(Part 2) Irritable Bowel Syndrome: WHAT ARE THE CAUSES?




IBS and the Gut Microbiome


A potential cause of IBS is SIBO, or small intestinal bacterial overgrowth. SIBO occurs when the bacteria that live normally in the large intestine move up into our small intestine, causing unwanted bloating and gas production. As the research into the gut microbiome continues to grow, more and more studies are finding that IBS is very much correlated to our gut bacteria and how we feed our gut bacteria through our dietary choices.


Our gut microbiome plays a huge part in the gut-brain axis, in other words, the connection between our gut and brain. This connection seems to be responsible for the majority of symptoms that are present with this disease. The gut-brain axis is made up of both the human nervous system and our gut bacteria that is housed primarily in the large intestine. Rather than the brain sending the signals and the gut listening, the gut also appears to have its own “voice” mainly through the microbes that live in our colon.

Essentially, when these microbes are unhappy because of poor dietary choices, genetic influences, or even environmental factors, the gut becomes irritated or inflamed. This then causes the symptoms that are largely associated with IBS. This is one major theory of how IBS symptoms have come to be. However, there is still new research literature appearing every day about the relationship between the gut microbiome and the brain.


Are restrictive diets good for IBS?

Ok, so if my dietary choices affect my microbiome, what types of diets should I be on? Depending on who is on your care team, a restrictive diet might be on the table for you. Currently, however, restrictive diets are controversial in the treatment of IBS. It’s important to note that removing common trigger foods, like gluten, may be a good place to start if you want to reduce symptoms. Though only a small portion of the population have Celiac's disease, gluten is associated with inflammatory gut symptoms. Egg whites, lactose or dairy products can also be inflammatory for many people. Eliminating these common trigger foods can help in alleviating symptoms and finding remission. In some cases, restricting major inflammatory nutrients and foods can be beneficial, though extremely restrictive diets that remove a significant category of food are also controversial and have a higher likelihood of causing longer term issues.

In current literature, one of the most common treatments for IBS specifically are systematic restrictive diets-- the most common is the low FODMAP diet. This diet has become more and more popular (similar to the gluten-free and dairy-free diets), however it is controversial, and may not be a life-long diet. FODMAPs stand for the fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These are compounds that are found in food that tend to cause more gas and bloating within an individual who is dealing with IBS. Working with a dietitian who is trained in this diet can be helpful for immediate remission, however the foods that have “high FODMAPs”-- which are the ones that would be temporarily eliminated from the diet-- are often good prebiotics, and important in facilitating a #GoodGut microbiome.

Experienced dietitians know, unfortunately, that when individuals remain on the low FODMAP or other restrictive diets for too long, they find that they are only able to tolerate 10 different foods while still having some symptoms of IBS. On top of that, these individuals are most likely to be nutrient deficient due to the lack of diversity in their diet. The approach that should be taken on an IBS health-focused journey is not to limit foods indefinitely, but recognize root causes and how to reintroduce fiber, and eventually tolerate problematic foods. If you start your IBS journey with a dietary restriction protocol, make sure to work with a dietitian that is experienced in gut issues, and can assure that you get all the nutrients that you need through your diet.


If you are interested in working with an RDN, we would love to support you! You can schedule a personalized visit with us and we would love to collaborate with you on your journey! We see clients from all over the world.


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