Everything You Need to Know About Fiber

Published date: November 7, 2018 | Modified date: October 11, 2019

Fiber is a long-time favorite treatment for IBS. People with digestive problems are often told that they need more fiber. It’s easy to say and it’s simple to try. But this seemingly simple food based solution to digestive problems can have a lot of surprises.

Fiber is far more complicated than it sounds. There are many different kinds of fiber, and one person often responds very differently to a fiber than the next person does.  Just because it’s fiber doesn’t mean that it’s benign or that it’s good for everyone. Fiber may help you.  In fact, it’s easy to underestimate how effective it can be.  Unfortunately, it’s also tempting to assume that it’s harmless. Beware that fiber is perfectly capable of causing as many digestive problems as it solves. Many people react poorly to some types of fiber, and many fiber products are also filled with other things that your digestive tract may find problematic.

Fiber does have the potential to help you feel better, especially if you have diarrhea or constipation. If it does help, ask yourself, are you treating the symptom or the cause? Can you live without it? If not, then you probably haven’t solved the true cause of your problem. If it helps, that is good news. but getting to the root cause of the problem will eliminate your need for fiber and truly solve your digestive problem.

What is Fiber

What is fiber, anyway? Well, this is an interesting question. Fiber comes from plants. Historically, fiber was the term used to define the parts of plants that you ate, but which were not digested. Typically, this was the cellulose and other fibrous materials in plant foods.

Other terms for fiber are bulk and roughage. We need a certain amount of it to keep our digestive systems running smoothly. More recently fiber is being used as a word for anything you might eat that provides bulk to the stool and is not digested.

Soluble vs Insoluble Fiber

There are two main categories of fiber, soluble and insoluble. Soluble fiber partially dissolves in water, insoluble fiber does not.

Soluble fiber is also called viscous fiber, and is found in foods such as oatmeal, okra, or legumes, such as garbanzo beans. It can be helpful in treating IBS symptoms, especially constipation and diarrhea.

Soluble fiber forms a thick gel that helps to properly form the stool in the digestive tract and move it through the bowel. It also adds bulk to the stool. Because it slows the stool’s transit time, it helps to prevent diarrhea. Soluble fiber also prevents constipation, because the colon becomes filled with gel, as opposed to being clenched tightly around dry, hard stools. Basically, fiber moves bulk through the intestines and helps to balance the acidity level in the intestines. It is also helps to keep healthy the good bacteria that live in your digestive tract.

Insoluble fiber is more of a “scratchy” fiber; it adds bulk to the stool. A good example of insoluble fiber is celery.

There are many other fiber options available in pure form, such as bran, ground flax, or acacia.


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Recommended Fiber Intake

The USDA recommends that adults take in a minimum of 25 to 38 grams of fiber daily, and soluble fiber should account for one-third to one-half of the total. As many as 60 grams of fiber per day is required for optimal health.

If you eat at least five servings of fruits and vegetables as well as at least five servings of grain products per day, you are very likely meeting your fiber requirements. One serving of vegetable is 1/2 cup cooked vegetable or 1 cup of a raw leafy vegetable. One serving of fruit is one medium sized apple, pear, or 1/2 cup berries. One serving of grain is 1/2 cup cooked grain.

Unfortunately, the typical American eats only 10 to 15 grams of fiber daily, much less than the daily recommendation.

Most foods that are high in fiber have a mix of both soluble and insoluble fiber. Because the average diet contains three times as much insoluble as soluble fiber, it is best to focus on foods that are higher in soluble fiber.

However, the problem with recommending a generic list of high-fiber foods is that individuals may have an intolerance to one or more of them. If you have a problem with soy, wheat, gluten, or the like, then increasing your consumption of these foods may actually make your digestive symptoms worse.

Fiber Side Effects

Fiber isn’t always helpful. In fact, there is a dirty little secret about fiber that is usually ignored. Adding fiber to your diet can just as easily make you feel worse rather than better. And it’s not a little worse, it’s a lot worse. Many patients report that when they take fiber they feel horrible. It feels like it is literally tearing them up. The pain is worse, the gas is worse, and they immediately stop their fiber and feel better.

Not everyone can digest fiber well. This is especially true when you have an already inflamed and irritated digestive tract. In these cases, fiber will only exacerbate the problem. This often surprises people, but it’s an unfortunate fact that many people figure out for themselves.

You can also be allergic to fiber. People are shocked when we tell them that we frequently see allergies to psyllium. Psyllium is the most popular fiber on the market, and many fiber supplements contain psyllium.

Fiber comes in all shapes and sizes, and all fiber is not created equal. Food is definitely the best source of fiber, but that doesn’t mean that it will be any more tolerable.

Just because you have digestive symptoms doesn’t necessarily mean that you should be taking more fiber. Proceed cautiously when taking fiber and trust your instincts if you think it makes you feel worse rather than better.

What are Some Fiber-Rich Foods?

Arguably the best, and probably tastiest, sources of fiber are vegetables, fruits, and whole grains.

  • Leafy vegetables such as kale, spinach, chard, and collard greens are rich in nutrients and fiber. Be sure to eat them with some safe form of oil or butter/butter substitute to help better absorb the nutrients.
  • Starchy vegetables like sweet potatoes, pumpkin, squash, rutabagas, parsnips, and turnips are high in fiber. They are relatively easy to add into soups and stews or eat on their own. Rutabagas even make a delicious mashed “potato.”
  • Avocados contain nearly eight grams of fiber per fruit. These can be added to salads, eaten on top of a hamburger, or sprinkled with a little salt and eaten with a spoon.
  • Some fruits like pears, apples, and berries are rich in nutrients and fiber. Raspberries pack nearly 10 grams of fiber into one cup of berries. When possible, it’s best to eat the peel of the fruit, as the peel and the flesh, not the juice, contain most of the fiber.
  • Beans and legumes can be an outstanding source of fiber. Lentils are easy to prepare and can be a good dinner side or soup addition without too much extra work.

If you’re unfamiliar with any of these foods or unsure how to prepare them, please remember that you’re in good company. We encourage our patients to experiment with preparing one or two new fiber-filled foods per week. Just make sure you avoid any with which you have an allergy.

Walking through the produce section of your favorite grocery store or looking for recipes online can be helpful in identifying foods that might be new and tasty.

Commercial Fiber Products

Fiber is big business. You’ve seen commercials for it on your TV. You’ve been told that it’s good for you and that you need more. And if you have IBS or many other digestive problems, then you have probably tried fiber.

One way to get more fiber in your diet is to purchase one of the popular fiber products on the market. What you may not know is how different these products are from each other. They have almost nothing in common. Some contain artificial colors and sweeteners. Others contain wheat, dairy, corn, and psyllium.

The results and the effectiveness from the various forms of commercially available fiber will vary widely from person to person, so you will have to experiment with them to get the right fit. And don’t be surprised if fiber doesn’t solve your problem at all.

Some popular fiber supplement products and what they contain are:

  • Benefiber:
    • Active ingredient: wheat dextrin
    • Benefiber orange contains: wheat dextrin, citric acid, natural orange flavor, potassium citrate, aspartame, gum acacia, acesulme potassium, maltodextrin, lactose (milk), triglycerides, sucrose acetate isobutyrate, modified cornstarch, yellow 6, red 40
  • Citrucel:
    • Active ingredient: methylcellulose (from undisclosed source)
    • Citrucel® orange contains: methylcellulose, citric acid, dibasic calcium phosphate, FD&C yellow #6, maltodextrin, orange flavors (natural and artificial), potassium citrate, riboflavin, sucrose, titanium dioxide, tricalcium phosphate
    • Citrucel® sugar free contains: methylcellulose, aspartame, dibasic calcium phosphate, FD&C yellow #6, malic acid, maltodextrin, orange flavors (natural and artificial), potassium citrate, riboflavin.
    • Recommended for either constipation or diarrhea.
  • Metamucil:
    • Active ingredient: psyllium husk
    • Metamucil orange coarse contains: psyllium husk, citric acid, FD&C yellow no. 6, natural and artificial orange flavor, sucrose
  • Fibercon:
    • Active ingredient: calcium polycarbophil
    • Fibercon contains: calcium polycarbophil, caramel, crospovidone, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, silicon dioxide, sodium lauryl sulfate. Note: calcium polycarbophil is a synthetic polymer the calcium salt of polyacrylic acid cross-linked with divinyl glycol.
    • Recommended for constipation
  • Konsyl:
    • Active ingredient: psyllium husk.
    • Konsyl contains: psyllium husk, FD&C yellow# 6, gelatin, polyethylene glycol, polysorbate 80


As you can see, the commercial fiber products include many ingredients. Most contain artificial colors and sweeteners. Psyllium has the potential to be either helpful or to cause problems or do both at the same time. Some patients are allergic to psyllium.

Methylcellulose, found in Citrucel, is a chemical compound derived by chemical processing of an undisclosed source of cellulose. It is not a naturally occurring part of a plant and is not fermentable.

Calcium polycarbophil, found in Fibercon, is a synthetic polymer, not a plant fiber.

Most people are not suffering because of a lack of fiber in their diet, but for some people, the addition of fiber will help alleviate unpleasant symptoms.

If you think, or know that you need more fiber, there is often no need to take a special, commercially processed and packaged product to get the additional fiber. You can buy psyllium powder in bulk or all by itself. There are many other fiber options available in pure form, such as bran, ground flax, or acacia.

A Patient’s Personal Story

Sometimes, fiber can make IBS symptoms worse instead of better. Cheryl, a 45-year-old woman, came to us with alternating constipation and diarrhea. Thinking back, she recalled having had an upset stomach for at least 15 years. However, things took a turn for the worse about five years ago, when she noticed that sometimes after a meal she would get urgent diarrhea. Then she might go three days before having another bowel movement. The sheer unpredictability of it all was causing her great anxiety and negatively impacting her life.

Cheryl had been to her regular physician, who told her that she should try Imodium and use more fiber. The Imodium helped, but it certainly didn’t solve the problem, and then it made her constipated. She wasn’t sure if the fiber helped her at all. It possibly made her feel worse.

Her physician referred her to a gastroenterologist, who performed a colonoscopy. When the colonoscopy results came back fine, the gastroenterologist told Cheryl her diarrhea was probably just a symptom of IBS. The only advice he provided was to eliminate coffee and alcohol. Although Cheryl followed these recommendations, and removed coffee and alcohol from her diet, her problems persisted. On her own, she also avoided gluten, which helped a little, but didn’t really solve the issues.

Cheryl was totally fed-up with the medical system and her own health. While doing an online search for help with IBS, she found the IBS Treatment Center. After sharing her history of digestive and elimination problems with the doctor at the IBS Treatment Center, Cheryl learned that it is common for patients to feel worse after taking fiber, not better.

No one had ever even suggested that was a possibility. We often remind our patients to trust their instincts and to be aware of their own physical responses to recommended treatments. If something makes you feel worse, then it may not be the right thing for you.

After some investigation and detailed testing, we discovered that Cheryl had allergies to cane sugar as well as baker’s yeast and brewer’s yeast. She had mentioned craving sugar, and with the discovery of the sugar allergy, the cravings were explained.

The tests results also explained why the elimination of gluten from her diet offered some relief. Baker’s yeast and gluten are often found in the same foods, and by eliminating the gluten, she was unknowingly avoiding one of her top allergens.

After a few months of working with and educating Cheryl about the foods she should avoid, she experienced tremendous improvement. She no longer has unpredictable diarrhea, and is able to go out without having to take Imodium ahead of time. Cheryl is now able to live a happy and healthy life.

The testing and food counseling at IBS Treatment Center can help you feel better. If you have questions about whether or not adding fiber-rich foods may be beneficial to your diet, please contact our office to schedule a consultation with one of our physicians.