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7 biggest benefits of prebiotics for digestion, immune function, and more

Written by John Davis

Last updated: March 26, 2023

Prebiotic supplements provide the nutrients that healthy bacteria need to thrive in your body. Gut bacteria support not only digestive function, but immune function, hormone synthesis, and even neurotransmitter function.

Having a healthy gut microbiome requires not only a solid combination of healthy bacteria, but the nutrients they need to sustain themselves. A prebiotic supplement provides exactly that.

Some of the simplest prebiotics are just naturally-sourced fiber, like psyllium husk, but the best supplements go beyond this, supplying an array of nutrients that help foster probiotic bacteria growth.

Looking to leverage prebiotics to improve your health and wellness? Check out these key benefits our research team uncovered when sifting through the scientific research on

Prebiotics benefits

1. Prebiotics are “food” for beneficial bacteria

A prebiotic supplement provides the food and the substrate that probiotic bacteria need to take hold in your digestive system. Probiotics can digest substances that your body can’t, like fiber and long chains of sugars called oligosaccharides. 

Taking probiotics for a healthier gut bacteria population is great, but it doesn’t do a whole lot of good if they can’t grow and multiply effectively. 

2. Prebiotics can improve gastrointestinal health

One of the earliest avenues of research into the function of probiotic bacteria was in chronic conditions of the gastrointestinal tract like inflammatory bowel disease and Crohn’s disease.

It appears that fiber-based prebiotic supplements are helpful for treating these conditions, according to a scientific article published in 2014 by researchers at the Royal Marsden NHS Foundation Trust in London (1).

In a review of previous research, the authors conclude that taking supplemental fiber helps increase the growth of beneficial bacteria in the digestive tract in people with inflammatory bowel diseases, which in turn decreases inflammation and improves symptoms.

Prebiotics also tend to improve the function of the mucous layer that lines the stomach and intestines, protecting it from damage by substances that are in the digestive tract.

3. Prebiotics can improve immune function

 Emerging research is demonstrating that your immune system and your digestive system are closely linked.

According to a study published in 2005 in the British Journal of Nutrition, consuming oligosaccharides, which are digestible by probiotic bacteria, increases production of a component of the immune system called natural killer cells (2).

These are what seek out and destroy harmful pathogens inside your body.

The same properties appear to be associated with inulin, which explains why it’s in so many prebiotic supplements. The authors even hypothesize that the increased immune function could potentially decrease risk for colon cancer, and call for future research to examine that topic.

4. Prebiotics can help prevent weight gain

A study published in the Journal of Pediatrics in 2007 by a team of researchers at Baylor College of Medicine examined the effects of a year-long prebiotic supplement routine in comparison to a placebo (3).

Nearly 100 adolescents were given either a prebiotic supplement or a placebo, and the medical researchers tracked their increase in body mass index over the course of the year. The results showed that the prebiotic supplement resulted in less of an increase in body mass index at the study’s conclusion.

5. Prebiotics can lower your stress levels and increase positive emotions

Beyond just the physiological, the benefits of a prebiotic supplement appear to extend into the psychological realm too.

A study published in the journal Psycho-Pharmacology examined the emotional and hormonal effects of a fiber-based prebiotic supplement on levels of the stress hormone cortisol and self-reported positive and negative emotions (4).

The researchers tested the prebiotic supplement in comparison to a placebo over the course of three weeks and found two remarkable results.

First, the prebiotic supplement lowered levels of cortisol, which indicates lower levels of stress.

Second, the prebiotic resulted in decreased attention to negative emotions and increased attention to positive emotions, indicating that a prebiotic supplement could boost your mood and decrease stress.

6. Prebiotics can help older adults boost the levels of beneficial bacteria

Much of the research on probiotics and prebiotics to date has focused on people with various health problems, or on young and healthy volunteers, but new research is showing that prebiotics can be beneficial for older adults too.

A study published in 212 in the British Journal of Nutrition recruited a group of older adults (age 50 and older), and randomly assigned to receive either a juice with four grams of prebiotics per day, or a placebo juice (5).

After three weeks, the groups were switched. Throughout the study, the researchers tracked the levels of specific beneficial bacteria in the volunteers by monitoring levels of these bacteria in fecal samples taken regularly.

The levels of beneficial bacteria were significantly higher in the volunteers while they were taking the prebiotic supplement compared to the placebo, which suggests that adults over 50 can benefit from prebiotics even at fairly moderate doses.

7. Prebiotics can help lower blood triglycerides

A systematic review published in the journal Clinical Nutrition in 2015 showed that prebiotic supplementation resulted in a significant decrease in blood triglycerides, as well as a decrease in blood cholesterol levels (6).

These findings suggest that prebiotics could be an incredibly useful tool for reducing risk factors for heart disease, particularly in people who have other risk factors for heart disease as well, such as type two diabetes or obesity.

Prebiotics side effects

Prebiotics are very safe. From a medical standpoint, prebiotic supplements are very safe—their ingredients are not particularly biologically active.

You might get bloating and gas initially when you start taking a prebiotic. However, one well-documented side effect seen in many studies is bloating and gas, which results from the rapid growth of probiotic bacteria in your stomach and the resultant increase in production of gas.

This side effect appears to be worse in people who do not have much fiber in their diet. The good news is that these side effects do decrease over time as your body acclimates to higher fiber intake.

You can also try gradually ramping up your dosage over time to acclimate to prebiotics without inducing these side effects.

Prebiotics dosage

A good strategy is to start with 4 grams per day of inulin or FOS. Research on probiotics is in its early stage, so scientific studies are all over the board with their dosage of prebiotics. The best review on dosing guidelines so far comes from researchers at the University of Reading in the United Kingdom (7).

They recommend a minimum of four grams per day for prebiotics that use inulin or oligosaccharides, and a maximum of 20 grams per day. Doses beyond this level may create the gastrointestinal side effects that characterize some prebiotic supplements.

If you aren’t getting the results you want, you might try a higher dose. Prebiotic supplements appear to follow a dose-response relationship: that is, more tends to be better.

A study by researchers at the University of Nebraska Lincoln compared a 2.5 gram, a 5 gram, and a 10 gram daily dosage level of a prebiotic supplement and found that the best results came from higher doses of the prebiotic supplement (8).

Prebiotics benefits FAQ

Q: What is a prebiotic?

A: “Prebiotic” is a broad term for any nutrient that promotes the growth of probiotic bacteria in your body. Prebiotics include things as simple as dietary fiber, and things as sophisticated as fructooligosaccharides or special fruit or vegetable extracts.

Typically, these ingredients can be consumed by bacteria, but not your body, for energy. Take dietary fiber, a simple example: it can’t be digested for calories by your body, so it lasts a lot longer in your digestive tract than a standard nutrient like carbohydrates or sugar.

A probiotic bacteria, however, like bifidobacterium, can digest fiber, so the increased presence of this nutrient helps boost the levels of these bacteria.

Q: What is the difference between a prebiotic and a probiotic?

A: A probiotic is an easier supplement to define: to be considered a probiotic supplement, a product must contain live bacterial cultures that will multiply once inside your body. A good probiotic will specify exactly how many colony-forming units (CFUs) are included per serving of a probiotic.

A prebiotic, on the other hand, contains nutrients that boost the ability of probiotic bacteria to thrive and multiply in your body. Prebiotics, such as those in our rankings, will include ingredients like fructooligosaccharides or various fiber sources.

Confusingly, prebiotic-focused supplements can sometimes include live bacterial cultures as a secondary ingredients, and probiotics will sometimes also include prebiotic ingredients.

The distinction comes in the primary purpose of the supplement: Is it to deliver live bacteria? If so, it’s a probiotic. Is it to provide nutrients for beneficial bacteria? If so, it’s a prebiotic.

Q: What is an example of a prebiotic?

A: One good example of a common prebiotic is fructooligosaccharides. This compound can be found in small amounts in plant sources like bananas, jicama, and chicory root. It’s a sweetener, but your body can’t digest it for calories the way it can digest fructose or glucose.

Probiotic bacteria strains, on the other hand, do digest fructooligosaccharides quite well, so when you take a prebiotic supplement that contains this compound, the levels of probiotic bacteria in your body increase substantially thanks to the extra “bacteria food” present.

However, one caveat to this is that you do need your beneficial bacteria to have a foothold already before you take a prebiotic for it to be beneficial. If your gut microbiome is not in good condition, you’ll want to take your prebiotics alongside a probiotic supplement or probiotic food.

Q: Do prebiotic supplements have to include fiber?

A: Natural sources of fiber like inulin and psyllium husk are indeed great ways to nourish probiotic bacteria, but they aren’t the only way.

Other compounds, like FOS (fructo-oligosaccharides) are not usually lumped into the same category as generic dietary fiber, but are nevertheless excellent prebiotic supplements.

While fiber is useful, other ingredients can also nourish probiotic bacteria, and fiber is not a mandatory ingredient.

Related: Our best prebiotics picks


Prebiotics are a great way to ensure your body’s probiotic bacteria have the nutrients they need to sustain themselves.

A prebiotic supplement is a great add-on to any probiotic routine, but they can be especially useful for people who want better digestive heath, improved immune function, or more effective mood regulation.

Best of all, prebiotics are safe and have a very mild side effect profile, making them a versatile addition to any long-term health supplementation routine.


John Davis

John Davis is a Minneapolis-based health and fitness writer with over 7 years of experience researching the science of high performance athletics, long-term health, nutrition, and wellness. As a trained scientist, he digs deep into the medical, nutritional, and epidemiological literature to uncover the keys to healthy living through better nutrition.