Can a new pill fix our gut problems? Are postbiotics a new opportunity or just a bad shortcut?

Rafal Nazarewicz, Ph.D. 

Key concepts:

Prebiotics-  types of fiber that are utilized by beneficial gut host microorganisms, conferring a health benefit. They act as "food" to help beneficial gut bacteria grow and thrive.

Probiotics- These are the beneficial bacteria themselves that add to the existing gut microbiome. They are often found in fermented foods like yogurt, kefir, and sauerkraut, or taken as supplements.

Postbiotics- These are the beneficial metabolic byproducts (like short-chain fatty acids, enzymes, and peptides) produced by probiotics when they break down prebiotics. Postbiotics are stable and do not carry the risk of infection that live bacteria might in immunocompromised individuals.

If you follow nutrition trends, you have probably seen postbiotics marketed as a more innovative, easier way to “fix your gut” and boost performance. The idea is seductive: keep your usual diet, take a capsule of microbiome magic, and improve your health and recovery.

The science behind postbiotics is genuinely interesting. The problem is when they become an excuse to cut corners on the basics.

What postbiotics actually are

To be clear, we have known postpiotics for quite some time. They were just not called that way. Postbiotics are defined as bioactive substances of probiotics. We have used them as markers of gut microbes' functions. For example, butyrate has been used as a marker of a healthy gut for decades. Butyrate is produced when our diet is rich in whole grains, legumes, fruits, vegetables, nuts, and seeds, as these feed the bacteria that make it. While we have known about these substances for a while, the concept of delivering postbiotics as a treatment is new and interesting. If the health of our gut depends on substances produced by bacteria, why not directly provide those substances to our gut to support its functions?  

Early studies show some promising signs. Research shows evidence that postbiotics can strengthen the intestinal barrier, modulate immune responses, inhibit pathogens, and influence metabolic and inflammatory pathways. Postbiotic components (short-chain fatty acids, cell wall fragments, etc.) exhibit anticancer, antimicrobial, and immunomodulatory activities. Postbiotics could serve as adjunct tools for chronic disease management, suggesting they can help modulate inflammation, improve gut barrier function, and even alter drug absorption and pharmacokinetics. However, most of the hard data is still from animal models and small human trials. 

A 2024 systematic review in Nutrients looked at postbiotics specifically for exercise performance and recovery. It found some encouraging signals for immune outcomes, upper respiratory symptoms, perceived fatigue, and a few performance markers, but most trials were short, small, and used different products and protocols. 

So the science is real, but the evidence is still early and very context-dependent.

Why trying to “hack” your gut can backfire

Endurance athletes love efficiency: faster, lighter, easier. Supplements that promise to replace much of the tedious diet work fit right into that mindset. But there are some hard limits here.

The gut responds to patterns, not one-off molecules

Dietary patterns rich in diverse fibers support a microbiota that produces short-chain fatty acids (SCFAs) like butyrate, acetate, and propionate. These metabolites support barrier function, regulate inflammation, and influence metabolic health. 

You only get that kind of coordinated effect from the overall structure of your diet, not from sprinkling a single postbiotic ingredient on top of ultra-processed carbohydrates and low-fiber meals.

Diet quality affects far more than the microbiome

High fiber, minimally processed diets bring polyphenols, micronutrients, and healthy fats that influence oxidative stress, vascular function, and glucose control, independent of any microbiome effects. Reviews consistently tie Western-style, low fiber, ultra-processed patterns to dysbiosis, chronic low-grade inflammation, and metabolic risk.

There is no plausible mechanism where a capsule of inactivated bacteria fully offsets that environment.

 Stacking “gut products” on a poor diet can make GI issues worse

Prolonged endurance exercise already strains the gastrointestinal tract through reduced blood flow, heat, mechanical jostling, and high carbohydrate loads. That contributes to the very high rates of GI symptoms reported in endurance events. 

If your baseline diet is low in fiber and then you suddenly add aggressive doses of fermentable prebiotics or multiple “gut health” products, you can easily increase gas, bloating, cramping, and urgency. Recent reviews of nutrition strategies for managing exercise-associated GI symptoms highlight that both excessive fiber intake close to exercise and sudden large changes in fermentable intake can aggravate GI symptoms. 

The athlete data on postbiotics is still modest

The 2024 Nutrients review concluded that postbiotics are promising but that current evidence is limited by study design, small sample sizes, and heterogeneous interventions. 

In other words: interesting tool, not a proven shortcut.

Endurance athletes, GI stress, and why basics matter first

For endurance athletes, the gut is as much a piece of performance equipment as your shoes. Reviews on “training the gut” show that the gastrointestinal tract adapts to repeated exposure to higher carbohydrate intakes and specific fueling patterns, improving comfort and tolerance.

At the same time, surveys and observational work indicate that a huge proportion of endurance athletes report GI symptoms, and many attempt ad hoc dietary strategies like drastic fiber restriction, low FODMAP diets, or cutting entire food groups. A strategy that backfires in the long term.

Overlaying complex supplements on top of:

• inconsistent energy intake
  

• low overall fiber
  

• high reliance on ultra-processed sports foods and snacks
  
  

is usually the wrong order of operations. The foundation has to be consistently high quality, mostly minimally processed food, with thoughtful timing, before specialized microbiome tools make sense.

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How to increase prebiotic intake without wrecking your gut

So what does a sensible, performance-oriented approach look like if you want to feed your microbiome and still race without scouting every porta-potty on course?

Principle 1: Change slowly

General clinical guidance on fiber emphasizes gradual increases to allow microbes and the gut to adapt, rather than abrupt jumps that tend to cause gas and bloating.

A practical rule: increase daily fiber by about 2–3 grams every few days rather than jumping 10–15 grams overnight.

Principle 2: separate “gut training” from key sessions and races

Reviews on GI issues in endurance sports and gut training point to two consistent ideas:

• The gut can be trained through repeated exposure to specific feeding strategies.
  

• Hard sessions and races are not the time to test new high-fiber foods or supplements.

In practice, that means:

• Use easy days and low-priority workouts to test new prebiotic foods or products.
  

• Keep nutrition well-rehearsed and straightforward for long runs, races, and key interval days.
  
  

Principle 3: Place most fiber away from hard training

• Eat the highest-fiber meals at least 3–4 hours before intense training.
  

• In the 1–2 hours pre-workout, focus on lower-fiber, easily digested carbohydrates and modest protein.
  

• During exercise, use fuel sources you have already tested in race-like conditions.
  
  

Stepwise approach to more prebiotics

Here is a structured way to build up prebiotic intake.

Step 1: Add gentle prebiotic foods in small portions

Start with foods that are usually well tolerated and provide fermentable fibers or resistant starch, such as:

• Oats
  

• Ripe bananas
  

• Cooked and cooled potatoes or rice (for resistant starch)
  

• Well-cooked lentils in small portions
  

• Chickpeas or hummus in modest amounts
  

• Mixed nuts and seeds
  
  

These foods are known to support SCFA production and beneficial taxa when incorporated into a regular pattern.

Sample starting point for a week:

• Half a cup of cooked oats at breakfast
  

• Half a banana as a snack
  

• Two tablespoons of hummus or a small handful of nuts with lunch
  

• A few tablespoons of lentils with dinner on an easy day
  
  

If symptoms are minimal after a week, you can gradually increase amounts.

Step 2: Keep experimentation away from race pace

When you introduce a new prebiotic food or increase portion size:

• Do it on days with easy or moderate training.
  

• Avoid trying it in the meal directly before a long run, tempo, or key bike session.
  
  

This mirrors the “train the gut” research, where tolerability improves when athletes repeatedly practice fueling strategies under controlled, lower-risk conditions. 

Step 3: If you use prebiotic supplements, go low and slow

A recent pilot study in recreational endurance athletes tested 12 weeks of B-galacto-oligosaccharides (B GOS) supplementation and monitored wellness and exercise-induced GI symptoms. The results suggest potential benefits, but also showed individual variability in tolerance.

If you decide to experiment with a prebiotic supplement:

• Start with half the label dose or less.
  

• Take it with a meal instead of on an empty stomach.
  

• Stay at that dose for at least a week before increasing.
  

• Change one variable at a time so you can see what is helping or hurting.
  
  

Avoid products that combine high doses of fermentable fibers with large amounts of sugar alcohols (sorbitol, mannitol, xylitol), which are well known to trigger gas and loose stools at relatively low thresholds in many people.

Step 4: Treat race week as a “simplify and protect” phase

In the 24–48 hours before a key race, especially if you have a history of GI issues it is recommended

• Reduce very fermentable, gas-forming foods, such as large servings of beans, onions, and cruciferous vegetables.
  

• Prioritize familiar, lower-fermentable carbohydrate sources if you know you are sensitive.
  

• Keep the overall diet high quality but simpler, with fewer surprises.
  

• Avoid new pre, pro, or postbiotic products during race week if you haven’t tested them in race conditions
  

This does not mean switching to junk food. It means minimizing last-minute novelty while still eating minimally processed, well-tolerated foods.

 

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Where postbiotics actually fit

Putting it all together, a reasonable hierarchy for an endurance athlete looks like this:

1. Foundation
   

• Mostly whole, minimally processed foods.
  

• Consistently adequate energy intake.
  

• Diverse plant foods and fibers across the week.
  

• Adequate healthy fats and quality protein.
  
  

2. Targeted gut training and timing
   

• Practice your race-fueling strategy in training.
  

• Position high fiber meals away from hard workouts.
  

• Use low-risk days to test new prebiotic foods. 

3. Careful use of microbiome-focused products
   
   

• If the basics are solid and you are curious, choose postbiotic or prebiotic products that:
  
  

• Identify the strain/preparation and dose
  
  

• have at least some human data, ideally including active populations
  
  

• Introduce them gradually and monitor GI symptoms, illness days, and training quality.
  
  

4. Guardrails
   

• If ultra-processed sugars and starches still dominate your usual diet, fix that first.
  

• If a product repeatedly causes GI distress, it is not “your” tool, no matter how good the data look on paper.
  
  

Postbiotics are a sign of how far microbiome research has come, and they may well find specific, useful roles for athletes. But they are not a free pass to ignore the unglamorous work of eating real food, in a consistent pattern, that your gut can handle both at rest and at race pace.

For performance, long-term health, and a calmer stomach on course, the biggest “gut hack” is still a solid, high-quality diet.

References

1. Salminen S, Collado MC, Endo A, et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics. Nat Rev Gastroenterol Hepatol. 2021;18(9):649–667. Nature+1
   
   

2. Vinderola G, et al. Frequently asked questions about the ISAPP postbiotic definition. Front Microbiol. 2023;14:1324565. Frontiers
   
   

3. Kerksick CM, Moon JM, Jäger R. It’s dead. Can postbiotics really help performance and recovery? A systematic review. Nutrients. 2024;16(5):720. MDPI+2News-Medical+2
   
   

4. Li N, et al. Unlocking the power of postbiotics: a revolutionary approach to gut health. Clin Nutr. 2024;in press. ScienceDirect
   
   

5. Silva LG, et al. Effects of dietary fibers on short chain fatty acids and gut microbiota composition: a systematic review. Nutrients. 2022;14(14):2769. PMC+1
   
   

6. Louis P, Flint HJ. Formation of propionate and butyrate by the human colonic microbiota. mBio. 2019;10(1):e02566–18. ASM Journals
   
   

7. Costa RJS, Snipe RMJ, et al. Systematic review: exercise associated gastrointestinal symptoms in endurance athletes and nutritional interventions. Sports Med. 2017;47(S1):S99–S112. SpringerLink+2Gatorade Sports Science Institute+2
   
   

8. Papadopoulou SK, et al. Nutritional strategies for minimizing gastrointestinal symptoms during endurance exercise. Int J Sport Nutr Exerc Metab. 2025;35(3):151–167. Taylor & Francis Online+2Frontiers+2
   
   

9. Mielke JG, et al. Fueling gut microbes: interaction between diet, gut microbiota and athletic performance. Curr Nutr Rep. 2022;11(4):675–690. ScienceDirect
   
   

10. Davison H, et al. The effects of 12 week prebiotic supplementation on general wellness and exercise induced gastrointestinal symptoms in recreationally trained endurance athletes. Nutrients. 2025;17(21):3390. 

Notes: 

In 2021, an expert panel from the International Scientific Association for Probiotics and Prebiotics (ISAPP) proposed a now widely used definition: postbiotics are preparations of inanimate microorganisms and/or their components that confer a health benefit on the host. Nature+1

Key points baked into that definition:

• The microbes are inactivated (for example, heat killed), so they are not live probiotics. Frontiers
  
  

• The preparation can include whole cells, cell fragments, and metabolites such as organic acids, peptides, exopolysaccharides, or other bioactive molecules. ScienceDirect+1
  
  

You cannot call something a postbiotic unless there is evidence of benefit in an appropriate model or clinical study. Frontiers