The Truth About Fiber and Gut Health
I’m sure at one point or another you have heard that to help with digestive concerns you should “just eat more fiber!” While there is of course truth behind this, it is not always so black and white. Fiber is a crucially important macronutrient that should be prioritized every day. It is found in plant foods, and provides us with a wide range of vitamins and minerals. Fiber-rich foods that typically come to mind include legumes such as beans, lentils, and peas, grains, nuts and seeds, cruciferous vegetables like brussels sprouts, fruits such as apples and berries, and avocados.
What is important to note about fiber is that it comes in two forms: soluble and insoluble. Soluble fiber dissolves in liquid to become gel-like. It attracts water and helps to soften stool and delay gastric emptying. Insoluble fiber cannot be dissolved in liquid. It adds bulk to stool and helps us to maintain regular bowel movements. Unlike the other macronutrients fat and protein, fiber is unique in that we, as humans, cannot digest it. Our bodies do not create the digestive enzyme to break down fiber, so as it travels through our digestive tract and changes form, it is never completely broken down and digested. But this is what makes fiber so uniquely supportive to us. As the soluble fiber bulk travels through our systems, it helps to sweep up, bind to, and eliminate debris on its journey, including hormones and toxins. This effective system of mopping up this matter prevents such debris and waste from recirculating through our bodies, and causing lots of trouble. Soluble fiber also delays gastric emptying which slows the absorption of glucose into the bloodstream, increases satiety (the feeling of fullness), and improves nutrient absorption.
In addition to the benefits listed above that fiber provides us (among many others), fiber is specifically known to be supportive of the health of our gut microbiome. Our gut microbiome consists of trillions of microorganisms. This includes bacteria, fungi and viruses and the exact makeup of this will look different in everyone. Many of these microbes that take residence in our gut are extremely beneficial, and we want to see these at present levels.
When we consume fiber, bacterial fermentation takes place, producing byproducts called short chain fatty acids. These include butyrate, acetate, propionate, and valerate. These are the main players in what specifically makes fiber beneficial for our gut health. They play an important role in our gastrointestinal health as a whole and help to prevent gut dysbiosis, an imbalance in our microbiome of our “good” and “bad” bacteria. SCFAs also lower the pH of the intestines, creating an inhospitable environment for pathogens to take hold. Our gut microbiome, located primarily within our intestines, is protected by a mucosal lining. When this barrier is strong, it helps to maintain intestinal integrity, keeping the good bacteria in and the bad bacteria out for a healthy gut microbiome. Short chain fatty acids have a direct impact in maintaining the integrity of this mucosal barrier, as they directly build and maintain the mucus for this lining, specifically butyrate.
The “good” bacteria, that we want to see present, feed on this mucosal layer, and when it is strong, they thrive. With a suboptimal mucosal barrier, we can see these beneficial bacteria become suppressed, and opportunistic, or “bad,” bacteria take hold (as well as other pathogens). So as we can see, dietary fiber → SCFA production → strong gut musical integrity → “good” bacteria at present levels → lower risk of “bad” opportunistic bacteria → an overall healthy and diverse microbiome. So with all of the benefits of fiber on our gut health, when do we need to be mindful about our consumption of it?
When we are experiencing compromised digestive function, and suspect leaky gut, the way we consume fiber needs to be considered. Certain carbohydrates and fiber-rich foods, specifically fermentable fibers and raw foods, can be difficult to tolerate. “Leaky gut,” or intestinal permeability, is when this protective mucosal lining around our gut has been compromised. This lining is held together by tight junctions that act like the gatekeepers of the gut, and are selective about what they allow to pass through. When these junctions are loosened up, they allow larger particles through. And if overall digestion is already suboptimal, these food particles won’t be fully broken down, and the large particles will pass through the gut lining, which then enters the bloodstream leading to inflammation, triggering a response from our immune system, which can then lead to a long downstream effect of systemic inflammation and symptoms that follow.
While carbohydrate-rich foods can be very beneficial, with a compromised musical lining and suboptimal digestion, we can also experience carbohydrate malabsorption which can lead to undesirable conditions to take hold. With optimal digestive function, we can consume carbohydrate and fiber-rich foods, properly break these down, and reap the benefits explained above. However, many bacteria strains as well as yeast feed on sugars (from these carbohydrates) that have not been broken down and absorbed. A common way we see this presented is in cases like SIBO, which stands for small intestinal bacterial overgrowth, where bacteria that should not be located in the small intestine proliferates, or Candida, which is a strain of yeast that can proliferate. In the most basic terms, once SIBO is present, many carbohydrates can exacerbate symptoms. Many healthy plant foods, even just fruits and vegetables, are high in “FODMAPs”, which stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. These are basically just different forms of sugar that exist in plant foods that are fermented. There are several different diets that manipulate carbohydrate consumption to lower the exposure to foods that may be causing symptoms, however these are temporary therapeutic diets to follow while foundational gut healing takes place, and the end goal would be to consume these foods freely, without digestive distress. As for yeast, while it is harmless when found at normal levels and is present in most individuals, there are many things that can cause it to easily grow and thrive, as it is very adaptive. Put simply, sugar feeds yeast, so those dealing with yeast need to be extremely mindful of their carbohydrate consumption, which we know to be high in fibrous plant foods. This is best done alongside a practitioner who can curate a specific program for you to ensure your success.
If your digestion and gut health is compromised, fiber-rich foods that are typically gut supportive such as legumes, raw vegetables, and fermented foods, can be quite hard on your stomach, difficult to digest, and may cause more discomfort and harm than good for the time being. Once gut healing has taken place and digestion has been optimized, these foods can be great ways to incorporate nutrient dense, gut-supportive fibrous foods into your diet. While working to heal your gut (alongside your personalized protocol for your needs) some gentle and supportive ways you can incorporate fiber rich foods can include: soaking and sprouting your legumes and cooking vegetables slow and at a low heat such as roasting or steaming. You can think of these methods as “pre-digesting” your food, to make it easier on your digestive system, once it reaches it. Also be sure to drink lots of water across the day to support the fiber intake. And of course, make sure you are chewing extremely thoroughly, as this is the body’s first step in the digestive process!
