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The idea that diet is a major determinant of health and well-being goes back to at least the ancient world, with Hippocrates’ famous (but probably apocryphal) dictum “let food be your medicine”. Modern scientific attempts to define a healthy diet were kickstarted in the 1890s when nutrition pioneer Wilbur Atwater at Wesleyan University in Connecticut published the first ever dietary guidelines. He recommended variety, moderation and the avoidance of too much fat, sugar and starch. Although that advice has largely stood the test of time, today more than ever we have to contend with scare-stories about which foods are good and bad. Here is what the evidence says about common food myths and how to eat healthily.…

We are often told not to eat between meals, and there is a general perception that snacking is unhealthy. But, as usual when it comes to food, temptation prevails. Snacking is very common, and increasingly so. In the early 1970s, for example, US adults consumed about 18 per cent of their total calories in snack form. By 2010, that had risen to 23 per cent. Similar numbers have been recorded in the UK, Brazil and Norway. Given how common snacking is, it would be nice to know whether the received wisdom is true. But research on the health effects of snacking has produced a dog’s dinner of results. Some studies have found that, as expected, snacking has negative health consequences. But others have found the opposite. To get a clearer…

The question of whether we are drinking enough for optimal health has been a matter of contention for decades. You may have heard that we should drink eight glasses of water per day, but this figure was based on a misunderstanding of a decades-old study that was never intended as lifestyle advice. In 2022, an international consortium of researchers set out to find a new figure. “We found a typical man in their mid-20s, in the US or Europe, will require around 1.5 to 1.8 litres per day, and a typical woman will require around 1.3 to 1.4 litres,” says John Speakman at the University of Aberdeen, UK. That equates to 6 or 7 small glasses of water per day, minus whatever you get from food. If you are more…

When it comes to regular exercise, life has a habit of getting in the way. And when it does, it doesn’t take long for the body to start making savings by cutting down on luxuries like big muscles and extra blood capacity. Before long it can feel like an uphill battle to get back to where you were. The first place that our bodies make savings is in our aerobic fitness. Evidence suggests that VO2 max, the maximum rate at which the body can absorb oxygen, drops significantly after a mere 12 days of inactivity, largely due to a roughly 10 per cent decrease in the amount of blood your heart can pump with each beat. Some changes occur even sooner. For instance, blood volume decreases after two days of…

In principle, it is impossible to avoid knowing yourself. We each have privileged access to our own personal history – only we truly know what we think, feel and what we do when no one else is looking. Research, though, suggests that despite this, we have less insight into our character than we might think. Part of the problem is that self-perception presents a thorny case of the “criterion problem” – that is, how can you assess the accuracy of the way you perceive yourself without an objective criterion for comparison? In a few studies, researchers have tried to get around this by comparing self-perceptions with third-party observations. One study compared people’s self-ratings on core personality traits with behavioural ratings of each of those traits in a lab environment, and…

TREAT YOURSELF WITH COMPASSION Looking after yourself can feel like an indulgence. But multiple recent studies show that it is anything but. Self-compassion is not only essential for our mental health, it can make us kinder to others, too. Scientists measure self-compassion using selfreport scales featuring questions such as: “Getting on in life is about being tough rather than compassionate,” and “I fear that if I become kinder to and less critical of myself my standards will drop.” Studies using these kinds of measures have found that people who are harshest on themselves are less emotionally resilient and more vulnerable to mood disorders. Importantly, people who are most self-compassionate have also been found to have more empathy and to maintain better relationships with others. One way to cultivate self-compassion is…

Most people think of health along the lines of the standard dictionary definition: “the condition of the body and the degree to which it is free from illness”, according to the Cambridge Dictionary. The World Health Organization (WHO) definition is a little stricter. According to its view, health is “a state of complete physical, mental and social well-being and not merely the absence of disease”. This meaning was adopted by 61 countries in 1946, but it has since been criticised. The requirement for “complete” well-being in all aspects of life means most of us could qualify as unhealthy most of the time. It is also possible to feel perfectly healthy while having an underlying serious illness. A newer proposal has since been put forward, that “health is homeostasis”: the ability…

10,000 STEPS In the mid-1960s, a small, plastic pocket watch-like device went on sale in Japan. Called the “manpo-kei”, it was the world’s first commercial pedometer. Roughly translated, manpo-kei means “10,000 steps meter”. The 10,000 figure “likely originated as a marketing tool”, says I-Min Lee, an epidemiologist at Harvard University. Not only is 10,000 an easy number to remember, the character for 10,000 in Kanji, a script used in Japanese, looks a little like a person walking. This health target, then, didn’t originate with science. Can we scrap it and have a nice sit down? Herman Pontzer, an evolutionary anthropologist at Duke University in North Carolina, studies the Hadza, hunter-gatherers in Tanzania, as a window into the levels of activity our bodies were built for. He has found that Hadza…

Huge piles of research on diet are published every year. The most shocking, alarming or counterintuitive of these get reported in the media. All of them claim to be based on the latest research and each claims to prove the last study wrong. Do scientists really not know what’s good for us, or is the media to blame for the confusion? Misleading media coverage is certainly part of the problem. But a broader issue is that bias is built into nutritional research at every stage. One issue is what is known as publication bias: studies that show interesting or surprising results are more likely to get published than those that don’t. This bias happens at nearly every stage of the long process from the initial research to publication in a…

On a list of the body’s priorities, blood sugar regulation would come somewhere near the top. Glucose is a vital nutrient for our health and is the preferred energy source for the brain. Behind the scenes, and outside of conscious awareness, the body works hard to make sure there is always enough to go around. When we eat, its levels in the blood naturally rise, and so the pancreas makes the hormone insulin, triggering some of the glucose to be stored as glycogen in our muscles and liver. Several hours after eating, as blood sugar gets low, the glycogen can be released and converted back into glucose. When this process goes wrong, it leads to diabetes. In type 1 diabetes, the pancreas stops being able to make insulin, so people…

The key to improving fitness is, in essence, simple. You need to exceed your “habitual load”, which is a fancy way of saying doing more activity than you are accustomed to. This will stress your body and force it to adapt. When it comes to starting cardio exercise as a beginner, “one of the first things that happens is you get more blood volume”, says Abbi Lane at the University of Michigan. Within 24 hours of working out, this increases by up to 12 per cent due to water retention, which increases the amount of blood plasma, boosting the amount of oxygen that can be supplied to the muscles. After two weeks of training, peak blood volume is normally reached, which is about 15 to 20 per cent higher in…

SLEEP When we are asleep, the body gets busy fixing and growing tissues that keep us fit and strong. Which is why, according to Matthew Morrison, a researcher at the Australian Catholic University, simply getting better sleep could make us stronger and fitter. When we are sleep-deprived, we are not only less motivated to exercise, it leaves us physically less able to perform. This is partly because restricted sleep reduces testosterone levels and alters the release of growth hormone, both of which are thought to be important for how the body recovers from and adapts to exercise. A severe lack of sleep over five nights has also been shown to have a negative impact on the amount of energy produced by mitochondria, the tiny structures within cells that create the…

A 2022 study that followed more than 400,000 US adults over nearly two decades found that 1 hour of aerobic exercise per week was associated with a 10 to 20 per cent lower risk of dying during the study period. The biggest gains come from changing from doing nothing to doing something, and the health benefits for people aged over 60 seem to be stronger than for younger adults. A number of studies show that you don’t need to be a committed athlete to gain near-maximal health benefits from exercise. Just 150 to 300 minutes per week of vigorous physical activity, 300 to 600 minutes of moderate activity or an equivalent combination of both will do the trick.…

Depression is characterised by persistent low mood, a lack of hope or motivation, low self-esteem, fatigue and indecision. Although it is often seen as a modern complaint, people have long experienced depression, often under other names such as “nerves” or “melancholia”. The precise causes of depression aren’t yet known, but genetics, the microbiome, social stress and child abuse are among the many factors that have been implicated in the condition. Our immune system may be involved too – there is evidence suggesting that brain inflammation may be an underlying cause. Antidepressants are commonly prescribed as a treatment for depression. Other treatments include talking therapies, such as cognitive behavioural therapy. There is some evidence to suggest that regular exercise, and even hot baths, may help prevent or relieve symptoms.…

You may, quite reasonably, think you are an individual of the species Homo sapiens, but there is far more to us than that. The microbes that colonise us, collectively known as the microbiome, include bacteria, viruses and fungi. There are so many of them that some researchers are beginning to see human bodies as “metaorganisms”. As well as forcing us to rethink what it means to be human, this suggests that managing our microbial populations could be the key to unlocking better health. We must learn to work with our bacteria, fungi and viruses, not fight against them.…

Whether the first signs come as wrinkles and grey hair, aches and pains or with the shocking realisation that the 1990s were three decades ago, there is no escape from the march of time. But while ageing comes to us all, you only have to look around at others your age to notice that the accumulation of the years doesn’t affect everyone the same way. In recent years the concept of “biological age” has emerged, which is based on various biomarkers of the speed at which your cells are accumulating damage. Depending on lifestyle and other environmental factors, this number might be very different from the number of years since birth. This new understanding has led to various commercial tests that claim to reveal how things are going on the…

Vaccines have been a part of preventative healthcare since Edward Jenner invented the smallpox vaccination in 1796. According to a recent analysis, since 1974, vaccines have averted 154 million deaths worldwide, including 146 million among children under 5. The rationale of vaccination is to present the immune system with small chunks – called antigens – of an infectious organism to provoke an immune response and lay down an immune memory so that subsequent contact with the real pathogen is quickly dealt with. The problem with using a similar approach against non-infectious diseases is that, unlike bacteria and viruses, which the body recognises as “non-self”, many of them arise from a person’s own cells. This makes it more challenging to spark such a protective response – but not impossible. In fact,…

Why does wellness sell? Wellness sells because it’s always just out of reach. It’s like the myth of Tantalus, who was condemned to standing in a pool of water that would disappear when he tried to drink it. Even as you pursue wellness, there is always more you can do to achieve the ideal of wellness. In my interviews with people who use wellness products, they easily slipped back and forth between using the logic of “restoration” and the logic of “enhancement”. They described using wellness therapies to restore themselves to a prior state of functioning, such as taking melatonin for insomnia. But they also described wellness as a way of enhancing themselves, to become better, healthier, stronger, smarter and more productive versions of themselves. For example, they might continue…

As the saying goes, “a calorie is a calorie is a calorie”. Or, to be more specific: a calorie is a measure of the amount of potential energy contained in a fuel – in this case, the food that we eat. In the late 19th century, Wilbur Atwater demonstrated that the different macronutrients contain different numbers of calories per gram. Protein and carbohydrates contain 4 calories per gram, while fats contain 9. Together, these insights led to the idea of the body as a furnace and food as its fuel. Atwater’s calculations went on to inform the calorie content seen on food labels everywhere. The scientific basis of calories, then, is sound. The problem is that when food enters the human body, things get complicated. For one thing, calorie counts…

When it comes to our diet, there is an ever-changing list of things touted as the key to better health: cutting out carbs, eating like a caveman or dosing up on supposed superfoods such as turmeric. Most fail to live up to the hype – but there is one supernutrient that bucks this trend. It is common knowledge that dietary fibre is good for you, but few of us appreciate just how far‑reaching its health benefits go. Being in the know is worth your while, though, especially given that the diets common in high-income nations mean it is all too easy to miss out. Many of us will have experienced first hand the effects of dietary fibre on our body. Sometimes dubbed “nature’s laxative”, a lack of it can cause…

Humans evolved to crave sweet foods for good reason: our ancestors needed the energy they provide to stay alive. Back then, sweetness mostly came from ripe fruits and perhaps a bit of honey. Now our diets are laden with added sugars and our inability to resist the stuff comes at a heavy price for our health, increasing the risk of heart disease, type 2 diabetes and chronic inflammation. Not to mention rotting our teeth. The WHO recommends that to minimise these risks, we should consume less than 25 grams per day of added sugar, equivalent to six teaspoons. But with so many processed foods containing hidden sugar, this guideline can prove difficult to stick to. So, the search is on for an alternative to sugar that gives us the sweetness…

Researchers are getting closer to developing a pill that mimics the effects of exercise. In 2022, for instance, a study showed that a drug called locamidazole could increase the number of mitochondria in the muscles and bones of mice, one of the typical consequences of exercising. Mice that received locamidazole also had greater bone mineral density, wider muscle fibres and greater endurance on a treadmill. Another promising substance is an amino acid called Lac-Phe, which is released in the blood during endurance and resistance training. Another 2022 study found that giving Lac-Phe to mice for 10 days helped reduce their levels of body fat. At present, however, there are no trials of these substances in humans.…

As any regular exerciser will tell you, moving makes you feel good. Research proves them right. In an analysis of data from 1.2 million US adults over several years, people who exercised, experienced 43 per cent fewer days of poor mental health in the past month, than those who didn’t. This held true no matter the person’s age, gender, race or income, and the effect was larger in people with a previous diagnosis of depression. The same study also showed that you don’t need to do hours at a time to get the benefits; for most kinds of exercise, 30 to 60 minutes per day was the ideal, associated with the lowest mental health burden. The strongest link was for team sports, followed by cycling, aerobic exercise and gym workouts.…

A couple of decades ago, we seemed to be on the verge of understanding mental health conditions. The culprit was thought to be irregular levels of various brain chemicals, which could be remedied with drugs. Depression, for example, was thought to stem from a lack of the brain signalling chemical serotonin, partly because the most common kind of antidepressants raise levels of this compound. What’s more, genetic studies found that people with depression were more likely to have a gene variant that lowers serotonin. Schizophrenia, meanwhile, was thought to be caused by excess activity of circuitry involving a different brain chemical, called dopamine. But this neat picture turned out to be a mirage. The latest evidence suggests that low serotonin isn’t a cause of depression, and many early genetic studies…

Imagine a remote island, recently formed by volcanic activity, in the middle of the ocean. At first, it is lifeless, but a growing variety of plants take hold, providing food for pioneering animals, until eventually there is a diverse and flourishing ecosystem. When a baby is born, it is quickly colonised by microbes in the mother’s birth canal, from her skin and bodily fluids and from the environment. The first individuals that colonise an island can have long-lasting influences on its ecosystem, an idea known as the founder effect. Until recently, the thinking went that if the founder bacteria in a baby’s gut were unusual – because the baby was born by Caesarean section, for instance – this might disrupt their bacterial ecosystems in ways that might predispose them to…

This kind of research is helping to build a better picture of the microbial make-up associated with good health and the factors that influence such a state. Unsurprisingly, diet is key. “Increasing the diversity of the foods we eat increases the diversity of the microbiome,” says John Cryan, a neurobiologist at University College Cork in Ireland. There is also some evidence that fermented foods, such as yogurt, kefir, kombucha and kimchi, could increase diversity and reduce inflammation – so if you enjoy those, add them to your diet. Increasing the amount of fibre you consume is also helpful, assuming your digestive system can tolerate it. “Fibre is broken down by lots of microbes and provides lots of key molecules,” says Cryan. ← See chapter 2 for more on what makes…

Anti-ageing is big business. From books encouraging diets such as intermittent fasting to cosmetic creams to combat wrinkles, a multibillion-dollar industry has been built on promises to make us live longer and look younger. Given the pervasive stereotypes about old age as a one-way street, and the increased risk of disability and some illnesses as we age, it’s hardly surprising we are so determined to stop the clock. But there are good reasons not to panic. Public health campaigns have already improved middle-aged health and fitness in many different countries and this may be why we are seeing a noticeable difference in people’s health. Older adults aren’t a monolith of dependent, frail and forgetful people. In fact, good cognitive ability and health remain intact for the majority of older people,…