What Causes Food Intolerances?
Nobody really knows for sure what causes food intolerances. Research is beginning to help us uncover some of the likely ...
Twenty years ago, almost nobody had heard of SIBO: most experts thought it was a rare disorder that only happened after surgery on the gut. Fast forward to today, and it’s widely acknowledged as one of the major causes of IBS. Read on to find out all you need to know about SIBO.
What Is SIBO?
Why Does SIBO Happen?
How Common is SIBO?
What Are The Symptoms Of SIBO?
What diseases are linked to SIBO?
How Does Small Intestinal Bacterial Overgrowth Affect Us Long Term?
How Do You Know For Certain If You Have SIBO?
What Happens If SIBO Is Left Untreated?
Can SIBO Go Away On Its Own?
How Do I Get Rid Of SIBO?
What Foods Should Be Avoided With SIBO?
SIBO: Is It Auto-immune?
Is IBS Really SIBO?
SIBO stands for small intestinal bacterial overgrowth.
If you have SIBO, it means you have too many bacteria living in your small intestine, where numbers should be much lower than in your lower intestine, or colon.
Your small intestine should house less than 10,000 bacteria per millilitre of fluid. Your large intestine, or colon is home to a staggering 1,000,000,000 bacteria per millilitre of fluid. And, because your small intestine has a different role to play in your digestion to your large intestine, the types of bacteria that live there are a bit different too (Source: NCBI).
Your small intestine does a lot more work than its larger counterpart when it comes to digesting food and absorbing nutrients. It is also an important part of your immune system, containing an impressive network of lymphoid cells (cells of the immune system that help fight infections and regulate the immune system) (Source: NCBI).
The finding that there are ‘normal’ bacteria that live there, and that they do essential jobs, is relatively new: until the end of the last century most experts believed that the small intestine was free of bacteria in most people (Source: PUBMED), but we now know that a balanced microbiome in the small intestine is important for many reasons (Source: NCBI). For instance:
SIBO can happen for a number of reasons. Here are just a few:
Your stomach acid kills the bacteria that you swallow along with your food. If you don’t have enough, they can find their way into your small intestine and multiply (Source: PUBMED).
Bile is another substance your body uses to defend the small intestine against invading bacteria. Insufficient levels of bile can allow bacteria in the small intestine to get out of control (Source: NCBI).
If your body isn’t producing enough digestive enzymes, your food can remain in your small intestine and instead of feeding you, feed your bacteria (Source: PUBMED), encouraging numbers to grow.
Many researchers have noted a link between SIBO and something known as post-infectious IBS (IBS symptoms that begin after a bout of food poisoning). There’s also evidence that people with SIBO and IBS have higher levels of inflammation in their guts (Source: NCBI), suggesting that an imbalanced immune reaction is at play.
Your immune system is designed to fight off any unwelcome bacteria that appear where they shouldn’t. If it’s not working as well as it should, bacteria can grow and multiply in the small intestine, resulting in SIBO.
Your ileocaecal valve is the ‘door’ that sits between your small and large intestines. It’s designed to enable food to flow down from the small intestine into the large intestine, and prevent it from going backwards. For a variety of reasons, that doesn’t always happen.
If it doesn’t shut when it’s supposed to, the hundreds of trillions of bacteria in your colon can start to migrate to your small intestine (Source: NCBI).
To push your food through your GI (gastro-intestinal) tract—the ‘tube’ that runs all the way from your mouth to your anus—your body performs a complex, tightly coordinated series of events. In between meals, your migrating motor complex (MMC) happens approximately every 90-120 minutes to sweep what you’ve just eaten through your GI tract.
Several studies have demonstrated that abnormalities in your MMC make it more likely that you’ll develop SIBO (Source: PUBMED).
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While we can’t be sure about the number of people with SIBO in the general population, some studies suggest that between 6 to 15% of healthy people with no gut symptoms have SIBO, while up to 85% of people with IBS have SIBO (Source: NCBI).
Chris Kresser, a naturopathic doctor based in the US, says that SIBO is largely under-diagnosed. “Many people don’t seek medical care for their SIBO symptoms, and many doctors aren’t aware of how common SIBO is”, he says on his website.
Dr. Hazel Veloso, a gastroenterologist at Johns Hopkins University in the US, said in the magazine for the American College of Physicians that doctors used to think of SIBO as something rare: “We were just labelling patients with IBS before, and they were not getting better because there was actually an underlying cause”, said Dr. Veloso.
The best way to test for SIBO is with a breath test measuring levels of hydrogen and methane gas. But while this is an accurate and very useful tool, the test still can give false negatives (meaning the test results come back as negative but you actually do have SIBO) (Source: PUBMED).
This is why it’s important to use the test with the guidance of an experienced practitioner who looks at your symptoms and health history—and any other test results—alongside your SIBO test results. A positive or negative SIBO test result is just one piece of your health puzzle. Good practitioners look for all the pieces to find the reasons for your symptoms.
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Many typical symptoms of SIBO are also the symptoms of IBS. Research has found that people with IBS are five times more likely to have SIBO than people without IBS (Source: PUBMED).
Common SIBO symptoms include:
Because you can have these symptoms without having SIBO, and the breath test isn’t 100 percent reliable, it’s difficult to know if you have SIBO for sure.
Again, that’s why you need the help of an experienced practitioner to guide you through the maze. While the breath test is an indispensable part of their tool kit, our Functional Medicine Practitioners and Registered Nutritional Therapists look at other clues too. Here are some examples:
Some people with SIBO can take probiotics and prebiotics without any problems, but many find their symptoms worsen (Source: NCBI). This is likely to be because they’re feeding an already overpopulated small intestine: in a ‘normal’ situation, they would simply travel through the first part of our guts and take up residence in the large intestine, where the bacteria already there work their magic with them.
With SIBO, the misplaced bacteria in the small intestine get them first, welcoming the arrival of even more new friends in the case of probiotics, and chowing down on the free party food in the case of prebiotics. Either way, the pesky bacteria give off more gases and bingo: you feel worse.
FODMAPs are special kinds of carbohydrates that bacteria love to eat. You can find out more about them, and what to do about FODMAP intolerance in our blog on the FODMAP diet and the NHS.
If FODMAP foods make your symptoms worse, it’s another red flag for SIBO (Source: NCBI). In fact, practitioners often use the low-FODMAP diet as part of a protocol to tackle SIBO.
As far back as the 1940s, doctors had identified starches and some types of fibre as contributing to digestive disease. Dr Sidney Haas was a pediatrician who treated celiac disease and other gastrointestinal disorders with the diet he developed: the Specific Carbohydrate Diet (SCD), that eliminates grains, most root vegetables, sugar and most dairy products (Source: EUROPEPMC).
The diet then fell out of favour until more research towards the end of the last century revealed that the types of carbohydrates not allowed on the SCD did indeed feed bacteria in the small intestine, and that eliminating them relieved many people of their digestive symptoms (Source: NCBI).
Another nutrient on the menu for SIBO bacteria is iron. If they eat yours before you can absorb it, you end up with an iron deficiency, which in turn may result in anaemia, or just an iron deficiency without anaemia. In either case, otherwise unexplained iron deficiency may be a clue that SIBO is present (Source: NCBI).
One of the many jobs of our beautiful bacteria is producing vitamins and nutrients to help our body work optimally. An example is folate, or vitamin B9. So if your folate levels are high on a blood test, it’s another sign you might have SIBO (Source: NCBI).
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SIBO is associated with many disorders, as a cause, an effect or as a coexisting condition: the below list is a small sample of papers from a huge amount of research looking into the links between SIBO and chronic disease.
If you have one or more of the following conditions, it could be a good idea to get a SIBO test:
At the moment, we just don’t know for sure whether SIBO affects us in the long term. We can only speculate based on what we know about how SIBO affects the small intestine: for example, we know SIBO can cause both nutrient deficiencies and leaky gut. Let’s unpack both of those.
SIBO can damage your small intestine and interfere with how you digest your food, preventing your body from getting the nutrients it needs to function at its best. This is because the bacteria and the substances they produce can harm the cells lining your small intestine (Source: NCBI), stopping them from doing their job of absorbing nutrients.
SIBO can lead to nutrient deficiencies in another way, too: SIBO bacteria can ‘eat’ your nutrients, before your body can even try to absorb them. The most common nutrients affected by SIBO include:
SIBO is linked to leaky gut: a condition where your intestinal barrier starts to let large protein molecules out into your bloodstream (Source: PUBMED). Leaky gut has been linked to a whole host of chronic illnesses, autoimmune diseases, food allergies and sensitivities (Source: PUBMED).
Although there’s definitely a connection between SIBO and leaky gut, we don’t know that one causes the other. It could be that both conditions share the same underlying imbalance (Source: NCBI).
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Unfortunately there is no perfect test for SIBO. The small intestine is a hard place to get to, so if doctors want to see or take a sample from it, endoscopy (a tube down the throat) only reaches into the top portion of your GI tract, and a colonoscopy (a tube up your bottom) only reaches into the large intestine. The whole part in the middle, which is about 17 feet long, is only accessible with surgery or a wireless capsule.
Stool testing is a fantastic way to get a window into the goings-on of your gut, but it mostly gives a picture of the large intestine. Luckily, there is an easy to use, non-invasive test that scientists, doctors and practitioners all over the world routinely use: the hydrogen and methane breath test.
The SIBO test measures the hydrogen and methane gas produced by bacteria in the small intestine.
If you decide to take a SIBO test, you’ll get a sugar solution to drink. Soon after you drink it, the solution hits your small intestine, where the bacteria there eat those sugars and produce gases. Small amounts of gas are normal, but larger amounts mean there’s too many bacteria there, and you have SIBO.
You expel 80% of this gas through your intestines, but the other 20% is absorbed into your blood. By measuring the levels of gases in your breath, a lab can estimate the degree of bacterial overgrowth.
So, technicians at the lab aren’t measuring the actual bacteria, but looking at the levels of the gases to estimate the numbers of bacteria. Because the gases they’re measuring (hydrogen and methane) are gases produced by bacteria, not by humans, we know that levels of those gases present in your breath reflect levels of bacteria in your small intestine.
Some SIBO breath tests only measure hydrogen, but it’s better to measure hydrogen and methane to get a more accurate picture of potential overgrowth. Here at Healthpath, we perform a hydrogen and methane SIBO test.
Healthpath’s at-home SIBO breath test is easy to use, and comes with simple instructions to guide you through. You can read more about it on our blog: SIBO test: all you need to know.
There are some things you need to be aware of well in advance of taking the actual test:
When you’ve finished the test, you’ll need to send back the bags (with your breath in them!) to our lab. You should get the results within seven working days.
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Because SIBO has only been recently widely recognised as a potential cause or complication of chronic conditions, we can’t say for sure if any disease is a direct consequence of leaving SIBO untreated. However, on top of the conditions listed under ‘Symptoms Of SIBO’ above, the following conditions have strong links to SIBO:
SIBO has also been associated with various types of cancer, mostly in the digestive tract (Source: NCBI). It’s really important to say here that this doesn’t mean if you have SIBO, you’ll get cancer. It could be that there are underlying reasons why people get SIBO—for instance, a problem with immunity—and it’s those things that make it more likely that someone will develop cancer, not the SIBO itself.
It could also be that the SIBO developed after the cancer for the people in these studies. Like so many questions on health and disease, we just don’t have the answers yet.
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The only truthful answer at this stage is: we don’t know if SIBO will go away on its own. At Healthpath, we believe that there’s a reason you got SIBO in the first place. If you want to tackle your SIBO symptoms and beat them long term, you need to fix the underlying imbalances.
If you have symptoms of SIBO, like diarrhoea, constipation or bloating, you probably don’t want to wait to see if they go away on their own. If you think you have SIBO, the best plan of action is to take a SIBO test and talk to an experienced practitioner who can guide you through the results and what to do next. Here at Healthpath, every SIBO test comes with advice from a Registered Nutritional Therapist or Functional Medicine Practitioner, so there’s no need to pay separately for guidance on what to do after a positive result.
Because SIBO is a sort of dysbiosis (an imbalance of the bacteria and other microbes in your gut) it’s possible that changes in your lifestyle or environment could re-balance your microbiome and squash your symptoms (see below for more on that line of thought). For instance, it’s quite common for pregnant women with IBS to go into ‘remission’, and stay symptom-free after the baby is born. The opposite can also happen: women can develop IBS symptoms in pregnancy that persist after the birth (Source: NCBI).
This is likely to be because pregnancy induces changes in a woman’s microbiome: it usually results in a drop in diversity of the species that reside in the gut (Source: NATURE). So, it makes sense that if one of the species that disappears is one that contributes to her gut symptoms, pregnancy may resolve those issues permanently.
Many people find lifestyle changes help their SIBO symptoms. Anything that calms you down and reduces stress chemicals in your body has a direct impact on the gut (Source: NCBI). So much research now backs this up that nobody can credibly argue with it: stress is one of the top enemies of good gut health (Source: NCBI).
The bottom line? Although there’s no studies on whether or not SIBO can go away on its own, we know that your gut is incredibly responsive to your environment. While diet is arguably the most important factor, we know other factors like stress, hormonal fluctuations (like pregnancy or the menopause) or exercise levels have a massive impact on your gut health.
So while you can ‘get rid’ of SIBO with various antimicrobials and antibiotics, that’s only one element of a much bigger plan you need to employ if you want to beat SIBO long term.
Which brings us to…
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As SIBO is an overgrowth of bacteria in the small intestine, you might assume that if you get rid of the bacteria, it will get better.
That’s partly true. But SIBO is a complex condition, and everyone responds differently to treatment. While some people find relief soon after they begin a SIBO protocol, and manage to stay symptom free for good, others may need to try a few different avenues before they feel better.
Eradicating, or at least lowering the numbers of bacteria in your small intestine has a good chance of working to reduce your SIBO symptoms (Source: BSG). Plenty of studies prove this, but each approach has varying results, and even the same approach yields different results in different studies, so there’s no guarantee the approach you go for will work right away.
Looking at all the research carried out over the last two decades or so, it’s clear that completing one or more courses of antibiotics (only prescribed by doctors) or antimicrobials is the most important part of tackling SIBO (Source: NCBI).
Conventional doctors use antibiotics to treat SIBO, while a Functional Medicine Practitioner/Registered Nutritional Therapist will usually use a combination of antimicrobial herbs, along with other nutrients, digestive aids and methods to support gut healing and health.
Because SIBO was only accepted by the medical establishment as a legitimate condition not so long ago, right now, the NHS doesn’t have a standard way to approach it. Currently, many of the NHS trusts that test for SIBO only test for hydrogen levels, meaning that if you have methane SIBO, you’ll get a false negative result.
If you go to your GP with symptoms of SIBO, they won’t necessarily refer you to a gastroenterologist, who can give you the breath test. On the other hand, they might. It depends on your district, your GP, and the information you tell them.
If you do see a gastroenterologist, and you get a SIBO test, a positive result will usually mean you’ll get a course of antibiotics. Your doctor will decide which antibiotic is appropriate, and for how long you should take them.
At Healthpath, we believe that there’s a reason why you got SIBO: at least one underlying issue that ‘allowed’ too many bacteria to set up shop in your small intestine.
So while it’s important to address SIBO with an antimicrobial protocol, it’s also crucial to address the root cause, because if you don’t, it’s likely to come back: one study showed 44 percent of patients who had cleared SIBO (proved by a ‘normal’ breath test result) saw it return within nine months (Source: NCBI). However the authors noted that the underlying causes of SIBO were not investigated or addressed in any of the participants.
The protocol your Healthpath Functional Medicine Practitioner or Registered Nutritional Therapist gives you depends on whether you have hydrogen or methane overgrowth. You can also have suspected hydrogen sulphide SIBO: this gas isn’t measured on the test but there are pointers that suggest it’s likely.
Tackling SIBO for good means not just getting rid of the bacteria, but improving the ‘terrain’ of the digestive system as a whole. We treat every person as an individual. Some of the tools we might use include:
There are several diets like this, such as the low-FODMAP diet, the Specific Carbohydrate Diet and the Bi-Phasic Diet. We create a SIBO diet guide for everybody who gets a positive result.
The antimicrobials you’ll take depend on whether you have hydrogen, methane or hydrogen sulphide-predominant SIBO, but common choices include oil of oregano, berberine, neem and garlic.
The jury is still out on whether probiotics and/or prebiotics help or hinder SIBO. Everyone appears to have a different response.
Studies suggest that the species Lactobacillus casei, Bifidobacterium breve and Bifidobacterium bifidum (amongst others) are effective against SIBO (Source: PUBMED).
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Bacteria primarily eat carbohydrates (Source: NCBI), and they favour some more than others. Certain types of bacteria also prefer certain kinds of carbohydrates (Source: NCBI).
The diet with by far the most weight of evidence behind it for tackling SIBO is the low-FODMAP diet, which restricts the carbohydrates most bacteria love to munch. You can read all about it on our blog NHS FODMAP diet: the complete guide.
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SIBO expert Allison Siebecker says that SIBO and autoimmunity are related in several ways. “SIBO is common in many autoimmune diseases, such as IBD, scleroderma, celiac disease, and Hashimoto’s hypothyroidism, although the exact nature of these associations isn’t fully known,” Siebecker says on her website.
Leaky gut, which is often found alongside SIBO, is one of the three underlying causes of autoimmunity, as demonstrated by many studies (Source: NCBI), along with an environmental trigger (for instance stress or exposure to toxins) and your genes. “SIBO, with its high likelihood of generating leaky gut, will need to be corrected for both prevention and treatment of autoimmunity,” she says.
So while SIBO doesn’t appear to be an autoimmune disease in itself, there are strong associations between SIBO, leaky gut and autoimmune disease. We just can’t say for sure—yet—which leads to which.
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It’s estimated that up to 22% of people in the general population have SIBO, and it’s now believed to be the leading cause of IBS, with up to 85% of people with IBS symptoms testing positive for SIBO (Source: NCBI).
If you think you have SIBO, the only way to find out is to take a test. Although the test is the most reliable method we have today of determining whether or not you have SIBO (Source: NCBI), and it’s used all over the world by doctors, research scientists and health professionals, it’s not 100% perfect. That’s why it’s important to work with a Functional Medicine Practitioner or Registered Nutritional Therapist who will look at your symptoms alongside your test result to create a personal plan to tackle your SIBO.
IBS is a term given to symptoms. That means that nobody has yet identified the cause, or causes of it. So far, research is telling us that there are many reasons for the unexplained diarrhoea, constipation, bloating and pain IBS sufferers experience. While SIBO looks to be a major one of those, it’s not the only one.
As always, let your doctor know if you have the symptoms of IBS or SIBO, or if those symptoms change.
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SIBO can feel like almost anything, from a severe pain anywhere in your gastrointestinal tract (from your mouth to your anus), to feeling generally unwell, tired, depressed, or anxious.
Because SIBO can cause nutrient deficiencies, the list of how SIBO can make you feel is endless. However, the most common symptoms our practitioners hear about are:
If you’re wondering what on earth FODMAPs are, check out our blog NHS FODMAP diet: the complete guide
SIBO pain tends to be in your abdomen. That’s because the gases that the bacterial overgrowth produces can cause pressure to build up in your small intestine.
However, because SIBO also causes inflammation throughout your body (Source: PubMed), pain can appear in other parts of your body too. For example, SIBO is very common in people with rheumatoid arthritis, a painful condition where your joints become swollen and inflamed.
That’s not to say that SIBO causes rheumatoid arthritis, or that rheumatoid arthritis causes SIBO. We don’t yet know how the two conditions are connected, we just know that they often happen together (Source: PubMed).
While SIBO won’t necessarily ‘give’ you fatigue, feeling tired is a common complaint among people with SIBO, and there’s evidence that if you have chronic fatigue syndrome (CFS), you’re a lot more likely to have SIBO than someone without CFS (Source: PubMed).
There’s a lot of overlap between SIBO and IBS.
Because IBS is a label for a set of symptoms, not a disease, IBS symptoms happen alongside a lot of other conditions.
If you have diarrhoea, constipation, bloating or abdominal pain for over six weeks, your doctor will probably tell you that you have IBS. But there are reasons why you have those symptoms, and SIBO is a common one of those.
If you have IBS symptoms, you’re five times more likely to have SIBO than someone without IBS symptoms (Source: PubMed)
While IBS isn’t a disease, SIBO is, and there’s treatment for it. Treating SIBO involves either antibiotics from your doctor or antimicrobials from a Registered Nutritional Therapist or Functional Medicine Practitioner.
To get a diagnosis of SIBO, you need to take a breath test that measures hydrogen and methane. You may be able to get this from your GP, but many don’t yet recognise SIBO. If they do, they’ll refer you to a gastroenterologist who will carry out the test.
You can find out about SIBO testing on our blog SIBO test: all your questions answered.
So, if you have IBS symptoms, it’s quite likely that you have SIBO, but not definite. Other reasons for IBS symptoms include:
Of course, you could have these conditions and have SIBO too. To find out more about IBS symptoms, read our blog IBS: how can the NHS help?
In general, and according to the research, hydrogen SIBO is more likely to cause diarrhoea than methane SIBO, which is more likely to cause constipation.
However, our practitioners often see people who have methane SIBO with diarrhoea, and people with hydrogen SIBO who have constipation.
Methane has been shown to slow down the movements of your gut, causing constipation, but just because you test positive for methane SIBO, it doesn’t mean that methane gases are the only thing causing your symptoms.
The microbes in your gut produce lots of different gases. For instance, they also produce hydrogen sulfide, carbon dioxide and nitric oxide (Source: PubMed). Right now in the UK, we don’t have the testing available to measure these gases, but they could also be driving your SIBO or IBS symptoms.
A new test—developed in the US—measures hydrogen sulfide. Unfortunately it’s not available in the UK yet.
Other factors like stress, hormonal issues or medication could be affecting the movement of your gut too. So, there’s a lot more to the SIBO picture than hydrogen equals diarrhoea or methane equals constipation.
If you have SIBO, treating it is just one part of the puzzle of your health. For a truly holistic approach that can find and address the reasons you got SIBO in the first place, work with a Registered Nutritional Therapist or Functional Medicine Practitioner.
Alexandra Falconer MA (Dist) DipCNM mBANT is a Registered Nutritional Therapist specialising in IBS and related conditions. A graduate of Brighton’s College of Naturopathic Medicine, she is committed to fighting the root causes of chronic illness and bringing functional medicine to everyone who needs it.
Before her natural health career, Alex was a journalist and copywriter. She continues to write for magazines and media agencies, and now combines her two great passions—writing and health—by creating content that empowers people to claim their right to a healthy body and mind.
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