We have reached the end of the food label, and before we check out it is worth summarising the major diet myths, their fallacies, and what we can do to improve our own diets and our health.
The most dangerous of these myths is the notion that we all respond to food in the same way, that when we eat food or follow certain diets our bodies behave like the bodies of identical lab rats. They don’t. We are all different. This is why the obsession with the limited view of nutrition and weight as calories-in versus calories-out is unhelpful and distracting. The truth is that each of us responds to food differently even if the food and the environment are identical. Remember the remarkable Canadian study I described at the beginning of the book that involved overfeeding lean student twins: although they were on identical food and exercise regimes, there was found to be a three-fold difference between the weights individuals gained over the two months (one gained 4 kg and the other 13).
Our bodies vary entirely in how they respond to everything, from food to exercise to environment, and this variation affects how much fat we deposit and how much weight we gain as well as our food preferences. As we have discovered, the variation is due in part to our genes, but also to the different microbes that populate our guts. Certain groups and species are associated with protecting individuals against many diseases and against weight gain, while others increase susceptibility to these factors.
But despite the caveat that everyone is unique and will be affected differently, there are certain facts about diet that are unarguable: diets that are high in sugar and processed foods are bad for our microbes, and by extension for our health, and diets that are high in vegetables and fruits are good for both. The US writer on food and health Michael Pollan’s simple seven-word message sums it up: ‘Eat food, mostly plants, not too much.’ And to modify another bit of his advice: ‘Don’t eat anything your great-grandmother’s microbes wouldn’t recognise as food.’
Our microbial diversity is declining every decade, which is definitely a bad thing and likely to be a major contributor to the modern epidemics of allergy, auto-immune disease, obesity and diabetes. It is clear that the more diverse your diet, the more diverse your microbes and the better your health at any age. But how easy is it to change old habits?
A new approach to food: never dine alone
In the five years that I spent researching and writing this book I have learnt a lot about myself and my relationship with food. I know that I would have to be at great risk of some fatal disease to give up cheese for ever and I would now miss yoghurt. My body seems to need some minimal amounts of the nutrients in meat protein – once or twice a month, to stave off vitamin deficiencies. I have worked out that a Mediterranean-style diet suits me very well. This may be because of my southern European genes or due to the chances I have to eat Mediterranean food in nice sunny places.
I am happy with yoghurt and fresh fruit in the mornings, plenty of varied salad, olive oil, and a wide range of other foods including fish in the evening. I have found that reducing amounts of over-refined carbs (white pasta, rice, potatoes etc.) is beneficial to my health and that replacing them with wholegrain varieties is fairly easy, although doing so has lengthened the time it takes me to prepare my meals. Since adding the extra fat from the olive oil, I found I didn’t miss them so much anyway. A very pleasant surprise was that items I thought were naughty but that I enjoyed immensely, like strong coffee, dark chocolate, nuts, high fat yoghurt, wine and cheese, are actually likely to be healthy for me and my microbes. So to quote Barbara Kingsolver, who wrote the book Animal, Vegetable, Miracle, ‘Food is the rare moral arena in which the ethical choice is generally the one more likely to make you groan with pleasure’ – we might add that this is the choice more likely to make your microbes groan with pleasure too.
Diversify your diet and your microbes
Most diet plans contradict each other in their advice on meat versus vegetables and on low carbohydrates versus low fat. But the one thing that every diet guru, book and plan can agree on is that processed and fast foods are to be avoided. I’ve found that I can survive without eating processed foods apart from the occasional indulgence of soft liquorice or potato crisps. If you want to change your diet and to eat more healthily, say by consuming more fruit and particularly more vegetables, I’ve found that it’s easier to give up something such as meat temporarily. This enables you to fill the space with other items and it’s also a good excuse for saying no without upsetting hosts. Juicing was a new experience for me, and despite the washing-up afterwards, is quite a fun diversion at weekends. Certainly, the product tastes much better than it looks. It’s a great way to use up spare vegetables in the fridge and increase the diversity in your diet. When on an alcohol fast for a few weeks in ‘dry January’ I found juicing was a great substitute.
As I learned to listen to my stomach more, I found that I was breaking with tradition and mealtime culture, which was very illuminating. I tried different ways and times of eating, which was also instructive. I learnt that on busy days I could skip breakfast or lunch and that intermittent fasting was much easier than I thought. Total fasting, like for my colonoscopy, was fine for short, well-defined periods. However, I realised this is much more difficult if you’re not busy and distracted; for me it would have been tough to do at home at weekends. Just performing a fast of some kind is a useful exercise in itself; it shows that you can survive psychologically and that you’re not risking death or coma by skipping a meal or a drink. It also allows your microbes to give your gut lining a useful spring clean.
I never tried a very low or zero carbohydrate and high protein option because my tolerance for meat is now limited, having been weaned off it. I am also now against deliberately avoiding any ‘proper foods’ altogether (like grains or pulses), especially when these are sources of nutrients or fibre. We need to eat more diverse foods, not fewer. Trying new foods is part of my new philosophy, as is eating as diverse a diet as I can within the constraints of a busy modern life. As a measure of good diversity I suggest aiming for ten to twenty food types, per week, that are good for your microbes. Rather than eating dull meals from the hospital canteen on a busy day, I usually now eat a piece of fruit and a handful of mixed nuts. I tell myself I will make up for this at dinner – which I do.
Exploring your own gut residents
Over the last year I have tested my own gut microbes dozens of times on different diets, although not as much as some colleagues, who collect samples every day of their lives (you wouldn’t want to share a fridge with them). As I mentioned earlier, I have also set up the British Gut Project (www.britishgut.org), which is a copy of the larger American version that allows anyone to check out their own microbes by post and internet.1 This service is provided for a small donation as long as the participants – we call them ‘crowd-funders’ – agree to share their data with the citizen scientists in the rest of the world. To participate, you simply wipe a cotton bud on some used toilet paper and send the sample to us in the post for sequencing. It is also strangely exciting when you receive your results and compare them to those of the rest of the world. Even I got emotional looking at my gut’s contents. I found my profile was quite unusual at the big picture level: I had much lower levels of Bacteroidetes (18 per cent) than average and lots of Firmicutes, which was potentially a worry.
A few years ago it was believed this kind of ratio was a ‘bad’ profile that led to obesity and disease, but this was too simplistic a view. We have since found that many hundreds of species within the broad groups can have opposing effects, especially on obesity. These species, although we group them together, are very different from each other genetically – it’s rather like comparing ourselves to starfish. Plotting all my gut microbes against the averages from the US, Venezuela and Malawi, I come out as a cross between North American and South American, which means I have a greater diversity than does the average American – I turned out to be strangely similar to the microbial make-up of the writer Michael Pollan – but am not nearly as diverse as an average African.
Diversity or gene richness is a better indicator of health than the presence of any one microbial species. After my colonoscopy my prebiotic feast of vegetables managed to shift my microbes in a healthy direction, but not so much as to make anyone mistake me for a hunter-gatherer.
But what should you do if you want to change things more radically, even permanently? For a start, you could follow the lead of my unorthodox colleague Jeff Leach who decided he didn’t like his Western gut microbes and wanted a change.
Time for a radical makeover
‘I struggled to keep my legs in the air with my toes pointing towards what I thought was the faint outline of the Southern Cross rising in the evening sky. With my hands under my hips and butt perched against a large rock for support, I pedalled an imaginary upside down bicycle in the air to pass the time as I struggled to make sure my new gut ecosystem stayed put inside me. As the sun set over Lake Eyasi in Tanzania, nearly thirty minutes had passed since I had inserted a turkey baster into my bum and injected the feces of a Hadza man – a member of one of the last remaining hunter-gatherer tribes in the world – into the nether regions of my distal colon.’
This might seem a bit drastic, but as we saw earlier, Jeff is no wimp. He had tried to alter his microbial community by living and eating with the foraging Hadza for several days during their wet season. He consumed their baboon-dropping-infested water, their wild honey, tough tubers and the occasional zebra. His microbes had changed, but not as much as he would have liked. This is what led to his unorthodox experiment – standing on his head with the oversize turkey baster inserted into his rear end containing the ‘donation’ from a thirty-year-old male (tested for HIV and hepatitis). Jeff is a pioneer but others call him mad, particularly as he is not ill and is doing this ‘for science’.
But Jeff’s impulse to repopulate his gut using a donor is not as unique or crazy as it may seem. Around the world thousands of people who are seriously ill with C. diff infections have stool transplants (I still don’t like the term ‘faecal transplant’), mostly in specialised clinics with good success rates, although sometimes they need several attempts with beneficial species to eradicate the C. diff populations. Unlike Jeff’s, most transplants are not conducted with turkey basters (which I found, incidentally, are also used for DIY artificial insemination). Bona fide transplant clinics use tubes passing into the colon as for colonoscopy, or for higher success rates they pass a thinner tube through the nose and down past the stomach.
For obvious reasons, researchers have perfected a more acceptable way. They freeze-dry a donor’s stool after cryo-preserving it and insert it into capsules that are acid-resistant but dissolve in the colon releasing the microbes from their cold-induced slumber. These capsules produce high rates of success, over 70 per cent per treatment, and volunteers unsurprisingly prefer to swallow fifteen small ‘organic’ pills over two days rather than having plastic tubes inserted in different orifices with the tiny but nasty little thought of potential leakiness.2
Moreover, companies now offer fully tested super-healthy donor stools for transplants to reverse severe C. diff infections and treat some cases of colitis and severe bowel problems.3 Like sperm and egg donors in the US, if you are healthy you get paid on delivery ($40) and the companies supply hundreds of hospitals around the country.
Can a change of microbes cure obesity?
Although only mice have been found to benefit at present, it’s just a question of time until stoal transplants are used to treat obesity in humans. One thirty-two-year-old lady from Rhode Island who was cured by a transplant of her recurrent C. diff infection caused by too many antibiotics was extremely grateful to be able to stop going to the bathroom twenty times per day. She had never had weight problems and her weight was steady before her infections. But sixteen months later she returned to the clinic complaining of weight gain. She had increased from an average weight of 62 kg to an obese 80 kg with a BMI of 34. A further ten months of monitored dieting failed to shift the weight. The lady had picked her own sixteen-year-old daughter as her preferred donor. At the time she was healthy and only slightly overweight at 63 kg but teenagers can change quickly and she rapidly gained 14 kg in the next two years and became obese. Another lady who gained weight after transplant from an anonymous donor was reported from New Orleans.4 While these unfortunate cases are rare and other explanations are possible, it shows the potential of microbes to cause or cure obesity not just in mice but in humans – and the message is clear: choose your donors wisely.
Perhaps this will start for ex-athletes and supermodels a lucrative new career as donors, although you may want to avoid the anorectic microbes. Most people find the idea of a stool transplant, even if it is technically called an FMT (faecal microbiome transplant), too extreme. So if you are overweight and unhealthy but this is not for you, bear in mind that there is always bariatric surgery (gastric bypass), a form of auto-transplant that dramatically shifts the microbiota from one site to another. This appears to be permanent based on follow-up studies lasting nine years.
But if you don’t fancy either of these procedures, what else can you do? How can you use these new insights into diet, microbes and food to help you lose weight?
If you want to lose a few pounds, avoid bursts of unsustainable dieting on restrictive food plans that inevitably rebound. The key, in fact, lies in not starting a classic diet in the first place, but in maintaining minor weight loss in a nutritionally sensible and sustainable way by remaking your whole diet as regards not just amounts but composition, variety and timing. Once again we need to remind ourselves that we and our microbes are all very individual and we must find the method that best suits us, not some inflexible formula. One bonus is that if you can lose weight even briefly and without major rebounds, it can lower your heart disease risk over your whole life.5 Rapid weight loss through intermittent fasting looks as if it may be more likely to alter your microbial community for the better. The trick is to maintain it.
The thirty-ingredient heavy petting diet
‘Knowing about my microbiome has totally changed my diet and what I put in my mouth.’ Karen is a thirty-seven-year-old single Mum who works in research in London. ‘I became interested in microbiome research because of my weight problems and IBS since the age of fourteen. This got worse when I rapidly put on nearly five stone in a few years after having my daughter and giving up karate. I had tried lots of traditional diets and none of them had worked for me, so I was keen to try something different. I found out about this new DIY microbiome diet from the internet. The idea was for sixty days to eat as many different fruits, pulses [legumes] and vegetables [raw and unwashed, if possible] – ideally over thirty types per week, while petting a different animal per day. You could eat any other real [non-processed] foods you wanted, although grains were discouraged. It was far from a normal diet.
‘I lost three kilos easily, although the exotic vegetable shopping was harder and more expensive than I had thought. Chasing squirrels to pet was also tricky. I continued with a less intensive regime of twenty items per week for another six months. I lost another three kilos in the next three months before putting most of it back on. The bad news was, after nearly a whole year my weight hadn’t shifted dramatically – although the good news was my guts for the first time in fifteen years seemed normal. I went to the loo only once a day, not ten times, which was fantastic.’
Although feeling healthier, Karen repeated her varied prebiotic twenty-item diet, but this time after a kick-start by clearing out her colon with laxatives. She lost another five kilograms, and I then suggested longer-term intermittent fasting as a way of changing her microbes and losing weight. After three months, she lost a further five kilos, so she is now ten kilos lighter and, more importantly, she feels a lot better. We don’t know whether the effects of the intermittent fasting would be permanent on her microbiome if she stopped, but we do see major changes in the species during fasting periods when mucus-eating microbes start their cleanup operations.6
Karen’s story, although just one anecdote and far from a trial or proof, illustrates several points. Simply being aware of the new parallel universe living inside you helps the way you deal with food at a psychological level. As Liping Zhao the Chinese obesity specialist told me, ‘My dieting patients in Shanghai really respond to knowing about their microbes and how they affect your health. It helps them comply with changes in their diet without being obsessed with weight scales.’ It is also important not only to focus on body fat but to try to improve overall health first. So Karen’s bowel disturbance, IBS, probably needed sorting before she could deal with the longer-term problem of fat, and the prebiotic diet appeared to do that very successfully.
People who are basically fit but want to be healthier can achieve this in a fairly straightforward way by helping their microbes in the ways I’ve suggested. Try to eat a greater variety of foods, particularly fruits, olive oil, nuts, vegetables and pulses plus fibre and polyphenols. Avoid processed foods and reduce your meat intake. Eat traditional cheese and yoghurt, avoiding high-sugar low-fat varieties. I like the concept that our ancestors ate in very irregular and seasonal ways, so intermittent fasting or giving up meat for months at a time or skipping some meals seems sensible to enhance your perception of variety. Throughout the year try to eat fruits and vegetables that are in season so as to increase the diversity of the foods you consume. Also, cutting back on liquid calories, such as sugar in juices and other drinks, as well as calories in cakes and snacks, is sensible, as is avoiding artificial sweeteners as a regular alternative.
Can poison be good for you?
Friedrich Nietzsche said: ‘What does not kill me makes me stronger.’ The data suggests our gut microbes like variety and the occasional shake-up, so could the odd drop of poison do us some good? Many believe that little doses of arsenic can be helpful. (Don’t try this at home.) The concept of low doses of bad things being good for the system is called ‘hormesis’, from the Greek meaning ‘to set in motion’. This idea is taken way too far, in my opinion, by homeopathy gurus who claim that dilutions of less than a molecule can have important biological effects – akin to peeing in the Atlantic Ocean and claiming to notice the difference.
Nevertheless, in much of biology, from the cell to the whole body, low levels of stress are good for the organism. Take, for example, short bursts of oxidants or heat stress, which make worms live longer, or low-dose antibiotics which make microbes much stronger, and too-low doses of anti-cancer drugs, which make cancer cells more resistant.7 Even exercise is a form of stress, and we know that’s good for us. In the same way, intermittent fasting can make small animals live longer – even fasting overnight or skipping breakfast may offer us a form of beneficial hormesis.
So we have to keep an open mind. Indulging in a once-a-year junk food blow-out or a greasy fry-up for breakfast could, counter-intuitively, keep us on our toes while fine-tuning our microbes and immune systems. Similarly, a once-a-year steak for a vegetarian or an exotic salad for a meat eater could do wonders. It is also a good excuse to lose a bit of control, but don’t forget this only works if it comes in the form of an occasional shock, not a daily or hourly one.
The hormesis concept is helpful even if we don’t yet understand how it works, and if used sparingly it contributes to the general aim of diet diversity. Every gardener knows that it can be hard to predict which plants will grow best in which soils without some trial and error. Given that our natural soils vary so much, self-experimentation and an open mind may offer us another useful route to health.
I met an entrepreneurial Goan scientist called Darryl on a plane. He gained a lot of weight when he moved from Oxford to New York and had bad experiences with expensive diet gurus. Since then he has taken a DIY approach. He obsessively takes photographs of every meal he eats on his iPad, and using the Timeline program links this to a diary of how he feels. When he tried a high-protein low-carb diet of kefir (like yoghurt and full of probiotics) and meat twice a day, his waist size dropped by two inches in six weeks and he felt energised and didn’t need sleep. But the energy spilled over into aggression, and for the first time in his adult life he got into a fight. He realised high protein was not for him. He experimented with a fruitarian diet comprising little veg and plenty of fruit and coconuts, but found his weight increased. He is still experimenting with other variations, but seems to be settling into a low-refined-carbohydrate, high-vegetable and -legume Mediterranean-style diet. He enjoys the challenge of trying to increase his microbial diversity each week, and is happy with his weight.
Darryl gives us a glimpse of the future. As well as our genes, our microbes will soon be tested routinely from birth, as the cost of carrying out these tests will soon drop below routine blood tests. As technology becomes ever better and cheaper we can envisage more and more innovations and more personalised diet prescriptions. There are already mobile apps like Magic Snap, which can roughly estimate calories from photos of the food on your plate, and which will improve. These apps could be easily modified to provide microbe-friendly prebiotic food scores that we could combine with genetic read-outs of our daily microbes, providing a truly personal nutritional advice service.
Looking after your microbial garden
Most of you – the interested people reading this book – can make informed decisions about changing your dietary habits or not, about eating more of one food or less of another – or you could ignore me and your microbes altogether. However, many people because of limited resources or education cannot. But we are all responsible for the global sickness and obesity epidemic and must exert pressure on governments to start reversing the situation. Let’s try to reduce the massive taxpayer subsidies for corn, soy and sugar which all go into processed foods, and make it worthwhile for farmers to grow cheaper fruits and vegetables.
There are other global actions that could be taken to improve our microbes and our health. We need more incentives to reduce the massive abuse of antibiotics, particularly in vulnerable children. We need to reduce the number of C-sections and focus on normal deliveries.
Furthermore, ‘hygiene’ is something we should redefine and bother less about – it used to be a term for avoiding excreting in the open, but has turned into an obsession with eliminating all natural smells and microbes from our bodies and especially our mouths. Our homes have become sterile laboratories, modern kitchens more like operating theatres, and food comes smothered in plastic. Children should be allowed to play outside in the dirt and swap their microbes with playmates and animals as much as possible. Perhaps we shouldn’t over-wash our foods. One study has shown that you ingest many more healthy live microbes when you have a varied diet with fresh fruit and vegetables, and this could prove to be healthy.8 We should also rethink our resistance to GM crops if they can reduce our far less natural dependence on pesticides and antibiotics, which are the greater worry. Gardeners are reported as being on average healthier and less depressed than the rest of us, and it could be that it’s the close contact with dirt and microbes that makes the difference.
There is no such thing as a one-size-fits-all diet. A recurring theme of this book is that our guts and brains are so individual, and the ways we react to foods so different and yet flexible. Our lives can be a voyage of discovery to find out what works best for us. Having overturned, I hope, many diet and food myths, I also hope that you are now more sceptical about claims concerning food and diet, however convincingly they are sold to you. No one is the infallible expert or completely impartial in this massive field, where we find ten thousand times more recycled theories than rigorous experiments. We can create synthetic DNA and clone animals, but we still know incredibly little about the stuff that keeps us alive.
This book is about dispelling diet myths and arbitrary rules. I have tried not to replace them with new rules or restrictions, but rather with knowledge. You won’t go wrong if you just treat your own microbes like you would treat your own garden. Give them plenty of fertiliser – prebiotics, fibre and nutrients. Plant new seeds regularly in the shape of probiotics and new foods. Give the soil an occasional rest by fasting. Experiment, but avoid poisoning your microbiotic garden with preservatives, antiseptic mouthwashes, antibiotics, junk food and sugar.
These treatments will maximise the diversity of the species that flourish, producing the greatest range of nutrients. In this way your personal garden will cope better with the occasional floods or droughts or invasions of toxic weeds – feasts and famines, infections and cancers. After riding the storm and inevitably suffering a few casualties, the range and balance of your gut flora will allow everything to regrow even more robustly, so allowing you and your microbes to stay healthy. Rather than thinking of your body as a temple, think of it as this precious garden.
Although we still have much to learn, my hunch is that diversity is the key.