Fiber 101: What You Need to Know for a Healthy Gut

Adapted from episode 96 of The Perfect Stool podcast and edited for readability with your host, Lindsey Parsons, EdD, Gut Health Coach.

As a gut health coach coming from a functional medicine perspective, I believe in treating the root cause of disease rather than just masking symptoms. And when it comes to gut health, fiber is one of the most important factors to consider.

First of all, fiber plays a critical role in maintaining regular bowel movements. With a standard American diet full of sugar and processed foods, you definitely don’t get enough fiber. And without enough fiber in your diet, you may get constipated or at minimum have a less healthy gut microbiome, which may be one of the reasons that people who are constipated have an increased risk of gastrointestinal cancers, as well as breast, ovarian and other cancers, in particular in the year following constipation, although the direction of causality is not definitive in the studies, and undiagnosed cancer could be causing constipation as well. But the theory is that stool sitting around has toxins that get reabsorbed into the body.

So fiber is good for you because it serves as food for the trillions of bacteria that reside in our gut microbiome, which plays a critical role in our immune system, our metabolism, and our mood, as well as our gut health. Research has shown that a diet high in fiber can reduce inflammation, improve cholesterol levels, and even lower the risk of chronic diseases such as heart disease, diabetes, and certain types of cancer. So I recommend that most of my clients prioritize their fiber intake, except when it’s contradindicated, which I’ll discuss later. Normally I suggest this in the context of diet, but for those who may struggle to get enough fiber from their diet alone, fiber supplements can also be a useful tool to consider.

What are the different types of fiber?

So you’ve probably heart that there are two main types of dietary fiber: soluble and insoluble, and a healthy diet will give you some of both types. Soluble fiber dissolves in water and forms a gel-like substance in the digestive tract, which can help slow down the digestive process, which is beneficial in particular for those with blood sugar concerns or while you’re eating anything sugary. Soluble fiber is also known for its prebiotic effects, which means that it feeds the beneficial bacteria in the gut. This will support a healthy gut microbiome and reduce inflammation in the body. Good sources of soluble fiber include oatmeal, beans, peas, lentils, and fruits like apples and citrus.

On the other hand, insoluble fiber does not dissolve in water and passes through the digestive system mostly intact. This type of fiber promotes regular bowel movements, prevents constipation and supports healthy digestion and nutrient absorption by adding bulk to stool and preventing it from becoming too loose. Good sources of insoluble fiber include whole grains, vegetables like broccoli and carrots, and fruits like berries and kiwi, although most foods have a combination of both types of fiber.

Resistant starch is another type of dietary fiber that resists digestion in the small intestine and reaches the large intestine intact. In the large intestine, it acts as a prebiotic and feeds the beneficial gut bacteria, promoting a healthy gut microbiome and in particular higher butyrate production, which is important for feeding the cells lining the large intestine or colonocytes. Resistant starch has been linked to improved digestion, reduced inflammation, improved insulin sensitivity and lower blood sugar levels. It may also promote feelings of fullness, leading to a reduced calorie intake and potential weight loss.
Sources of resistant starch include foods such as green bananas, legumes (beans, lentils, chickpeas), oats, some whole grains and cooked and cooled potatoes or rice. When cooked and cooled, potatoes and rice undergo a process called retrogradation, which changes the structure of the starch, making it more resistant to digestion. My favorite way of getting resistant starch is just making a large batch of jasmine rice and putting it in the fridge to eat with leftovers. If you eat it cold or don’t reheat it too much, you retain much of the resistant starch.

Which fiber supplements are best for gut health?

I often recommend that my clients incorporate fiber into their diets to support recovery of a healthy gut microbiome, because for some reason, pathogenic bacteria tend to like things like sugar and white flour and commensals or beneficial bacteria, like fiber. I think about this particularly during treatment for H pylori, which typically causes reflux and constipation, but not so much bloating, either through diet or through supplements, and after SIBO treatment, especially for diarrhea or soft stool, to help restore butyrate producers in the colon.

Here are some types of fiber supplements you may want to consider.

Psyllium husk is a type of soluble fiber that comes from the husks of plant seeds and is one of my favorite to recommend. Research has shown that psyllium can help to reduce constipation and firm up stool for those with softer stool. What’s more, psyllium has been shown to help reduce LDL cholesterol levels, making it a potential adjunct therapy for those with high cholesterol. My husband swears by his daily psyllium husk. You can build up slowly to a tablespoon of psyllium husk powder in 8 oz. of liquid, but drink it fast because it gums up quickly. Or put it in less liquid but follow it up with the rest of 8 ounces of liquid. It’s best to do this away from any supplements you take as it may impede absorption of the supplements. You can also take it in capsule format, but it takes 6 to get to a tablespoon, so it’s a bit impractical. By the way, Metamucil is primarily psyllium husk, but it’s got other non-beneficial chemicals, so I’d avoid it and get a pure psyllium husk product.

Inulin* is a type of soluble fiber that is found in many plants, including chicory root, Jerusalem artichokes, asparagus, garlic, onions and leeks and can also be purchased as a supplement. Studies have shown that inulin can help to improve gut microbiota composition and reduce inflammation in the gut. Inulin may also have potential benefits for those with diabetes, as it has been shown to help regulate blood sugar levels.

Guar gum* is another type of soluble fiber that is derived from the seeds of the guar plant and is used as a thickening agent in many gluten-free foods. Research has shown that guar gum can help to improve stool frequency and consistency in individuals with chronic constipation. Additionally, guar gum has been shown to have potential benefits for those with high cholesterol, as it can help to reduce LDL cholesterol levels. Partially hydrogenated guar gum (PHGG) or Sunfiber (which you can find in my Fullscript Dispensary*), however, is particularly used in IMO (Intestinal Methanogen Overgrowth) as a beneficial fiber to help with constipation. It’s a type of guar gum that has been partially broken down enzymatically, making it easier to digest and less likely to ferment in the gut. PHGG has been shown to have similar benefits to regular guar gum, such as improving stool frequency and consistency, without the risk of worsening symptoms in individuals with SIBO or IMO.

Acacia fiber*, also known as gum arabic, is a type of fiber derived from the sap of the Acacia Senegal tree. It is commonly used as a food additive to provide texture and stability, but it can also be taken as a dietary supplement. Acacia fiber is a highly soluble fiber that is fermented slowly by gut bacteria, producing short chain fatty acids that can support gut health. Research has shown that acacia fiber can have a range of health benefits, including improving gut barrier function, reducing inflammation, and supporting healthy immune system function. Acacia fiber is a better choice in SIBO as it’s less likely to cause bloating.

Pectin* is another type of soluble fiber that is commonly found in fruits and vegetables, particularly apples and citrus fruits. It is also used as a food additive to thicken and stabilize products like jams and jellies. Pectin is fermented quickly by gut bacteria, producing high levels of SCFAs that can support gut health. Studies have shown that pectin can have a range of health benefits, including reducing inflammation, promoting healthy gut barrier function, and improving lipid metabolism. Modified citrus pectin* is also used in particular to help with chelation of heavy metals.

Glucomannan* is a type of soluble fiber derived from the root of the konjac plant. It is commonly used as a dietary supplement to aid in weight loss, as it has been shown to promote feelings of fullness and reduce appetite. Glucomannan is fermented slowly by gut bacteria, producing SCFAs that can support gut health. Research has shown that glucomannan can have a range of health benefits, including improving glycemic control and reducing constipation.

If you’re not dealing with bloating, you may want to try a combination fiber product like Thorne FiberMend or Pure Encapsulations PureLean Fiber, which you can find in my Fullscript Dispensary*. When starting any new fiber product or adding fiber to the diet through sources like beans and legumes, be sure to start slowly and build up so that your microbiome has time to adjust to avoid gas, bloating or constipation. Aim to increase fiber intake from food or supplements by 5 grams per day until you reach the recommended daily intake of 25-30 grams per day. I like the tool Cronometer, which is an online nutrient, calorie and macro checker, to see how you’re doing with your current levels of not just fiber but all nutrients. You can even enter your supplements in there to see if you’re getting the recommended daily allowances.

How can I get enough fiber from my diet?

If you want to avoid fiber supplements, my best advice for a diet high in fiber is to eat beans and legumes. I know they’ve gotten a bad rap because of lectins, saponins and phytic acid but I don’t find that most people are sensitive to lectins, and you can do things like soak them and cook them slowly to get rid of most of those problematic substances. And I’ll provide a link on how to do that. Unfortunately, most canned beans do not undergo pre-soaking so it’s best to make them yourself from dried beans.

While fiber is found in a variety of foods, including fruits, vegetables, whole grains, nuts, and seeds, beans and legumes really stand out for their high fiber content, and in my opinion, it’s very hard to hit the RDA for fiber (25-30 grams of fiber per day, based on your calorie intake) without eating them. Overall, beans contain more fiber per serving than any other type of food.

For example, here’s a comparison of ½ cup of the highest fiber beans with many other fruits and vegetables:

•             Black beans: 7.1 grams of fiber

•             Kidney beans: 7.3 grams of fiber

•             Pinto Beans: 6.9 grams of fiber

•             Lima Beans: 6.6 grams of fiber

•             Chickpeas: 5.3 grams of fiber

Compare that to:

•             Raspberries: 4.2 grams of fiber (but think about how expensive raspberries are and realistically, who ever eats an entire ½ cup of raspberries at a sitting? That’s like the entire container)

•             Artichoke: 4 grams of fiber

•             Broccoli: 2.3 grams of fiber

•             Blueberries: 2 grams of fiber

•             Carrots: 2 grams of fiber

•             Green beans: 2 grams of fiber

•             Cauliflower: 1.5 grams of fiber

•             Cooked cabbage: 1 grams of fiber

•             Raw Spinach: 0.8 grams of fiber

•             Romaine lettuce: 0.5 grams of fiber

One way I recommend getting more beans and legumes into your diet is adding them to breakfast. Just make a batch and use them as your breakfast carb. Start with a tablespoon and work your way up. Or do a combo of rice and beans. That was a common breakfast that went great with an egg with a soft yolk over it when I lived in Costa Rica. They called it gallo pinto there, but there are many varieties of this from different Latin American countries. I’ll include that recipe in the show notes. I suggest breakfast because most people don’t vary their breakfasts a lot, so it makes it easier to make it a habit.

Nuts are also another good source of fiber but for a ¼ cup serving, it’s still only 2-4 grams of fiber. And of course it’s important to note that fruits and vegetables also provide a wide range of other important nutrients, such as vitamins, minerals, and antioxidants, that are important for overall health, so it’s best to get some of your fiber from other fruits and veggies, and balanced diet will include a variety of fiber-rich foods, including fruits, vegetables, nut and legumes.

Should I take fiber with IBS or IBD?

So as I mentioned earlier, there are some contraindications for taking fiber or getting much fiber in your diet in certain gut health conditions.

If you are in an active flare of inflammatory bowel disease, meaning Crohn’s Disease or colitis, studies a show that a high fiber diet will cause increased inflammation and disease activity. Therefore, low-fiber diets like the Specific Carbohydrate Diet, low FODMAPs or IBD-AID are recommended during times of active cramping or diarrhea. However, slowly introducing fiber once your symptoms have settled and could be described as mild or not present, one food at a time, is recommended to help keep your condition in remission.  In human studies, psyllium husk, inulin and germinated barley foodstuff all showed positive results for decreasing remission rates, while wheat bran showed no benefit.

If you’re suffering with IBS-like symptoms, in particular bloating and gas after eating, or have diagnosed SIBO (small intestine bacterial overgrowth), it’s also recommended that you decrease your fiber, and avoid prebiotics like inulin, fructans and GOS (galacto-oligosaccharides), because they are high in FODMAPs, aka Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols, which feed the bacteria and archaea that are typically overgrown in SIBO. So for people with active SIBO, I usually recommend either a low FODMAPs diet, Nirala Jacobi’s Biphasic Diet or Marc Pimentel’s low fermentation diet. If you do want to continue fiber supplementation to help with bowel movements by either bulking up the stool and decreasing diarrhea or to help promote more frequent bowel movements during a low fiber diet, acacia fiber* is a SIBO safe fiber, and partially hydrogenated guar gum or PHGG, aka Sunfiber (find in my Fullscript Dispensary*) is helpful in IMO or methane SIBO.

Because fiber can be irritating in certain conditions, one way I help people get the microbiome benefit of fiber without the irritation of it, while healing from gut health conditions, is to recommend supplemental butyrate or tributyrin, the preferred form of butyrate, while healing. This is something I tend to recommend only to people with soft stool or diarrhea, as it can be constipating. It’s one of the short-chain fatty acids that people tend to most lack when they have conditions like SIBO-D and IBD, which tend to go along with overgrowths of proteobacteria, which do not produce butyrate. And I’m sure you’re heard that I have my own tributyrin supplement called Tributrin-Max, which you can get for 15% off your first order with the code INTRO15 or super exciting, I now finally have it for sale on Amazon, and discount code TMINTRO15 will get you 15% off your first order there.

You may be asking yourself about prebiotic fibers too beyond traditional fiber supplements, and I have done another podcast on that, which may have some overlapping material, episode 28 Prebiotics and Fiber.

And of course if you’re struggling with some type of chronic disease, chronic inflammation, bloating, constipation, diarrhea, soft stool, acid reflux, etc. and want to get to the bottom of it, that’s what I help my clients with. You’re welcome to set up a free, 30-minute breakthrough session with me (Lindsey). We’ll talk about what you’ve been going through and I’ll tell you about my 3- and 5- appointment health coaching programs in which I recommend lab tests, educate you on what the results mean and the protocols used by doctors to fix the problems revealed. Or if you’re ready to jump in right away or can just afford one appointment at a time, you can set up an 1-hour consultation with me.

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