Health: quotes, facts and reflections

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DrivePhilosophy

A good laugh and a long sleep are the best cures.

In Irish the full proverb runs “Gáire maith is codladh fada, an dá leigheas is fearr i leabhar an dochtúra”: a good laugh and a long sleep are the two best cures in the doctor's book. Struck in 1964 by a crippling, painful illness, the American journalist Norman Cousins watched comedy films and reported that ten minutes of real belly laughter gave him at least two hours of pain-free sleep. How much this helped him recover is debated, but his 1979 book Anatomy of an Illness made the story famous.

Irish ProverbRead card

DriveHealth

When the head is foolish, the body suffers.

The card gives a free English version of a Ukrainian proverb, “Za durnoyu holovoyu rukam i noham nemaye spokoyu”: because of a foolish head, the hands and feet get no rest. The picture is an everyday one: forget your keys and your legs must carry you back for them. German says that what the head lacks, the legs must make up for. People also use the saying of groups, when a careless decision at the top is paid for by everyone below.

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DrivePhilosophy

A sound mind in a sound body.

The phrase comes from the tenth Satire of the Roman poet Juvenal, written in the early 2nd century AD. The poem mocks people who pray for wealth, power, fame, beauty or a long life, since such wishes often bring ruin. If you must pray, Juvenal says, ask for “mens sana in corpore sano”, a sound mind in a sound body, and a brave heart that does not fear death. It later became a motto of sport, and in Turkey its Turkish form is often credited to Atatürk, the republic's founder.

Latin, Roman ProverbRead card

DrivePhilosophy

He who has health has hope, and he who has hope has everything.

English quotation books have called this an “Arabian proverb” since at least the 1860s; Tryon Edwards's A Dictionary of Thoughts (1891) is one, but these books give no Arabic original, so the label is best taken loosely. The idea is widely shared: good health gives people the strength to plan and to recover from setbacks. Turkish says “Her şeyin başı sağlık”, health comes first, and when a glass breaks people say “Sağlık olsun”: never mind, as long as everyone is well.

Spanish, Arabic variants ProverbRead card

WonderHistory

Britain's National Health Service (NHS) opened on 5 July 1948. It brought hospitals, family doctors and other services into one system, paid for mainly through taxes, so that anyone could be treated without paying at the time of care.

The plan grew out of the 1942 Beveridge Report, in which the economist William Beveridge proposed a comprehensive health service as part of a welfare system for post-war Britain. Aneurin Bevan, a former coal miner from Wales and health minister in Clement Attlee's Labour government, pushed it through despite opposition from many doctors. On its first day the NHS took over some 2,700 hospitals in England and Wales. Before 1948 people relied on charity hospitals, council hospitals and insurance schemes, but coverage was patchy and many women and children were left out. The care did not stay entirely free: charges for glasses and false teeth came in 1951, leading Bevan to resign, and prescription charges followed in 1952.

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WonderScience

Deliberately smiling can make people feel slightly happier. In 2022 a study of nearly 4,000 people in 19 countries found that posing a smile, or copying a smiling face, raised reported happiness a little; a subtler method, holding a pen between the teeth, gave less clear results.

The idea that the face can feed back into feelings, called the facial feedback hypothesis, goes back to Charles Darwin and William James. In a famous 1988 experiment, Fritz Strack and colleagues had people hold a pen in their teeth, which forces a smile, or between their lips, which prevents one, and those in the first group rated cartoons as funnier. In 2016, seventeen laboratories repeated that experiment exactly and found no effect. A 2019 review of 138 studies concluded that the effect is real but small and varies from study to study. The 2022 Many Smiles Collaboration, led by Nicholas Coles and designed jointly by supporters and sceptics of the idea, found that deliberate smiling could both strengthen and start feelings of happiness, while the pen method remained inconclusive.

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WonderScience

A 2016 estimate found that a typical adult man weighing 70 kg has about 30 trillion human cells and 38 trillion bacteria. That overturned the old claim that bacteria outnumber our own cells ten to one: the two numbers are roughly equal.

The estimate comes from Ron Sender, Shai Fuchs and Ron Milo of the Weizmann Institute of Science in Israel. Their reference man is 20 to 30 years old, 170 cm tall and weighs 70 kg. The ten-to-one figure, they found, went back to a single rough calculation from 1972 that had been repeated for decades. Almost all the bacteria live in the colon, the last part of the gut, and together they weigh only about 0.2 kg. Among human cells, red blood cells dominate the count, making up about 84 per cent, while fat and muscle cells, far fewer but much larger, make up most of the body's cell mass. The balance also shifts through the day: a single trip to the toilet empties a quarter to a third of the colon's contents.

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WonderScience

An adult body replaces about 330 billion cells every day, around 80 grams of cells, according to a 2021 estimate by scientists at the Weizmann Institute of Science. Close to nine in ten of those cells are blood cells.

Ron Sender and Ron Milo combined the number, mass and lifespan of every major cell type in the body. Short-lived cells dominate the count. Red blood cells live about four months, and neutrophils, the most common white blood cells, only days, so the bone marrow must make vast numbers of them every day. By mass, the largest shares come from blood cells and from the cells lining the gut, which are shed and replaced within days. At this pace, a number of cells equal to all the roughly 30 trillion human cells in the body is replaced in about three months. That does not mean the whole body is renewed: most nerve cells in the brain last a lifetime, and heart muscle cells are replaced only very slowly.

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WonderScience

Your gut and brain communicate through nerves, hormones, immune signals and microbes, which is why stress and digestion can affect each other.

Scientists call this link the gut–brain axis. The gut has its own network of about 500 million nerve cells, the enteric nervous system, sometimes called the “second brain”, which can run digestion largely by itself. It is connected to the brain mainly through the vagus nerve, a long nerve running from the brainstem down to the abdomen, and most of its fibres carry messages upwards, from the gut to the brain. More than 90 per cent of the body's serotonin, a chemical messenger, is found in the gut. Gut bacteria play a part too: in a 2004 Japanese study, mice raised entirely free of germs overreacted to stress. Stress can speed up or slow down the gut, one reason it often worsens irritable bowel syndrome, a common gut disorder. Most research on the microbes' role has been in animals, and human evidence is still limited.

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WonderScience

A placebo is a dummy treatment, such as a sugar pill. In pain studies, placebos can reduce the pain people report and also dampen activity in the brain areas that process pain, even though they contain no active drug.

The word placebo is Latin for “I shall please”. One of the first clues that the effect is physical came in 1978, when Jon Levine and colleagues studied patients recovering from wisdom tooth removal. They gave them a placebo and naloxone, a drug that blocks the effect of endorphins, the body's own painkilling chemicals. In patients who had responded to the placebo, naloxone increased the pain, which suggested that the placebo relief came from endorphins. In 2004 Tor Wager and colleagues used brain scans to show that a placebo painkiller reduced activity in pain-processing regions during a painful stimulus. Expectation works the other way too: in the nocebo effect, from the Latin for “I shall harm”, expecting harm makes symptoms worse. None of this means the pain was imaginary, or that placebos can replace effective treatment.

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WonderScience

Emotions are not only feelings in the head. Fear speeds up the heart and breathing, grief can take away appetite and sleep, and joy changes posture and expression. These bodily changes are part of the emotion itself, and sensing them may be part of how we come to feel it.

In 1884 the American philosopher and psychologist William James turned the usual order around in an essay called “What Is an Emotion?”. We do not tremble because we are afraid, he argued; we feel afraid because we tremble. The physiologist Walter Cannon attacked the idea in 1927, and the debate ran for decades, but modern research keeps finding the body at the heart of emotion. In 2014 Lauri Nummenmaa and colleagues in Finland asked 701 people to colour in body outlines to show where they felt activity rise or fall with different emotions. Most emotions showed up in the chest, where breathing and heartbeat change; anger and happiness also lit up the arms, sadness appeared as weakened arms and legs, and disgust centred on the throat and stomach. The maps were similar for Finnish, Swedish and Taiwanese participants.

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WonderScience

A small patch of specialised cells in the heart, the sinoatrial node, fires an electrical signal on its own that starts every heartbeat. The nerves do not create the beat; they only speed it up or slow it down.

The sinoatrial (SA) node is a strip of tissue about 15 millimetres long in the wall of the right atrium, the heart's upper right chamber. The electrical charge of its cells drifts upwards on its own until it reaches a trigger point and fires, again and again, so no outside command is needed. The signal spreads across both atria, pauses briefly at a second cluster, the atrioventricular node, so the upper chambers can empty, and then races through the lower chambers so they contract together. Arthur Keith and Martin Flack described the node in 1907. At rest the heart beats about 60 to 100 times a minute, with the vagus nerve from the brain holding the node below its own faster pace. If the node fails, other parts of the heart's wiring can take over at a slower rate, or doctors fit an artificial pacemaker.

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WonderScience

After many infections and vaccines, the body keeps memory cells, types of white blood cell that recognise the germ involved. They can last for decades, so if the same germ returns, the immune system responds faster and more strongly.

There are two main kinds of memory cell. Memory B cells can quickly produce antibodies, proteins that latch onto a specific germ, while memory T cells direct the attack or kill infected cells. An early careful record of lasting immunity came from the Danish doctor Peter Panum, who studied a measles epidemic on the Faroe Islands in 1846. Measles had not reached the islands since 1781, and none of the elderly islanders who had caught it then fell ill again. Modern studies agree. In 2003, researchers found memory B cells against smallpox in people vaccinated more than 50 years earlier, and these cells responded strongly to a new dose. In 2008, survivors of the 1918 flu pandemic still had B cells making antibodies against that virus, nearly 90 years later.

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WonderScience

A fever is not the body overheating by accident: signals from the immune system tell the brain to raise its target temperature, rather like turning up a thermostat. The extra heat can help immune cells work and slow down some germs.

Body temperature is controlled by the hypothalamus, a small region at the base of the brain. During an infection, substances called pyrogens trigger the release of a molecule called prostaglandin E2, which raises the hypothalamus's target, or set point. Until the body reaches the new target it feels cold, so you shiver and get the chills; when the fever breaks, you sweat to shed the extra heat. Paracetamol and ibuprofen lower a fever by blocking prostaglandin production. Fever is an ancient defence: even cold-blooded animals such as lizards run one by moving somewhere warmer. In 1975, Matthew Kluger and colleagues infected desert iguanas with bacteria and kept them at different temperatures; the lizards kept warm enough to have a fever survived more often. A very high or long-lasting fever still needs a doctor.

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WonderScience

Sleep is more than rest: during the night the brain strengthens and sorts what it learned during the day and helps keep emotions in balance, while the body releases growth hormone and carries out repairs.

A night's sleep runs in cycles of about 90 minutes. Each cycle moves from light sleep into deep sleep and then into REM sleep, named after the rapid eye movements that come with it and the stage with the most vivid dreams. As early as 1924, the psychologists John Jenkins and Karl Dallenbach found that two volunteers remembered more of the nonsense syllables they had learned if they slept afterwards than if they stayed awake for the same time. In 2007, brain scans showed that after a night without sleep, the amygdala, an area involved in emotional reactions, responded far more strongly to upsetting pictures. In 2013, a study in mice found that the spaces between brain cells widen by about 60 per cent during sleep, helping fluid wash away waste. Regularly sleeping too little harms attention, learning and mood.

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WonderScience

Scientists still have no single accepted explanation for why we dream. Dreams are most vivid in REM (rapid eye movement) sleep but also occur in other stages, and research links them with memory, emotion and the brain's own activity at night.

In 1953, Eugene Aserinsky and Nathaniel Kleitman at the University of Chicago noticed bursts of rapid eye movements (REM) during sleep and linked them to dreaming; people woken during REM sleep report a dream about 80 per cent of the time. Later studies found that people woken from other stages also report dreams, usually shorter and less story-like. Explanations differ. Sigmund Freud, in The Interpretation of Dreams (1899), saw dreams as disguised wishes. In 1977, Allan Hobson and Robert McCarley proposed that dreams are the brain's attempt to make a story out of random signals from the brainstem, the part of the brain that joins the spinal cord. Other researchers argue that dreams help us rehearse threats, sort memories or soften emotional experiences. Each theory explains some dreams, and none explains them all.

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WonderScience

Pain is not a direct reading of damage: the nervous system produces it, weighing signals from the body against danger, attention, memory and context. That is why the same injury can hurt very differently from one person or moment to the next.

Nerve endings called nociceptors detect heat, pressure or chemicals that could harm tissue and send warning signals to the spinal cord and brain, but it is the brain that decides whether, and how much, it hurts. During the Second World War, the American anaesthetist Henry Beecher found that most of the badly wounded soldiers he treated did not ask for morphine, perhaps because surviving and leaving the battle outweighed the injury. In 1965, Ronald Melzack and Patrick Wall proposed the gate control theory: signals can be turned up or down in the spinal cord, which is partly why rubbing a knock helps. Phantom limb pain, felt in an arm or leg that has been amputated, shows that pain can exist where there is no tissue. In 2020 the International Association for the Study of Pain revised its definition, noting that pain and nociceptor activity are not the same thing.

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WonderScience

The first vaccine, made by the English doctor Edward Jenner in 1796, protected against smallpox. In 1980 the World Health Organization declared smallpox eradicated, the first and still the only human disease wiped out worldwide.

Long before Jenner, people in China, India and the Ottoman Empire protected children by variolation, deliberately giving them a mild dose of smallpox. Lady Mary Wortley Montagu, the British ambassador's wife, saw it in Istanbul and had her son inoculated there in 1718. Jenner noticed that milkmaids who caught cowpox, a mild disease of cattle, seemed to be safe from smallpox, and in 1796 he tested this on an eight-year-old boy, James Phipps. The word vaccine comes from vacca, Latin for cow. Even so, smallpox killed an estimated 300 million people in the 20th century. In 1967 the WHO stepped up a global campaign built on surveillance and ring vaccination: finding every case and vaccinating everyone around it. The last natural case was a hospital cook in Somalia, Ali Maow Maalin, in October 1977.

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WonderScience

In 1928, at St Mary's Hospital in London, Alexander Fleming saw that a stray mould had stopped bacteria growing around it on a lab dish, and later named its active substance penicillin. From 1939 an Oxford team led by Howard Florey and Ernst Chain purified it and proved it could cure infections.

Fleming came back from a holiday in September 1928 to find a dish of Staphylococcus bacteria spoiled by a Penicillium mould, with a clear ring around it where the bacteria had died. He published his findings in 1929 but could not make the substance pure or stable enough to use as a drug. In Oxford, Florey, Chain, Norman Heatley and colleagues learned to grow the mould and extract penicillin, and in May 1940 showed that it protected infected mice. In February 1941 they gave it to their first patient, an Oxford policeman; he improved, but the supply ran out and he died. American factories then scaled up production, and 2.3 million doses were ready for the Normandy landings in 1944. Fleming, Florey and Chain shared the 1945 Nobel Prize in Physiology or Medicine. In his Nobel lecture Fleming warned that taking too little penicillin could make bacteria resistant to it.

Alexander Fleming, 1928Read card

WonderScience

On 8 November 1895, in his laboratory at the University of Würzburg in Germany, Wilhelm Röntgen found invisible rays that pass through skin and flesh but are stopped by bone and metal. He called them X-rays, X for unknown, and in 1901 received the first Nobel Prize in Physics.

Röntgen was passing electricity through a glass tube covered in black cardboard when he noticed a coated screen on a nearby bench begin to glow. For weeks afterwards he almost lived in his laboratory, studying the new rays. About six weeks after the discovery he made an X-ray image of his wife Anna Bertha's hand, showing her bones and her ring, and his paper 'On a New Kind of Rays' appeared on 28 December 1895. News spread within days, and doctors were soon using X-rays to look at broken bones. Röntgen refused to patent the discovery so that everyone could benefit from it. Many languages, including German and Turkish, still name the rays after him, which is why an X-ray is a 'röntgen' in Turkish.

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DriveHealth

Protein helps with satiety, the feeling of fullness that lasts after a meal. Meals that include beans and lentils, eggs, fish, dairy or other protein sources can help people feel full for longer, although appetite and digestion vary from person to person.

In studies that compare meals with the same number of calories, the higher-protein version usually keeps people satisfied for longer, although the effect is modest. One reason is that protein prompts the gut to release more of the hormone PYY, which tells the brain that food has arrived; a 2006 study led by Rachel Batterham at University College London found the strongest PYY response after high-protein meals. Another is that the body works harder to process protein: a 2004 review by the Maastricht University physiologist Klaas Westerterp reports that digesting and using it burns 20 to 30% of its calories, against 5 to 10% for carbohydrate and up to 3% for fat. UK guidance puts adults' needs at about 0.75 g of protein per kilogram of body weight a day, around 45 g for women and 56 g for men, and average intakes are well above that.

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StillnessHealth

The fibre we eat comes from plant foods: fruit, vegetables, wholegrains, beans and lentils, nuts and seeds. Meat, fish, eggs and dairy naturally contain none.

Fibre is the part of plant food that our digestive enzymes cannot break down. Much of it comes from the walls of plant cells, which give stems, peel and seeds their structure. Animals do not make these substances, so meat, fish, eggs and milk contain none. Mushrooms, which are fungi rather than plants, also supply a little fibre from their own cell walls. Nutritionists divide fibre into two kinds. Soluble fibre, found in oats, barley, apples and beans, dissolves in water in the gut, can form a gel and helps lower cholesterol. Insoluble fibre, in wholegrains, brown rice, nuts and the skins of fruit and vegetables, adds bulk and helps food pass through. Once fibre reaches the large intestine, gut bacteria ferment part of it into short-chain fatty acids, compounds that feed the cells lining the bowel.

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StillnessHealth

Whole fruit keeps its fibre and cell structure, so it takes longer to eat and fills you up more than juice. Juicing breaks the cells open and frees their sugars, which are harder on teeth. The NHS therefore counts juice as one of your five daily portions at most, and advises no more than 150ml a day.

In a 2009 study at Pennsylvania State University, Julie Flood-Obbagy and Barbara Rolls gave 58 adults an apple, apple sauce or apple juice 15 minutes before lunch, each with the same weight and calories. After the whole apple, people felt fuller and ate about 15% fewer calories across the starter and lunch together than on days with no starter. Juice did not have that effect, even with the apple's fibre added back. A larger Harvard analysis of about 187,000 American health professionals, published in the BMJ in 2013, found that people who ate more whole fruit, especially blueberries, grapes and apples, were less likely to develop type 2 diabetes, while those who drank more fruit juice were slightly more likely to. Long-term observational studies like this show a link rather than proof of cause, but the two kinds of evidence point the same way.

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StillnessHealth

Water makes up about 60% of an adult's body weight. The body needs it to control its temperature, keep blood flowing, digest food and keep organs working. When lost fluid is not replaced, thirst can come with tiredness, headache, dizziness and poorer concentration.

Every day we lose water in urine, in sweat and even in our breath, and more in hot weather or during exercise. About a fifth of what we take in comes from food, especially fruit and vegetables, and the rest from drinks. The NHS suggests 6 to 8 glasses of fluid a day, and water, lower-fat milk, tea and coffee all count. Thirst is the body's alarm: when the blood becomes slightly too concentrated, sensors in the hypothalamus, a small region at the base of the brain, trigger the urge to drink. This alarm weakens with age, which is one reason older people become dehydrated more easily. A simple check is the colour of urine: the NHS advises drinking enough to keep it a clear pale yellow, and darker urine is a sign to drink more.

Harvard T.H. Chan School of Public HealthRead card