[Last updated 16th November, 2016]
A healthy and diverse gut bacteria is important for health.
However, an overgrowth of this bacteria in the small intestine – known as SIBO – can cause serious problems.
This article takes a detailed look at SIBO and which dietary changes are scientifically shown to help.
What is SIBO?
This is caused by a disturbance in the body’s own mechanisms to control which bacteria thrive.
Unlike the large intestine (also known as the gut or colon) which contains your gut bacteria, the small intestine should not contain a high concentration of bacteria.
SIBO is uncommon in young and middle-aged adults, but thought to occur in at least 14% of older patients on average (2).
Summary: Excessive bacterial growth in the small intestine is known as SIBO. It is much more common in the elderly.
Many SIBO patients experience different signs and symptoms.
- Nausea and vomiting
- Bloating and diarrhea
- Poor nutrient absorption leading to deficiencies
- Malnutrition and weight loss.
The intensity of symptoms can differ too.
While some patients may have diarrhea and milder vitamin deficiencies, others may experience severe nutrient malabsorption and impaired digestion (2).
Left unmanaged for several months, SIBO usually causes several vitamin and mineral deficiencies.
Vitamin B12 deficiency is one of the most common, alongside the fat-soluble vitamins such as A, D, E and K (2).
Mineral deficiencies such as iron, calcium and magnesium are also common in SIBO patients.
Summary: SIBO symptoms range from digestive stress to severe nutrient deficiencies. They are often similar to IBS.
Diagnosing SIBO: Hydrogen Breath Test
SIBO is a severely under-diagnosed condition (2).
This is because a large portion of our small intestines is impossible to reach without surgery.
It’s not perfect, but reliable enough for researchers.
Breath Test for SIBO
The two types of Hydrogen Breath Test used for SIBO are the Lactulose Breath Test (LBT) and the Glucose Breath test (GBT).
Both tests measures concentrations of hydrogen and methane in the breath.
These two gases are only produced by bacteria (in the small intestine) and not directly by humans. High levels indicate increased bacterial activity and/or overgrowth.
In order to give an accurate reading, prior to the test patients follow a specialised diet for 1-2 days that does not feed the bacteria. On the day of the test a formulated sugar drink is given in order to get a clear reading of the patient’s reaction to carbohydrates.
The test can be done with take-home kits or with your doctor in the clinic. But interpretation of results should always be with a health care professional.
Summary: The best non-invasive method for diagnosing SIBO is with a Hydrogen Breath Test.
Common Risk Factors for SIBO
Certain health conditions may increase your risk of developing SIBO:
- Chronic use of antacids: Long-term antacid use (such as omeprazole) reduces acid production in the stomach. Consistently low levels of stomach acid can lead to bacterial overgrowth in the stomach and small intestine (3, 4).
- Immunodeficiency Syndrome: Disorders that can suppress our immune system – such as AIDS and IgA antibody deficiency – provide an ideal environment for harmful bacteria to thrive (5).
- Celiac disease: Celiac disease can disturb how food moves through the intestines, particularly if it remains undiagnosed or is poorly managed. This leads to increased bacterial growth in the gut (6, 7).
- Aging: Older people in general are at increased risk for SIBO because our digestive tract gets weaker with age. This is thought to be caused by reduced physical activity, weight gain, ongoing medication use and general weakening of the gastrointestinal tract (8, 9).
- Alcoholism: Chronic alcohol consumption appears to increase risk of SIBO (10).
Summary: Your risk of SIBO is greatly increased by several conditions and factors, most often related to reduced function and efficiency of the intestines.
Diet Changes During A Bout of SIBO
Diet is the most important aspect for sustainable SIBO treatment.
An appropriate diet not only treats SIBO-related nutrient deficiencies, but can also help prevent recurrence of SIBO.
It also has a role to play during a bout of SIBO when you’re having symptoms. The following steps are a good place to start:
1. Choose easily digestible foods
As digestion and absorption of nutrients are impaired with SIBO, foods that are easily digested are recommend.
This allows the body to absorb more nutrients quickly before the harmful bacteria can interact with them (11).
Good choices include lightly steamed vegetables, ripe fruits, oatmeal, yoghurt, lean meat and fish.
2. Limit fibre when having symptoms
Foods high in fibre should be restricted if you are experiencing bad symptoms.
Fibre is a type of carbohydrate that “feeds” bacteria in the gut. In some individuals it can cause digestive stress and may also interfere with the nutrient absorption (12).
This restriction should only be temporary, however, as fibre is necessary to feed the beneficial bacteria too.
3. Drink more water
It’s important to replace those fluid losses to optimise health, particularly bowel motility.
There are no set rules for the amount each individual needs, but you should carry a water bottle with you to sip throughout the day.
Summary: Diet changes are important for both short-term and long-term SIBO treatment. Drink plenty of water and avoid high-fibre foods when experiencing symptoms.
SIBO and Antibiotics
Conventional treatment for unwanted bacterial growth is antibiotics (2).
Antibiotics are designed to kill bacteria, which is why they are prescribed when you have an infection.
Rifaximin is the most well-studied antibiotic for SIBO, with a success rate of about 50% after 1 week. A combination of rifaximin and other antibiotic, neomycin, has been shown to be around 85% effective after 10 days (14, 15).
Herbal antibiotics are also an option, with around 50% of patients who fail on rifaximin reporting success with herbal treatment (16).
However, the problem with antibiotics – pharmaceutical or herbal – is they do not differentiate between good and bad bacteria. They destroy all bacteria.
SIBO antibiotics are also only a temporary “band-aid” treatment, and do not address the root cause of the problem. This is why those only treated with antibiotics are likely to relapse and experience SIBO again (19).
So antibiotics are useful in the short-term (and often necessary), but are not a permanent solution, and certainly not a solution themselves.
Summary: Antibiotics are useful in the short-term, but patients who rely on them are likely to relapse. They also kill both bad and good bacteria, which is very harmful to health long-term.
SIBO and Probiotics
Probiotics is the name given to bacteria we intentionally eat for health benefits.
They are essentially the opposite of antibiotics (20).
It seems counterintuitive to treat SIBO – bacterial overgrowth – with additional bacteria, but recent research has seen success using probiotics instead of antibiotics.
One small study of 14 IBS patients with SIBO found that a daily probiotic drink altered fermentation patterns in the intestine, consistent with reducing SIBO (21).
Another early study found that 82% of patients receiving probiotics for 5 days reported improvements compared to only a 52% improvement in those receiving the antibiotic metronidazol. These findings are in line with previous animal studies that observed similar benefits of probiotics (22, 23).
Until we know more, antibiotics may still be required, especially for more advanced cases.
Summary: Early studies have found probiotic supplementation may help with SIBO treatment. Its effectiveness has not been proven in clinical trials though, but it’s a promising area.
Low FODMAP Diet and SIBO
FODMAPs are a type of fermentable carb common in the foods we eat.
They act as necessary “food” for our gut bacteria, but can cause severe digestive problems in sensitive people. The process of identifying and removing problem FODMAPs from the diet is known as a low FODMAP diet, and is clinically proven to treat IBS (26).
Due to this strong overlap, researchers suspect a low FODMAP diet may be beneficial for SIBO patients too, as it would “starve” the problem bacteria in the small intestine.
But current evidence is not clear.
A study on antibiotic therapy alone versus antibiotics plus guar gum supplementation (a fermentable carb) found that success rates were improved from 62% to 87% with the guar gum added (31).
This seems counterintuitive because it showed the addition of guar gum (which feeds gut bacteria) was more beneficial than harmful. It’s also in line with studies showing probiotics – additional bacteria – are beneficial.
It seems the low FODMAP diet may be helpful when starting off, but requires a bit more flexibility for SIBO when reintroducing fermentable carbs. To learn more about the Low FODMAP diet, click here.
Summary: A low FODMAP diet may help initially by “starving” the problem bacteria in the small intestine. But studies have not yet confirmed it as a reliable SIBO treatment.
SCD and GAPS Diet Plan for SIBO
There is a lot about gastrointestinal diseases and conditions that science does not yet understand.
SIBO is no exception, which is why the perfect diet plan just doesn’t exist yet. Several potential diets have emerged that are worthy of consideration, but we should be cautious and only trial them under medical supervision.
The following two diets are well-supported by anecdotal evidence (testimonials):
The Specific Carbohydrate Diet (SCD) claims to help treat several forms of bowel disease.
This includes ulcerative colitis, Crohn’s disease, diverticulitis and celiac disease.
- Meat, chicken, fish, eggs, some legumes, lactose-free dairy, ripe fruit, non-starchy vegetables, nuts and seeds, and honey.
Foods not allowed:
- All grains, starchy vegetables (such as potato, corn), regular dairy, some legumes, sugar.
Basically it shares many similarities to the low FODMAP diet, but without the scientific evidence or credibility.
The Gut and Psychology Syndrome diet (GAPS diet) is similar to SCD but with a few modifications.
It contains a different introductory phase, fewer legumes, and dairy protein is reintroduced more slowly.
There is some anecdotal evidence to support it, but these are for autism and other conditions related to brain function (hence the name), rather than digestive issues.
There are no studies of the GAPS diet in the medical literature, and the creator makes a lot of extraordinary claims which is often a red flag.
Summary: The SCD and GAPS diet have emerged as potential diets to help treat SIBO, however neither was actually designed for this condition. They may be useful, but are not evidence-based.
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Overall Recommendation for Diet and SIBO
It reportedly takes about 2 to 5 years on average for SIBO to be completely corrected.
For this reason it’s important to explore the different treatment options and find what works for you. Unfortunately, there is no single diet guaranteed to treat SIBO 100% effectively.
From the weight of evidence, it seems like 1 week of antibiotics is warranted first in order to deal with acute symptoms. This should be followed by a revised long-term low FODMAP diet (ensuring not to “starve” bacteria) alongside consistent probiotic supplementation.
This all needs to be done under the supervision of your doctor and dietitian.