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Prebiotics 101: The Essential Guide to Gut Health

Prebiotics 101: The Essential Guide to Gut Health

Did you know that current research shows that there are only two ways to actually change the composition of the bacteria in your gut?

The first, less common, and more specialized way is through a procedure called a fecal transplant, which is typically reserved as a medical intervention. The second, highly approachable way is through your diet - with a special focus on prebiotics!

Prebiotics also come in supplemental form, but they are abundant in plant-based, whole foods! You can think of prebiotics as the facilitators of the proverbial “field of dreams.” Remember the phrase, “if you build it, they will come?” Well, “if you eat probiotics, the good bacteria will come.”

Gut health is pivotal to our overall longevity and quality of life, and prebiotics are a major player. In fact, I would argue that once you’ve returned to a state of balance after addressing an imbalance, long-term gut health can be maintained with food, especially prebiotics, alone!

In this post, we will explore a technical definition of probiotics and by the end, you should better understand how they work, where they come from, and how they can benefit your long term health!

What are Prebiotics?

To start, you can think of prebiotics as the food or fuel for the normal or beneficial bacteria in our guts! Prebiotics come before probiotics, which we’ll explore more in a separate post. Practically speaking, a majority of our prebiotics come from plant fibers that we can’t digest on our own.

The technical definition of a prebiotic food has three facets that must be true for a food to be classified as such! This three-part definition of prebiotics was originally coined in 1995 by Gibson and Roberfroid.

For a food to be considered a prebiotic, it must:

  • NOT be digestible by the host (meaning we humans don’t have the digestive enzymes to break down the substance ourselves)
  • Selectively stimulate microbes within our gut
  • Bring about a benefit to the host

All three of these must be true, and you can see how directly prebiotics act to stimulate the growth and activity of our good microbes and how these interactions impart various benefits to the host!

How Do Prebiotics Work?

In essence, prebiotics work by encouraging and directing the growth and maintenance of the beneficial species of your gut microbial populations.

They do this primarily by performing chemical reactions that aren’t normally available in the human digestive tract alone. They can ferment indigestible plant fibers, process phytonutrients, and even detoxify hormones and environmental toxins to transform them into more beneficial compounds.

Perhaps one of the most fascinating reactions that takes place is the way that gut bacteria act on these undigested plant fibers. In many ways, this is as phenomenal as the way plants take water, sunlight, and carbon dioxide to create sugars through the process of photosynthesis.

The fermentation process of prebiotic plant fibers, which are complex carbohydrates, produces short-chain fatty acids (SCFAs), which are fats. These microbes literally create fat from carbs, and these fats serve as a critical energy source for colon cells, help maintain the gut barrier, and reduce inflammation!

Top Food Sources of Prebiotics

There are several types and subclassifications of prebiotics based on their molecular structure and functional properties. While we dive into some of the top food sources, let’s briefly explore some of the main categories of prebiotics as well.

  1. Fructooligosaccharides (FOS) are a well-known prebiotic made from a chain of fructose molecules and are known for their ability to selectively promote the growth of beneficial bacteria such as Bifidobacteria. Common food sources include garlic, onions, leeks, asparagus, bananas, and chicory root.
  2. Galactooligosaccharides (GOS) are another prebiotic made from chains of galactose molecules. They effectively enhance the growth of Bifidobacteria and Lactobacilli. Common food sources include beans, lentils, and certain root vegetables.
  3. Inulin is a well-researched soluble fiber found in many plants. It is often used as a dietary supplement to improve digestive health and promote the growth of beneficial bacteria. Common food sources include chicory root, jerusalem artichokes, garlic, onions, and wheat.
  4. Resistant starch is another type of indigestible plant fiber that ferments in the large intestine. It feeds beneficial gut bacteria, resulting in the production of short-chain fatty acids Common food sources include cooked potatoes, green bananas, legumes, and whole grains.
  5. Pectin is a form of soluble fiber commonly found in fruits that promotes the growth of beneficial bacteria in the gut. Common food sources include apples, citrus fruits, carrots, and berries.
  6. Beta-glucans are another prebiotic that naturally occurs in the cell walls of cereals, bacteria, and even fungi. They have immune-boosting properties and promote microbiome diversity as well. Common food sources include oats, barley, mushrooms, and seaweed.

Including these and other prebiotic-rich foods in your diet can help impart health benefits that we will explore further. I generally recommend trying to get a minimum of 25 grams of prebiotics/fiber in your diet every day but consult a health or wellness practitioner for your specific needs.

Health Benefits of Prebiotics

So what are the health benefits that are associated with prebiotics? They are numerous, and directly influence our gut health and other systems throughout the entire body.

A 2018 study looked at eight key health benefits of prebiotics. You may be surprised by some of these findings, but know that these are just scratching the surface of the wide actions of prebiotics on our overall health!

The eight benefits of prebiotics in this study include the following:

  • They increase the populations of Bifidobacteria and Lactobacilli species, both beneficial microbes in the human microbiome.
  • They produce important products from chemical reactions, including short-chain fatty acids for energy and anti-inflammatory functions.
  • They increase calcium absorption, which supports bone health and cardiovascular health.
  • They decrease the fermentation of protein, which is less beneficial and even potentially harmful if prebiotics are not available.
  • They compete for resources with and can “starve out” potentially pathogenic bacteria.
  • They decrease the risk of allergies.
  • They help promote integrity and healing of the gut lining and protect against “leaky gut.”
  • Improve the strength of our immune system response.

Again, this is just a snapshot of the many benefits that prebiotics give us, but these eight highlight the breadth and depth of healing influence that they have.

Potential Side Effects of Prebiotics

As with nearly anything, some people may experience side effects when focusing on incorporating or increasing prebiotics, both from foods or supplements.

Here are a few of the most common side effects associated with increased prebiotic intake:

  • Bloating, distension, gas, pain - because of the fermentation process, gas is a byproduct and may produce these side effects.
  • Loose bowel movements or constipation - prebiotics and increased fiber intake may lead to either loose bowel movements or constipation.
  • This depends on the individual and the current state of your hydration and microbiome composition.
  • Flare ups of existing conditions - Some individuals with irritable bowel syndrome (IBS), diverticulitis, small intestinal bacterial overgrowth (SIBO), or other conditions may experience an increase of symptoms.

As always, I recommend consulting with a healthcare or wellness practitioner about your personalized needs. If you have such reactions or side effects from probiotics, it might warrant some further investigation such as through a comprehensive functional medicine stool test or conventional investigation.

Tips to Decrease Side Effects & Maximize Benefits of Prebiotics

If your goal is to harness the potential benefits of prebiotics in your life while minimizing potential side effects, there are a few tips that you can follow:

  • “Start low, and go slow” - Slowly increase and introduce new sources of probiotics so as not to “shock your system” too quickly.
  • This is a great general rule of thumb with therapeutic interventions, whether food, supplements, or otherwise.
  • Optimize hydration - Hydration is important to encourage ideal fluid balance. Since increasing prebiotic corresponds with an increased intake of fiber, it’s important to balance the bulk with hydration to maintain normal bowel function.
  • Increase variety - To maximize benefits of prebiotics, try to incorporate a wide variety of sources rather than just an increased amount of a single prebiotic source or category. Increased diversity of plants corresponds to increased diversity of helpful microbes!

Conclusion and the Future of Prebiotics

As we have explored, prebiotics play a crucial role in fostering a healthy gut microbiome, which is fundamental to our overall health and well-being.

Another highlight is that prebiotics are accessible as sources range from everyday foods like garlic and onions to Jerusalem artichokes and supplements. Prebiotics are a direct representation of Hippocrates: “Let food be thy medicine.” Integrating prebiotics into your diet is a practical and effective way to nurture your gut health. I recommend trying the Horizon supplement if you don't know where to start.

By incorporating a variety of prebiotic-rich foods into your meals, you are essentially tending and fertilizing your internal garden - your microbiome. Remember, “if you build it, they will come.”

The future of prebiotics in overall health is promising. As science continues to uncover the extensive benefits of prebiotics, it becomes clear that maintaining long-term gut health can be effectively achieved through diet, particularly by emphasizing prebiotic intake.

To stay connected with more exciting and practical health topics, follow Cielo and Dr. Kenny on Instagram and check out more information blog topics on their websites! I hope you took something practical and implementable away from this exploration of the power of prebiotics!

About the Author

Dr. Kenny Mittelstadt, DACM, DC, L.Ac., Dipl.OM.

Kenny Mittelstadt is a functional health practitioner and acupuncturist based in San Antonio, Texas. He is trained through the Institute for Functional Medicine and received both of his doctorate degrees with highest honors from Southern California University of Health Sciences. He focuses on empowering patients through wellness education and root-cause healing – transforming health through personalized, lab-based functional medicine programs!



Barbara Walters

I have been taking a prebiotic/inulin off and on for many years and find it has been very effective in maintaining a healthy stool. Occasionally I will add a probiotic tablet just in case but this does not have an added effect from my point of view. Your article confirms my experience and is very appreciated.l


Thank you for publishing this helpful article related to prebiotic.

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