Consume prebiotic fiber. Prebiotics are defined as non-digestible, fermentable carbohydrates that promote the proliferation of beneficial microorganisms in the GM (14). Prebiotic fiber increases the number of probiotic microorganisms in the GM, decreases the number of pathogenic microorganisms, and it is fermented by probiotics into short chain fatty acids (SCFAs) that are used to reduce intestinal inflammation and repair the gut lining (14,15,16,17,18). In fact, research from the American Gut Project shows that people with the healthiest and most diverse gut microbiomes are the ones who consume over 30 different types of plants per week (19).
Now, I realize that fiber is a very controversial topic in the IBD community, and for good reason. Some think fiber only exacerbates and further damages the intestines, while others think it’s necessary for optimal digestion. I think there’s truth on both sides, and here’s why. There are two main types of dietary fiber found in whole food sources. Insoluble fiber, meaning it does not dissolve in water, and soluble fiber, meaning it does dissolve in water (20). Both types of fiber are indigestible, but there is a key difference. Soluble fiber, while it is not technically digested, is fermented and broken down by probiotic microorganisms in the GM into SCFAs that are used to modulate physiological functions of the host (14). Some of the most well-known functions of these SCFAs are reducing inflammation, increasing the number of intestinal epithelial cells, providing energy for colonocytes, which are cells within the colon, and regulating the assembly of TJ proteins (14,15,16,17,18,40,41). So they literally stop inflammation, help reverse leaky gut, and repair the lining of the intestines. At the most basic level, Ulcerative Colitis is just damaged, hyperpermeable, and inflamed intestinal epithelial cells. So a quick recap- soluble fiber is a prebiotic that is fermented and broken down by probiotic bacteria in the GM to produce SCFAs that inhibit inflammation, assemble TJs, and repair the intestinal lining (14,15,16,17,18,40,41). That sounds to me like a functioning optimized gut microbiome is able to reverse and prevent Ulcerative Colitis.
On the flip-side, insoluble fiber is not generally fermented by probiotic bacteria very well, so it does not provide SCFAs that inhibit inflammation or repair the intestinal lining, or at least not to the same extent that soluble fiber does (14). Insoluble fiber does not form a gel when chewed or blended, and can irritate an inflamed and ulcerated colon. So is insoluble fiber bad? Not necessarily. I think of fiber in terms of three separate categories - soluble fiber, insoluble fiber, and roughage.
We know from the literature that soluble fiber is integral for optimizing the GM and repairing the intestinal lining. So that is something I make sure to consume. However, whole food plant based sources of soluble fiber, like fruits and tubers, always come packaged with insoluble fiber as well. Soluble fiber cannot be consumed from whole food sources without consuming insoluble fiber with it, they go hand in hand. Now when fruits and tubers are blended up they form a thick gel like mixture because of the soluble fiber content, think of applesauce and mashed potatoes (20).
But Roughage is different. Roughage is made up almost entirely of insoluble fiber with little to no soluble fiber whatsoever. Roughage typically comes in the form of leafy greens like spinach, cabbage, and kale. When leafy greens are blended they do not form a gelatinous mixture the way that fruits and tubers do because they essentially have little to no soluble fiber content. Consuming roughage while sick with IBD can wreak havoc on the already sore and ulcerated gut lining. Since roughage is mainly insoluble fiber it is virtually indigestible, it decreases stool transit time, and does not form any type of soothing gelatinous mixture. Instead, when chewed or blended, it becomes shard-like bits of fiber that can poke, scrape, or get caught on the wounds inside the intestines, causing urgency to increase, and other symptoms to worsen (20). Which is why I tried to avoid roughage as much as possible when I went through this process. But I made sure to consume foods that contain prebiotic soluble fiber in them. I did this because of the GM optimizing properties soluble fiber contains, regardless of the fact that these foods also contain insoluble fiber. The mixture of soluble and insoluble fiber is not the problem, the problem is insoluble fiber by itself which is roughage. The mixture of soluble and insoluble fiber from fruits and tubers does form a gelatinous soothing mixture, unlike roughage. However, even though fruits and tubers solubilize into a gel because of the soluble fiber, they may cause some irritation in the beginning since they contain insoluble fiber as well.
But as the gut microbiome is optimized through the intake of probiotic and prebiotic foods, the gut lining should begin to heal and that irritation should fade more and more until it’s non-existent. Again, the gut lining should heal over time from the SCFAs produced by probiotic microorganisms breaking down prebiotic soluble fiber. That is why optimizing the gut microbiome is the key to the whole healing process. Once the GM is functioning optimally, it can break down prebiotic soluble fiber into the necessary SCFAs, such as butyrate, that it needs to reduce inflammation, increase the number of intestinal epithelial cells, provide energy for colonocytes, and restore TJ proteins (14,15,16,17,18,40,41).
When beginning a GM optimizing protocol, I recommend planning out the prebiotic foods you will eat based on tolerability. I say tolerability because each individual person with IBD is likely to respond differently in the beginning to different amounts and types of fiber, even prebiotic soluble fiber from fruits, berries, roots, tubers, and certain grains. Individuals are likely to respond differently because one person may have a much higher degree of inflammation compared to another individual, and thus more susceptible to exacerbating those inflamed areas.
So, because even foods that contain mostly soluble fiber can irritate highly inflamed intestines, I would suggest splitting such a protocol into two separate phases. Phase 1 approved foods, provided in Module 4, were chosen because the majority of them are very soft soluble fiber foods and will hopefully cause as little irritation as possible. However, they will still offer much needed prebiotics that will be used to improve the GM and repair the gut lining. Certain foods in Phase 1 may still cause irritation to you depending on your levels of inflammation, among other factors, and if that is the case, do not eat the foods that cause irritation.
I regularly consumed smoothies consisting of high amounts of thoroughly blended fruits and berries while I was going through my own GM optimizing process. For those just starting out, smoothies of this nature might be fantastic for you and be very soothing, or they might simply contain too much fiber at one time, even though it’s good prebiotic soluble fiber, and exacerbate those highly inflamed areas within your intestines. So what I would recommend is this- after receiving your doctor’s approval, cautiously consume foods from Phase 1. You may choose to incorporate smoothies made with fruits and berries, or simply stick to the cooked foods that are listed. If you notice that you do not tolerate a certain food very well, avoid that food for a period of time and stick to the foods that you feel best when consuming. Over time, as the mucosal gut lining should theoretically be healing, your tolerability for foods should increase and foods that you may not have tolerated very well at first, may become foods that you do tolerate well.
Once you are able to comfortably tolerate all of the approved foods for Phase 1, or nearly all of them, you may choose to begin incorporating approved foods from Phase 2 as you deem appropriate. At this point, the process should be repeated. Avoid foods that cause irritation, and consume foods from Phase 1 and Phase 2 that do not exacerbate symptoms when consumed. Once you are able to comfortably tolerate all, or nearly all, of the approved foods from both phases, you may now begin to choose to add in any foods that you would like that are not currently on the approved foods list for either phase. The same philosophy still applies once you are able to expand outside of Phase 1 and Phase 2 foods- if it bothers you, avoid it. If it does not bother you, feel free to continue consuming it.
The amount of time it takes to progress from Phase 1 to Phase 2 and then beyond Phase 2, depends entirely on you and how comfortably you are able to tolerate foods from each phase. Eventually and ideally, all varieties of plant foods should be comfortably tolerated when eubiosis is achieved.
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