Discover all about your unique gut bacteria – known as the microbiome – and how food, medicines, lifestyle factors and more can affect it.
We’re all familiar with eating plans that aim to help you lose weight, boost energy or fuel your fitness – but how often do you think about eating for good gut health?
Within all of our bodies hides a unique microbiome – a complex ecosystem of around 100 trillion microscopic organisms – and we’re only just starting to understand the part that these microbes play in our health and wellness.
Our new series, in collaboration with BBC Future, looks at all the factors that affect our unique microbiomes – from dietary choices to lifestyle factors.
We’ve worked with dietitian Emer Delaney to bring you expert information and specially selected recipes that will help you to understand how to eat for better digestive health.
Learn how healthy gut bacteria affect overall well-being, the best foods for digestive health, and how diet, antibiotics and stress can affect the microbiome. How does diet affect gut health?
Discover the benefits of probiotics and prebiotics, the best foods, drinks and supplements, and how to boost good gut bacteria for a healthy digestive system. What are probiotics and what do they do?
Discover delicious, plant-based dishes packed with nutritious ingredients to promote digestive health. These recipes have been selected by dietitian Emer Delaney. Gut-friendly vegan recipe collection
Boost your digestion with our specially selected recipes. Unless you follow a specific diet for health reasons these ingredients will promote the health and function of your digestive system.
Inside your gastrointestinal (GI) tract are trillions of micro-organisms, including bacteria, fungi and viruses. You have roughly the same number of micro-organisms in there, mostly in the large intestine, as you do human cells in your entire body. But only 10% to 20% of the bacteria you have in your gut will be shared with anyone else.
In the series, we’ll be looking at recent research into the microbiome of bacteria that lives inside us.
We’ll be exploring how it affects our health, what could be having detrimental effects on it, and recommending recipes that might help it thrive.
These microbiomes differ hugely from person to person, depending on diet, lifestyle and other factors, and they influence everything from our health to our appetites, weight and moods. But despite being one of the most-researched parts of the body, there's still a long way to go to fully understanding our guts. BBC Future reviewed the findings of some of the science so far.
Scientists hope that population-wide research will advance existing findings. One such project, the ongoing American Gut Study, is collecting and comparing the gut microbiomes of thousands of people living in the US. So far, research suggest those whose diets include more plant-based foods have a more diverse microbiome, and one that is "extremely different" from those who don't, says Daniel McDonald, the project's scientific director.
"We can't say one end is healthy or unhealthy yet, but we suspect that those who are eating a diet rich in fruits and vegetables have very healthy microbiomes," he says. However, McDonald adds, it's unclear if and how radically switching from a diet high in plant-based food to a diet low in healthy food would change the microbiome.
Probiotics
There has been a lot of hype around the health benefits of prebiotics and probiotics in recent years, but while they're increasingly used in treatments including inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis, several reviews suggest there needs to be further research on which strains and dosages are effective.
Eran Elinav, an immunologist at the Weizmann Institute of Science in Israel, has recently found that some people are immune to probiotics – although he did this in a relatively small study that would require future research to come to any concrete answers. He gave 25 healthy individuals either 11 strains of probiotics or placebos, and tested their microbiomes and gut function with colonoscopies and endoscopies before and three weeks after the intervention.
Siome people have a gut biome which welcomes probiotic supplements (Credit: Getty Images)
"People could be divided into two groups – those in which probiotics were welcomed by indigenous microbiome and allowed to colonise the GI tract, where probiotics were able to change the microbiome, and those who were resistant. In this group, the probiotics weren't allowed to settle in, and did almost nothing," he says.
The researchers were able to predict which category a person would fall into by examining features in their microbiome. Elinav says his findings suggest a need for more advanced tailoring to personalise probiotics to the needs of individuals.
Health
Gut microbiota has a major role to play in the health and function of the GI tract, with evidence that conditions such as as irritable bowel syndrome (IBS) often coincide with altered microbiota. But it also plays a much wider role in our health, and this is largely determined in the first few years of life.
Our microbiomes start developing when we're born, when microbes colonise the human gut. Babies delivered by natural birth have been found to have higher gut bacterial counts than those delivered by Caesarean section because of the contact they make with their mother's vaginal and intestinal bacteria, says Lindsay Hall, microbiome research leader at Quadram Institute Bioscience.
"C-section-born infants miss out on that initial inoculation, and some of the microbes they come into contact with will be from the skin and environment" says Hall.
Numerous studies have shown that C-sections affect health long-term – Lindsay Hall
"This is very important for infants to develop their immune systems. Recent work has suggested that disturbances in early life gut microbiome have negative consequences for host health," she says.
"Numerous studies have shown that C-sections affect health long-term, and there's strong evidence to suggest they lead to a higher risk of developing allergies, and a less robust ecosystem, meaning you're more susceptible to changes and disturbances, such as antibiotics.
“However, there is no robust evidence on what this difference means specifically for the immune system."
"We know that Bifidobacterium are able to digest components found in breast milk. These components are not normally found in formula milk, which is why formula-fed babies have less of them," Hall says.
One problem with supplements is that every person's gut microbiome is subtly different (Credit: Getty Images)
Scientists are getting closer to understanding how the gut can also be used to treat disease. One of the newest treatments in the field is faecal microbiota transplants, where a healthy person's microbiota is put into a patient's gut.
The procedure is used to treat antibiotic-resistant intestinal bacteria clostridium difficile, which can infect the bowel and cause diarrhoea. Though there's no conclusive evidence on the underlying mechanism, it's believed that the transplant repopulates a microbiome with diverse bacteria that helps to fight the virus off.
We haven't established what's normal, but also what's normal for each individual – Fiona Pereira
The big question around these transplants is defining what a normal gut microbiome is.
"We haven't established what's normal, but also what's normal for each individual. It depends on their ethnicity, environment and other things they body has gone through," says Fiona Pereira, head of business development and strategy for the department of surgery and cancer at Imperial College London, which oversees research into the relationship between the microbiome and diet.
Pereira says if scientists can gain a clear understanding of what is healthy in different ethnic groups and age groups, they can then profile a person and see how their gut varies and what this is related to – it could be diet, environment, or genetic predispositions to certain diseases.
Antibiotics
It is already well established that antibiotics can dramatically alter our gut microbiota.
The gut is an environment where harmless and beneficial bacteria are in very close contact to opportunistic pathogens that cause infections, says Willem van Schaik, professor at the University of Birmingham and lead researcher of a new study identifying more than 6,000 new antibiotic-resistance genes in pathogens.
He found that most of these pathogens weren't associated with DNA that can transfer between bacteria, which means there's no immediate risk of spread of these genes from normal bacteria to pathogens.
Our findings highlight how many resistant genes are in the microbiome and could potentially be mobilised to be opportunistic pathogens - Willem van Schaik
However, many of the genes thought to be fixed in certain bacterial environments can start spreading by overuse of antibiotics, which can put pressure on the resistant genes locked up inside a single bacterial cell, causing them to mobilise.
"Our findings highlight how many resistant genes are in the microbiome and could potentially be mobilised to be opportunistic pathogens. They should be seen as a warning that there is a large reservoir of these genes we don’t want to start mobilising," van Schaik says.
Further investigation is uncovering how interlinked the gut is to the brain, however, including our mood and mental health, says Katerina Johnson, a researcher of the microbiome-gut-brain axis at the University of Oxford.
There is a recent trend toward taking probiotic supplements because we are only now realising the extent to which the gut microbiome affects us (Credit: Getty Images)
"Research shows that if we take gut bacteria from depressed humans and colonise the guts of mice with it, the mice show changes in their behaviour and physiology that are characteristic of depression," she says.
Gut microbes can produce most of the neurotransmitters found in the human brain, including serotonin, which plays a key role in regulating mood. It is hoped that scientists will soon be able to understand how microbes can be used to produce neurotransmitters to treat psychiatric and neurologic disorders liked to our microbiomes, including Parkinson's disease and multiple sclerosis.
Behaviour
We’ve also started to glimpse how gut microbes can influence behaviour. Some studies, largely conducted in animals, for example, suggest that certain types can affect brain chemistry and behaviour to make animals act more socially.
Germ-free animals who've had no exposure to microbes, on the other hand, have shown deficits in social behaviour, and researchers have found that this can be restored by adding specific types of bacteria such as Lactobacillus, often found in yoghurt, according to Johnson.
Behavioural changes are likely to be a by-product of processes that help microorganisms grow and compete in the gut, such as fermentation
A recent paper titled 'Why does the microbiome affect behaviour?' examined the theory that the gut microbiome has evolved to manipulate its human host for its own success, much like parasites, by making the host more sociable in order to be transmitted.
The paper argued, however, that this theory is unlikely, and behavioural changes are likely to be a by-product of processes that help microorganisms grow and compete in the gut, such as fermentation.
"The gut microbiome is so diverse that, even if there was a type of bacteria producing active chemicals to manipulate our behaviour, this bacteria would quickly be outcompeted by other bacteria not investing any extra energy to produce the compound," says Johnson, one of the paper's authors.
The future
Science has not yet defined what a healthy microbiome looks like, and a conclusion appears some way off yet. But there is growing consensus that environmental factors, such as diet and antibiotics, affect our microbiome more than our genes, and that a more diverse microbiome is better for us.
"While we can change our microbiome with our diet, they seem to have a set point to which they often return after a temporary disturbance," says Johnson. "But one thing we can do is eat more fibre, to increase the diversity of the gut, which is frequently associated with health."
While there have been many advancements within microbiome research in recent years, there also remain some challenges.
One of these is the reliance on a method called 16S rRNA sequencing, says McDonald, which looks at a specific region of a single gene believed to exist in all bacteria. E. coli is an example of why this method is too broad, McDonald says.
It has been proven that antibiotics can have a powerful effect against gut bacteria (Credit: Getty Images)
"While there are pathogenic E.coli, there are also E.coli that play a neutral or beneficial role in the gut, which would all be indistinguishable with the current method we use. An increase in the level of E.coli doesn't mean it's bad for you."
McDonald's advice is that we should remain cautious.
"There are a lot of cool things microbiome research will lead to, and there are exciting developments going on now, but while continued advances will lead to improvements in health, a lot of this stuff is tied up in basic research, and there's a lot of research we can do with mice that we can't translate to humans, because it's not safe to do so."
Simmered beef dishes were once incredibly common in Rome when butchers developed slow-cooked recipes to tenderize tough cuts of beef. Today, meat is much more affordable than it used to be, so some of those traditional dishes have fallen out of fashion.
At Mordi E Vai in the Testaccio Market, however, allesso di bollito – simmered beef – is very much alive. The stall serves the tender meat on bread dipped in the meat’s savoury juices and the sandwich is one of the most delicious revived classics the city has to offer.
2. Artichokes
This flavourful thistle has become somewhat of an ambassador for Roman food and carciofi alla giudia (Jewish style fried artichokes) appear on every gastronomic traveler’s hit list. Due to the demand from both tourists and locals, you can find artichokes sold in markets and served in restaurants all year-round.
But for a taste of the carciofo romanesco (the celebrated local globe artichoke) visit Rome in the colder months when it’s in season. Aside from the famous fried preparation which is popular in the Ghetto, Rome’s historic Jewish quarter, you’ll find carciofi alla romana (artichokes simmered with oil and herbs) on just about every menu.
3. Cacio e Pepe
The clue's in the name for one of the city’s most iconic pasta dishes, cacio e pepe: “cacio” is the local word for Pecorino Romano, a salty, aged sheep’s milk cheese, while “pepe” means black pepper.
The two ingredients are combined with cooked pasta and a bit of its cooking water, then stirred vigorously to create a smooth sauce. You’ll find a brilliant version at Salumeria Roscioli, whereas Cesare al Casaletto is known for its loose and more liquid variation on the classic dish.
4. Carbonara
Many dishes in Rome inspire passionate debate and carbonara is the focus of the most spirited ones. Every cook and eater has very strong opinions about the dish’s origins and ingredients and is totally inflexible when confronted with variations. There's one thing all Italians agree on however: carbonara should never have cream added to it.
Generally speaking, the dish is made with spaghetti or rigatoni, guanciale or pancetta, egg yolk or a whole egg, Pecorino Romano or a combination of Pecorino Romano and Parmigiano-Reggiano, and black pepper. The eggs are gently heated to create a thickened sauce, which should cling to the pasta for a silky and non-scrambled effect.
5. Gelato
Rome is home to thousands of gelateria selling scoops of classic flavours and whimsical originals. With such a glut, virtually every Roman has access to gelato en route to work or home, so it should come as no surprise that many locals enjoy this frozen treat on a regular basis.
While there’s certainly plenty of tempting gelato around, not all shops are created equal and relatively few use all-natural ingredients—for proof just peek at the ingredients list posted in most shops and you’ll be shocked at how many vegetal oils, artificial colors, and other junk appear—so stick to places like Otaleg, Fatamorgana, and Fior di Luna.
6. Maritozzi
These days, Rome’s go-to breakfast pastry is the cornetto, an industrially produced, margarine-based faux croissant. But in the past, maritozzi ruled. These sweet, leavened buns are sliced open and filed with barely sweetened whipped cream.
At Regoli, a historic bakery near Piazza Vittorio, maritozzi are heaped with whipped cream and displayed at the entrance. There’s no glamourous way to eat these cream-filled treats, so consider yourself warned.
7. Pizza al Taglio
Pizza has a fairly broad meaning in Rome and the word is applied to a range of flatbreads and round personal pizzas. Pizza al taglio (pizza by the slice) is a distinctly Roman style of pizza and features either adorned dough cooked in sheet pans or worked into an oblong shape, then baked.
In all cases, the pizza is served by the slice and is cut with a knife or scissors into the diners’ desired portion. Depending on the joint, the pizza may be served folded or on a tray, but it’s always served in a casual way with no frills and no table service.
8. Porchetta
Porchetta is a deboned, slow-roasted pig. The precise cuts may vary but often include belly and loin seasoned with salt, pepper, and herbs. Although porchetta is pretty ubiquitous and appears at takeaway joints and delis as a sandwich filling, a truly exceptional specimen can be elusive.
For a truly delicious, moist, and perfectly seasoned porchetta experience, visit Panificio Bonci near the Vatican and order slices of pork sandwiched between crispy pieces of pizza bianca, the simple local flat bread.
You’ve doubtless had the experience when, across a noisy, crowded room, you lock gazes with another person. It’s almost like a scene out of the movies – the rest of the world fades to grey while you and that other soul are momentarily connected in the mutual knowledge that they are looking at you and you at them.
Of course, eye contact is not always so exciting – it’s a natural part of most casual conversations, after all – but it is nearly always important. We make assumptions about people’s personalities based on how much they meet our eyes or look away when we are talking to them. And when we pass strangers in the street or some other public place, we can be left feeling rejected if they don’t make eye contact.
This much we already know from our everyday experiences. But psychologists and neuroscientists have been studying eye contact for decades and their intriguing findings reveal much more about its power, including what our eyes give away and how eye contact changes what we think about the other person looking back at us.
You may have noticed these effects particularly strongly if you’ve ever held the intense gaze of a monkey or ape at a zoo: it is almost impossible not to be overcome by the profound sensation that they are a conscious being judging and scrutinising you. In fact, even looking at a portrait painting that appears to be making eye contact has been shown to trigger a swathe of brain activity related to social cognition – that is, in regions involved in thinking about ourselves and others.
Research shows that gazing eyes command our attention (Credit: Getty Images)
Not surprisingly, the drama of realising we are the object of another mind is highly distracting. Consider a recent study by Japanese researchers. Volunteers looked at a video of a face while simultaneously completing a word challenge that involved coming up with verbs to match various nouns (to take an easy example, if they heard the noun ‘milk”, a suitable response would be “drink”). Crucially, the volunteers struggled much more at the word challenge (but only for the trickier nouns) when the face in the video appeared to be making eye contact with them. The researchers think this effect occurred because eye contact – even with a stranger in a video – is so intense that it drains our cognitive reserves.
Similar research has found that meeting the direct gaze of another also interferes with our working memory (our ability to hold and use information in mind over short periods of time), our imagination, and our mental control, in the sense of our ability to suppress irrelevant information. You may have experienced these effects first hand, perhaps without realising, whenever you have broken eye contact with another person so as to better concentrate on what you are saying or thinking about. Some psychologists even recommend looking away as a strategy to help young children answer questions.
Too much eye contact can also make us uncomfortable and people who stare without letting go can come across as creepy
As well as sending our brains into social overdrive, research also shows that eye contact shapes our perception of the other person who meets our gaze. For instance, we generally perceive people who make more eye contact to be more intelligent, more conscientious and sincere (in Western cultures, at least), and we become more inclined to believe what they say.
Of course, too much eye contact can also make us uncomfortable – and people who stare without letting go can come across as creepy. In one study conducted at a science museum, psychologists recently tried to establish the preferred length of eye contact. They concluded that, on average, it is three seconds long (and no one preferred gazes that lasted longer than nine seconds).
The drama of realising we are the object of another mind is highly distracting (Credit: Getty Images)
Another documented effect of mutual gaze may help explain why that moment of eye contact across a room can sometimes feel so compelling. A recent study found that mutual gaze leads to a kind of partial melding of the self and other: we rate strangers with whom we’ve made eye contact as more similar to us, in terms of their personality and appearance. Perhaps, in the right context, when everyone else is busy talking to other people, this effect adds to the sense that you and the person looking back at you are sharing a special moment.
The chemistry of eye contact doesn’t end there. Should you choose to move closer, you and your gaze partner will find that eye contact also joins you to each other in another way, in a process known as “pupil mimicry” or “pupil contagion” – this describes how your pupils and the other person’s dilate and constrict in synchrony. This has been interpreted as a form of subconscious social mimicry, a kind of ocular dance, and that would be the more romantic take.
But recently there’s been some scepticism about this, with researchers saying the phenomenon is merely a response to variations in the brightness of the other person’s eyes (up close, when the other person’s pupils dilate, this increases the darkness of the scene, thus causing your pupils to dilate too).
When you look another person deep in the eye, do not think it is just their pupils sending you a message
That is not to say that pupil dilation has no psychological meaning. In fact, going back at least to the 1960s, psychologists have studied the way that our pupils dilate when we are more aroused or stimulated (in a physiological sense), whether by intellectual, emotional, aesthetic or sexual interest. This has led to debate about whether faces with more dilated pupils (sometimes taken as a sign of sexual interest) are perceived by onlookers to be more attractive. At least some studies, some decades old and others more recent, suggest they are, and we also know that our brains automatically process the dilation of other people’s pupils.
Even staring at a portrait painting's eyes triggers the kind of brain activity associated with social cognition (Credit: Getty Images)
Either way, centuries prior to this research, folk wisdom certainly considered dilated pupils to be attractive. At various times in history women have even used a plant extract to deliberately dilate their pupils as a way to make themselves more attractive (hence the colloquial name for the plant: ‘belladonna’).
But when you look another person deep in the eye, do not think it is just their pupils sending you a message. Other recent research suggests that we can read complex emotions from the eye muscles – that is, whether a person is narrowing or opening their eyes wide. So, for instance, when an emotion such as disgust causes us to narrow our eyes, this ‘eye expression’ – like a facial expression – also signals our disgust to others.
Yet another important eye feature are limbal rings: the dark circles that surround your irises. Recent evidence suggests that these limbal rings are more often visible in younger, healthier people, and that onlookers know this on some level, such that heterosexual women looking for a short-term fling judge men with more visible limbal rings to be more healthy and desirable.
Look into the eys of a gorilla, and you are aware you are being scrutinised by another intellect (Credit: Getty Images)
All these studies suggest there is more than a grain of truth to the old adage about the eyes being a window to the soul. In fact, there is something incredibly powerful about gazing deeply into another person’s eyes. They say that our eyes are the only part of our brain that is directly exposed to the world.
When you look another person in the eye, then, just think: it is perhaps the closest you will come to ‘touching brains’ – or touching souls if you like to be more poetic about these things. Given this intense intimacy, perhaps it is little wonder that if you dim the lights and hold the gaze of another person for 10 minutes non-stop, you will find strange things start to happen, stranger perhaps than you’ve ever experienced before.
People are searching for veganism on Google more than they have at any point over the last year - no doubt thanks in part to Greggs's hugely popular new vegan sausage roll.
Plant-based diets are very much on the menu every January - as people try their hand at Veganuary - so it makes sense there are more questions being asked.
So we've answered some of most googled vegan-related queries to help you out:
How do vegans get calcium and protein?
It's been drilled into us all from a young age that calcium "makes your bones grow stronger" - as a well-known advert goes.
Traditionally that's been associated with animal products like milk and yoghurt.
If you're considering a plant-based diet you'll want to stock up on alternatives like lettuce, rocket salad, parsley and kale - as well as stuff you might not normally buy like edamame beans, pak choi and dried figs.
Protein can be another big worry for people trying a vegan diet.
But there's a fair amount of choice, including cheap and cheerful snacks like nuts and seeds - and the huge amount of protein bars sold these days that contain them.
Whole grains are something else to consider - you can dream up a tasty protein-packed menu by combining grains like brown rice with legumes such as chickpeas and lentils.
And you can even get pasta made of lentils these days if Indian isn't your flavour.
If you love nothing more than a can of baked beans, you're in luck - beans of all kinds can also be a good source of protein, as well as soy products like tofu and tempeh.
All these common cake ingredients are vegan to begin with or readily available in a vegan form - except the eggs.
Many vegans like to use egg replacers, which are easy to make at home.
Typical substitutes can include things like banana, flaxseed, applesauce and chia seeds.
Vegan Amy Kennedy, 21, from Essex, tells Radio 1 Newsbeat: "Vegan cakes are becoming more and more accessible, and a lot of the big supermarkets are releasing vegan cupcakes.
"A lot of biscuits are accidentally vegan too."
Are vegans against pets?
There isn't a straight yes or no answer to this one.
Amy says: "I think pets is a very blurred area for veganism, the reason being how they're acquired.
"I'm personally against pets that are acquired through pet shops due to the practices that bring the animals into existence.
"If you rescue an animal and have all the correct facilities and abilities to keep them happy and healthy I see no issue."
Raoul, from The Vegan Corner, YouTube's first professional cookery channel dedicated entirely to plant-based cuisine, says he doesn't believe vegans are against pets but it depends on how they are treated.
"For example, keeping a bird or a hamster in a small cage 24 hours a day for your own amusement isn't something I would personally consider a nice thing.
"I do not have pets, but I've had dogs in the past and my goal has always been to live a great life together, and in this I can't see any non-vegan behaviour."
Are vegans against wool?
Most vegans are against wool, according to Raoul.
This is because wool is obtained by raising sheep with the sole purpose of shearing their woollen fleece.
Amy says she's also against wearing wool as "it feels wrong to me to wear an animal's coat".
"If people own items that contain animal products before going vegan they should definitely re-gift them as to avoid waste."
Are vegans healthier?
Recent analysis, which compared the health of vegetarian and vegans against that of meat eaters, suggests they are.
Researchers found being a vegetarian or vegan was associated with a significantly lower risk of heart disease and cancer.
But the analysis found that being vegetarian or vegan doesn't necessarily mean you'll live longer.
Sophie Blakeley, 24, from Salford, told Newsbeat: "I'm doing Veganuary so I am more conscious of what I'm eating as well as a meat-free and animal product-free lifestyle is more ethical.
"I think some vegan diets are healthier such as the raw vegan diet and the clean eating vegan diets but there is still a lot of junk food products that are suitable for vegans so that really depends on the person's diet preference."
The definition of vegan is "a person who refrains from using any animal product whatever for food, clothing or any other purpose", according to the Collins English Dictionary.
The term is said to have been coined in the 1940s by Donald Watson, the founder of The Vegan Society, as a way of describing non-dairy vegetarians.
"Most of the labels like pescatarian, freegan, and lacto-ovo vegetarian, are created to identify one's way of eating, while being vegan is not something related to food only, but a way of living aimed at reducing any sort of animal exploitation," says Raoul.
"It is a common mistake to think that a vegan is simply someone who doesn't consume animal products, as the reality is much deeper than “that”.