Читать книгу First Bite: How We Learn to Eat - Bee Wilson - Страница 10

The women have a lot to talk about;

they remember their homes,

and dinners they made.

Poem written by EVA SCHULZOVA, aged twelve, in the Terezin Concentration Camp

When Abi Millard was four, her mother Dawn started to notice that Abi was acting strangely at mealtimes. She seldom seemed hungry and often put down her fork after a bite or two. Though generally happy and well behaved, Abi was, in Dawn’s words, ‘a nightmare’ when the family went out to eat with friends, ‘messing around and not eating her dinner’. They took her to the doctor who diagnosed congenital anosmia: an inability to smell, which also means an inability to taste food properly, given almost all of what we call ‘taste’ is really flavour perception through the nose.

To consider anosmia is to see how central food memories are, both to the way we learn to eat and the way we relate to the world. When I met her, Abi Millard was nine. In most respects she is a self-assured, happy girl. She likes swimming and Tae Kwon-Do. She lives with her mum and dad in a rural village and goes to the local primary school. Yet her experience of life is different from most. Without the ability to smell or perceive flavour, Abi experiences food more or less as pure texture. Blindfolded, she can’t tell the difference between houmous and strawberry yoghurt. Salad leaves tickle her throat and tomatoes are slimy, though she will eat broccoli and carrots and peas. She has few of the drives that motivate most people to seek out certain beloved foods because she lacks the memories that would make her expect them to be rewarding. Dawn says she lacks any real enjoyment in food – except for one time when they were out at a restaurant and Abi ate a gammon steak and said, ‘That’s lovely’, perhaps because it was intensely salty (Abi can detect strong concentrations of salt or sugar on her tongue, but without any of the flavour nuances). Dawn worries that when Abi is grown up, she may forget to eat. The illness is also isolating: when Abi’s friends at school talk about favourite meals, it’s hard for her to join in. She has no idea what a batch of warm vanilla shortbread smells like; or chocolate; or garlic. She has no memory of the taste of her own mother’s cooking.

It is extremely rare to have anosmia from birth, as Abi does. What is far more common is to develop anosmia later in life, often after a head injury (though it may also be caused by sinusitis, nasal polyps, dementia, chemotherapy, stroke, liver disease or sometimes for no clear reason at all). At a conference organized by the anosmia support group Fifth Sense in spring 2014, anosmia sufferers spoke of how doctors were often dismissive of their condition: ‘be thankful you’re not deaf’ was a common refrain. But it’s hard to be thankful for a malady that separates you from the food memories that define so much of who you believe yourself to be. One woman at the conference who had been in a cycling accident talked about how her marriage had broken down after she became anosmic. Her relationship could not survive her inability to share her husband’s continuing pleasure in food. Before the accident, they had both loved throwing dinner parties, but her husband couldn’t understand that elaborate cooking now did nothing for her. Every meal was a cruel reminder of what she had lost. The predicament of those who are born with anosmia, like Abi Millard, is that they can’t share the pleasurable food memories that the rest of us have. The predicament of those who develop anosmia later in life is that they have the memories, but no means to access them. They are cut off from their own past.

It was a bright spring day in San Francisco in 2011 when Marlena Spieler, a food writer with more than twenty cookbooks to her name, was knocked down by a car at a crossing. Both her arms were broken and she suffered concussion. As the initial excruciating pain gradually lessened, Marlena – a sunny optimist with Marilyn-platinum hair – noticed another injury, which to her was far worse than the broken limbs. The head trauma had damaged the nerve connecting to her olfactory bulb – the part of the brain that interprets flavour – and she could no longer enjoy food. Coffee had been one of Marlena’s great pleasures since she was very young. Now it was tasteless. ‘Cinnamon drops, a childhood favourite, were bitter, horrible,’ she wrote in the New York Times. ‘Tamales were as bland as porridge. Bananas tasted like parsnips and smelled like nail polish remover.’ As for chocolate, it was ‘like dirt’.¹

I got to know Marlena in 2002 on a press trip to Parma organized by the consortium of producers of Prosciutto di Parma. For three days we ate ribbons of pink salty ham at every meal and Marlena, with great Californian ebullience, talked about the foods she loved the most. These were long – very long – conversations. She spoke of artichokes and lemons; earthy dried mint and pungent truffles; bread and cheese; and how she would rather be in Italy than anywhere in the world. She ate with a dainty slowness, as if trying to extract the essence from each bite.

After the accident, she could still perceive the heat of pungent spices such as mustard, Aleppo pepper or cinnamon, because her trigeminal nerve, the part of the body that tingles when you eat hot food, was not damaged. But without the flavour to offset it, the tingling sensation was offensive. Her beloved cinnamon felt abrasive. Meanwhile, she developed new cravings, for intensely sweet desserts and for fish. When I first knew Marlena, she was indifferent to desserts and hostile to fish. Now, suddenly, she had yearnings for smoked mackerel and anchovies. She also developed a very sweet tooth. A scientist working on flavour and the brain told her that this might be because she could no longer detect the qualities in fish and sweets that she had previously been disgusted by. They only seemed desirable because she couldn’t recognize the ways they had once repelled her.

People sometimes speak of anosmia as ‘loss of taste’ but damage to the taste buds themselves is actually very rare. More than 90 per cent of cases of taste-related disorders involve a weakening or loss of the sense of smell. The taste buds in our mouths only supply a fraction of the complex pleasures that we enjoy as ‘flavour’. The rest is perceived via our noses, through something called retronasal olfaction. We smell coffee by breathing in – is any scent better than a warm bag of freshly ground beans? But we taste a cup of coffee by smelling it backwards, or retronasally. The hundreds of chemical compounds that go together to make up the flavour of a particular blend and roast of coffee travel to the back of our mouths and sneak backwards through the nasopharyngeal passage into the nasal cavity.² As we sip and swallow, we are not conscious that the splendid flavours – the nuttiness of the roast, the notes of cherry and peach – are created in the nose, not the mouth. This spectrum of retronasal joy is lost to anosmia sufferers. All they have left are the harsh and basic tongue-notes of sweet, sour, bitter and salty. Like Abi Millard enjoying a salty gammon steak, anosmia sufferers often seek out extremely salty or sweet foods to compensate for the loss of flavour.

Anosmia is a surprisingly common problem – as many as 2 million people in the US have some form of smell or taste disorder.³ It is not a trivial disability. The ability to pick out the jasmine aroma in a cup of espresso or to spot the difference between grapefruit and pomelo might seem of little importance to anyone except for food writers. But medicine and neuroscience are now starting to recognize that anosmia can be an extremely traumatic condition, and not just because of the danger in emergencies of not detecting the smell of smoke or gas. Sufferers often end up depressed and malnourished. Without flavour, the motivation to eat is lost. When nothing can be smelled, there is a yearning for familiar tastes that can never be satisfied. Christmas goes by without the background aroma of turkey or spice; summers are no longer marked by the perfume of strawberries and cut grass. Sufferers often describe it as a deep loss. Duncan Boak, the founder of Fifth Sense, who became anosmic after a head injury, said that he feels as if he is looking at life through a pane of glass.⁴

Part of what is missing for the anosmia sufferer is the safe place of childhood, which the rest of us can return to whenever we eat the foods we have always loved. A couple of years on from the accident, Marlena Spieler found that glimmers of her former responsiveness to flavour were returning. Depending on the level of damage to the brain, some anosmia sufferers do recover. Marlena slowly trained herself to love chocolate again, starting with the blandest milk chocolate and working onto 70 per cent cocoa solid dark chocolate. Occasionally, her morning coffee gave her pleasure rather than just blankness. We met for lunch at an Italian restaurant and she seemed well, exclaiming over the blood orange slices in our cocktails and nibbling on a deep-fried sage leaf. But even as her flavour perception was improving, she continued to feel unsettled, she said. It wasn’t just that food tasted bad. It was that, she told me, she no longer felt quite ‘like Marlena’. As she explained to the BBC Radio 4 Food Programme, our sense of taste is something that anchors us to the person we have always known ourselves to be: ‘Your world has a certain taste. Your mother makes something a certain way. You’re used to certain flavours in your life and if you take that away, you start saying who am I?’⁵

Memory is the single most powerful driving force in how we learn to eat; it shapes all our yearnings. Sometimes the memories are very short-term ones – for instance, whether or not we’ve just eaten. In one study, when a profoundly amnesiac patient was offered another meal only minutes after he had completed the first, he willingly took it.⁶ Minutes after that one, he ate a third meal. Only when a fourth meal was offered did he refuse, telling the experimenters that his ‘stomach was a little tight’.⁷ This suggests that having a conscious memory of our last meal matters as much as hunger in determining how much we eat.

For most of us, though, the food memories that really matter go much further back. You may not be able to remember what you had for lunch last Tuesday, but I bet you can recall the habitual meals of childhood; the breakfast you were given for a weekend treat and the way bread tasted in your house. These are the memories that still have emotional force years or even decades later.

Such memories, conscious or unconscious, are what drive us to seek out the old habitual foods – particularly packaged foods – even if, judged objectively, they do not really taste nice or do our bodies any good. There have been experiments done with rats and mice where the animals are given dopamine blockers, drugs that interfere with the part of the brain that governs reward. These drugs take away much of the chemical reward of eating food. Yet the dopamine blockers do not extinguish the rodents’ food-seeking behaviour, at least not straight away. At first, the animals continue to press the lever (or run through the alleyway, or whatever the task might be) and eat the pellets, even though the dopamine blocker means that the food no longer offers the same gratification.⁸ Next, they carry on pressing the lever to earn the pellets, but do not eat them. Finally they stop pressing the lever, indicating that at last their desire for the pellets has gone. The interesting thing is that it takes so long for the desire to fade. As the neuroscientist Roy A. Wise has observed, it is only when ‘the memory of the reward is degraded through experience that the desire is lost’.⁹ The craving for the pellets is more a function of memory than of how they taste. Memory propels human food urges in much the same way. As we traverse the supermarket aisles in a trance-like state, we are like rats in an alleyway, steered to this or that food by memories of rewards long gone.

One of the reasons that we do not usually think of our tastes as learned is that most of the learning tends to happen in the very early years of life; and then it stops. For those of us who believe in personal development, it is depressing to learn that a person’s food ‘likes’ aged two generally predict their tastes at twenty. In 2005 researchers in Turkey interviewed nearly 700 undergraduate students and their mothers.¹⁰ The mothers were asked about their children’s eating habits when they were two and the students were asked about how they ate now. There was a remarkable continuity between then and now. The students who were ‘picky eaters’ as children still described themselves as picky eaters. The ones whose mothers recalled that they always ate too much still did so. And the three people in the study who ‘never’ ate vegetables as children still had no vegetables in their diet. So much for putting aside childish things.

When we talk of memory and food, we generally assume that nostalgia is a phenomenon that occurs late in life – like Proust being transported to his youth by a madeleine dipped in lime-blossom tea. But food memory is there from the start. Even babies have nostalgia! It’s a large part of how we learn to eat. The foods parents give to babies provide them with powerful memories that trigger lasting responses to certain flavours. This process begins before birth. We are all born with echoes of our mother’s diet, which mean that no one is a totally blank slate when it comes to flavour. We arrive predisposed to respond to certain foods by our experiences in utero.

It’s hard to know what a newborn thinks about taste, since we can’t exactly ask them. Or rather, they can’t exactly answer. But in 1974 the Israeli doctor Jacob Steiner realized that a baby’s reactions to the basic tastes of sweet, sour, salty, bitter could be gauged by their facial expressions, which are vivid and mobile, even in the first week.¹¹ Steiner took babies just a few hours old and offered them a range of tastes on a cotton swab, filming their facial expressions. When given salt, which you’d think might make them cry, the babies surprisingly showed little reaction, continuing to look expressionless (a liking for salt only emerges later, around four months). But all the other basic mouth-tastes produced strong reactions. The sour swab made the babies pucker their lips. Bitterness provoked an expression of abject distress and an open mouth, as if trying to spit or vomit it out. As for the sweet swab, Steiner found that it produced a dreamy look of ‘relaxation’ with an ‘eager licking of the upper lip’ and even a ‘slight smile’ – and this at an age when babies are not supposed to be capable of smiling. Such is the power of sugar.

The test has since been repeated many times, with similar results. What it confirms is that, as we have seen, all human babies, from Sweden to China, have a strong innate preference for sweetness and a dislike of bitterness and sourness. Basic tastes are not a question of memory: we are hard-wired to think sweetness is wonderful and that bitterness is scary. No one has to learn these simple tongue-reactions. But flavour is another matter. Flavours – these memories generated backwards through our nose – are all learned. What we think about flavour in all its myriad forms, from toasted cumin to sea bass, from parsley to spaghetti carbonara, is not fixed. Each of us will have a different bank of memories and feelings about these; and it exists from day one, if not before.

Taste buds appear at seven or eight weeks of gestation. Already, by thirteen to fifteen weeks, the taste buds are mature. A thirteen-week-old foetus weighs maybe an ounce, with no fat under the skin, no air in the lungs. Yet already they can not only swallow but taste, and these sips of fluid leave memories.

In 2000 some French scientists did a remarkable experiment showing that newborns arrive in the world with a memory of how their particular amniotic fluid tasted.¹² The mothers studied came from the Alsace region where strong-tasting anise sweets are a local delicacy. Some of the women had eaten anise regularly during pregnancy and some had not. The babies were tested straight after birth and four days later, having tasted nothing outside the womb but milk. When an anise odour was wafted in front of them, the babies born to anise eaters showed a marked and ‘stable’ preference for anise. They turned their heads towards the anise smell, sticking their tongues out with a licking gesture. They remembered it and apparently it pleased them.

Further experiments have confirmed that other strong flavours such as garlic can also find their way into amniotic fluid. In one study, women agreed to swallow garlic capsules forty-five minutes before they were due for an amniocentesis; when it was tested, their amniotic fluid smelled garlicky.¹³ Babies born to voracious garlic eaters will have been floating in a sac of garlic water for nine months. It has been shown that babies exposed to garlic before birth are more likely to enjoy garlic in food later on. Likewise, mice whose mothers had been fed on artificial sweeteners when pregnant had an exaggerated taste for sweetness.¹⁴ Pregnant rats fed on junk food – including savoury snacks, sweetened cereals and chocolate-hazelnut spread – had babies who also selected these foods over regular rodent pellets, though the babies’ preference for junk was lessened if the mothers switched to a healthier diet during lactation.¹⁵

The flavours our mothers ingest most regularly can become like mother’s milk to us. Julie Mennella and Gary Beauchamp are biopsychologists working at the Monell Chemical Senses Center in Philadelphia who have done a series of experiments on how flavour in utero and in breast milk leaves children with lasting memories and preferences for certain foods.¹⁶ One of their most celebrated studies, from 2001, involved carrot juice. The babies of a group of mothers who drank carrot juice during the last trimester of pregnancy and again during the first two months of breastfeeding were predisposed to like the flavour of carrot. When the babies were weaned onto solid food, several months after the mothers stopped drinking the carrot juice, they showed a marked preference for cereal flavoured with carrot juice over plain cereal flavoured with water.

The early exposure of babies to flavour – both in utero and through milk – works as a kind of ‘imprinting’, as Gary Beauchamp puts it.¹⁷ We become emotionally attached to these early aromas. As we saw in Chapter One with the ‘flavour window’, younger babies are more open than older ones to new tastes. When it comes to weaning, this is an argument for ignoring the advice on exclusive breastfeeding for six months and offering early, varied bites of vegetable purées between four and six months. When it comes to the pre-food stage, however, flavour may be one of the strongest arguments for mothers attempting to breastfeed, at least for the first few months, to eat as varied a diet as possible while doing so. Some psychologists suggest that instead of saying to mothers: ‘breastfeed for the baby’s good’ healthcare advisers should say: ‘breastfeed for your own good’ because you are likely to have a baby who is less fussy to deal with in the early stages of eating.¹⁸ Then again, I’ve known children (not my own) who’ve gone from formula milk at four months to black olives and spinach tart at twelve months, so it doesn’t always follow.

It is curious that we talk so little about the flavour of formula, given that it is the main food many babies taste for that crucial first year. Because any given brand of formula milk does not vary, it seems to have an even greater ‘imprinting’ power than breast milk. Babies who cannot tolerate regular cow’s milk formula are sometimes given special ‘hydrolysate’ formula, whose proteins have been broken down (hydrolysed) to make them more digestible. To adult tastes, these formulas taste especially nasty, with a sour cheesy tang and a strange hay-like odour. Mennella and Beauchamp followed children who had been fed with two different hydrolysate formulas.¹⁹ Objectively, both of these milks tasted equally unpleasant. But to the infants, the particular formula they had been assigned – sour or not – taught them how food should taste. When the two brands were switched round, the infants drank less: they preferred their own bad-tasting formula to the other one. More strikingly still, children aged four to five who had been fed on these sour-tasting hydrolysates as babies showed more positive feelings about sour tastes and smells than children who had been fed on breast milk or regular formula. This is vivid proof that anything can start to taste good if you have enough positive memories of being fed it by a parent. The obvious implication is that formula-fed babies would benefit from having their milk flavoured with vegetables.

Formula can never match the myriad benefits of breast milk, which range from lessening the risk of eczema and ear infections to reducing the likelihood of type 2 diabetes later in life to promoting healthy gut microbiota. But in the developed world, as we’ve seen, most mothers are unable or unwilling to breastfeed exclusively for the first six months. With each of my own babies, I gave it up for one reason or another (illness, work, bereavement and a child with feeding difficulties) at three months. Until they were a year old, when they were old enough for regular whole cow’s milk, I’d have been glad to buy formula that was mildly scented with a range of green vegetables, just enough to give them a memory of spinach when the time came for them to try veg for real.

Instead, in many countries, formula milk has been flavoured, if at all, with vanillin, the artificial vanilla flavour that goes into industrially produced sweet foods, from ice cream to biscuits to cake. Vanilla milk has a long history. Back in 1940, the head nurse of the children’s hospital in Philadelphia recommended tempting reluctant feeders with three drops of vanilla essence in each bottle.²⁰ Internet forums suggest that there are still many desperate parents who resort to vanilla extract when a baby rejects the bottle.²¹

Since 1981, international food standards (the Codex Alimentarius of the World Health Organization) have stated that no flavourings should be added to infant formulas aimed at newborns. But vanillin is still a key ingredient in many of the ‘toddler milks’ marketed at children aged one and over. In China, vanillin is prohibited in infant formula but it continues to be illegally added by many manufacturers. In 2014, a team of chemical analysts found vanillin in four out of twenty samples of infant formula randomly purchased from supermarkets in the city of Wenzhou.²²

Of all the flavours you could think of with which to ‘imprint’ a child, this is possibly the least useful from a health standpoint (except, perhaps, for chocolate: in 2010 the American company Mead Johnson withdrew its ‘premium’ chocolate-flavoured Enfagrow toddler milk amid complaints from leading nutritional scientist Marion Nestle that it was training kids to ‘like candy’).²³ The effects of vanilla milk are lasting. In 1999 some researchers in Germany tested the effects of the vanilla that had been in German ‘bottle milk’ for some years.²⁴ They asked 133 people to try two different ketchups, one of which was straight-up tomato ketchup and the other, bizarrely, had been flavoured with vanillin. (The reason the researchers chose ketchup was precisely because it is not normally associated with vanilla.) Of the respondents, the majority of those who had been breastfed had a preference for the pure ketchup, while the majority of those who had been reared on vanilla formula preferred the strange vanilla ketchup. Their baby milk had brainwashed these unfortunate people into thinking that vanilla made everything taste better.

Clearly, spinach milk would be a better plan, assuming it could be made safe for tiny infants. It will probably never take off, though. Over time, the odds are that babies would accept it and even prefer it, just as the hydrolysate babies with their bad-tasting formula think that milk is meant to taste sourish and cheesy. It’s the parents who would find vegetable milk hard to accept. We want our babies to have milk that corresponds to our own memories of childhood. Manufacturers know that you can only sell baby food by making it appealing to adults, which is why baby rusks are sometimes sweeter than doughnuts and why for decades, until it was banned, jars of baby mush came seasoned with MSG, to give it more savoury taste. When vanilla is found in baby foods, it has been put there to attract not the children themselves – who, as we’ve seen, can become emotionally bonded to flavours that are strange, sour or strong given the right memories – but to please adults. The babies are not the ones who buy the food. It is the grown-ups’ memories that the food companies are trying to appeal to.²⁵ As they warm the sterilized bottle, parents sniff their baby’s milk; or maybe take a tiny sip. It is they, not the babies, who have memories of how childhood milk ought to taste: creamy and sweet, like milk left behind in the cereal bowl.

Do you remember your first passion fruit, your first avocado, your first Thai green curry? Such flavour memories can seem inconsequential, the stuff of gastronomes. ‘Ah yes, it was in Marseille in 1987 that I first tasted an authentic bouillabaisse.’

Yet, from the perspective of neuroscience, food memories are not something slight. Registering different flavours is one of the main ways that our bodies interact with the world around us. Amazingly enough, the human olfactory bulb is the only part of the central nervous system that is directly exposed to our environment, through the nasal cavity. Our other senses – sight, sound and touch – need to travel on a complicated journey via nerves along the spinal cord up to the brain. Smell and flavour, by contrast, surge direct from plate to nose to brain.

Conventional wisdom used to be that humans have rather a weak sense of smell, compared to that of other animals: dogs, say (witness the fact that we don’t have sniffer humans at airports). But recent research suggests the contrary. We may not have a bloodhound’s ability to track a scent, but our olfactory discernment is second to none. We can detect a drop of Worcester sauce in a glass of tomato juice; or the scent of fear in another person’s sweat.²⁶

When I say that we discern smells and flavours, what I should really say is that we create them. Flavour is not actually in food, any more than redness is in a rose or yellow is in the sun. It is a fabrication of our brains and for each taste we create a mental ‘flavour image’, in the same way that we develop a memory bank of the faces of people we know. The difference is that whereas faces fade when you haven’t seen them in a while, flavours and smells have a way of lodging themselves indelibly. What you taste as a child is still there in your adult brain, even if you haven’t thought of it for years. The Norwegian Trygg Engen, the ‘founding father’ of the study of smell and memory, characterized our sense of smell as ‘a system designed not to forget’.²⁷

In 1991 the biologists Richard Axel and Linda Buck discovered that olfactory receptors – cells in the nose that detect odour molecules – make up the largest single family in the human genome. Out of around 19,000 genes, Axel and Buck found, nearly a thousand – 5 per cent – are olfactory receptors. Their research finally unlocked some of the mystery of how humans can remember and discriminate between so many flavours and smells (and, thirteen years later, won them a Nobel Prize).

What makes the human system of olfaction so sophisticated is not just the receptors themselves, but the way they interact with our large brains. Each receptor cell is fairly specialized: it can detect only a small number of substances. But when you smell or taste something – a loaf of freshly baked bread, say, or lemon zest sprinkled over a stew – the receptors send messages to the olfactory bulb in the brain. Here, each flavour becomes encoded in its own particular pattern in a part of the olfactory bulb called glomeruli. A glomerulus has been described as a ‘detection point par excellence’. Each and every time you taste or smell something, the relevant glomerulus will take a snapshot of it. These snapshots show up in the brain as patterns, like a map.

Humans can distinguish around 10,000 separate smells, estimates Linda Buck. We walk into the house and instantly know that someone is cooking roast chicken for supper and that they decided to stuff it with rosemary instead of thyme. Our olfactory systems have an immense power to discriminate between different flavours. Molecules that look near-identical to a specialist chemist in a lab will be easily distinguished by an ordinary person who smells them. Our brains will also interpret the same chemical in radically different ways depending on how concentrated it is. Buck and colleagues note that a ‘striking example is a substance called thioterpineol, whose odor is described as “tropical fruit” at a low concentration, as “grapefruit” at a higher concentration, and as “stench” at a still higher concentration’.²⁸

Once we move beyond smell to consider flavour, however, the images processed in our brains become vastly more complex. In addition to the odour signals from our noses – this coffee is good! – there will be taste signals from the mouth – oh, but it’s bitter! – as well as feelings of texture – smooth crema! – and temperature – that burned my tongue! The experience of tasting food is far more multi-sensory than is the case with hearing, sight or touch, which is why it requires the most sophisticated part of our brain to process it. In fact, eating is influenced by hearing, sight and touch as well as flavour: we prefer apples that crunch loudly, steaks that look blood-red, sauces so smooth they seem to caress the inside of our throats.

If there are 10,000 smells, the number of different flavours that our brains can potentially create is infinite. Professor Gordon M. Shepherd, a biologist based at Yale University, has coined the term ‘neurogastronomy’ to explain our brain’s unique flavour system.²⁹ In Shepherd’s view, complex flavour recognition is at the core of human identity, separating us from other mammals. Cats cannot even detect something as basic as sugar – they lack a taste receptor for sweetness. Humans, on the other hand, can differentiate fake maple syrup from real maple syrup; Coke from Diet Coke. Shepherd notes that the images humans build up of different flavours are processed in the prefrontal cortex, the area of the brain that is most important for decision-making and abstract thought; but also memory. Shepherd’s work has shown that the human brain can potentially generate any number of flavours ‘since every soluble body has a special flavor which does not wholly resemble any other’.³⁰

The way our brains interpret flavours speaks to the human love of patterns. Professor Shepherd and colleagues have done experiments using fMRI and other brain scanning technologies to show that different flavours register as different patterns in the brain. It is startling to see scans of these flavour maps and realize that there is a separate place in our brains for bananas and Cheddar cheese or that strawberries and sugar show up as dots in similar locations. The way our brains map flavour is similar to the way that we perceive visual images. When we ‘see’ something, what we are actually doing is creating an abstract 2D representation of it, with some features enhanced and others suppressed. By the same token, when we put food in our mouths, the flavour molecules that drift to our nose are turned into abstract patterns in the brain. These patterns help us to recognize the food when we taste it again. Our olfactory receptors give different patterns to the sweet and the savoury; the rotten and the fresh. The receptors also modify the patterns depending on what is happening in the rest of the body: whether we are happy or depressed or nauseous.

Through these patterns, our brains make sense of the bewildering world of flavour. Take umami, the so-called fifth taste, which corresponds to the savoury qualities in meat, cheese and certain vegetables such as tomatoes or broccoli. Umami is what gives mushrooms their oomph and the reason it’s so hard to stop pouring gravy on your potatoes. We all have neurons that are specifically tuned to umami. Yet by itself, umami – which is made in artificial form as MSG – doesn’t really taste of much. It is only in conjunction with other flavours that it becomes delicious. We can see this from neuroimaging studies. When glutamates are tasted in conjunction with a savoury vegetable odour, they generate far more brain activity than when the two flavours are tasted separately. The whole is more than the sum of its parts. This makes sense. Our brains are smart enough to see that a dish of Asian greens with soy sauce warrants a more sizeable flavour image than the same greens and soy sauce eaten separately.

What is most significant about our flavour images is the way that they lead to what scientists call ‘images of desire’. Once we have a memory in our heads of a flavour we love, we build up ‘images of desire’ as we seek to acquire it again. In 2004 researchers put subjects on a bland diet and asked them to imagine their favourite foods. Just thinking about these beloved dishes created a response signal in the hippocampus, insula and caudate – the same areas of the brain that are activated during drug craving. Canadian researchers found that people who described themselves as ‘chocolate cravers’ showed different brain activity when eating chocolate than self-diagnosed non-cravers. The cravers’ brains continued to respond favourably to pictures of chocolate long after their bodies had reached a point of fullness. Neuroscience confirms that chocolate means more to some people than others.

To anticipate pleasure in the next meal – something that can take up the greater part of the day, in my experience – is always a form of memory. And each mouthful recalls other mouthfuls you’ve eaten in the past. It stands to reason, therefore, that the flavour patterns in each of our brains are highly dependent on all the things we’ve tasted in the past, especially during childhood. Among North Africans settled in France, fresh mint tea, often served in ornate teapots, is a way of life. Children grow up with that familiar herbal steam rising from the table as adults sit and talk. A particularly refreshing mint tea is served in the courtyard of the Mosque in Paris, a tranquil place to retreat on sweltering days in the city.

For French Algerians, mint tea is imprinted on the mind, in a way that doesn’t hold true for the non-African French population. In 2009 a group of subjects, half of them ‘Algerian-French’ and half of them ‘European-French’ were asked to smell mint and say what they thought of it. All of them – French or Algerian – found it pleasant and all of them correctly identified it as mint. But when gold electrodes were attached to the scalp, the Algerians showed a significantly greater level of neural activity in response to the mint than the Europeans. Because of the mint tea they drank at home, the smell induced a different cortical pattern in the brain. Put simply, mint was a flavour that resonated more with Algerians than the non-Algerians. This was an image their brains had already recognized many times before. If mint were a sound instead of a taste, you could say that the French heard the notes; but only the Algerians appreciated the music of it. Because their memories of it were more expansive, mint actually took up more of their brain.

When we are unable to obtain the flavours we remember from childhood, it can give rise to longings so intense it is hard to think of anything else. The anosmia sufferers we met at the start of the chapter such as Marlena Spieler would confirm this: she hankers for the flavours that would make her feel ‘like Marlena’ again.

Some of the most poignant examples of this flavour-yearning are the food obsessions of prisoners of war. When Primo Levi was imprisoned in a work camp near to Auschwitz called Buna, he remembered that fellow prisoners not only groaned in their sleep, but licked their lips: ‘They are dreaming of eating; this is also a collective dream … you not only see the food, you feel it in your hands, distinct and concrete, you are aware of its rich and striking smell.’

Among memoirs by POWs of the Second World War, a common theme is not just hunger but the fevered memories it gave rise to of all the things they would eat again once they were free. Very seldom did they build these dreams about the grown-up food of sophisticated restaurants, but the food of childhood and of home: stodgy, filling and safe. One British ex-POW remembered dreaming two nights in a row about ‘omelettes and treacle pudding’. He also remembered his bitter disappointment on waking up, since ‘Either was as obtainable as a slice of the moon’.³¹

Food obsession reached a particularly feverish pitch among European, American and Australian POWs in the Far East, where the mismatch between their rations of rice and the food they longed for was enough to make them slightly unhinged. Food historian Sue Shephard writes that most of the men in the Japanese camps ‘regressed to a childish state’. They all hallucinated about sugar: for the British it might be chocolate eclairs, suet puddings and steaming bowls of buttercup-yellow custard; for the Americans, Hershey bars, mother’s apple pie and every kind of layer cake, from devil’s food to coconut. Some men refused to join in the collective discussions of food because it was too painful to be reminded of how far they were from home, but for most of them, the crazy food talk became a survival mechanism to get through the endless days of boredom and brutality. A long-term POW recalled that after the first year and a half or so, the food talk had completely supplanted daydreams about women.

Some men went so far as to write down elaborate menus and even recipes on scraps of paper. Film-maker Jan Thompson, who spent twenty years interviewing former American POWs for her 2012 documentary Never the Same, found that a common theme was writing down Thanksgiving menus, reconstructed from ‘memories of childhood gatherings’.³² All memory is a distortion, and in their half-starved state, these men constructed holiday menus more lavish than any of them can have actually enjoyed as a child. In Japan, Mess-Sergeant Morris Lewis felt oppressed by the responsibility of looking after his soldiers as well as himself. Sergeant Lewis kept himself ‘sane’ by writing down an extraordinary Thanksgiving dinner that included Virginia baked ham, fried rabbit, cranberry sauce, snowflake potatoes, candied sweet potatoes, buttered sweetcorn, buttered asparagus tips, green stuffed olives. Then, ‘Assorted Cookies’, ‘Assorted Nuts’, ‘Assorted Candies’, ‘Assorted Ice Cream’; also ‘Ass. Jams’ and ‘Fresh Ass. Fruit & Grapes’.

This word ‘assorted’ is heart-rending, coming from a man whose diet has been reduced to abject monotony. Prison can famously expand the imagination. After all this time without biscuits, nuts, sweets and ice cream in any form, Sergeant Lewis was planning a meal where all these treats are freely offered in multiple varieties. He had returned to that old childhood pipe dream of being given free rein in a sweet shop.

POW yearnings for childhood food were like an exaggerated version of the food nostalgia we all feel. What you are seeking to recover is not just the flavour in itself, but all the things that went with it: your family sitting round the table, the feeling of being cared for, the freedom from responsibility. This is why it’s possible to long for bad food too, just because of the happy connotations it may have. Not everyone grows up with a mother who turns out perfect apple pies. POW Russell Braddon, a ‘cheeky young Australian gunner’ who spent three years in Japanese camps, was thrilled to get a card from his sister. It arrived sixteen months after she first posted it and it had to be short because the limit was twenty-five words: ‘Dear Russ, Mum’s puddings are still as lumpy as ever. Oodles of love from us all. Pat.’ Braddon later said that this letter told me ‘all I wanted to know’: that his family did not accept he was dead and that ‘the old household jokes about my mother’s rather abandoned cooking still flourished’.

The childhood foods that we ache for are very specific to the place and the time where we grew up. The American POWs did not dream of ‘sweetness’ in the abstract but of candied sweet potatoes and pie. E.P. Köster is a Dutch psychologist, an emeritus professor at the University of Utrecht, who works on the knotty question of why we choose some foods and not others. Köster is particularly preoccupied by the role of memory in shaping our gastronomic desires. His career has been unusual in that his work spans the cutting edge of both psychological thought and consumer science. In 2009 he lamented the fact that among many consumer scientists there was such ‘lack of understanding’ of the ‘fundamental insights from psychology’. Köster regrets that consumer research tends to be founded on the assumption that our food choices are rational and conscious when, most of the time, they are anything but.

He traces his own strong preference for dark Bournville chocolate made by Cadbury’s – which during the war was the main brand of dark chocolate in Britain – to his memories of being thirteen years old in 1944, when the German-occupied Netherlands was suffering from extensive starvation. One day Köster was out riding his bicycle when a British RAF plane circled overhead. He saw one of the pilots throw a pack containing three bars of Bournville from the cockpit. He quickly grabbed them before anyone could stop him.

On the way back, I slowly sucked morsels of one bar. It was heaven. The other two bars I shared with my brother and we ate them for days, a little each day. For the rest of my life I have longed for the taste of that chocolate and whenever I came to Britain the first thing I did was to buy a bar of it. I admit that there may be finer chocolates than Cadbury’s, but for me there is no chocolate more delicious.³³

Childhood food memories, like family jokes, are often untranslatable to outsiders. If I gave you a small dinner plate containing three mounds, one of cottage cheese, one of chopped apple and one of raisins, you might think me a little odd. You might wrongly suspect me of trying to put you on some kind of low-carb or gluten-free diet. But if I served this to my sister, she would understand at once that I was giving her a nice bedtime snack, just like the ones my mother made for us when we crept downstairs in our pyjamas because we couldn’t get to sleep.

The importance of shared childhood food memories for bonding families together can be seen among expats who carry their ‘homeland’ with them in the form of ingredients smuggled in suitcases. In Greece, they sometimes refer to this desire for the food of home as a ‘burning of the lips’.³⁴ When Greeks move abroad, their mothers will often send care packages of food containing such treats as ‘oregano, thyme, mountain tea, locally produced honey, figs, almonds, hard cheese and dried dark bread rings’. At college, I had a Greek friend called Athena, like the goddess, who received the most wonderful parcels from her mother, with slabs of sweet halva and vast bags of the freshest, crunchiest pistachio nuts. She laid them out in exotic pottery dishes. Somehow Athena’s student room always felt different from the rest of ours, though underneath it was the same scruffy bedsit. Surrounded by her foods from home, she had the air of someone who was never alone.

Until it became easier to buy in supermarkets all over the world, Greeks also travelled with feta cheese. Often, they did not realize how much they would miss this damp white cheese until they were away from home, at which point they became desperate for another salty taste of it. In the words of a Greek academic who got a job at a university in Wales and once travelled back from Greece with a vast 10kg tin of feta cheese: ‘I would cut a piece with my meal every night. It was like “white gold” to me.’³⁵

One of the functions of traditional cuisines is to reinforce these shared childhood food memories. Food anthropologist David Sutton found that there was a conscious element of remembering in many of the feasts held on the island of Kalymnos in the Aegean. Kalymnians use big ritualized meals as a way of planning to remember events in the future. There is nothing accidental about this remembering. When roast lamb is shared for Easter, it anchors all those eating it in a particular place and time. During a meal, Sutton found that his Kalymnian friends would often say to him, ‘Eat, in order to remember Kalymnos.’