other 90%, the possibilities would be limitless. It is completely false. The brain at any given moment is not 90% inactive. It is doing an enormous number of things simultaneously across all its regions, all the time, even during sleep. The idea that a vast reserve of unused gray matter is sitting there waiting to be unlocked has no basis in neuroscience. Damage to almost any part of the brain produces consequences. If 90% of it were truly dormant, that would not be the case. And the brain consumes approximately 20% of the body's total energy, despite being only 2% of its mass. Evolution does not maintain expensive idle tissue. So where did this come from? Nobody's entirely sure. It is most commonly misattributed to the psychologist William James, who wrote in the early 1900s that most people failed to realize their full mental and physical potential. He was talking about motivation and energy, not anatomy. He never claimed 90% of the brain was physically unused. The number then circulated through the self-help industry of the 1920s, appeared in the 1929 World Almanac as apparent fact and was used by Dale Carnegie in how to win friends and influence people. And it never really left. The self-help industry, it turns out, had every commercial reason to tell people they had vast untapped potential waiting to be unlocked for a fee. And Albert Einstein, a reliable magnet for misattributed quotes, was credited with this one at various points, which helped considerably. The neuroscience is clear. Brain imaging technology, MRI and PET scans, allows us to watch the brain in real time. And what those scans consistently show is that there is no vast unused territory waiting to be unlocked. Even while you sleep, significant portions of your brain remain active, consolidating memory, regulating body functions, processing the day. What is genuinely interesting is why the myth persists so stubbornly. And I think it is because it is a comforting idea. It implies that we are not operating at our ceiling, that there is more to discover about ourselves, that untapped potential is waiting, which in a way is true, just not because of unused brain capacity. It is true because learning, practice, experience, and connection genuinely change how the brain works. Neuroplasticity, the brain's ability to rewire and adapt throughout life, is one of the most beautiful things in neuroscience. Growth is real. The 10% figure is not. The brain you have is fully operational. It has been working at full capacity this entire time. It is, in fact, working right now to process the information that the thing it was told about itself for decades was entirely made up. You know, there are so many of these that kept coming to mind when I was putting this episode together. I had to stop myself. Things like sugar makes children hyperactive, cold weather gives you a cold, don't swim for an hour after eating, hair and nails keep growing after death. The list, it turns out, is very long, and every single one of them has a story behind it: a misread study, a parenting shortcut, or a myth that simply refuse to leave. And finally, for today, a story about perhaps the most universally scolded habit in human history. One of the great social crimes of the living room, the office, the classroom, and the quiet waiting room. The sound of knuckles being cracked. For most people, it is one of the most viscerally irritating things another human being can do in a shared space. Etiquette guides have weighed in on this for decades. Emily Post, the American Authority on Manners, whose name became synonymous with social correctness, considered knuckle cracking a form of rudeness, a habit to be suppressed in company. The general consensus of the etiquette world is clear. Do it alone, never in public, and certainly not in a meeting. Growing up, for me and my sister, it was a non-bailable offense. My mother informed us with complete confidence that cracking our knuckles would make our fingers crooked like a witch's. This was not open to debate. And for most of the 20th century, people had a very satisfying medical reason to back up their. Irritation. How many of you have heard this said with absolute confidence? Cracking your knuckles causes arthritis. Do it enough, and you will pay for it later with swollen, painful joints. It is not true. The sound that deeply satisfying or deeply offensive pop, depending on which side of the knuckle you are on, is caused by the collapse of gas bubbles in the fluid surrounding the joint. Your joints are surrounded by synovial fluid, a thick, lubricating substance. When you stretch the joint past its usual range, pressure drops rapidly inside and dissolved gases escape as a small bubble. That is the pop. No bones grinding, no cartilage tearing, just gas. The bubble then disperses, and in about 20 minutes, the conditions are right to do it again. And we know this partly because of one man's extraordinary commitment to proving a point. Dr. Donald Unger, a physician who, as a child, was repeatedly told by his mother that cracking his knuckles would give him arthritis. So he decided to find out. For 60 years, he cracked the knuckles on his left hand at least twice a day, every single day, while leaving his right hand as a control, never cracking it once. That is at least 36,500 individual cracks on the left hand. And for 50 years, whenever anyone tried to tell him to stop, he simply said the results weren't in yet. And then he compared both hands. No arthritis. No difference whatsoever between the two. He published his findings in 1998 in the journal Arthritis and Rheumatism. He received an IG Nobel Prize in 2009. Now the IG Nobel Prize is not the Swedish one. IG Nobel Prize is awarded annually at Harvard by a science humor organization called Improbable Research for research that first makes you laugh, then makes you think. It celebrates science that is both rigorous and delightfully human and in its own way just as hard to earn. Dr. Anger collected his prize in person, travelling all the way from California to Harvard to do so. For a man who had spent 60 years being told he was wrong, I imagine the journey felt entirely worth it. His mother was alive to hear the result. I absolutely love this story. So the arthritis claim is false. Thoroughly, repeatedly, 60 years worth of evidence, false. But the etiquette objection remains entirely valid. The science may have spoken. The dinner table remains unmoved. You're not damaging your joints. You are damaging the atmosphere. And I can almost guarantee that somewhere right now a child is still being told their fingers will go crooked or they will get arthritis because some warnings are simply too useful to retire. Regardless of the evidence, you are vindicated. You are also still asked to stop. So here we are. I truly hope you enjoyed these stories on a hot day in a lighter episode. And what I love about them is not the wrongness in them, it is what the wrongness reveals. Science changes and it changes because it is honest. It looks at new evidence and adjusts. The willingness to say we got that wrong is the whole point. It is what makes it science rather than dogma. And I think there's something quietly reassuring in that for all of us, not just scientists. Most of us are carrying something we believed about health, about food, about ourselves, about other people. That time and experience have since updated. Something we held on to long after the evidence suggested a different direction. Something we defended, perhaps because admitting we were wrong felt like too much. The willingness to revise what we think we know is one of the most honest things a person can do. It is how we move forward. Being wrong is not the end of anything. It is usually where the more interesting part begins. I hope something today stirred a thought, gave you a smile, or simply made you pause. Whatever time it is where you are, I hope you carry a little feel good factor with you. Thank you for listening. I'm Dr. Mohi. Until next time, remember this changing your mind takes courage, and sometimes it is the clearest sign that you're still learning, still growing, and still finding your way back home to yourself.