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The Effects Of Fiber On Your Gut Microbiome
Updated on November 14, 2023
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The Effects Of Fiber On Your Gut Microbiome

The gut microbiome describes the community of harmful and beneficial bacteria in your gastrointestinal (GI) tract. Its importance to your overall health is not limited to the digestive system.

It also influences many other body systems, like your immune and central nervous systems. Research shows that the gut microbiome affects your stress and immune response.1

If you’re looking for proactive ways to optimize your health, it may be best to start with your gut. Improving your gut microbiome through fiber intake can affect your overall health and how you feel every day. 


The harmful and beneficial bacteria in your gut comprise your gut microbiome. It influences not only your digestive health but also other functions of your body.

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How Fiber Affects Your Gut Microbiome

Fiber, or dietary fibers, is a type of macronutrient your body can’t break down. It ends up in the colon undigested, where the gut bacteria ferment it.

Studies suggest that fiber promotes good gut bacteria growth by nourishing them. Yes, that’s right—they become food to the friendly microbes in your colon.2

By encouraging the increase of helpful bacteria, fiber helps maintain the balance in your gut microbiome.

Research shows that fiber-rich foods boost the population of friendly microbes like Bifidobacterium. It’s an important strain because it helps prevent infection and inflammation in your gut.3

Some types of fiber support the gut bacteria in producing short-chain fatty acids (SCFAs). SCFAs can help prevent inflammation in the gut by strengthening the intestinal barrier.

SCFAs enhance the function of tight junction proteins (TJps). Tight junction proteins are like seals located between the cells in the gut.4

They control the permeability of the gut lining, only allowing the absorption of nutrients and water. They prevent foreign bodies, like undigested food particles and bacteria, from leaking into the bloodstream.4


Fiber is a form of carbohydrate that your body can't digest. Instead, it makes its way to the colon, where friendly bacteria ferment it.

Does Increasing Fiber Intake Improve Your Gut Microbiome?

Yes, it does.

Consuming high-fiber foods can improve the composition of your gut microbiome. It's especially true if you haven't been getting enough fiber in your diet.

Health experts recommend eating between 25 and 30 grams of fiber daily to optimize your digestive health.5

However, abruptly increasing your fiber intake can cause digestive discomfort, like bloating.  To optimize your gut health, you should gradually increase your fiber intake.


Increasing your fiber intake can improve your gut microbiome. However, to avoid digestive discomfort, you need to do it gradually.

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Soluble and Insoluble Fiber: What’s the Difference?

Fibers have two main types: soluble and insoluble. Both are helpful for your health but differ in a few ways.

Soluble Fiber

Soluble fiber dissolves in water and when exposed to intestinal fluid. When it dissolves, it forms a gel-like material that moves through your system and cleans out the “bad” stuff it encounters.

It also feeds the helpful gut bacteria once it’s in the colon. Soluble fiber can be a type of prebiotic fiber.6

Prebiotics are fibers that serve as a food source for the live microorganism in your gut. Your body can't digest them, so they make it pass to the colon undigested. Once in there, the gut bacteria ferment them.

Soluble fibers like inulin and oligofructose are considered prebiotics.

The common sources of soluble fibers include:

  • Oat bran
  • Barley
  • Nuts
  • Seeds
  • Beans
  • Lentils
  • Peas
  • Some fruits and vegetables


Soluble fiber dissolves in water to form a gel that moves through and cleanses the GI tract. It also helps feed the friendly gut bacteria once in the colon.

Insoluble Fibers

Insoluble fibers don't dissolve in fluids. They absorb what they encounter or stick to other materials to form stools. Increasing your insoluble fiber intake leads to softer, bulkier, and more regular stools.

Although insoluble fiber doesn't provide food for the beneficial bacteria in the gut, it has benefits for your gut health that may indirectly impact your gut microbiome.

For instance, insoluble fibers can help lower gut inflammation by binding to toxins and preventing their harmful effects on your body.

Insoluble fibers are found in the following foods:

  • Wheat bran
  • Vegetables
  • Whole grains


Insoluble fiber doesn't dissolve in water. But it helps form stools by absorbing materials they encounter in the gut. It benefits your gut health in a different way than soluble fibers.

What are the Best Food Sources of Dietary Fiber?

Dietary fibers can be found in many types of whole, nutritious foods.

You can help raise the population of friendly bacteria in your digestive tract by increasing your dietary fiber intake from different food sources.

Whole-grain Products

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Most whole-grain products are rich in fiber, such as

  • Whole wheat bread
  • Whole wheat pasta
  • Brown rice
  • Oats


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Fruits are excellent sources of fiber. Fibers from fruits can help ease constipation and improve digestive symptoms. 

The following fruits have the highest fiber content:

  • Apples
  • Avocados
  • Bananas
  • Blackberries
  • Blueberries
  • Guavas
  • Kiwi
  • Mango
  • Orange
  • Passion fruit
  • Pear
  • Persimmon
  • Pomegranate
  • Prunes
  • Raspberries
  • Strawberries


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Adding more vegetables to your diet is one way of getting enough fiber. These are the best high-fiber vegetables to include in your meals: 

  • Artichokes
  • Carrots
  • Cauliflower
  • Collard greens
  • Beetroot
  • Bitter gourd
  • Brocolli
  • Brussels sprouts
  • Eggplant
  • Potatoes
  • Swiss chard

Beans and Legumes

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A family of plants called Fabaceae produces fruits or seeds that are known as beans and legumes. Beans and legumes are great sources of nutrients, including fiber. 

Here’s a list of the most common fiber-rich beans and legumes. 

  • Split Peas
  • Lentils
  • Pinto Beans
  • Mung Beans
  • Cranberry Beans
  • Black Beans
  • Chickpeas
  • Great Northern Beans
  • Kidney Beans
  • Large White Beans
  • Black-Eyed Peas
  • Boiled Soybeans

Nuts and Seeds

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Nuts are nutritious powerhouses packed with fiber and other macronutrients, including protein and healthy unsaturated fats.

The most common high-fiber nuts and seeds you can add to your diet are:

  • Chia seeds
  • Flax seeds
  • Squash seeds
  • Pumpkin seeds
  • Dried coconut
  • Sesame seeds
  • Sunflower seeds
  • Almonds
  • Pine nuts
  • Pistachios
  • Chestnuts

Start by increasing your fiber intake slowly. Add about 2 to 5 additional grams of fiber every few days until you reach your goal. Women should aim for 21 to 25 grams a day, and men 30 to 38 grams a day added to an otherwise healthy diet.

Why Should You Eat A High-Fiber Diet?

A high-fiber diet can help you have healthy digestion and a healthy gut microbiome. High fiber intake makes bowel movements more comfortable because fiber can help relieve constipation.

But in addition to these benefits, eating high-fiber foods can also help:

  • Reduce your risk of colorectal conditions, such as hemorrhoids and diverticulitis
  • Lower your risk of colorectal cancer
  • Lower your cholesterol and blood sugar levels
  • Lower blood pressure levels
  • Reduce your body's fat absorption
  • Potentially lower your risk of cardiovascular disease
  • Help your body process waste better
  • Achieve healthy weight loss

Health Benefits of Improving Your Gut Microbiome

Scientists can’t stress enough how important the gut microbiome is to your overall health. For instance, you've gotta keep the balance between the good and the harmful bacteria, or else gut dysbiosis can occur. 

Gut dysbiosis happens when the population of harmful microbes in your GI tract becomes greater than the beneficial ones. 

It can lead to various mild or serious digestive symptoms, such as stomach upset, diarrhea, bloating, and bad breath.

But besides your digestive system, the gut microbiome also affects other aspects of your health, like the immune system. Did you know that 80 percent of your immune system is in the gut?

The gut microbiome influences your immune response. Your microbiota helps strengthen your immunity against harmful microbes, infections, and diseases.

The gut microbiome also affects the other aspects of your wellness, such as:

  • Metabolic health – A healthy gut microbiome contributes to better food digestion and nutrient absorption, which can lead to improvements in your energy levels and weight management. 
  • Inflammation – An balanced microbiome can help fight inflammation and its chronic effects in your body. 
  • Moods and mental health – A healthy gut microbiome supports the production of serotonin and dopamine hormones. These two are also neurotransmitters essential in mood stabilization and mental health.7


A balanced gut microbiome is crucial for overall health. It helps boost your digestion, immune function, and metabolism. It can have a positive impact on the state of your mental health.

Key Takeaway

What you eat directly impacts the delicate balance in your gut microbiome. You can help encourage the growth of beneficial bacteria by making fiber-rich foods a regular part of your diet.

Focus on adding more high-fiber whole foods, like fruits, vegetables, whole grains, and others, to your meals. If you feel you’re still not getting enough fiber, consider taking fiber supplements

However, we recommend talking to your doctor first before taking any supplements.

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Updated on November 14, 2023
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Updated on November 14, 2023
Kelly Jamrozy
Kelly Jamrozy
Content Contributor
Kelly has experience working with clients in a variety of industries, including legal, medical, marketing, and travel. Her goal is to share important information that people can use to make decisions about their health and the health of their loved ones. From choosing the best treatment programs to improving dental and vision health to finding the best method for helping anyone who is struggling with health issues, she hopes to share what she learns through informative content.
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