Fiber- When you need more and when you need less...
What's the scoop on fiber anyways? Some sources say "get more fiber!" and some say "you just don't need it!" Who do we believe? We see some diets be fiber-filled, such as the Mediterranean diet or the vegetarian/vegan diet, yet some recommend against many forms of fiber, such as carnivore, keto-style or high-protein/low-carb.
We also may hear our doctor suggest a low fiber diet or to avoid nuts and seeds (a huge source of fiber), then at times hear them say to increase fiber and fruits and vegetables. This can be confusing at times and lead to just "giving up" on fiber altogether!
In order to understand things better, lets first start with what fiber really is. Fiber in food refers to a type of carbohydrate not digestible by the human body. There are two types of fiber- Soluble Fiber and Insoluble Fiber.
Soluble Fiber dissolves in water and creates a gel-like substance in the gut.
Insoluble Fiber does not dissolve in water and adds bulk to stools.
It is important to know the difference between the two, because often both kinds are looped into the same category, yet they have very different uses and purposes in the body.
Firstly, fiber is the "food" for our gut bacteria. Both kinds can help healthy bacteria grow and flourish, which is essential for our body in order to prevent dysbiosis, or a term for an imbalance in healthy gut bacteria. Dysbiosis has been proven to cause leaky gut, intestinal damage, inflammation of the GI tract, as well as has been linked to many chronic diseases, such as Parkinson's, Autism, Anxiety/Depression, Obesity and Diabetes. If we do not consume fiber, our bacterial population in the gut can become compromised. In addition, many important compounds are made in our gut, such as serotonin, insulin, progesterone, leptin, ghrelin, GLP-1 and more. I consider fiber more as our "long-term investment" that will compound interest and earnings in our health for years. If we don't invest in our gut bacteria population early on, we will spend years trying to catch up, or even see ourselves being in debt in regards to our healthy bacterial population.
So when would we say its not great to eat fiber?
There are a few instances where we tell clients to be cautious with their fiber intake.
In any acute (short-term) flare-up of a gastrointestinal disease, such as Crohn's, Colitis, IBS, Diverticulitis, Ulcerative Colitis or immediately post GI surgery
In cases of SIBO or SIFO (Small Intestinal Bacterial/Fungal Overgrowth)
In extreme constipation or diarrhea
In a gut-healing regimen
Gastroparesis (fiber amount is regimented based on the person)
Gastric bypass (fiber amount is regimented based on the person)
You can see I clearly state that fiber should be limited or regimented in many of these situations, but typically not completely removed. In these instances, we often have to go to a specific type of fiber for tolerance or healing.
I like to think of soluble fiber as the soft "pillow-like" fiber that goes through the GI tract and gently attaches to substances that are floating through the GI tract on their own. It takes them into its grasp, then soaks in all the water and liquids in the GI tract to keep things moving along. When we lack soluble fiber we often experience watery diarrhea, hard stool or a combination of diarrhea and constipation, back and forth. We also can experience more gas and bloating due to material being left behind in the gut and fermenting. Introducing soluble fiber early is important post-GI surgery to promote gentle motility, as well as during some acute GI attacks to ensure the stool does not become impacted and cause pain or discomfort. Soluble fiber should be consumed regularly for all people to help feed a healthy microbiome, scavenge and excrete unnecessary cholesterols and remove toxins from the body.
Insoluble fiber has some pretty important roles as well, but often this is the fiber people are afraid of when thinking about foods with fiber. Why? Well insoluble fiber can cause issues in some people who have a damaged gut with lesions, ulcerations, diverticula or inadequate digestive enzymes. This is because this type of fiber doesn't dissolve in water and can stay in its whole form, which leaves it capable of irritating problem sources in the GI tract. However, if we lack consumption of insoluble fiber, we may not create the volume of stool in the gut necessary to promote motility and regular bowel movements. We also can be left feeling hungry due to the lack of volume of stool as well. Insoluble fiber should be avoided in acute phases of GI irritation, damage, post-surgery and in SIBO protocol or gut-healing.
How do we know which foods have soluble or insoluble fiber?
Many foods contain both forms of fiber, but some foods contain primarily one type. See the breakdown below for guidance.
Soluble Fiber: Rolled, oats, flaxseed, chia seed, hemp hearts, peeled apples/applesauce, pears, peaches, oranges, grapefruit, banana, plantain, sweet potatoes, potatoes, beets, ground nut flour, barley, farro, brown rice, peeled zucchini, squash of any kind, carrots, tofu, psyllium husk
*It's important to note that most forms of fiber are easily digested in their ground/puree form and also through cooking. This softens and breaks down fiber to prevent irritation to the gut.
Insoluble Fiber: Wheat bran, oat bran, beans of any kind, berries with seeds including strawberries, blackberries, goji berries, apple peels, skins of plums and pears, prunes and raisins, grapes, lettuce, kale, spinach, escarole, broccoli, cauliflower, cabbage, tomato peels, green beans, asparagus, celery, seeds and nuts, coconut, popcorn
*When incorporating more insoluble fiber to start, try blending into smoothies to aid in digestion before increasing in whole sources. Cooking can also help break down fibers slightly for digestion.
In order to move forward with knowing the amount of fiber YOU need, it is important to work with your doctor and dietitian to understand the state of your gut, your body's specific needs and possible limitations or risks to the amount of fiber you can consume. Important things to watch as you change your fiber intake is your gut habits, including how often you go to the bathroom, the consistency of your stool, signs of blood or mucus in your stool and water retention/bloating or distension. You will often be asked to monitor your intake and symptoms while working with a Registered Dietitian, like myself or my colleague, Heather Robinson, in order to help follow the best plan for you.
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