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The Effects Of Fiber On Your Gut Flora
Updated on January 4, 2023
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The Effects Of Fiber On Your Gut Flora

The gut microbiome describes the harmful and helpful collection of bacteria in a person’s gastrointestinal tract. The microbiome plays an important role in someone’s overall health. It affects everything from stress to how susceptible someone is to serious illnesses.

There are more than three million genes in the gut microbiome. Each person’s microbiome is unique and affects his or her digestion, mood, immunity, and psychological processes. 

Improving your gut microbiome can have a profound effect on your overall health and how you feel every day. 

This is because gut microbes affects:


Nutrition and your gut microbiome work in a cyclical nature. 

What you eat affects it and it affects how your body processes the food you eat. An unhealthy gut microbiome is unable to absorb nutrients from food as well as that of a healthy microbiome. 


People inherit their initial microbes from their mothers. 

Without these, you’d never develop adaptive immunity. These microbes teach your body how to respond to harmful and helpful bacteria. 

Over time, you can strengthen or weaken your gut’s microbiome based on what you eat and other factors.


Your gut’s microbiome affects your brain, which plays a role in digestion. This is why some refer to the gut as the body’s “second brain.” 


People with an unhealthy gut microbiome might have a higher risk of developing various inflammatory bowel diseases and metabolic syndrome. 

The health of your gut also affects your risk of:

  • autoimmune conditions
  • allergies
  • cognitive function
  • brain development
  • energy

Disturbing or weakening a healthy gut microbiome, which often happens when you take antibiotic medications, can lead to diseases.

Increasing fiber intake is one of the most effective ways to improve your gut’s microbiome.

The Effects Of Fiber On Your Gut Flora 2

How Does Fiber Affect the Gut Microbiome?

What you eat plays a significant role in the health of your gut microbiome. 

But increasing how much fiber you eat isn’t enough to improve the situation. The type of fiber and the quality of the fibrous foods you eat matters, too. 

Dietary fiber supports the production of short-chain fatty acids. Unfortunately, the standard American or Western diet is high in saturated fat and low in fiber. This approach to eating damages the gut’s microbiome and our overall health.

Nutrition experts recommend eating between 25 and 30 grams of fiber a day to reduce the risk of heart disease, stroke, type 2 diabetes, and colon cancer. 

However, increasing fiber intake can be uncomfortable and might aggravate some digestive issues. This is why a low-fiber diet might be recommended for people with inflammatory bowel disorders. 

The key to getting enough fiber to maintain good gut microbiome health is to gradually increase fiber intake and choose the healthiest sources of fiber.

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Does Increasing Fiber Intake Improve Your Gut’s Microbiome?

Some people don’t need to see research to know that increasing their fiber intake makes them feel better. 

Eating a high fiber diet improves bowel regularity. Additionally, they feel better overall when their gut microbiome is healthier. 

There’s also evidence that gut bacteria improves when you increase dietary fiber intake.

One Australian review of existing data concluded that increasing the intake of certain high-fiber foods and supplements increased Bifidobacterium and Lactobacillus species, as well as in fecal short-chain fatty acids compared to the control group. The research shows that increasing high-quality prebiotic fiber. 

The increase in dietary fiber did not affect the abundance of other bacteria, including Faecalibacterium prausnitzii, Roseburia spp., Eubacterium rectale, and Ruminococcus bromii.

The review also showed that supplements were more effective than food for increasing the helpful gut bacteria, but they believe that could be due to study participants eating cereals and grains as food sources of fiber. 

In most cases, medical professionals recommend dietary improvements first and then supplementing to “fill in the holes.”

The study concluded that different fiber sources have varying impacts on the gut’s microbiome. However, researchers believe that fiber supplements improve gut health.

What are the Best Food Sources of Dietary Fiber?

If you’re interested in adding more fiber to your diet, you have plenty of options. 

Start by increasing your fiber intake slowly – about 2 to 5 additional grams 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.

The following foods are high in fiber:

  • Raspberries
  • Pears
  • Apples
  • Bananas
  • Strawberries
  • Green peas
  • Broccoli
  • Turnip greens
  • Brussels sprouts
  • Cauliflower
  • Whole-wheat spaghetti
  • Barley
  • Bran flakes
  • Quinoa
  • Oat bran
  • Oatmeal
  • Split peas
  • Lentils
  • Black beans
  • Chia seeds

These are not the only sources, but they’re good options if you’re just getting started with adding more fiber to your diet. Ideally, you’ll want to choose organic, high-quality sources and avoid added sugars and processed chemicals. 

For example, if you choose to switch to oatmeal for breakfast to increase fiber, avoid pre-packaged, high-sugar oatmeal mixes and opt for plain oats.

What’s the Difference Between Soluble and Insoluble Fiber?

Both types of fiber are helpful for your health, but they are different in a few ways.

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. 

Insoluble fiber, on the other hand, doesn’t dissolve in fluids. 

It absorbs what it encounters or sticks to other materials to form stool. Increasing your insoluble fiber intake leads to softer, bulkier, and more regular stools.

In addition to improving the health of your gut’s microbiome, both types of fiber improve:

  • Digestion
  • Heart health
  • Cancer, especially colorectal cancer and breast cancer.
  • Diabetes
  • Lifespan
  • Weight management

There are also benefits specific to each type of fiber. For example, soluble fiber:

  • Reduces your body’s ability to absorb fat
  • Lowers cholesterol and blood sugar levels
  • May reduce heart disease risk
  • Increases healthy gut bacteria, which lower inflammation in the body and help you digest better

Benefits of insoluble fiber include:

  • Helps your body process waste better
  • Improves bowel health
  • Prevents and treats constipation
  • Reduces your risk for colorectal conditions, such as hemorrhoids and diverticulitis

The health benefits of eating more fiber from plant foods is undeniable. In addition to improving your gut microbiome, eating more fiber reduces your risk of colorectal cancer and improves the health of your entire digestive tract.

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Updated on January 4, 2023
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5 sources cited
Updated on January 4, 2023
  1. Cresci, Gail A., and Emmy Bawden. “Gut Microbiome.” Nutrition in Clinical Practice, vol. 30, no. 6, 8 Oct. 2015, pp. 734–746, 10.1177/0884533615609899,

  2. Makki, Kassem, et al. “The Impact of Dietary Fiber on Gut Microbiota in Host Health and Disease.” Cell Host & Microbe, vol. 23, no. 6, June 2018, pp. 705–715,, 10.1016/j.chom.2018.05.012.

  3. So, Daniel, et al. “Dietary Fiber Intervention on Gut Microbiota Composition in Healthy Adults: A Systematic Review and Meta-Analysis.” The American Journal of Clinical Nutrition, vol. 107, no. 6, 2018, pp. 965–983,, 10.1093/ajcn/nqy041.

  4. Mayo Clinic. “How Much Fiber Is Found in Common Foods?” Mayo Clinic, 2018,

  5. What’s the Difference between Soluble and Insoluble Fiber?” Health Essentials from Cleveland Clinic, 1 Feb. 2021,

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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