When I first got diagnosed with SIBO, my practitioner put me on the extremely restrictive Low FODMAP/SCD combination that seems to be the go to protocol by many in the SIBO community. I was on the diet for about 4 months in conjunction with herbal and antibiotic treatment. Although I was following the diet to a tee, my health continued to deteriorate. I struggled to maintain my weight, my gut symptoms were even worse than before and my hormones were cray cray. I was so afraid to feed the beast that I failed to properly feed myself.
Through this disastrous experience, I was able to come to an important realization. SIBO can’t be starved with a diet. SIBO must be killed and the underlying cause addressed in order to heal. (The only real exception to this rule would be the elemental diet, which has shown some efficacy to starve out the overgrowth, but I consider that a therapeutic treatment, not a long term diet). There are a number of different SIBO diets, but they are based on reducing or eliminating fermentable fibers in the diet. Whether it’s the Fast Tract, Low FODMAP or SCD, these diets will reduce the total bacterial load in the GI tract. In the initial stages of treatment, reducing the bacterial load is crucial and these diets can be helpful. But, in my opinion, these diets should be used as a short term therapy and not a long term prevention strategy. I think when you start using these types of diets for longer than 3 months you run the risk of creating other issues. I have compiled a list of the top 7 issues with SIBO diets:
1. Dysbiosis in the large intestine. These diets starve all your gut bacteria, not just the bacteria in the small intestine. The low FODMAP diet has been shown to reduce symptoms of IBS, but they have also been shown to significantly reduce Bifidobacterium and the total microbiota in GI tract. Interestingly enough, one study found that people with IBS had a 2-fold reduction in bifidobacteria compared to healthy controls. This leads me to wonder….if low bifidobacteria is associated with gut dysfunction, is a diet that further reduces these good bugs a good option for SIBO?
Bifidobacteria, like Lactobacillus, are essential for a healthy microbiome. They have been shown to increase transit time, promote short chain fatty acid production, protect the gut lining, increase immunity, prevent GI infections and even help in the production of bile acids. Without a healthy bifido population, SIBO will be impossible to overcome.
When we feed our good bacteria, they produce short chain fatty acids like butyrate, acetate and propionate. Butyrate is the preferred fuel for the cells lining the GI tract and increases immune function in the GI tract. Acetate and proprionate improve motility and reduce inflammation. Low levels of these acids are associated with autoimmunity and systemic inflammation.
Jeff Leach, a researcher involved in the Human Microbiome Project, points out that these acids are key to providing the optimal pH in the gut to promote the growth of good bacteria like Bifidobacteria and to prevent the growth of pathogenic bacteria. He explains that “many pathogenic bacteria are pH sensitive” and when we reduce fermentable fibers our colon becomes less acidic. He explains that this unfavorable shift is like “opening pathogen’s door.”
Chris Kresser also adds some valuable insights to this discussion. He says that many of his low carb patients that eat less than 50g of carbs a day have alkaline stool with many low SCFAs, low diversity and other markers of dysbiosis. Jeff Leach completely supports this stance, he writes “whether you draw that line at 25, 50, or 75g a day of carbs, its low I’m afraid from the perspective of your gut bugs. Especially if those carbs contain a limited amount of resistant starch and other dietary fibers – food for gut bacteria.” Most SIBO diets seem to meet the low fiber and low carb criteria that Leach warns against.
It’s not just the reduction in fiber in these diets that can be problematic, but the reduction in variety can also lead to dysbiosis. Different bacteria like different fibers. When you restrict your diet to 5 types of plants foods, you run the risk of overfeeding one bacteria and starving others, which leads to microbial imbalances.
I was able to see the unfortunate shifts from a low fermentation diet in my own gut bacteria with my pre and post treatment stool test results. I had no pathogenic bacteria before my treatment, but after months of fiber restriction and herbals, I had developed a massive overgrowth of a pathogenic bacteria called Proteus Vulgaris. Not to mention, my lactobacillus population fell sharply and my diversity was very low.
Although low fermentation diets may alleviate symptoms, they can be damaging in the long term health of your colonic bacteria. As I discussed in my probiotics post, a balanced large intestine is essential for a healthy functioning small intestine. So, we cannot treat SIBO through a singular lens that only focuses on the small intestine. The large intestine bacteria play a pivotal role in restoring motility and function.
2. You need to feed the beast in order to take down SIBO. Dr. Pimental, a leader in SIBO research, has said that “happy and well fed bacteria are more sensitive to antibiotics and easier to kill.” He recommends his patients eat plenty of fermentable foods during treatment to keep them active so that the antibiotics can effectively wipe those bad bugs out!
There is growing scientific evidence to support this feed to kill concept. A recent study found that eradication rates improved from 62% to 87% when Rifaximin was used in conjunction with a prebiotic (guar gum) compared to treatment with Rifaximin alone. The researchers concluded that “the prebiotic effect of PHGG (partially hydrogenated guar gum) is likely to provide a synergistic action with rifaximin inside the bowel lumen, by improving intestinal clearance and favouring the microflora balance.”
Kelsey Marksteiner, a dietician that specializes in digestive health, recommends that her clients undergoing SIBO treatment eat as many FODMAPs as they can tolerate and at the very least 100g of carbs a day. As far as what the best diet is after treatment, she writes “in my eyes, that’s the million dollar question right now and it’s a question we don’t have the answer to quite yet.” Until that question gets a clearer answer, she recommends her clients eat a whole foods diet and to avoid foods that cause symptoms.
Based on these insights, prebiotic foods should be seen as powerful tools in helping to eradicate the overgrowth. During pharmaceutical or herbal antibiotics, (in my opinion) you should eat all the prebiotic and high FODMAP foods that you can tolerate. Although, I don’t think this warrants a junk food bingefest that many SIBO sufferers indulge in while they are on antibiotics. Junk food, while tasty, can induce intestinal permeability and inflammation that is preventative to healing. But, luckily there are plenty of nutritious and tasty whole food FODMAPs that you can eat instead! Onions, garlic and apples oh my!
3. These limited diets are a recipe for nutrient deficiencies. When you are on a really restrictive diet and eliminating foods that you may tolerate just fine, your diet is at high risk of developing nutrient deficiencies. Nutrient deficiencies can effect virtually every aspect of health. And when you are battling SIBO, nutrient deficiencies become even more problematic.
In a recent webinar, Kiran Krishnan, a Microbiologist specializing in the microbiome, discussed how really restrictive diets can disrupt the healthy function of the immune system in the gut by reducing the secretory IgA in the gut mucosa. Secretory IgA is an antibody found in the mucous layer above the gut lining that serves as the first line of defense in protecting us from toxins and pathogenic microorganisms that we consume. It is important to remember that food, bacteria and toxins have to absorb through the gut lining in order to truly enter the body. IgA neutralizes any threats in the mucous on top of the gut lining in order to prevent entry into the body.
In terms of SIBO, IgA is essential for fighting off and preventing overgrowths of bacteria in the small intestine. When IgA becomes low, bacteria, toxins and food will bypass the mucosa causing an immune response which creates an inflammatory cascade in the body. The immune cells in the gut lining essentially think they are under attack and this chronic over stimulation of our immune system can lead to both immune and gut barrier dysfunction. So, when levels of IgA are low, your immune system won’t be able to remove unwanted pathogens and your gut will be inflamed preventing SIBO recovery.
Krishnan says that when individuals with gut issues and food sensitivities limit the diversity of their diet, their secretory IgA usually declines. He attributes this mostly to nutrient deficiencies that ensue from a restricted diet. Zinc, vitamin C, selenium, choline, glutamine, glycine and omega 3 fatty acids are key nutrients for IgA formation.
Based on the restrictive diets that I have observed in various online SIBO groups, I think many SIBO suffers are at higher risk of Vitamin C deficiencies since they avoid fruit and many cruciferous vegetables that are high in C. If your diet is limiting in foods that provide the nutrients necessary for IgA, you may consider broadening your diet or supplementing accordingly.
Krishnan also mentions that diversity in the large intestine is also associated with higher levels of IgA. So eating chicken, carrots and zucchini at every meal is going to result in lower microbial diversity and lower IgA. Eating as diverse a diet as possible while treating SIBO is therefore going to be important in maintaining healthy IgA levels.
4. If you starve your gut bacteria, they could start eating you. In a recent interview, Stanford microbiome researcher, Dr. Justin Sonnenburg, stated “when you starve these microbes they start eating you. When you don’t eat dietary fiber…you are forcing the microbes into a position where they are forced to consume the important immunological barrier in your gut.”
The important immunological barrier that Dr. Sonnenburg is referring to is the gut lining. Above this gut lining, is a mucous layer that serves as a protective buffer preventing direct contact of the epithelial lining with bacteria and toxins. This mucosa also serves as a habitat and food source for our colonic bacteria. When your mucous layer is thin, bacteria and toxins will come into contact with the epithelial lining and elicit the same inflammatory immune response that occurs from low IgA.
The goblet cells within the gut lining produce mucins, which are the building blocks of the mucous layer. The primary fuel source for these goblet cells are the short chain fatty acids that are the product of intestinal bacteria fermenting fiber. So, when you don’t eat fiber, your goblet cells can’t produce enough mucous. Without fiber and mucous, the bacteria become ravenous, eating through all the mucosa and they will eventually start consuming your gut lining. This degradation of the gut barrier will not only lead to gut dysfunction, but system wide inflammation.
SIBO suffers, myself included, are guilty of demonizing fiber to such an extent that we lose sight of how important it is to the overall health of our digestive system. We must not fear fiber. Fiber helps keep a mucous rich digestive tract ensuring a strong gut barrier.
5. It is very easy to under eat and maintain a healthy weight. When you are following a strict low carb low fermentation SIBO diet, it becomes much more difficult to consume the right amount of calories. I am not saying that it can’t be done, but I think the restrictions lead many to under eat.
I become alarmed when I read post after post from SIBO sufferers on Facebook who are struggling to keep weight on and are continuing to drop more foods from their diet. I personally lost 15 pounds in the first 2 months of being on the low FODMAP/SCD combo, which contributed to my low energy levels and hormone dysfunction. With a considerable amount of effort and tweaking, I was able to add more fats to maintain my weight for the remaining months that I was on the restricted diet.
I think there are 3 main reasons people tend to under eat on these diets. First, most people don’t increase their fat intake to compensate for the decrease in carbohydrate intake. You need to eat multiple tablespoons of fat at each meal in order to maintain your weight on these types of diets. And, when you are switching from a more balanced higher carb diet, it can be difficult to grasp the boat loads of fat you will actually need to maintain your weight.
Second, when you are so limited, nothing sounds appetizing and you just don’t eat. I experienced this first hand when I was eating the same 10 foods on a regular basis. Eating became a chore.
Third, eating a high fat/high protein diet can cause hormonal shifts that reduce appetite, creating a vicious cycle of undereating that is hard to overcome. A high fat or high protein meal that is typical of a SIBO diet can trigger the release of the hormone cholecystokinin into the small intestine. This hormone sends signals to the brain that produce a sense of fullness and satiety. This fullness can cause problems because your appetite doesn’t match your calorie needs. I was never hungry while eating the high fat and high protein meals, which led me to under eat.
The consequences of chronic undereating are vast, but perhaps the most detrimental consequence (in terms of SIBO) is the rise in the stress hormone cortisol. Essentially cortisol activates your sympathetic nervous system and your “fight or flight” response. Your body can not properly digest and absorb food when you are in this “flight or fight” mode. Instead, your parasympathetic nervous system needs to be activated in order for you to enter into “rest and digest” mode. With this rest and digest mode disrupted, high cortisol can slow digestion and increase inflammation in the GI tract both of which will hamper recovery.
I am hoping to go into detail about the stress gut connection at some point in the future so stay tuned, but if you want to learn more info now I highly recommend this podcast episode of the Ancestral RDs podcast.
It is crucial that whatever diet you choose to adopt, that you can do so without starving yourself. The first priority of any diet should be to provide enough calories to maintain a healthy weight. Starving your gut bugs should always take a back seat if you are struggling to keep the pounds on.
6. Promotes food related anxiety and stress. I tend to believe that the stress of maintaining these restrictive diets tends to outweigh the benefits. Being constantly worried about how you are going to react to a food activates your sympathetic nervous system and can lead to a chronically elevated cortisol levels. When I was on the diet, I always felt like I was walking on thin ice and even consuming one Brussel Sprout was going to send me crashing through the ice. All this stress seemed to make my digestion even slower
Plus, the restrictions can lead people to social isolation, because they don’t want to go out to eat with friends or go to parties with foods they cannot eat. This isolation can (in my opinion) be just as detrimental to a person’s recovery as eating a food on the naughty list.
A better solution would be to adopt a diet that you know you can maintain that will allow you to minimize symptoms without stressing you out or hindering all of your social interactions.
7. Many low carb SIBO diets totally disrupt thyroid function. Many SIBO experts seem to preach that the lower the carb intake the better when dealing with SIBO. Usually this leads to a severe restriction of starches and fruits and the adoption of a more fat based diet. A long term adoption of a low carb diet can lead to thyroid dysfunction.
Insulin is needed in order to convert T4, the inactive thyroid hormone, into T3, the active thyroid hormone. If you adopt a ketogenic (very low carb diet) diet, your insulin production will be low and your conversion of T4 to T3 could be negatively affected. The low levels of T3 will present with all the unfortunate symptoms of hypothyroidism. As I discussed in my last post, thyroid hormones are essential for the gut motility and immunity in the GI tract. If your diet is inducing low T3 production, then your motility will slow and exacerbate your SIBO symptoms.
When you eliminate starches and many fruits, it can be very hard to get enough carbohydrates to maintain proper thyroid function. I have seen many experts recommend that SIBO patients should stay below 50g of carbs a day. In my opinion, this level of carb restriction is unnecessary and can be detrimental to your hormones if maintained for long periods of time.
So, what diet is right for SIBO?
I don’t have a clear answer, but I think removing any food that could potentially feed the bacteria will create more problems than it will solve. I think a short term low FODMAP or fermentation diet may be helpful during the initial phases of eradication and healing, but reintroducing fermentable fibers in the diet becomes crucial for reestablishing balance further downstream in the large intestine to correct the root of the SIBO problem.
Finding the optimal diet for SIBO treatment and prevention should be determined on a case by case basis. You should not be afraid to experiment to find the right diet for you! It wasn’t until I broke free from the constraints of the expert endorsed SIBO diet that I began to make improvements.
Tips for creating your own SIBO diet:
- Embrace a whole foods diet. Remove all the processed foods and stick to fruits, vegetables, healthy fats and grass fed protein. Limiting pesticide exposure by purchasing mostly organic is also important since pesticides can create more inflammation in the gut.
- Gluten free is a must. Some may want to try grain free as well. Not only is gluten incredibly hard to break down, it can also cause intestinal permeability and inflammation in the body. Gluten causes the release of zonulin from the cells along the gut lining which causes the tight junctions between the cells to open. This causes a “leaky” gut which allows toxins, bacteria and food to escape the intestinal tract into the body. This inflammation can make it incredibly difficult to heal from SIBO. Phytates and lectins in gluten free grains can also inflame the gut and are best avoided while managing SIBO
- Limit dairy to hard cheeses, yogurts and kefir. Non-fermented dairy products are higher in lactose which is a sugar that is hard to break down in our GI tract and can exacerbate SIBO.
- Pinpoint your trigger foods. Everyone with SIBO has certain foods that they are very sensitive to and removing those items for longer periods of time while healing can be helpful. But, don’t be afraid to reintroduce them in the future!
- Trust your body. You shouldn’t base your food choices on an arbitrary list of no and yes foods. Most people have certain FODMAPs that they react to, but they do fine with others. Have the confidence that you know what foods work best for your body and don’t let anyone convince you otherwise!
- Reintroduce foods slowly. Allowing your body to adjust to foods you haven’t eaten in a while can make the transition to a broader diet much more comfortable. A few bites of a formerly forbidden food can be a good place to start. If you tolerate that, then you can add a few more bites the next time you eat it.
- Consider the large intestine implications of your diet choice. Don’t focus only on what’s happening in your small intestine and think how your diet will affect the overall landscape of your digestive system.
- Don’t focus your treatment solely on diet. No diet will fix the root cause of your SIBO. You are much better off choosing a more relaxed diet that you can comfortably maintain and turning your focus primarily on fixing the mechanisms that could be causing your SIBO like thyroid dysfunction, impaired MMC function, stress, colonic dysbiosis and other potential root causes.
- Work with a practitioner. Sometimes you may need some help from a SIBO specific practitioner to determine the best diet for you. If you feel lost and totally overwhelmed with figuring out what the heck you should be eating, consider booking a free 20 minute consult to see if I may be able to help!
Now that I have written the longest blog post ever, I am going to go enjoy some forbidden FODMAPs for dinner….until next time 🙂