Probiotics vs. Prebiotics: What’s the Difference, and Do You Actually Need Them?
Walk into any grocery store or scroll through wellness content online, and you’ll see probiotics and prebiotics everywhere—yogurt labels, powders, capsules, snack bars, kombucha, you name it. They’re often lumped together, but they actually play very different roles in supporting gut health.
If you’ve ever wondered whether you need one, both, or neither, this guide breaks down what the science actually says (without the jargon) and how to choose what’s right for you.
First Things First: What Are They?
Probiotics = helpful microbes
Probiotics are live microorganisms—usually certain types of Lactobacillus, Bifidobacterium, and Saccharomyces—that can provide health benefits when taken in adequate amounts. Think of them as the “good guests” you invite into your gut.
But here’s the important part:
Not all probiotics do the same thing.
Different strains have different purposes, and the benefits are very condition-specific.
Prebiotics = fuel for your good microbes
Prebiotics, on the other hand, are non-digestible fibers that feed your existing beneficial bacteria. Examples include inulin, fructo-oligosaccharides (FOS), and galacto-oligosaccharides (GOS).
Instead of adding new bacteria, prebiotics help the good bacteria you already have thrive.
A simple way to remember it:
👉 Probiotics = the bacteria
👉 Prebiotics = their food
What Does the Research Actually Support?
When probiotics help most
Research consistently shows probiotics can be helpful for certain digestive conditions, especially:
Antibiotic-associated diarrhea
Some infectious diarrheas
Pouchitis
Certain types of acute gastrointestinal infections
Outside of these areas—like IBS, IBD, or mood/metabolic conditions—the evidence is more mixed or inconsistent. The American Gastroenterological Association recommends using probiotics only when the exact strain has been shown to help the specific issue you're targeting.
In other words: a probiotic that helps diarrhea won’t necessarily help constipation, bloating, or immune health. One size does not fit all.
Where prebiotics shine
Prebiotics help beneficial bacteria flourish, and research shows they may:
Improve stool consistency
Support immune function
Offer metabolic benefits
Increase the abundance of health-promoting bacteria like Bifidobacterium
The evidence on specific disease outcomes (like IBS, blood sugar regulation, or inflammatory conditions) is still developing, but overall, prebiotics are considered safe and useful for general gut support.
Food First: Getting Probiotics and Prebiotics from Your Plate
You don’t have to start with supplements. Many people can support their gut through food before considering pills or powders.
Best food sources of probiotics
Look for foods fermented with live cultures:
Yogurt with live and active cultures
Kefir
Sauerkraut
Kimchi
Miso
Tempeh
Certain fermented pickles
These foods bring a variety of microbial strains—not just one—plus extra nutrients, flavor, and texture.
Best food sources of prebiotics
These plant foods naturally contain inulin and oligosaccharides that feed beneficial bacteria:
Chicory root
Jerusalem artichokes
Onions, garlic, leeks
Asparagus
Bananas
Whole grains
Beans and lentils
Most people get prebiotic fibers from everyday foods without realizing it.
Should You Supplement? Here’s When It Might Make Sense
Probiotics
Supplements may be worth considering if:
You’re taking antibiotics
You have a condition with strong evidence for specific strains (e.g., pouchitis)
A healthcare provider recommended one for a targeted purpose
Because benefits depend on the exact strain and dose, a high-quality probiotic should list:
The full strain name (e.g., Lactobacillus rhamnosus GG)
The CFU count (the number of live organisms)
Evidence-based doses used in clinical trials
A clear expiration date
Storage instructions (some need refrigeration)
Third-party testing or quality certification (USP, NSF, ConsumerLab, etc.)
Avoid anything vague like “proprietary blend”—that usually means you can’t tell what’s in it.
Prebiotics
A prebiotic supplement may help if:
You struggle to get enough fiber from food
You’re working on regularity or supporting beneficial bacteria
You and your clinician agree on a specific prebiotic trial
The best-studied options include:
Inulin
Fructo-oligosaccharides (FOS)
Galacto-oligosaccharides (GOS)
Because prebiotics ferment in the gut, some people may notice gas or bloating at first—starting low and slowly increasing can help. If you’re not sure where to start, a clinician can help match the right product to your goals.
So… Do You Need Both?
Not necessarily.
Some people benefit from both, some from one, and some from neither. The right choice depends on:
Your digestive symptoms
Your health history
Your overall diet
What you hope to improve
For many people, a food-first approach—with consistent fiber and occasional fermented foods—is enough to support a thriving gut environment.
Supplements can be useful tools, but they’re not a requirement for good gut health.
The Bottom Line
Probiotics and prebiotics each play unique (and complementary) roles:
Probiotics add beneficial microbes—helpful in certain clinical situations.
Prebiotics feed beneficial microbes—supportive for general gut health.
Food sources are usually the best starting point.
Supplements should be chosen thoughtfully, based on evidence and transparency.
Gut health isn’t about perfection or complicated routines—it’s about small, consistent choices that feel sustainable for your body and your life.
If you’d like help choosing the right approach for your digestion, symptoms, or overall gut health, working with a dietitian can give you personalized, research-backed guidance.
References:
ACG Clinical Guideline: Diagnosis, Treatment, and Prevention of Acute Diarrheal Infections in Adults. Riddle MS, DuPont HL, Connor BA. The American Journal of Gastroenterology. 2016;111(5):602-22. doi:10.1038/ajg.2016.126.
Probiotics, Prebiotics, and Synbiotics. de Vrese M, Schrezenmeir J. Advances in Biochemical Engineering/Biotechnology. 2008;111:1-66. doi:10.1007/10_2008_097.
AGA Technical Review on the Role of Probiotics in the Management of Gastrointestinal Disorders. Preidis GA, Weizman AV, Kashyap PC, Morgan RL. Gastroenterology. 2020;159(2):708-738.e4. doi:10.1053/j.gastro.2020.05.060.
Scientific Evidence for Health Effects Attributed to the Consumption of Probiotics and Prebiotics: An Update for Current Perspectives and Future Challenges. Martinez RC, Bedani R, Saad SM. The British Journal of Nutrition. 2015;114(12):1993-2015. doi:10.1017/S0007114515003864.
Microbiota-Focused Dietary Approaches to Support Health: A Systematic Review. Hindle VK, Veasley NM, Holscher HD. The Journal of Nutrition. 2025;155(2):381-401. doi:10.1016/j.tjnut.2024.10.043.
Prebiotics: Types, Selectivity and Utilization by Gut Microbes. Yalçıntaş YM, Bolino MJ, Duman H, et al. International Journal of Food Sciences and Nutrition. 2025;:1-27. doi:10.1080/09637486.2025.2582557.
Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications. Davani-Davari D, Negahdaripour M, Karimzadeh I, et al. Foods (Basel, Switzerland). 2019;8(3):E92. doi:10.3390/foods8030092.
Role of Probiotics and Prebiotics in Mitigation of Different Diseases. Manzoor S, Wani SM, Ahmad Mir S, Rizwan D. Nutrition (Burbank, Los Angeles County, Calif.). 2022;96:111602. doi:10.1016/j.nut.2022.111602.
Effects of Probiotics, Prebiotics, and Synbiotics on Human Health. Markowiak P, Śliżewska K. Nutrients. 2017;9(9):E1021. doi:10.3390/nu9091021.
Probiotics and Prebiotics in Intestinal Health and Disease: From Biology to the Clinic. Sanders ME, Merenstein DJ, Reid G, Gibson GR, Rastall RA. Nature Reviews. Gastroenterology & Hepatology. 2019;16(10):605-616. doi:10.1038/s41575-019-0173-3.