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by Dr. Cheryl Reifer
PhD, RD, LD
Article Contents:
- What Are Probiotics?
- How Probiotics Work in the Gut
- Probiotics, Prebiotics, and Postbiotics
- What Happens When the Microbiome Is Out of Balance
- The Gut-Brain Axis Connection
- Choosing a Probiotic Supplement
- Safe Use and Storage
- About Dr. Ralf Jaeger
- References
- Disclosures and Disclaimers
What Are Probiotics?
The term “probiotic” comes from the Greek word pro-bios, meaning “for life.” According to the International Scientific Association for Probiotics and Prebiotics (ISAPP), probiotics are live microorganisms that, when consumed in adequate amounts, can confer health benefits on the host. In other words, probiotics are non-pathogenic—they don’t cause disease—and are considered “friendly” bacteria, according to the Biomedical and Pharmacology Journal.
The National Institutes of Health’s Office of Dietary Supplements explains that probiotics help maintain the balance of the gut microbiome—the community of microorganisms that plays an important role in overall health. Among probiotics, some of the most common types belong to the Bifidobacterium (“bifido”) and Lactobacillus (“lactobacilli”) groups, according to the National Center for Complementary and Integrative Health (NCCIH). For example, some brands of yogurt note that they contain live, active cultures. Other fermented foods—such as kefir, sauerkraut, kimchi, and kombucha—can also provide probiotics, and probiotics are available in dietary supplements.
How Probiotics Work in the Gut
Once consumed, probiotics act mostly in the digestive tract, where they can help support the gut microbiome—a community of microorganisms living in and on our bodies, including bacteria, viruses, fungi, and other microbes. Many of these microbes reside in the large intestine.
Probiotics may support digestion and gut function. Whole grains, fruits, vegetables, and a plant-rich diet promote a healthy gut microbiome. Prebiotics from fiber help nourish beneficial gut bacteria, supporting their growth and activity. When beneficial bacteria break down fiber, they create postbiotics—helpful compounds that, according to research in MedComm, may help keep your gut healthy and balanced.
A balanced gut occurs when probiotics help colonize the digestive tract, meaning they grow and multiply. Many probiotics don’t permanently stay in the gut but can still help support health while passing through.*
Probiotics, Prebiotics, and Postbiotics
Probiotics can contain various types of beneficial microorganisms, such as different strains (or types) of bacteria and certain types of yeast. Probiotics aren’t just for digestion—some strains have also been studied for benefits related to immune, women’s, and oral health, while research continues in newer areas like skin, metabolism, and mental well-being.
Building on this, nutrition scientist Dr. Ralf Jaeger explains:
“Combining scientifically validated probiotic strains with postbiotics can offer greater stability and potential health benefits supported by scientific studies.”*
What Happens When the Microbiome Is Out of Balance
The Cleveland Clinic describes the gut microbiome as a diverse garden that we rely on for nutrients and health. If the garden is healthy and thriving, you will thrive; however, if the soil is polluted or depleted, or overrun with weeds or pests, it can upset the whole ecosystem. This ecosystem is made up of trillions of microorganisms, such as viruses, fungi, and bacteria.
Dr. Jaeger notes:
“Shelf-life stability is often more important than survival through the digestive tract. Even if some probiotics don’t survive completely, consistent intake may still help deliver benefits.”*
Although some probiotic bacteria may not fully survive storage, manufacturing, or stomach acid, research from the ISAPP Consensus Statement, as well as studies published in MedComm and Advances in Nutrition, suggests that consistent intake may still help deliver benefits—thanks to bacterial components and postbiotic compounds that can interact with the gut and help support health. Postbiotics can be produced naturally by probiotics in your gut or added directly to supplements or foods as separate ingredients.
The Gut-Brain Axis Connection
Maintaining a healthy balance in our gut microbiome may also help support the gut-brain axis—the connection between our digestive system and brain that allows them to communicate and influence mood, focus, and overall well-being.
Research published in Gastroenterology describes how signals from the gut communicate with the brain and may help support mood and emotional well-being during occasional stress. Emerging research suggests certain probiotics may help support mood and overall well-being, potentially influencing focus and resilience.*
A study in Frontiers in Psychiatry linked probiotic use to better mood and sleep, though more research is needed.* Dr. Jaeger adds:
“Emerging research suggests certain probiotics may help support sleep quality and promote a healthy inflammatory response in the body.”*
Choosing a Probiotic Supplement
Not all probiotic supplements are the same. Because probiotics are living organisms, some supplements use special technologies or protective capsules to help them survive stomach acid and reach your gut. Products list how many live bacteria they contain (CFUs, Colony Forming Units), but higher numbers don’t always mean better results. Multi-strain formulas might offer broader benefits, while single-strain products focus on specific uses.
Safe Use and Storage
Store probiotics as directed, since some need refrigeration. While probiotics are usually safe for healthy people, anyone with health conditions or concerns should talk to a healthcare professional first.
Given that research is still evolving, it’s wise to choose supplements from reputable brands. The NIH’s Office of Dietary Supplements advises selecting products made according to current Good Manufacturing Practices (cGMP).* NCCIH also recommends looking for products from trusted sources.*
A quality probiotic label lists the specific strains included and the number of live organisms promised through the end of shelf life.* Remember that probiotics can work differently for different people, and not every product works the same way for everyone.
About Dr. Ralf Jaeger
Dr. Ralf Jaeger, PhD, MBA, is a scientific consultant specializing in nutrition, sports science, and dietary supplements, with expertise in probiotics, postbiotics, and innovative ingredient formulation. He holds multiple patents, has published extensively in peer-reviewed journals, and advises companies on evidence-based product development and clinical research. He is also a member of the Coral Club Scientific Advisory Board.
References
Bodke, H., and S. Jogdand. 2022. “Role of Probiotics in Human Health.” Cureus 14 (11): e31313.
Cleveland Clinic. 2023. “Gut Microbiome.” Last reviewed August 18, 2023. Accessed July 6, 2025. https://my.clevelandclinic.org/health/body/25201-gut-microbiome.
Ji, J., W. Jin, S. J. Liu, Z. Jiao, and X. Li. 2023. “Probiotics, Prebiotics, and Postbiotics in Health and Disease.” MedComm 4 (6): e420.
Marotta, A., E. Sarno, A. Del Casale, M. Pane, L. Mogna, A. Amoruso, G. E. Felis, and M. Fiorio. 2019. “Effects of Probiotics on Cognitive Reactivity, Mood, and Sleep Quality.” Frontiers in Psychiatry 10: 164.
National Center for Complementary and Integrative Health. n.d. “Probiotics: In Depth.” Accessed July 12, 2025. https://www.nccih.nih.gov/health/probiotics-usefulness-and-safety.
National Institutes of Health (NIH), Office of Dietary Supplements (ODS). 2023. “Probiotics: Fact Sheet for Consumers.” Updated November 23, 2023. Accessed July 6, 2025. https://ods.od.nih.gov/factsheets/Probiotics-Consumer/.
National Institutes of Health (NIH), Office of Dietary Supplements (ODS). 2025. “Probiotics: Fact Sheet for Health Professionals.” Updated March 25, 2025. Accessed July 6, 2025.
Mishra, Sanjukta, and Swastik Acharya. 2021. “A Brief Overview on Probiotics: The Health Friendly Microbes.” Biomedical & Pharmacology Journal 14 (4): 1869–1880.
Margolis, Kara G., John F. Cryan, and Emeran A. Mayer. 2021. “The Microbiota-Gut-Brain Axis: From Motility to Mood.” Gastroenterology 160 (5): 1486–1501.
Plaza-Diaz, J., F. J. Ruiz-Ojeda, M. Gil-Campos, and A. Gil. 2019. “Mechanisms of Action of Probiotics.” Advances in Nutrition 10 (Suppl 1): S49–S66.
Hill, C., F. Guarner, G. E. Reid, G. R. Gibson, D. J. Merenstein, B. Pot, L. Morelli, R. B. Canani, H. J. Flint, S. Salminen, P. C. Calder, and M. E. Sanders. 2014. “Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic.” Nature Reviews Gastroenterology & Hepatology 11 (8): 506–514.
Disclosures and Disclaimers
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Dr. Cheryl Reifer, PhD, MS, RD, LD, is the Director of Scientific Affairs for Coral Club North America (us.coral.club) and is a paid employee.
Dr. Ralf Jaeger, PhD, MBA, serves as a member of the Coral Club Scientific Advisory Board and is a paid consultant. The views expressed by Dr. Jaeger reflect his scientific expertise and are provided for educational purposes. They are not intended as specific endorsements of any Coral Club product unless explicitly stated.
