It was February 2003. I'd just arrived in China to start researching my second book, a collection of recipes from Hunan Province, and now I was in the midst of a major health panic. Hordes of frighted migrant workers were fleeing the centre of the growing epidemic in Guangdong Province, and many of them were returning to Hunan, which is precisely where I was planning to spend the next four months. And, of course, most of that time would be spent in the company of chefs, now pinpointed as the main human vectors of the epidemic.

It was one particular paragraph in the China Daily cover story that caught my eye. 'After four days of examination and investigation, the World Health Organisation team has found that most of the SARS (Severe Acute Respiratory Syndrome) patients in Guangdong, apart from local medical workers, are employed in the province's restaurant and food industries.' Oh shit.

In retrospect, my decision to write the book was altogether naïve. In my many years of travelling in China, I had never visited Hunan, and I knew no one who lived there. Furthermore, I knew virtually nothing about Hunanese cuisine, my attempts at preliminary research having been thwarted by the almost total absence of authentic Hunanese cookery books in either English or Chinese. In a way, that was the point: I wanted to write about an unexplored culinary region, and to discover it for myself. I was attracted, too, by the knowledge that Hunanese cuisine was hot and spicy like Sichuanese, that it was popular in the restaurants of Beijing and Shanghai, and that everybody told me it was delicious. There was also the intriguing fact that Chairman Mao had come from Hunan, and had retained a lifelong affection for its food. For a couple of years, I'd had the notion of writing a book in which recipes were interwoven with stories of China's revolutionary history, and Hunan struck me as being the perfect place to do it.

But as I scanned that newspaper report, I began to think that I might have made a serious mistake. I cast my mind back to the restaurant kitchen where I had spent that very morning -- a crowded, oil-blackened room where feeble extractor fans had done little to combat the savage fumes of sizzling chillies, which made us all choke and weep. Every so often, a junior chef had come up the stairs with a few freshly slaughtered chickens from a nearby poultry market, where birds and other creatures lurked in cramped cages, and the air was filled with drifting feathers and the smell of chicken waste. It was an ideal breeding ground for infection. Was this research project a good idea, I wondered?

It was a question that returned to me often over the next few weeks. I thought of it when I travelled on crowded minibuses, surrounded by coughing, spitting people. I thought of it after a banquet at a fashionable restaurant near the Hunanese capital, Changsha, to which I'd been invited by a new acquaintance, a local restaurateur. We sat in a pavilion decked out in Qing Dynasty style as the rain roared down outside. The ladies dominated the party, with their outrageous laughter and witty repartee; the men sipped their tea quietly, or knocked back cupfuls of strong and anaesthetising spirits. Towards the end of the meal, one of the waitresses brought in a clay pot of soup in which pieces of bony flesh mingled with slices of ginger. 'Civet cat!' announced my host, proudly. A few days later, civet cat was highlighted in the media as the possible source of the whole SARS epidemic.

With the benefit of hindsight, and the knowledge that SARS fizzled out after a few months, it is hard to remember how terrifying it was at the time. It really did seem for a while as if the whole of China might sicken, and many, many people die. There were those first, mysterious deaths in Hong Kong, traced back to a secret plague in Guangdong, covered up by the local authorities. Then came the spread of the virus across the country, the rapid explosion of cases in Beijing, the incarceration of the sick in makeshift hospitals.

In the end, of course, I decided to stay. This was partly because I had a limited window of time in which to research my book, on account of my BBC commitments: if I missed this opportunity, I didn't know when I could come back for so long to China. But it was also out of a kind of fatalism. In the course of my Chinese adventures I had been in many risky situations. I had rattled along the brink of plunging chasms in clapped-out lorries, been caught in a blizzard late at night on a Tibetan mountain pass, eaten all kinds of questionable and unhygienic foods. I had spent my twenty-sixth birthday at a sinister party hosted for me by a branch of the Lanzhou mafia, and had narrowly escaped a lynching in the anti-foreigner riots that blew up after NATO bombed China's Belgrade embassy in 1999. More mundanely, I had spent more days than I could remember in restaurant kitchens with slippery floors, dodging chefs who rushed around with sharpened cleavers and unsteady woks filled with boiling oil.

I remember one winter in Yunnan Province, taking a bus back to Lijiang after hiking the perilous Tiger Leaping Gorge. Three other English people were on the bus too, and they pointed out that our driver was falling asleep. It was true: I looked in the windscreen mirror, and his eyelids were drooping, he could barely keep them open. Meanwhile the bus was lurching down a multitude of hairpin bends, the mountainside falling away in a sharp drop to one side. An anxious Englishman urged me to go and speak to the driver in Mandarin. So I asked the driver if he was feeling all right, to which he replied that he was perfectly fine, and would not fall asleep. I shrugged my shoulders and returned to my seat, but the driver's eyelids continued to droop, and the Englishman, far from reassured, went and sat next to him, and spent the next two or three hours singing to him, trying to keep him awake. 'What shall we do with the drunken sailor, what shall we do with the drunken sailor…' all the way down the mountain. The driver glanced at him from time to time, as if he were mad. It was a measure of how blasé I had become that I, too, thought the Englishman was overreacting.

When I first went travelling in China, I was a worrier, rinsing my chopsticks and rice bowls in boiling water before I ate, asking bus drivers if they really needed to drink half a bottle of rice vodka before driving over the Tibetan plateau in pitch darkness. Later, I realised that if you want a real encounter with another culture, you have to abandon your cocoon. It is necessary to dine with the natives in a metaphorical as well as a literal sense, and danger is part of the territory. Over time, I became nonchalant about risk.

For the few few days, I was in a state of shock. I had expected Hunan as a neighbouring province to be akin to Sichuan, but in fact it was like another country. The local dialect was totally incomprehensible: for the first weeks I could understand nothing, unless people I met switched to standard Mandarin. The sounds of Hunanese, too, were a world away from the soft melodies of Sichuan dialect: the local tongue had a staccato beat, impatient and in-your-face, faintly aggressive. People in the streets, unused to foreigners, just stared at me blankly, without the warmth and curiosity I'd encountered in Chengdu. I had thought I knew China, but as always I had underestimated its vastness and diversity. In Hunan I realised, to my dismay, that I had to learn the workings of another culture, all over again.

But there was another reason for my decision to stay in Hunan: somehow I felt that I had bound myself to China, through thick and thin. It was an emotional as well as a professional commitment. My Chinese friends couldn't leave the country if a little trouble flared up; why should I? It was part of my life, like a marriage.

When I first arrived in Hunan, the slow train to Changsha disgorged me before dawn, at a forbidding Soviet-style station. Although I had no friends in the city, I had in my bag a clutch of phone numbers and letters of introduction from people in Chengdu food circles, including the number of a friend-of-a-friend who had found an apartment for me to rent. But it was not quite five in the morning, and far too early to call him or anyone else. Having nowhere to go, I hauled my luggage into the seedy station café, and sat for hours over a cup of tea, as shifty figures wandered around in the twilight. Later, I called my contact, and he came to pick me up on his scooter.

Talking about food is a particularly good way to make friends in China, because everyone talks about it all the time. As soon as I mention my area of research, the floodgates of conversation open. And I have discovered more about China in general through my food explorations than I ever did when I was interested in explicitly social or political issues. People let their guard down over dinner. Yet, while researching my Sichuanese cookery book was a joy from beginning to end, the Hunan book was a completely different experience, shattering in many ways.

I had no particular plan when I arrived in Changsha. My methodology for researching and writing about Chinese cookery is simple but chaotic. I just go somewhere with interesting food and find out everything I can about it. Usually I try to make contact with local chefs, food writers and members of the official culinary association. I comb bookshops and libraries for printed sources. Mainly, though, I just do what comes naturally to me, which is to talk to everyone I meet about food, and then follow them into their kitchens with my notebook. My work is like a treasure hunt, because I never know what each day may bring. I might waste days on a futile expedition, or, conversely, meet someone who in half an hour presses five out-of-print cookery books into my hands.

I moved into my apartment, a sub-let in a concrete block that was part of a state work unit. It was grim, like most of Changsha. The Hunanese capital must have been beautiful, once. It has a recorded history of some three thousand years, and has been a cultural centre for more than two millennia. But the city was torched in 1938 as part of a botched response to the Japanese invasion. Temples, courtyard houses and grand old restaurants all went up in smoke and flames. Little survived apart from a small section of the Ming-Dynasty city walls, and the Yuelu Academy, a school of classical learning that was founded in the year 976 and now forms the heart of Hunan University. The 'old' part of town that I found in 2003 consisted of one or two shabby streets by the river, dating back mainly to the post-war years; the only older remains were some ancient flagstone slabs with which one of these streets was paved (even they have since been removed, to make way for a pedestrianised shopping precinct). The rest of the city was a grim miasma of concrete and flyovers, shrouded in a suffocating pall of pollution. And in the spring of 2003, it rained almost every day.

Living in Hunan made me realise how exceptional Sichuan was, and how easy it had been to live there as a foreigner. The Sichuanese are so laid-back and charming; there is always an undertone of sweetness to their manner, as there is to their food. The spiciness of Hunan, by contrast, is bold and uncompromising. People have no patience with sweetness, here. Dishes are seasoned with fresh, dried and pickled chillies, more aggressively hot than they are in Sichuan, combined with the punchy sourness of vinegar and pickled vegetables, the forthright saltiness of fermented black soybeans. The mellow, autumnal red of Sichuan chilli-bean paste plays but a small part in the local cuisine: people in Hunan prefer the striking scarlet of fresh and pickled chillies.

The Hunanese are often similarly brusque in manner. The professional culinary people to whom I had been introduced were largely friendly, but they were busy, and not especially interested in either me or my work. Most of them were sceptical at the idea that an alien might write a book about their cuisine: the Hunanese themselves had barely written anything about the cultural and historical background to their food; how on earth could an outsider attempt it? (I once spent an amusing afternoon in a teahouse with two local journalists who chatted to me in Mandarin, and to each other in Hunanese. By then I was already becoming acquainted with the local dialect, but they didn't know it. So I listened to one of them explain to his friend that my ludicrous project was doomed to fail. To me, in Mandarin, he offered some patronising words of encouragement.)

Hunan also seemed to me, after ten years of travelling in China, to be provincial and old-fashioned in many ways. It was inward-looking, and way off the map for tourists. No foreigners went to Hunan unless they had to, for business or to adopt a Chinese baby. But to the Hunanese, as I quickly discovered, their province is the centre of the universe, no question. For the last two hundred years, it has produced a disproportionate number of movers and shakers, from the Qing Dynasty General Zuo Zongtang (the General Tso of chicken fame) to Mao Zedong and a whole host of communist luminaries. More recently, Hunanese television has gained a reputation for being the most advanced and creative in the nation.

In the eyes of the Hunanese, their province is the beating heart of the nation, an engine of talent that has powered China forth on its road to modernity since the nineteenth century. They see themselves as clever, capable and straightforward: an ideal blend of northern strength and southern softness, without the slippery cunning of the Sichuanese. Likewise, they think Hunanese cuisine is perfectly balanced, unlike the sickly-sweet fare of the East, and the irritating food of Sichuan, which is so tingly and numbing that you can't taste anything. Often, I had the impression that people in Hunan considered the rest of China, not to mention the rest of the world, to be largely irrelevant.

Some of the people I met in those first weeks were immensely kind to me. One female restaurateur took me under her wing. She gave me free rein in her kitchens, and had a habit of whisking me away in her chauffeur-driven car for day trips that involved lavish banquets, market shopping, and indulgent sessions in foot-washing emporia. The manager of the old Guchengge restaurant let me study in his kitchen, too, and it was there that I learned many of my favourite Hunanese dishes. Otherwise, it was hard going. Changsha felt deeply foreign to me, and I met no one with whom I really clicked. The few overseas teachers I ran into in my first week or so fled the country as the SARS epidemic spread, and I never saw any tourists. Most nights I spent hours on the phone to old friends in Chengdu, Beijing and Shanghai, but my days were long and lonely. Unwilling on principle to sacrifice my personal life for my work, I came to the brink of abandoning my entire Chinese food-writing career. That's when I met Liu Wei and Sansan.

Lei Feng himself met a tragic end -- he was killed by a falling telegraph pole in 1962 -- but his spirit lives on. Even today, Chinese schoolchildren are occasionally obliged to take part in 'Learn from Lei Feng' campaigns, although a certain cynicism has crept in to the public view of him. Lei Feng is not alone as a communist role model: in the nineties the party sought to revive flagging public morals with a campaign based on the heroism of another young soldier named Xu Honggang, who was reportedly stabbed in the stomach by thieves while defending a woman bus passenger. (The official media gave a memorable description of Xu's brave deed: 'Holding his dangling intestines with his sleeveless sweater, he jumped out of the window of the bus to chase the criminals despite acute pain.') But if Lei Feng is not the only star in the firmament of socialist heroes, he has always been my favourite.

It was another grey, wet, wind-swept day, and I took a minibus out of town to visit the Lei Feng Memorial Hall. I'd always had a soft spot for Lei Feng, the communist model soldier known as the 'rustless screw'. He was born in 1940, into an impoverished household just outside Changsha, and was orphaned at a very young age. Later, he joined the People's Liberation Army, where he distinguished himself by doing good deeds like darning his comrades' socks and making tea for his superiors. In 1963, his diary, a paean to the glories of communism, was 'discovered' by Chairman Mao and propagated as an inspiring set-text for generations of schoolchildren. A cheerful song was written in his honour: 'Learn from Lei Feng! What a good role model! Loyal to the revolution, loyal to the Party!'

The Lei Feng Memorial Hall was disappointing. Lei's childhood home, a mud-brick cottage, had been engulfed by a vast sprawl of pavilions filled with boring communist propaganda, and there were almost no visitors besides me. The children of Changsha, I supposed, were these days glued to the TV or the computer screen, their role models David Beckham and Britney Spears. At the foot of the Lei Feng statue near the entrance to the park, I fell into conversation with a stranger. When he saw the sketches in my notebooks he seemed to feel a certain affinity with me, so he gave me his phone number and told me to call if I felt like it. Two days later, desperately lonely, I did, and Li Rui took me out for dinner. Afterwards, he said he wanted to introduce me to some friends.

That night was a turning-point in my hitherto desolate life in Hunan. Through Li Rui I found myself entering a kind of oasis of friendship, with one couple, Liu Wei and Sansan, at its centre. As soon as Li Rui took me to their apartment, I felt at home. Their little son, Xuzhang, was playing on the floor when we arrived, and the main room was decorated with carved wooden panels and other antiques. They invited us to sit down in the 'tea room', where a carved Guanyin Buddha presided over offerings of fruit and incense, and old tapestries hung on the walls. Liu Wei set the kettle to boil, and started performing the delicate ritual of gong fu cha, a Fujianese tea ceremony. Sansan called some other friends, a calligrapher, a designer and an antique-collecting businessman, and we stayed up half the night, drinking fine oolong tea, nibbling nuts and sweetmeats, and talking about everything you can imagine. For the first time in Changsha, I was happy.

Liu Wei and Sansan introduced me to a gentler side of Hunanese culture. They and their friends, mostly writers, artists and other 'intellectuals', were nostalgic for the lost ways of the Chinese literati. They were hardworking and technologically savvy, but they gathered in the evenings to drink tea, practise calligraphy, and listen to classical Chinese music. Somehow they found, and created, places of beauty and tranquillity in the concrete jungle in which they lived; at weekends they went on day trips in search of Buddhist monasteries and ancient villages. They were curious and open-minded, and with them I could be honest about my thoughts and feelings: I didn't have to be a foreign diplomat.

Once we all drove out of the city on a moonlit night. The neon and high-rise buildings of the centre gave way to dusty suburban streets, and then to looming hills and scattered farmhouses. We left the car in a clearing and picked our way up an overgrown path, the darkness around us alive with the raucous chatter of frogs and the hum of cicadas. A low, mud-brick farmhouse lay at the foot of a hill, flanked by old camphor trees and teeming undergrowth. Its inhabitant, a reclusive painter, came out to join us on wooden stools in the yard, and a few minutes later a young musician arrived with his gu qin, or ancient zither, wrapped up in a cloth.

We set water from the spring to boil and Sansan made the tea, infusing the leaves of oolong in a small clay pot and pouring the hot liquid into tiny bowls. And as the musician plucked the strings of his qin, we sat back and sipped. The music was fluid and beautiful, evoking the strange melodic pulses of wind and water. The musician's hands moved gracefully over the strings. The fragrant tea, the moonlight, and the plaintive rhythms of the qin combined to make an evening of quite ethereal loveliness.

I spent most of my days in markets and smoky restaurant kitchens, researching my book. But in my free time, I was always with Liu Wei and Sansan, only going back to my apartment to sleep. They welcomed me without question into their extended family, and paved my way to other parts of the province with introductions to relatives and friends. Sansan and I went on several gastronomic excursions together, most memorably to the wild west of Hunan, where we climbed a Buddhist mountain, swam in a crystal-clear river, and bought wild honey in villages of the Miao and Tujia ethnic groups.

The next day Mr Li, shaking with nerves, told me that all my meetings had been cancelled. The chefs and food historians let me know that they'd been warned not to talk to me. The principal, it turned out, had decided that I was intent on 'stealing commercial secrets', and issued a blanket ban on any contact with me. So followed a horrible few days of secret late-night assignations in teahouses, where men in dark coats and hats handed over photocopies of essays on culinary history, and chefs, looking furtively around, answered my questions on cooking technique.

Events outside this golden circle of friends were often infuriating. Once, for example, I went to visit a cooking school in a northern Hunanese city. The deputy principal, Mr Li, welcomed me, and we spent a wonderful afternoon and evening together talking about our common fascination with food and cookery. He introduced me to chefs and food historians who offered to share with me some of their skills and knowledge. But then the principal of the school returned from a trip, and the atmosphere suddenly changed.

While in China, too, I have been assumed to be a spy on more occasions than I can recall. I've been shadowed by a plain-clothes policeman through the cornfields of northern Sichuan, and turned back at military checkpoints in the mountains of the far west of China. Most of the time these suspicious officials clearly feared that I was collecting information for human rights groups or news organisations rather than stealing the secrets of red-braised pork. Some Chinese cookery books that fell into my hands over the years were considered classified material: they bore the tell-tale characters nei bu fa xing, 'for internal circulation only'. But Hunan was the first place I'd actually been accused of culinary espionage.

Of course it wasn't the first time I had been taken to be some kind of spy. Some of my English friends have long been convinced that I am a secret agent. To begin with, I studied at an eccentric and notoriously conservative Cambridge college where one of my tutors was said to be a recruiting agent for MI5. Then there was that long spell as a 'sub-editor' at the BBC Monitoring Unit at Caversham, a mysterious organisation that most people confuse with the government spy station, GCHQ. Any early suspicions were more or less confirmed by my decision to study Chinese, and by my prolonged stays in remote and obscure regions of China, 'collecting recipes'.

But however sick I felt of Hunan and China during that difficult spring, I had only to return to the tea room in Liu Wei and Sansan's apartment for my anguish to melt away in love and laughter, and to feel that my struggle to show the world the best of China through its food was worth it. If it hadn't been for them, I doubt very much that my Revolutionary Chinese Cookbook would have been written.

In my twenties I adored this kind of subterfuge. But by the time I went to live in Hunan, my patience was wearing thin. 'Don't you understand?' I wanted to say to the old-style bureaucrat running the cooking school, 'the outside world has barely even heard of Hunan or Hunanese food! Here I am, exhausting myself in this difficult country, with its impossible script and thousands of incomprehensible dialects, trying to tell people that Chinese cuisine isn't just about junk food and sweet-and-sour pork, and you accuse me of theft and espionage! You should be paying me to take your recipes!' At times like these, I felt like giving up. I would call my friend Rob in Beijing to vent my exasperation with China, and he would say: 'Fuchsia, don't you think it's about time you wrote a Tuscan cookbook?'

Although Liu Wei was a successful designer, with his own business, he looked more like a Buddhist monk, with his shaven head, slight physique, and delicate features. And he exuded an aura of such peace and compassion that people were drawn to him, in search of something. I went to visit him one afternoon when I was in a particularly bleak mood, raw and jagged after another clash with a Chinese bureaucrat. As usual, Liu Wei's presence was balm. 'You don't want to dwell too much on these things,' he told me. 'Try to think of your life as a sketch. The world offers everything, but it's up to you what you include in your drawing. Try to choose the beautiful things, and to leave the ugly things out.' Perhaps it was this attitude that enabled Liu Wei to live a life of such grace in the unpromising surroundings of downtown Changsha.

As a compassionate man with Buddhist tendencies, Liu Wei refrained from eating the flesh of living creatures. His diet was not only vegetarian, but vegan, and he also avoided the pungent vegetables that are frowned on in Chinese Buddhist monasteries: garlic, onions, chives and their relations. (Eating such smelly foods was traditionally thought to be antisocial for monks who spent hours sitting together in meditation, although some people insist that they must be avoided because they inflame the carnal passions.)

Vegetarianism has a long association with Buddhism in China, but there were no explicit prohibitions on the consumption of meat in the rules of early Buddhism. In ancient India, Buddhist monks were allowed to eat whatever food was put into their begging bowls, including meat, as long as they didn't suspect an animal had been killed for their benefit. When Buddhism began to enter China around two thousand years ago, Buddhist acolytes fell in with mainstream Indian teachings in their acceptance of meat-eating under certain circumstances. It was Emperor Wu Di of the sixth-century Liang Dynasty who did much to promote vegetarianism as the norm for Chinese Buddhist monasteries. He was a Buddhist convert who became a lifelong vegetarian and advocated vegetarianism on compassionate grounds.

These days Chinese Buddhist monks live on a mainly vegan diet, while lay Buddhists can choose the degree to which they maintain a vegetarian regimen. Some renounce meat on certain days of the calendar or while visiting a temple; others are completely vegetarian. Buddhist monasteries all over China keep vegetarian kitchens, and in many of the larger establishments there are restaurants providing food for tourists and pilgrims. Such restaurants offer astonishing banquets, where vegetarian ingredients are used to create dishes that mimic the appearance, taste and texture of fish and meat. So you might have, for example, deep-fried 'beef' slivers made from the stalks of shiitake mushrooms, 'spare ribs' fashioned from pieces of wheat gluten impaled on 'bones' of hard bamboo shoot, and a 'fish' that is really a mass of seasoned mashed potato, wrapped in beanmilk skin, deep-fried and covered in sauce. Such culinary subterfuge enables monasteries to entertain their wealthy patrons in suitably opulent Chinese style, but these grand dishes bear little relation to the everyday diet of the monks themselves, which consists mainly of simple grains, legumes and vegetables.

I had realised quite how Chinese I was becoming in my tastes when, shortly before I left for Hunan, I went for a walk in a Kentish village and passed a field of geese. In my pre-China life, I would just have seen them as part of the scenery of the village. This time, before I knew it, I was imagining them braised in a sauce of chilli paste and Sichuan pepper, bubbling away on a gas burner. I caught myself at it, and smiled. It was true what they said about the Chinese: everything that moved, everything that ran across the earth apart from the motor car, everything that flew through the sky apart from the aeroplane, everything that swam in the sea apart from the ship, was a potential ingredient. Once in Hunan, embarrassingly, I assumed that a bagful of live frogs that Liu Wei's nephew had brought on a daytrip with us were for lunch -- when in fact he was planning to release them into the wild as part of his Buddhist practice.

At that time I was reaching my own peak of omnivorousness. The Hunanese were almost as extreme as the Cantonese in their wide-ranging eating habits, and in the course of my research, I ate dog hotpot, braised frogs and deep-fried timber grubs without giving it much thought. The carnage of the markets hardly bothered me.

Through my friendship with Liu Wei, I found myself spending much of my spare time with vegetarians. We paid a visit to a sprightly eighty-one-year-old monk in a Changsha temple, who talked to me about the health benefits of a meat-free diet, and assured me that the flesh of the dog was such an inflaming meat that eating it would drive the most devout friar to break his vow of celibacy. One weekend we went to a hilltop monastery where a renowned Buddhist sage was teaching: there, we lunched simply on rice and vegetables.

Any fool could see that the most dangerous place for a healthy person to go at that time was the respiratory diseases clinic of a hospital. But, as usual, I was faced with the simple choice: do I want to be sensible, or do I want to write this book? So I went to the respiratory diseases clinic, where I stood at the centre of a small crowd of spluttering, feverish people, trying not to breathe too much, as a doctor wearing a flimsy gauze mask listened to my chest with a stethoscope. He was apparently satisfied with what he heard, and gave me a certificate covered in official stamps. So I was able to regain access to my apartment compound.

Meanwhile, the SARS epidemic raged on. People were sick and dying in many parts of the country. Beijing had got it badly, and everyone suspected that Shanghai would be next. Six people in Hunan were ill with the virus, and one had died, although they had reportedly all caught the disease outside the province. Life in Changsha became increasingly difficult. One day I returned home to my flat and was stopped at the entrance gate by security guards. 'Health certificate,' one of them said, holding out his hand. 'But I live here,' I said, 'I've been living here for a month.' 'No, I'm afraid you need a health certificate,' he said. 'We'll let you in for now, but you'd better go to the hospital for a check-up or we won't allow you to return to the compound.'

Liu Wei never expressed any disapproval at my rapacious eating, but his own simple and compassionate diet made me feel a little guilty. This sentiment laid the seeds of a doubt that would later come back to haunt me.

The shadow of SARS began to darken every aspect of life in Hunan. Men and women in white coats would leap at me in the entrances of department stores and hotels, and take my temperature with a gun-like gadget. Posters hung all over the city, as they had done during the Cultural Revolution, this time warning not of 'capitalist roaders' but of the need for vigilance against coughs and fevers. The Guchengge restaurant where I had spent so many days of study closed down, like many others, because most people had stopped going out to eat. When Liu Wei, Sansan and I had lunch in one of the few fashionable restaurants that had remained open, waitresses in green surgical masks came to take our order, their voices muffled by the gauze. One night, a bored millionaire, a client of Liu Wei's design business, took us to a luxurious country club, where he hired a former member of the national tennis team to give us lessons on a floodlit court. Afterwards we showered in the vast, unpeopled changing rooms, and drank tea in a drafty café lounge where ranks of empty tables and chairs extended almost as far as we could see.

Trips out of town became a nightmare. When I pitched up at the bus station, I had my temperature taken by people clad from head to toe in germ-warfare whites; boarding a bus, I had to write down my name, passport number, address, telephone number, and seat number, just in case I or any other passenger fell sick. One day when I drove to Changde with some friends, our car was surrounded by a swarm of masked inspectors who covered it in disinfectant. And despite the fact that SARS had been hatched and incubated in China by a combination of official secrecy, poor hygiene and nasty slaughter practices, people were often wary of a foreigner like me, because they feared I might recently have arrived from the infected south. Sometimes I had my temperature taken four or five times in a single day.

Those were strange, disturbing times, and I felt as though I was moving around in ever-decreasing circles. First, I was unable to travel to other parts of China, later to other parts of Hunan. Then, with most of the restaurants shutting down, I couldn't continue with my kitchen research. The closure of all the Internet cafés was almost a last straw, as it meant I was cut off from easy communication with the outside world. But by then I had settled into my life in Hunan and I didn't want to leave.

The epidemic also threatened to have an effect on table manners. In general in China, shared dishes are placed at the centre of the table, and you serve yourself using your own chopsticks. Before the Cultural Revolution, which encouraged a certain proletarian boorishness, more refined people would avoid touching food on the common dishes with the tips of their own chopsticks. Instead, they would use the handles of their chopsticks to transfer food from the common dishes to their bowls, and then turn the sticks around again to eat. Alternatively, they would use gong kuai, 'public chopsticks' that would be placed at the side of each serving dish, and would never enter anyone's mouth.

During the height of SARS paranoia, people in Hunan started talking about gong kuai again. At dinner parties, 'public chopsticks' would be laid at the side of each serving dish, so we didn't have to risk contamination by each other's saliva. The host would say something ostentatious about the need for gong kuai, and invite everyone to use them, and then we would all talk about how important it was to be hygienic under the circumstances. But no one ever actually used the gong kuai in more than a token fashion. It just felt too artificial, and before long they were left forlornly at the side of the plates, and we all carried on helping ourselves and eating as normal.

Like many people I knew, I developed psychosomatic SARS symptoms that were quite alarming, including a nasty, hacking cough. I was fever-free, so felt sure I didn't have the deadly pneumonia, but I knew perfectly well that if anyone saw me coughing in public, I could be carted off to a hospital and kept there under lock and key until they were sure I was clean (or until I caught the fatal bug from another patient). Rumours abounded of people being incarcerated in isolation wards, their mobile phones confiscated. So I concealed my symptoms, trying to avoid breathing as I scuttled past the guards, zoomed across the yard to my staircase, ran up twelve flights of stairs, unlocked my door and threw myself onto my bed, where I could cough and splutter to my heart's content.

According to the official media, there was no local transmission of the SARS virus in Hunan. But it was hard to trust the official media, and the rumour mill was active. Was there a cover-up in Hunan? Well, yes, almost certainly to some extent, as I was to witness at first hand. The wife of a Very Important Person in Changsha had invited me back to her home for a family dinner. It was just the VIP (who was probably near the top of the SARS chain of command), his wife, their housekeeper and me. We talked for a while, and they showed me photographs of the VIP with various national leaders and other celebrities. Then we sat down for dinner.

And to my amazement, because I had thought I was among friends, they carried out a cover-up, right there at the table, in front of me.

Our meal was interrupted by a young man with a clipboard and an ear-piece who strode into the room with an air of urgency. Because he spoke with my hosts in thick dialect, I couldn't understand every word they said. But I did make out that they were talking about a disturbing development concerning SARS, in which someone who had just returned from Beijing was either sick or showing suspected SARS symptoms. They talked anxiously for a few minutes, and then the young man bustled out again. Naturally, I was worried. Did this mean that the epidemic was now snarling at the ankles of Hunan? I gently asked what had happened.

'Nothing has happened,' said the wife, with a glassy smile. 'It's nothing to do with SARS. Do have some more peas.'

Like everyone else, she had underestimated my growing comprehension of Hunan dialect. I emerged from that dinner almost hysterical, both with laughter at the brazenness of their evasion and all it said about official attitudes, and with terror that Hunan really was on the brink of a devastating epidemic.

Chinese people reacted to SARS either with nonchalance, or with deranged anxiety. Some continued to go out and about, smoking, spitting and coughing in the streets. Many security guards wore their obligatory facemasks slung low, so they could put cigarettes into their mouths. Meanwhile, other people barricaded themselves in their homes, refusing to receive visitors, sipping vinegar as a supposed prophylactic and using fumigation and disinfectant washes in an attempt to sterilise everything around them. But whatever their personal level of anxiety, almost everyone tried to maximise their chances of survival by eating and drinking rather more carefully than usual.

In China, more than anywhere else, you are what you eat. The right foods will sustain your health; the wrong ones will make you ill. As they say: 'bing cong kou ru (sickness enters through the mouth).' While the Chinese often find it embarrassing or difficult to discuss emotional matters directly, they use food as a way to address them. At moments when an Italian friend would have thrown her arms around me and encouraged me to talk, a Chinese friend would thrust another bowlful of soup into my hands, urging me sternly to 'Drink, drink!' The idea of food as medicine, medicine as food runs through every aspect of Chinese social intercourse: it is a constant background chatter. My private Chinese teacher at Sichuan University used to give me candied fruits or walnuts to 'build my brain' if she felt that my spirits were flagging. And that day in Gansu Province, when I disgraced Liu Yaochun's family by falling ill and weeping, his relatives demonstrated their concern for me by bringing out a frozen melon that they had kept, stowed away under the eaves, since October. Sometimes this ceaseless fussing over my diet would irritate me, but I came to understand that it was an expression of love.

Food is used to heal and balance the mind and body in many different ways. Chinese folk dietetics have much in common with the humoral systems of the Ancient Greeks, Persians and Indians, all of which classify foodstuffs according to whether they are 'heating' or 'cooling', and, to a lesser extent, 'moistening' or 'drying'. No one is sure exactly where the roots of these traditions lie, but it seems likely that they influenced China in the early part of the first millennium, when Buddhism was entering the country with all kinds of foreign ideas. The humoral system, anyway, must have resonated deeply with the ancient Chinese concepts of yin and yang.

In the heating-cooling scheme of things, some symptoms, like fevers and rashes, are the expression of an excess of fire; they must be countered with cooling foods like lettuce and cucumber; other symptoms, like diarrhoea, may indicate a surfeit of cold, and must be tackled by a warming diet of meat and ginger. The energetic balance of an individual's body is influenced not only by climate, but also by the seasons: this is why, in Hunan in midwinter, some people like to eat the exceptionally 'hot' meat of the dog. The classification of foods is a matter of both empirical observation and superstition: dog, for example, is a high-calorie food and really does help to raise the body heat of someone malnourished in winter, while the idea that walnuts nourish the brain and cashews the kidneys because they resemble the organs has its roots in sympathetic magic.

In Chengdu, there is a famous restaurant, Tong Ren Tang, that specialises in medicinal foods. The place is an offshoot of a long-established herbal pharmacy of the same name. Its menu, which changes with the seasons, lists the tonic properties of every dish. Salt-water chicken with Astragalus or milkvetch root, for example, 'nourishes the kidneys and boosts yang energy', while lotus root with carrot 'relieves internal heat and detoxifies'. In general, the most serious Chinese tonic dishes have bland and understated flavours: think, for example, of a broth, unsalted, made with a whole duck and the fabulously expensive Tibetan caterpillar fungus, or an unseasoned black-rice congee with barley, foxnuts, lily bulb, lotus seeds, jujubes and wolfberries. Tong Ren Tang, however, is a fashionable restaurant, where people go to enjoy themselves as well as to restore their health, so everything tastes delicious. Ironically, the last time I dined there, I ate so many dishes intended to rebalance my body that I thought I would simply explode.

In China, there is no strict boundary between ingredients that are considered primarily as foods, and those that are considered to be medicinal herbs. The white radish, a common vegetable, is cooling and can be used in the treatment of ailments of the lung and stomach. Ginseng is an expensive and age-old tonic medicine that you might find in your herbal prescription from a Chinese doctor, but you might equally well be served it in a venison soup. Some foods are taken to rebalance the body; others to enhance its functioning. Women seeking to become pregnant might cook with gou qi zi or Chinese wolfberries, because they act as a tonic on the reproductive organs. And if you see a group of businessmen tucking into an ox-penis hotpot -- well, you can easily guess what they have in mind.

Chinese bookshops now have enormous sections devoted to medicinal cookbooks that offer advice on the properties of different foods and the treatment of ailments. They might be modern and glossy, but they have ancient roots. Ritual texts on the staffing of the ancient Zhou Dynasty court referred to the lofty status of the 162 dieticians in charge of the daily menus of the royal family; while the Ming Dynasty Compendium of Materia Medica listed the curative properties of many ordinary foodstuffs, and included forty-four recipes for medicinal porridge. In China today, the older generation don't usually need to consult books on dietetics. They just know that you shouldn't eat aubergine with cucumber, and that the dangerously cold flesh of the hairy crab should be counterbalanced with Shaoxing wine and heating ginger. When they fall sick, they will self-medicate through diet long before they consider visiting the doctor. 'Yao bu bu ru shi bu' is a Chinese saying: 'repairing and nourishing with medicine is not as good as repairing and nourishing with food'.

Over the years, I have found myself deeply influenced by the Chinese approach to treating mind and body through food. If I have an outbreak of spots on my face, I steer clear of heating foods like pork and lychees; I know to drink green tea and eat cucumbers on a hot summer's day. This is partly an irrational response to familiarity with Chinese ways -- I've no idea if these food practices actually work. Yet it is also a rational acceptance of the pervasive Chinese notion that I as an individual should take responsibility for my own health, that I can't just gorge myself on inappropriate foods and then expect my doctor to sort me out with a pill. In China, people try to treat their illnesses at their roots, and now that's what I try to do, too. I accept the need for Western medicine in times of acute illness, but I rarely take pills for low-level complaints like headaches. Instead, I interpret such symptoms as a sign that I need to treat myself better, with healthy food, rest and exercise. And occasionally, of course, with a soup of caterpillar fungus.

In the plague days of 2003, the people of Changsha tweaked their diets in an attempt to boost their immunity to SARS. Waitresses in restaurants offered customers cups of anti-SARS herbal teas as an aperitif. People queued up to fill bottles with spring water from the ancient White Sand Well because they were sure it had curative properties.

One day the manager of the Changsha Food and Drink Company, Liu Guochu, invited me to lunch at the historic Huogongdian restaurant with some longstanding members of its staff. The dishes we ate included a whole stuffed duck, wrapped up tightly in lotus leaves and rice straw, stir-fried asparagus with the flesh of crayfish, and sticky-sweet glutinous rice dumplings. We talked at length about the history of the restaurant: its origins as a temple to the Fire God, and its heyday as a place where storytellers, musicians and snack sellers gathered to entertain the crowds of temple pilgrims. The conversation was fascinating and the food delicious, but the spectre of SARS hung over the feast. 'You must drink more of the chicken and papaya soup,' said Manager Liu, 'it'll be good against the pneumonia'.

All spring, we worried about the disease. I listened every night to the BBC World Service for bulletins on the progress of the epidemic, and kept my ears open anxiously for every rumour in Changsha. My cough worsened, and I slept fitfully. But despite the flood of labourers returning to Hunan from infected regions, the public spitting, and the steady march of the disease across parts of northern China, it never really hit Hunan. Most people were convinced that this was because they ate chillies. 'Look at the map,' they would say. 'Do you see any SARS in Sichuan, Hunan, Guizhou, Yunnan: all the places where they like to eat spicy food?'