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What Is Fiber, and Why Is It Vital for Digestive Health?

So far in this series on digestive health, we’ve looked at the following topics:

  1. The Basics of Irritable Bowel Syndrome (IBS)
  2. Small Intestinal Bacterial Overgrowth (SIBO)
  3. The Low-FODMAP Diet and Its Role In Treating IBS
  4. What is the Gut Biome and How Does It Affect Our Health?

Today’s topic in this series is FIBER. You’ve probably heard that fiber is important for digestion. For example, most doctors will tell you a high-fiber diet is necessary to prevent constipation. Yet, when some people increase their fiber intake, they can actually get MORE constipated, or they can experience stomach pain, bloating, or even diarrhea.

It seems baffling: if fiber is good for our digestion, how can it cause digestive problems? The truth is that fiber is a more complicated subject than most people realize. That’s why in this article, we’ll be looking at what fiber is, what it does, the different types of fiber, and how to eat the right type of fiber, so you can keep your digestive system healthy and reap all the wonderful benefits fiber offers.

What Is Fiber?

Fiber (also known as roughage or bulk) is the indigestible part of plants. It is different from fats, proteins, and carbohydrates, which are broken down by the body and absorbed into our blood stream. Instead, fiber passes through the stomach, small intestine, large intestine, and out of the body in almost the same form it took when you ate it.

What Are the Different Types of Fiber?

Fiber is classified into two categories: soluble and insoluble. Soluble fiber dissolves in water, taking on a gooey, gel-like consistency. Insoluble fiber absorbs water, and helps add bulk in the intestines. Most plant-based foods contain both soluble and insoluble fiber.

12 Amazing Health Benefits of Fiber

Both kinds of fiber work together to keep the digestive system healthy and to help prevent disease. While soluble and insoluble fiber each play a specific role in your digestive health, there is some overlap in the benefits they provide. Here’s just a short list of some of the impressive things fiber can do for you:

  1. Maintain regular bowel function – The bulking properties of insoluble fiber, and the gelatinous quality of soluble fiber, make it easier for stool to travel through the colon. This helps reduce the likelihood of constipation. Insoluble fiber also helps reduce diarrhea by holding onto water in the gut.
  2. Keep your “gut biome” healthy (see my previous article about the gut biome) – Bacteria in our gut feast on the fiber that comes from our diet. Fiber nourishes them and helps them to flourish so they can aid us in digestion and nutrient absorption.
  3. Prevent diverticulosis and diverticulitis – Diverticulosis is when the wall of your colon becomes stretched out. Over time, diverticulosis can develop into a more serious (and extremely painful) condition called diverticulitis. Consuming fiber on a regular basis helps keep the colon muscles toned, making them less likely to stretch out.
  4. Lower “bad” cholesterol – In its gel-like form, soluble fiber can bind to LDL cholesterol (the bad kind) and help eliminate it from your body.
  5. Stabilize blood sugar – Fiber helps slow down the absorption of sugar in the bloodstream, thus keeping glucose levels from going too high.
  6. Prevent type-2 diabetes – By reducing LDL cholesterol and helping you maintain healthy blood sugar levels, fiber reduces your risk of developing type-2 diabetes.
  7. Lower high blood pressure – According to a 2005 report published in the Journal of Hypertension, multiple studies have indicated that adding fiber to the diet can help lower high blood pressure.1
  8. Lower the risk of developing hemorrhoids – As constipation is a common cause of hemorrhoids, a high-fiber diet helps prevent them from developing.
  9. Reduce inflammation – Bad (or “pathogenic”) bacteria can lead to inflammation and diseases of the colon. Fiber helps keep good bacteria healthy and reduces the damage caused by bad bacteria.
  10. Help you maintain healthy weight – Fiber-rich foods are bulky, making us feel fuller faster. They also make us feel fuller longer because they take longer to digest than other foods. This combination can help keep us from overeating or snacking between meals. Fiber-rich foods also tend to be lower in calories than fats or proteins.
  11. Help with detoxification – Some toxins can enter our bodies via our food or environment. Others (such as excess hormones) can develop as byproducts of metabolism. Fiber binds to these toxins and helps our digestive system eliminate them from our bodies, so we are less likely to suffer their harmful effects.
  12. Lower the risk of developing colon cancer – Chronic constipation can lead to the development of polyps in the colon, which is one of the risk factors for developing colon cancer. As it helps prevent constipation, adequate dietary fiber lowers the risk of polyps from developing.

Is There Such a Thing as the WRONG Kind of Fiber?

At the beginning of this article, I mentioned that rather than feeling better when they increase their fiber intake, some people can actually feel worse. This unfortunate experience most frequently occurs in patients who struggle with irritable bowel syndrome (IBS) or small intestinal bacterial overgrowth (SIBO). Let me explain how this can happen.

Most varieties of soluble fiber can become fermented by gut bacteria. We call these fermentable foods “FODMAPs”. People with IBS or SIBO are especially sensitive to fermentation in the gut, which will create gas, bloating, and abdominal pain. Other people suffer from an overgrowth of yeast in the large intestine. As yeast thrives on fermented substances in the intestines, consuming soluble fiber is likely to make them feel much worse.

Thus, if you have any of these conditions, it’s NOT a good idea to increase your intake of fibers classed as “FODMAPs” until you have addressed the underlying problem and your digestive issues have stabilized. You can find a list of high- and low-FODMAP foods in my previous article “The Low-FODMAP Diet and Its Role In Treating IBS”.

Once you’ve reestablished the correct micro-ecology in your gut, you should be able to resume a diet containing all varieties of healthy fiber.

How Much Fiber Should You Eat a Day?

While the optimum amount of fiber you need per day will depend upon your individual health, a basic guideline for your minimum daily requirement is:

Men Age 50 or younger: 38 grams

Men Age 51 or older: 30 grams

Women Age 50 or younger: 25 grams

Women Age 51 or younger: 21 grams

Which Foods Are High in Fiber?

Soluble fiber is found in varying quantities in all plant foods, including (but not limited to):

Sources of insoluble fiber include (but are not limited to) the following. You’ll notice that many foods contain BOTH soluble and insoluble fiber:

NOTE: Refined grains have had their outer shells removed and are lower in fiber. Sometimes the outer part of the grain (the “bran”) is added back into foods to increase their fiber content (oat bran is one example). Processed foods, canned fruits and vegetables, and pulp-free juice are also lower in fiber.

Top 15 High-Fiber Foods

To get an idea of what should be a part of your diet to ensure you are getting enough fiber, here’s a list of my top 15 favorites, plus suggested portion sizes:

  1. Raspberries: 1 cup = 8 gm.
  2. Strawberries: 1 cup = 3.0 gm.
  3. Apple: 1 medium with skin = 4.4 gm.
  4. Pear: 1 medium with skin = 5.5 gm.
  5. Lentils: 1 cup = 15.6 gm.
  6. Black beans: 1 cup = 15 gm.
  7. Almonds: 1 oz. (23 nuts with skin) = 3.5 gm.
  8. Peas: 1 cup = 8.8 gm.
  9. Broccoli: 1 cup = 5.1 gm.
  10. Oatmeal: 3.5 ounces = 10 gm.
  11. Barley (pearled): 1 cup = 6.0 gm.
  12. Whole wheat spaghetti: 1 cup = 6.3 gm.
  13. Bran flakes: ¾ cup = 5.5 gm.
  14. Chia seeds: 1 TB = 5 gm.
  15. Popcorn: 3 cups = 3.6 gm.

Should I Take a Fiber Supplement?

Most people get enough fiber through their normal diet. But if you feel you need an extra boost, I recommend adding ground flax or chia seeds to smoothies or protein shakes. Their soluble properties also help add bulk to the mixture, so you feel satiated for longer.

If your lifestyle causes you to fall short of your targeted dietary fiber requirements, you could add a fiber supplement to your daily diet. For example, people who travel for work often have erratic dietary habits, and may be prone to bouts of constipation. Taking a fiber supplement can help keep them regular when on the road.

There are so many “fiber boosting” products on the market: powders, drinks, fiber bars, and fiber cereals. Insulin or chicory root are common ingredients in such products. Which product to choose is really a matter of convenience, taste, and ingredients (especially if you have food allergies or sensitivities).

IMPORTANT: Some people (even those without IBS or SIBO) will complain of gas and intestinal discomfort after eating foods with added fiber, especially if they are unaccustomed to it. Start with a small serving, and gradually work your way up over a period of a few weeks, until your body adjusts to the change. It is also important to drink more water when you increase your fiber to help it move more easily through your system, and to unlock many of its health properties.

If you still experience digestive distress from fiber after a few weeks, you may need to be evaluated for SIOB, and discuss going on a low-FODMAP diet, with your practitioner.

Closing Thoughts

As we’ve explored in this article, a diet rich in plant-based fiber keeps our digestive tract healthy, decreases our cholesterol, stabilizes our blood sugar, decreases our risk of colon cancer, and helps us maintain a healthy weight – to name just a few benefits. Unfortunately, the standard America diet tends to be low in fiber and high in processed refined foods, putting many people at risk of disease and overall poor health. That’s why I hope this article has inspired (and informed) you to include adequate fiber in your daily diet.

If you or someone you know suffers with dietary or digestive problems, I invite you to drop me a line on the “contact us” page on this site and request a free initial consultation to discuss your needs. I treat patients locally at my practice in Issaquah, Washington, and worldwide via phone or Skype.

Next time, we’ll look at the role of the gallbladder and the important part it plays in our digestive health. I hope you’ll subscribe to this blog so you can receive that article and all future articles on A Path to Natural Health.

“Health is a journey we travel over our lifetime.
Learn everything you can to make your journey a happier one.”


Dr. Maura Scanlan

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