Brain and body

111 cards about Brain and body, with explanations, methods and source links.

Cards about Brain and body

• Why does a chili pepper feel hot when it never warms your mouth?

  Eat a chili and the temperature in your mouth barely moves, because there is no source of heat anywhere in it. The sensation is still close to a burn. So what exactly is being switched on?

  Source: Caterina et al., Nature

• What does the brain do at night that it cannot get done by day?

  Every tissue in the body has a lymphatic system to carry waste away, and the brain has none, although it burns about a fifth of the body’s energy. To see how it clears anyway, researchers injected a glowing tracer into the spinal fluid of mice and filmed the living brain awake and asleep. What changed between the two?

  Source: Xie et al., Science

• Who decides which of today’s memories you still have tomorrow?

  Through the day the hippocampus takes in new experience fast, and it is not built to hold any of it for long. Something has to move what is worth keeping somewhere else. When does that happen?

  Source: Rasch and Born, Physiological Reviews

• Does a placebo still work if you are told up front that it is one?

  The standard explanation was that a placebo works because the patient believes they got a drug, which ruled it out as an actual treatment. To test that, a trial handed people pills while telling them plainly the capsules held nothing active, and compared them against a group given no treatment. What did the participants report?

  Source: Kaptchuk et al., PLoS ONE

• What did researchers find in blood samples from perfectly healthy people?

  Microplastic is plastic debris under five millimeters across, and it already turns up in water, in air and in food. The open question was whether the particles stop at the gut and the lungs or carry on. So someone went looking in blood. What came back?

  Source: Leslie et al., Environment International

• How do bacteria in a mouse’s gut change the way it behaves?

  Trillions of bacteria live in the gut and make molecules that reach the bloodstream and the vagus nerve. To test whether any of that touches the brain, researchers raised mice in complete sterility, with no bacteria anywhere in the body. What happened to them?

  Source: Sudo et al., The Journal of Physiology

• What happens to a mouse raised with no gut bacteria at all?

  Trillions of bacteria live in the gut, and they make small molecules that reach the bloodstream and the vagus nerve. To find out whether any of that touches the brain, researchers raised mice in complete sterility, with no bacteria anywhere in the body. What did those mice turn out like?

  Source: Diaz Heijtz et al., PNAS

• What happens to a brain after it memorises 25,000 streets?

  To get a taxi licence in London a driver spends three or four years memorizing a network of twenty-five thousand streets and thousands of landmarks. The test is called the Knowledge, and only about half the candidates pass. What does all that do to a brain?

  Source: Maguire et al., PNAS

• How many bacteria are there really in your body per human cell?

  For decades the claim repeated that the human body holds ten times more bacteria than human cells, and it appeared in textbooks and in lectures. Three researchers went looking for where the number itself came from, and recalculated. What is the real ratio?

  Source: Sender, Fuchs & Milo, PLOS Biology

• Why does somebody else’s yawn catch you in particular?

  A contagious yawn is one of the harder things to resist, and it feels like a simple reflex with nothing behind it. To see what is going on inside, researchers scanned the brains of people watching others yawn, and also tracked who catches it from whom. What sets it off?

  Source: Norscia & Palagi, PLoS ONE

• Are some people really "right-brained" and others "left-brained"?

  The idea that creative people use the right side of the brain more and analytical people the left is among the most durable neuromyths in popular psychology. To test it, researchers at the University of Utah analyzed resting brain scans, split the brain into thousands of regions, and checked which of them lean to one side. What did they find?

  Source: Nielsen et al., PLoS ONE

• What else does the tiny muscle that gives you goosebumps do?

  Goosebumps form when a small muscle at the base of each hair contracts and stands it up. In furred mammals that puffs the coat out and insulates against cold, and in us it has counted as a useless leftover. So why is that muscle still there?

  Source: Shwartz et al., Cell

• What is the appendix actually for?

  The appendix was presented for years as the textbook case of a vestigial organ, one that lost its job. Except that it is unusually rich in immune tissue, which does not suit an organ with nothing to do. So what is it doing?

  Source: Bollinger et al., Journal of Theoretical Biology

• How independent of your brain is your gut?

  Plexuses of nerve and sensory cells are set along the wall of the digestive tract, detecting stretch and chemical composition and driving muscles. They are wired to the brain through nerves and hormones, and how much they depend on it is another question. How independent is the gut really?

  Source: Furness, Nature Reviews Gastroenterology & Hepatology

• Which cell in your body gives up its own nucleus?

  The nucleus is a cell’s control center, and without it there is no repairing, no manufacturing and no dividing. A red blood cell starts out with a nucleus and, in the last stages of maturing, pushes it out and sheds the rest of its organelles too. Why would anything do that?

  Source: Ji, Murata-Hori & Lodish, Trends in Cell Biology

• How do immune cells trained in the gut end up protecting the brain?

  The immune system does not behave the same way everywhere in the body. In the gut it meets food and bacteria without pause, so cells maturing there are schooled into an unusually restrained response. Then cells like those were found next to the nervous system. What are they doing there?

  Source: Rojas et al., Cell

• What happened to the memory of mice when their gut bacteria were swapped?

  Is the aging of the gut tied to what happens in the brain? To test a direction of cause rather than a correlation, researchers transferred gut bacteria from old mice into young ones, and then put the young mice through memory tests. How did they do?

  Source: D’Amato et al., Microbiome

• What do you learn from measuring the same fingernail for 35 years?

  The physician William Bean marked and measured the same fingernail over and over for thirty-five years. It is a sample of one person, and there is almost no other record this continuous on a living human being. What did it show?

  Source: Bean, Archives of Internal Medicine

• You were told cracking your knuckles causes arthritis. What did they find?

  The sound comes from pulling the joint and changing the pressure in the fluid inside it fast. For years the habit was said to wear the hand out and lead to arthritis, and everyone has heard the warning. What turned up when it was tested?

  Source: Rizvi et al., Clinical Anatomy

• A jumping spider sleeps and its legs curl. Is it dreaming?

  Young jumping spiders have transparent bodies, so the retinas moving inside their eyes can be filmed at night. It is a rare chance to see what happens during rest. What showed up?

  Source: Rößler et al., PNAS

• What is the difference between jet lag and tiredness from a long flight?

  A ten-hour flight due north can be thoroughly exhausting and still produce no jet lag at all. So the tiredness and the jet lag are not the same thing, and perhaps not the same treatment either. What exactly is the difference?

  Source: Sack et al., Sleep

• Does a day of falls on the stock market show up in hospital records?

  A fall on the market is a number on a screen, and the distance between it and the body looks large. Daily data on share returns were joined to admission records from every hospital in California across decades. What did the authors find?

  Source: Engelberg & Parsons, The Journal of Finance

• Does an ice bath right after strength training help a muscle grow?

  Cold water after training feels like a fast route to recovery, and comfortable recovery and muscle growth are not the same goal. A review pooling eight studies compared strength training with cold water immersion straight afterwards against the same training without it. What did the comparison show?

  Source: Piñero et al., European Journal of Sport Science

• Why is exhaustion from a long flight not always jet lag?

  After a long flight you can be worn out from missing sleep, dry air and sitting still, and that happens on a flight within the same time zone too. Jet lag is something else entirely, so the remedy is different as well. What is the difference, and what helps each one?

  Source: Roach & Sargent, Frontiers in Physiology

• Can a board game really teach somebody a health habit?

  A board game sounds like entertainment rather than a tool for medical teaching. It does force a person to decide, get it wrong and try again, which a leaflet never does. A review pooled 21 controlled trials with 6,554 participants between them. What came out of the pile?

  Source: Gauthier et al., Games for Health Journal

• We keep finding microplastics everywhere. Does anyone know what they do to a body?

  Microplastic is not one substance. The particles differ in size, in shape and in which polymer they are, pollutants from the environment stick to their surfaces, and the plastic carries additives put in at the factory. They have turned up in food, in water, in air and in people. So what is known about what they do in there?

  Source: Campanale et al., IJERPH

• Why does the part of the brain that steadies movement also help you read intentions?

  The cerebellum, the folded structure at the back of the brain, is the motor and balance department in every textbook. Scans keep finding it active while people work out what somebody else intends or believes. Experts in the field pooled what is known. What do those two jobs have in common?

  Source: Van Overwalle et al., The Cerebellum

• The food hit the floor and you grabbed it. Do five seconds really save it?

  The five-second rule assumes a window during which food is still clean, because bacteria supposedly need time to cross. To test it, researchers contaminated stainless steel, ceramic tile, wood and carpet, then dropped watermelon, bread, buttered bread and gummy candy onto them for four different contact times. What transferred, and when?

  Source: Miranda and Schaffner, Applied and Environmental Microbiology

• A woodpecker strikes a tree thousands of times a day. Is its head really immune?

  A woodpecker meets forces of 1,200 to 1,400 g while pecking, and the assumption that evolution made it immune to brain injury is strong enough that its anatomy gets copied into football helmets. Nobody had checked the brain itself. Researchers stained preserved woodpecker brains and compared them with birds that do not peck. What showed up?

  Source: Farah, Siwek and Cummings, PLOS ONE

• Why is flying east harder on the body than flying west?

  Most internal clocks run a little longer than 24 hours. Flying west means staying up later, which stretches the day, and flying east means cutting it short. Researchers modeled the clock cells of the brain as thousands of coupled oscillators and moved the light cycle abruptly to simulate a flight. Which direction does the body forgive?

  Source: Lu et al., Chaos

• Why do bacteria hold on better to a paper note than a plastic one?

  Money passes from hand to hand dozens of times a day, which is why it has a reputation. Coins and banknotes keep showing up in the literature as carriers of microorganisms, and almost none of that work asks how well bacteria actually stick and persist. A paper note, a polymer note and a coin are three different materials. What does that change?

  Source: Vriesekoop et al., Microorganisms

• What does one sleepless night do to the brain?

  Sleeping badly over years goes with higher beta-amyloid, the protein that accumulates in Alzheimer’s disease. Acute deprivation had been shown to raise amyloid in mouse interstitial fluid and in human cerebrospinal fluid, and nobody had looked in the living human brain. One night was the test.

  Source: Shokri-Kojori et al., PNAS

• Does knee surgery for arthritis beat a fake operation?

  Many patients report relief after arthroscopy of the knee for osteoarthritis, and it was unclear how the procedure achieved that. The way to find out is to compare it against a convincing imitation of itself. So 180 patients were randomized, and some of them got skin incisions and nothing else.

  Source: Moseley et al., New England Journal of Medicine

• What are wrinkled fingertips for?

  Keep your hands in water and the skin of your fingertips wrinkles. The effect is striking and we know little about why it happens. One proposal is that the wrinkles channel water away from the contact surface, so a wet object can be grasped more readily, which is a claim about force rather than about appearance.

  Source: Davis, PLOS ONE

• Why does mint feel cold in your mouth?

  A subset of sensory neurons is thought to sense changes in thermal energy directly, through their endings in the skin, and very little was known about which molecules let them do it. One relative in the family was already known to answer noxious heat. The cold end was open.

  Source: Peier et al., Cell

• Can a mirror help a paralysed arm move again?

  In mirror therapy a mirror sits in the person’s midsagittal plane, so that movements of the unaffected side are reflected as if they belonged to the affected one. It is used after stroke to improve motor function, and the treatment is a visual trick rather than an exercise. Does it work?

  Source: Thieme et al., Cochrane Database of Systematic Reviews

• Does a calorie label on nuts tell you what you absorb?

  Food labels compute energy with the Atwater factors, a system that assigns fixed values per gram of protein, fat and carbohydrate. Earlier work showed that for some nuts the energy actually available to the body is less than those factors predict. Nobody had measured walnuts.

  Source: Baer, Gebauer and Novotny, The Journal of Nutrition

• Do the fungi in a gut do anything?

  The gut microbiome is a multi-kingdom community, and almost everything known about its effect on development concerns the bacteria. Fungi are there too, in far smaller numbers, and whether they contribute anything of their own was open. Telling the two apart needs an animal with neither.

  Source: van Tilburg Bernardes et al., Nature Communications

• Can a dog smell that you are stressed?

  Owners report that their dog notices a bad day, and earlier work suggests dogs pick up on human stress. Posture, voice and face all leak the same information, so a dog watching a person has plenty to go on. Smell alone, with the person absent, is a harder test.

  Source: Wilson et al., PLOS ONE

• What happens when a drug really does clear the plaques?

  Amyloid plaque has been the main suspect in Alzheimer disease for decades, and efficacious treatments remain few. Antibodies can now strip that plaque out of a living brain, which turns a theory into a test. Whether removing it changes how a person declines is the part the theory never promised.

  Source: Sims et al., JAMA

• Does the order you eat a meal in change your blood sugar?

  In type 2 diabetes, data suggest that nutrient order during a meal significantly affects glucose and insulin afterwards. Prediabetes is where that would be most useful, since nothing has been lost yet. Nobody had reported its effects there.

  Source: Shukla et al., Diabetes, Obesity and Metabolism

• Which receptors does a runner’s high actually need?

  A runner’s high is a subjective sense of well-being some humans experience after prolonged exercise. For decades the hypothesis was that exercise-induced endorphin release is solely responsible for it. Recent evidence suggested endocannabinoids may also play a role, which is a claim a mouse can settle and a person cannot.

  Source: Fuss et al., PNAS

• Does being cold burn more than being active?

  Brown adipose tissue is a thermogenic organ involved in energy expenditure, which makes it an attractive target against obesity and type 2 diabetes. Cold exposure and exercise training are the two stimuli most studied for switching it on. They are interesting together because their effects on it both converge and diverge.

  Source: Peres Valgas da Silva et al., Biology

• Where did the tool for rewriting genes come from?

  Modifying a gene in a cell used to be slow, difficult and sometimes impossible, which put a ceiling on what anyone could learn about how life works. The method that broke the ceiling took the Nobel Prize in Chemistry in two thousand and twenty, and it was not designed. It was found, in the middle of a project about a dangerous bacterium. What was it doing there?

  Source: Nobel Prize in Chemistry 2020

• Can something with no genes of its own pass on a disease?

  Every infectious agent anyone knew about carried hereditary material, DNA or RNA: bacteria, viruses, fungi, parasites. So when work on scrapie in sheep and on two human brain diseases suggested an agent with no nucleic acid at all, the idea was sensational and largely unwelcome. Stanley Prusiner spent a decade chasing it. What did he end up holding?

  Source: Nobel Prize

• How large is the health effect of having people around you?

  A nineteen eighty-eight review of five prospective studies concluded that social relationships predict mortality, and put the effect alongside smoking and blood pressure. That was a strong claim from a small base. Two decades later there was a literature to test it against. Holt-Lunstad, Smith and Layton pooled it. Does the number survive the scale-up?

  Source: Holt-Lunstad et al., PLOS Medicine

• What keeps time in a body that has no clock in it?

  Nearly every tissue and organ in a human being runs on a twenty-four hour cycle, and those cycles stay in step with each other and with the day outside. Light and dark matter most, though food, stress, activity and temperature all push on them. Something has to coordinate the whole set. The surprise is what that coordinator is made of.

  Source: National Institute of General Medical Sciences

• If bone is replaced continuously, why does the skeleton keep its shape?

  Bone gets replaced throughout life. Old and damaged bone is removed and new bone laid down, and yet nothing about a femur changes shape in the process. Bolamperti, Villa and Rubinacci review how that trick works, and the accepted answer has shifted: what was once a tidy two-stage production line now looks like something else. What changed?

  Source: Bolamperti et al., Bone Research

• How do you test a pig organ in a human body before any patient can consent?

  The organ shortage is severe enough that the domestic pig is being taken seriously as a source. Animal models had established safety and feasibility, but an animal is not a person, and no clinical trial can start on the strength of one. Porrett and colleagues needed a human test with no patient at risk. What did they do?

  Source: Porrett et al., American Journal of Transplantation

• What is the immune system doing while you are asleep?

  Popular wisdom says sleep helps you fight off illness, and over the last few decades neuroimmunology has accumulated surprisingly strong evidence for it. Separating sleep from the circadian rhythm it rides on is difficult, which makes the specific question hard. Besedovsky, Lange and Born review what the immune system actually does across a night. Is it resting too?

  Source: Besedovsky et al., Pflugers Archiv

• What would an onion taste like if it could not make you cry?

  Cut any Allium and an enzyme cleaves its sulfur compounds into reactive pieces. In garlic those pieces condense into allicin and its relatives. In onion they take a detour: one more enzyme converts the key intermediate into the irritant that stings your eyes. Eady and colleagues silenced that enzyme. The interesting part is not the tears. It is what appeared instead.

  Source: Eady et al., Plant Physiology

• Why does no two people share a fingerprint, not even identical twins?

  Fingerprint patterns fall into a few classes, arches, loops and whorls, and the pattern on each of your fingers differs from the pattern on the others. Pattern formation is largely genetic, yet identical twins have different fingerprints, and so do siblings. Something between the genes and the finished ridge is adding variation. What is it?

  Source: ANSI National Accreditation Board

• Is there anything a beard is good for in a fight?

  Facial hair is one of the most sexually dimorphic features humans have, and it is widely read as a signal of masculinity and dominance. One proposal goes further: that a beard works like a lion’s mane, shielding the throat and jaw. The jaw is among the most commonly fractured facial bones in interpersonal violence. Beseris, Naleway and Carrier built a test rig.

  Source: Beseris et al., Integrative Organismal Biology

• How do you treat a disease by switching a different gene back on?

  Sickle cell disease and transfusion-dependent beta-thalassemia both come from mutations in one gene, the hemoglobin beta subunit. Repairing that gene in a patient is hard. But a fetus makes a different hemoglobin, and a transcription factor called BCL11A is what shuts that production down after birth. Frangoul and colleagues went after the switch instead of the gene.

  Source: Frangoul et al., New England Journal of Medicine

• Why does a failing heart hurt in the arm?

  Pain from myocardial ischemia turns up in the chest and the left upper arm, and the reason is old textbook physiology. Cardiac and somatic nerve inputs converge in the thoracic spinal cord, so the brain cannot tell which source a signal came from. Cui and colleagues asked a question that runs the other way. Does the arm send anything back?

  Source: Cui et al., Neuroscience Bulletin

• Does a blade of volcanic glass leave a better scar than surgical steel?

  Obsidian can be flaked to an edge far finer than ground steel, and a run of clinical articles claimed wound healing and scar superiority from obsidian scalpels. All of it was anecdotal. Disa and colleagues put the two blades side by side in the same animal, so each wound had its own control, and then followed the wounds for six weeks.

  Source: Disa et al., Plastic and Reconstructive Surgery

• Does treating hearing loss slow cognitive decline?

  Hearing loss travels with faster cognitive decline and with incident dementia in older adults, which raises an obvious question nobody could answer from observation alone. Lin and colleagues ran the trial: nine hundred and seventy-seven people aged seventy to eighty-four with untreated hearing loss, randomly assigned to hearing aids or to health education, followed for three years.

  Source: Lin et al., The Lancet

• Why is a harmful blood mutation common exactly where malaria is worst?

  Sickle hemoglobin is damaging in a double dose, and more than fifty years ago researchers noticed its prevalence rises in the most malarious parts of the world, sub-Saharan Africa above all. Carrying one copy protects against severe disease and death from falciparum malaria. What stayed unclear was whether it also keeps the parasite out in the first place.

  Source: Billo et al., American Journal of Epidemiology

• Which organ grows back to exactly the size the body needs?

  Lungs, kidneys and the pancreas all adjust after tissue is lost, and none of them returns to what it was. One solid organ does. Cut part of it away and regenerative mechanisms bring it back to the ratio the body requires, every time, which raises the question of what is keeping score. Michalopoulos and Bhushan review what is known about it.

  Source: Michalopoulos and Bhushan, Nature Reviews Gastroenterology and Hepatology

• Why is there a hole in your vision that you never notice?

  Each eye has a small patch of its visual field where nothing registers at all, to the right of center in the right eye and to the left in the left. It is not damage and it is not rare: everyone has it, it has a known location, and you can draw it on a diagram. What is strange is how hard it is to catch yourself having it.

  Source: Britannica

• How fast do adults actually read?

  Figures for reading speed get quoted freely, in scientific writing as much as in advice about study and productivity, and the numbers tend to be generous. Brysbaert went back to the measurements: a hundred and ninety studies of silent reading, covering eighteen thousand five hundred and seventy-three participants. What does the pooled estimate say?

  Source: Brysbaert, Journal of Memory and Language

• Could a cancer therapy switch off an autoimmune disease for good?

  Severe lupus, inflammatory myositis and systemic sclerosis are all managed the same way: suppress the immune system and keep suppressing it. The alternative idea is to strip out the B cells deeply enough that the autoimmunity has to start over. CD19 CAR T cells do exactly that in blood cancers. So 15 patients with these three diseases received a single infusion. What happened to their medication?

  Source: Müller et al., New England Journal of Medicine

• Can lab-grown islets free somebody with type 1 diabetes from insulin?

  Type 1 diabetes destroys the insulin-producing islets, and donor islet transplants are limited by supply and by the immune suppression they require. Growing islets from a patient’s own reprogrammed cells would answer both. A first-in-human phase I trial transplanted such islets beneath the abdominal anterior rectus sheath, an unusual site chosen for access. This is the one-year result from the first patient. What did the glucose data show?

  Source: Wang et al., Cell

• Can a daily pill match what a cholesterol injection does?

  PCSK9 inhibitors cut LDL cholesterol hard, and they have all been antibodies given by injection, which limits who ends up taking one. Enlicitide is an oral version, and a phase 2 trial had already shown it lowers LDL. A phase 3 trial then randomized 2,909 adults at or after cardiovascular risk two to one against placebo for 52 weeks. How far does a tablet get you?

  Source: Navar et al., New England Journal of Medicine

• Does processing itself make you eat more, or is it the sugar and fat?

  Ultra-processed food tracks with obesity in survey after survey, and surveys cannot separate the processing from everything that travels with it. The way to isolate it is to match the two diets on everything else and let people eat freely. So 20 adults moved into a research ward and ate each diet for two weeks, with meals matched for calories offered, energy density, macronutrients, sugar, sodium and fiber. Did intake differ?

  Source: Hall et al., Cell Metabolism

• Can swapping the salt in the kitchen prevent a stroke?

  Salt substitutes cut the sodium and add potassium, and they reliably lower blood pressure. Blood pressure is not an outcome anybody suffers, so the question is whether the swap prevents events, and whether the added potassium hurts anyone. So 600 villages in rural China were randomized, covering 20,995 people who had either had a stroke or were over 60 with high blood pressure. Nearly five years later, what happened?

  Source: Neal et al., New England Journal of Medicine

• Does it matter when you eat, if the calories are the same either way?

  Time-restricted eating has been sold as a way to lose weight without counting anything, on the idea that the window itself does metabolic work. Most of the supporting trials were short and did not control intake. So 139 patients with obesity were randomized for twelve months to an eight-hour eating window plus calorie restriction, or to the same calorie restriction with no window at all. Did the clock add anything?

  Source: Liu et al., New England Journal of Medicine

• Fiber or fermented food: which one actually changes your immune system?

  Diet shapes the gut microbiome, and the microbiome shapes immune function. That chain is widely accepted and rarely tested head to head in people. So healthy adults were randomized for 17 weeks to a high-fiber diet or a high-fermented-food diet, 18 per arm, with deep immune and microbiome profiling throughout. The prespecified primary outcome was a cytokine response score. Which diet moved what?

  Source: Wastyk et al., Cell

• Why does the same slice of bread spike one person and not another?

  High blood glucose after meals drives prediabetes and type 2 diabetes, and dietary advice for controlling it works poorly. One possible reason is that the advice is universal and the physiology is not. So researchers fitted continuous monitors to 800 people for a week and recorded their responses to 46,898 meals. If identical meals produce different responses, the whole premise of general guidance is in trouble. Do they?

  Source: Zeevi et al., Cell

• What is left of the Mediterranean diet trial after its own authors withdrew it?

  PREDIMED was the trial that moved the Mediterranean diet from observational association to evidence, assigning 7,447 Spanish adults at high cardiovascular risk to one of three diets. Then the authors found protocol deviations: household members enrolled without randomization, participants assigned without randomization at one site, and inconsistent randomization tables at another. They withdrew the 2013 paper. This is the reanalysis. What survived?

  Source: Estruch et al., New England Journal of Medicine

• Can two injections a year prevent HIV better than a daily pill?

  Preexposure prophylaxis works when it is taken, and among cisgender women the gaps in uptake, adherence and persistence are wide enough to undo it. An injection every 26 weeks removes the daily decision entirely. So a phase 3 trial in South Africa and Uganda randomized 5,338 adolescent girls and young women to subcutaneous lenacapavir or one of two daily oral regimens. How many infections?

  Source: Bekker et al., New England Journal of Medicine

• Can a vaccine built from your own tumor stop a melanoma coming back?

  Checkpoint inhibitors are standard after surgery for high-risk melanoma, and many patients recur anyway. An individualized neoantigen therapy takes the mutations in one person’s resected tumor and builds an mRNA treatment aimed at them. So 157 patients with completely resected stage IIIB to IV melanoma were randomized two to one to that treatment plus pembrolizumab, or pembrolizumab alone. Did recurrence-free survival move?

  Source: Weber et al., The Lancet

• Does an avocado a day do anything to the fat around your organs?

  Short, well-controlled trials had suggested regular avocado favorably affects body weight, visceral fat and satiety. Short and well-controlled is also the setting where a food effect most easily appears. So the HAT Trial gave 1,008 free-living people with elevated waist circumference one large avocado a day for six months, against their habitual diet, and measured visceral fat by magnetic resonance imaging. What changed?

  Source: Lichtenstein et al., Journal of the American Heart Association

• Does a weight-loss drug prevent heart attacks in people without diabetes?

  Semaglutide already reduces cardiovascular events in people with diabetes, where the glucose lowering gives an obvious route to the benefit. Take diabetes out and the question reopens. So an event-driven superiority trial enrolled 17,604 patients aged 45 or over who had existing cardiovascular disease and a body-mass index of 27 or more, with no history of diabetes, and randomized them against placebo. What happened to the events?

  Source: Lincoff et al., New England Journal of Medicine

• Cut the salt or change the whole diet: which lowers blood pressure more?

  Two dietary strategies for blood pressure had each been tested alone. Reducing sodium is one, and the DASH pattern, rich in vegetables, fruit and low-fat dairy, is the other. Nobody had crossed them. So 412 participants were randomized to the DASH diet or a control diet typical of American intake, and then ate high, intermediate and low sodium within that diet for 30 days each, in random order.

  Source: Sacks et al., New England Journal of Medicine

• Can a starch supplement clear fat out of a liver?

  Non-alcoholic fatty liver disease is the liver’s version of metabolic dysfunction, and effective treatments are missing. Resistant starch passes undigested to the colon and feeds the microbiome, which makes it a candidate for a microbiota-directed intervention. So a four-month randomized placebo-controlled trial gave it to people with the condition, with metagenomics and metabolomics alongside. Did the liver fat move, and if so, how?

  Source: Ni et al., Cell Metabolism

• Could a brain implant learn when to treat a depression and when to leave it alone?

  Deep brain stimulation for depression has promise and a poor trial record, and one suspected reason is that it runs continuously whether symptoms are present or not. Firing only when they rise would need a neural signal that marks the rise, and that signal differs between people. So one team went looking for it inside a single patient before implanting anything. What did the closed loop do?

  Source: Scangos et al., Nature Medicine

• Can two pieces of fruit a day do what a fiber supplement does?

  Green kiwifruit is known to relieve constipation, and the evidence for the comfort side of it was thinner. An international crossover trial enrolled three groups: 63 healthy controls, 60 patients with functional constipation and 61 with constipation-predominant irritable bowel syndrome. Each person took two green kiwifruit daily for four weeks and psyllium for four weeks, in random order, with a washout between. What did the bowels do?

  Source: Gearry et al., American Journal of Gastroenterology

• If a placebo relieves pain, what is actually doing the relieving?

  A placebo that reduces pain has to be reducing it through something, and in 1978 the candidate was the body’s own endorphins. There is a way to test that: block the opioid receptors and see whether the placebo effect survives. So patients having impacted wisdom teeth removed received naloxone or a placebo under randomized, double-blind conditions, and rated their pain. What did the blocker reveal?

  Source: Levine et al., The Lancet

• How fast does a child’s body clock shift without electric light?

  Adults shifted onto a natural light-dark cycle move their body clock earlier, and whether children do the same was unclear. Children also differ in one respect that matters: their sleep habits are partly imposed. So two groups of healthy ten-year-olds spent about two weeks camping with little artificial lighting, one waking before sunrise and one waking with it, and had their melatonin timing sampled before and after.

  Source: Eto et al., Journal of Physiological Anthropology

• How often do you need to get up from a desk for it to matter?

  Breaking up long periods of sitting improves cardiometabolic markers, and the advice stops there because nobody had pinned down how often. A meta-analysis went looking for trials that compared two or more break frequencies against uninterrupted sitting in the same people. Thirteen randomized crossover studies with 211 participants qualified. The split was breaks at least every half hour against less often. Which markers cared?

  Source: Yin et al., Scandinavian Journal of Medicine and Science in Sports

• Why can humans keep up far more friendships than other primates?

  Other primates maintain their bonds by grooming, which takes physical contact and therefore time. Human social networks are much larger than grooming could sustain, so something cheaper must be doing the work. One proposal is that laughter triggers the same opioid release that grooming does. That had no direct neurophysiological support. So 12 healthy men were scanned after laughing with close friends. What was released?

  Source: Manninen et al., Journal of Neuroscience

• Does your morning coffee count against your fluid intake?

  The advice to offset coffee with extra water rests on caffeine being a diuretic, which it is at sufficient dose. Whether that produces actual dehydration in someone who drinks coffee every day is a different question, and it is answerable. So 50 male habitual coffee drinkers completed two three-day trials, one on coffee and one on water, with food, fluid and activity controlled and total body water measured directly.

  Source: Killer et al., PLOS ONE

• Is being lonely as dangerous as the risk factors doctors already watch?

  Both actual isolation and the feeling of being isolated have been linked to dying earlier, and they are not the same thing. One is a count of contacts and the other is a subjective state, so they might carry very different weights. A meta-analytic review gathered studies from 1980 to 2014 with quantitative mortality data on loneliness, social isolation or living alone. How large, and which one is worse?

  Source: Holt-Lunstad et al., Perspectives on Psychological Science

• Can reading a list out loud before surgery keep people alive?

  Surgeons worldwide carry out an estimated 234 million operations a year, and surgical complications are both common and often preventable. The proposal was unglamorous: a nineteen-item checklist read aloud to improve team communication and consistency. Eight hospitals in eight cities, from Toronto to Ifakara, collected outcomes on consecutive patients before it was introduced and then after. What changed in the numbers?

  Source: Haynes et al., New England Journal of Medicine

• Do Sherpas carry more oxygen, or just use it better?

  Low tissue oxygen is a feature of heart failure, lung disease, anemia and many cancers, and it also happens to healthy people high on a mountain. Himalayan populations have lived with it for generations, and the usual assumption is that they adapted by delivering more oxygen to the tissues. One study looked at the other end of the chain instead, at what the tissues do with it. Which adaptation did they find?

  Source: Horscroft et al., PNAS

• What was living in the stomachs of patients with ulcers?

  Stomach acid was assumed to sterilize the stomach, so bacteria living there was close to unthinkable. Ulcers were therefore explained by acid and stress. Two Australian doctors took biopsies from intact antral mucosa in 100 consecutive patients coming for gastroscopy and looked at what was on the slides. The paper that came out of it runs to a few hundred words. What did they see?

  Source: Marshall and Warren, The Lancet

• How much time outdoors does it take before anything shows up?

  That time in natural environments benefits health and well-being is well established, and the dose behind it is not. Physical activity has weekly guidelines; nature contact has none, because the exposure-response relationship has barely been studied. So a nationally representative English survey of 19,806 people, asked about their recreational nature contact in the previous seven days, was analyzed in hour-long blocks. Where does the line fall?

  Source: White et al., Scientific Reports

• Who, if anyone, does vitamin C actually protect from a cold?

  Whether vitamin C prevents or treats the common cold has been argued over for seventy years, which is itself a clue that the effect is not large. A Cochrane review pooled the placebo-controlled trials, excluding any using less than 0.2 grams a day. The interesting move was splitting the population: ordinary community trials on one side, and people under heavy physical stress on the other. Does the split matter?

  Source: Hemilä and Chalker, Cochrane Database of Systematic Reviews

• Could a mammal in respiratory failure take in oxygen through its gut?

  Loaches and some other aquatic animals breathe through their intestines when the water runs short of oxygen. Whether a mammalian gut could be pressed into the same service has been genuinely controversial. So one group tested two versions in animal models of respiratory failure: oxygen gas delivered into the rectum, and an oxygenated perfluorocarbon liquid. Mice and pigs first, then safety work in rats. Did any oxygen reach the circulation?

  Source: Okabe et al., Med

• Can eating ice cream during chemotherapy spare a patient’s mouth?

  High-dose melphalan before a stem cell transplant frequently leaves the mouth raw, and oral mucositis does more to wreck a patient’s quality of life than almost any other side effect. Cooling the mouth during the infusion is an established preventive strategy, usually with ice chips. One team looked back at records to ask whether commercial ice cream would do the same job. What did the charts show?

  Source: Jasiński et al., Scientific Reports

• What decides which way the whorl on the back of your head turns?

  The mechanisms setting the side and the rotation direction of a hair whorl are unknown, which is odd for something visible on every head. Twins are the obvious test of how much of it is genetic. And because vortex phenomena elsewhere depend on which side of the equator you are, the authors also compared children born in France against children born in Chile. What did the twins show?

  Source: Willems et al., Journal of Stomatology, Oral and Maxillofacial Surgery

• Does drinking beer make mosquitoes more interested in you?

  Alcohol consumption is rising in the countries where malaria is worst, which makes any link between the two a public health question rather than a curiosity. Mosquitoes find people by smell, so the testable version is whether beer changes a person’s odor enough to matter. Researchers in Burkina Faso put whole-body odor through a Y-tube olfactometer, before and after volunteers drank beer or water.

  Source: Lefèvre et al., PLOS ONE

• How does a bird sleep during a flight that lasts for days?

  Many birds fly without stopping for days at a time, which raises an awkward question about when they sleep. The standing assumption was that they sleep with one eye closed and one cerebral hemisphere at a time, keeping watch and staying airborne with the other half. Sleep had never actually been shown in a flying bird. So great frigatebirds were fitted with brain recorders over the ocean.

  Source: Rattenborg et al., Nature Communications

• Is there an age after which you can no longer learn to echolocate?

  Some blind people navigate by clicking their tongue and reading the echoes, and the assumption attached to it is that this needs a brain shaped by early blindness. If true, it would be useless to anyone losing sight later. So blind and sighted participants aged twenty-one to seventy-nine trained for 20 sessions over 10 weeks in practical and virtual navigation tasks. Did age or blindness set a ceiling?

  Source: Norman et al., PLOS ONE

• What shape does human sleep take when the nights are long?

  Most animals sleep in several bouts rather than one block, and humans are treated as the exception. Our single consolidated night is either a species trait or a product of the short dark period that electric light leaves us. Those predict different things. So normal individuals were moved from a conventional sixteen-hour photoperiod to an experimental ten-hour one, and their sleep was recorded.

  Source: Wehr, Journal of Sleep Research

• Why can nobody tickle themselves?

  A touch you produce yourself feels less ticklish than exactly the same touch delivered by somebody else. The sensation is identical at the skin, so the difference has to be made somewhere inside. One candidate is that the brain predicts the consequences of its own movements and subtracts them. So functional imaging compared self-produced against externally produced tactile stimulation. Where does the subtraction happen?

  Source: Blakemore et al., Nature Neuroscience

• Why do some people insist asparagus does nothing to their urine?

  Urine after asparagus has a sulfurous smell, close to cooked cabbage, and a reliable share of people report noticing nothing at all. Two entirely different things could explain that: either they do not make the smell, or they cannot smell it. Those are separate biological questions and they had been tangled together. So researchers tested production and perception separately, using a two-alternative forced choice.

  Source: Pelchat et al., Chemical Senses

• Where did the Tibetan adaptation to thin air come from?

  Tibetan adaptation to the low oxygen of the plateau is among the clearest cases of recent human natural selection. One gene in the hypoxia pathway, EPAS1, carries the most extreme signature of positive selection found in Tibetans, and tracks differences in hemoglobin concentration at altitude. Which left the question of where the beneficial version came from. Re-sequencing it in 40 Tibetans and 40 Han gave an odd answer.

  Source: Huerta-Sánchez et al., Nature

• Can you smell that somebody has come down with something?

  Animals read health status from body odor and adjust whether they approach. Experiments that make healthy humans temporarily sick, usually by injecting a bacterial fragment, suggest we do something similar. Those are induced illnesses rather than real ones. So odor samples were taken from 20 donors twice, once healthy and once with a genuine acute respiratory infection, and 80 raters tried to pick out the sick one.

  Source: Tognetti et al., Evolution, Medicine, and Public Health

• What is your eye waiting for while it adjusts to a dark room?

  Walking into a dark room leaves you blind for minutes, and the recovery is slow enough to be felt. Two very different ways of measuring it exist: asking a person when they can just see a light, and recording the electrical response of the retina itself. If both track the same underlying event they should recover together. So the two were compared after bleaches ranging from a few percent to nearly total.

  Source: Ruseckaite et al., Journal of Vision

• Can you tell where a smell is coming from with your nose alone?

  Two ears locate a sound by comparing them, and the received view is that two nostrils do not work that way for smell. Testing it needs the trigeminal nerve kept out of the way, because a pungent odor stings as well as smells and the sting is locatable. So blindfolded participants hunted an odor source at two meters and at 0.4 meters, with both nostrils open or only one, using a pure smell and a pungent one.

  Source: Welge-Lüssen et al., Rhinology

• Does it matter when in the day you take your walk?

  Physical activity guidelines for type 2 diabetes specify how much to walk and say nothing about when. If the point is managing the glucose rise after eating, the timing ought to matter. So 41 adults with type 2 diabetes did two weeks of advice to walk 30 minutes a day, and two weeks of advice to walk 10 minutes after each main meal, with continuous glucose monitoring. Both met the guidelines.

  Source: Reynolds et al., Diabetologia

• Is a walk better for your attention if you take it outdoors?

  Exercise raises cognitive function, and so does time in natural environments, which raises a question nobody had put cleanly. If both work, does combining them add up, and which of the two is actually doing the work? So 30 young participants did an oddball task with electroencephalography before and after a brief walk, one indoors and one outdoors, with everything else held the same. Which walk moved the brain response?

  Source: Boere et al., Scientific Reports

• Could a stool transplant make immunotherapy work for more patients?

  Immune checkpoint inhibitors transformed outcomes in lung cancer and melanoma, and more than half of patients show primary resistance to them. Gut bacteria are one suspect, so fecal transplantation becomes a candidate for overcoming it. Nobody had tested that combination in the first-line setting. So a phase 2 trial gave a single healthy-donor transplant by oral capsule before treatment, to 20 lung cancer and 20 melanoma patients.

  Source: Duttagupta et al., Nature Medicine

• What does a mosquito bite do to you besides itch?

  Mosquito saliva is a mixture of more than a hundred proteins, many with unknown function, and all of it goes into the skin during feeding. Most of what is known comes from ordinary mouse models, injected with salivary gland extract, which may not reflect a human response at all. So mice engrafted with human blood stem cells were bitten by living mosquitoes, and their human immune cells were tracked.

  Source: Vogt et al., PLOS Neglected Tropical Diseases

• Can someone blind from birth learn to aim their eyes after sight is restored?

  Several visual functions have sensitive periods, windows in early life after which they cannot fully develop. Whether aiming the eyes at something belongs on that list was unknown. The people who could answer it are hard to study, because sight restored after congenital blindness usually comes with pervasive nystagmus that wrecks eye tracking. So the authors built new calibration and analysis techniques and tested them anyway.

  Source: Zerr et al., Journal of Vision

• Does a parent stop finding their own child’s smell pleasant?

  Infant body odor is subjectively pleasant to parents and activates reward areas in the brain, which suggests smell plays some part in bonding. If that is what it is for, the pleasantness should not stay constant while the child grows up and needs less care. Nobody had checked. So 235 parents were asked to rate the personal odor pleasantness of their own 367 children, aged across childhood.

  Source: Croy et al., Chemosensory Perception

• How does a pregnant woman stay upright with the weight out front?

  Walking on two legs works because the lower back curves inward, a lordosis that stacks the trunk’s center of mass over the hips. Pregnancy breaks that arrangement, shifting the center of mass forward of the hips exactly when balance matters most. Either women cope with it or something about the spine is different. So lumbar vertebrae were compared between the sexes, and then against fossil vertebrae.

  Source: Whitcome et al., Nature

• Does a treatment work better when it has a side effect?

  Side effects are counted as pure cost, and patients read them as evidence that something is happening. If that reading changes expectations, it should change outcomes. So 77 healthy participants were told they would receive fentanyl nasal sprays before thermal pain. The sprays held no fentanyl: some contained capsaicin to produce a mild burning sensation, and some inert saline. Did the burn change the pain?

  Source: Schenk et al., Brain

• Is sweet really tasted at the tip of your tongue?

  The tongue map is probably the most recognizable diagram in the study of taste: sweet at the front, salty and sour along the sides, bitter at the back. It is still printed in textbooks and taught in classrooms. Chemosensory scientists debunked it long ago, which raises a better question than whether it is wrong. Where did a wrong diagram come from?

  Source: Smithsonian Magazine

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