Probiotics, prebiotics, and "psychobiotics" 101

After vitamins and minerals, probiotics and prebiotics are among the most widely used supplements in the U.S.—and for good reason. Gut health is increasingly recognized as a cornerstone of overall wellness, and emerging research shows it also plays a role in mental health.

These “good-for-you” microbes offer multiple benefits. A healthy gut microbiome helps your body absorb nutrients more efficiently, keeps harmful bacteria in check, and reduces inflammation—all of which support digestive health and overall well-being. And it’s not just about supplements—many everyday foods naturally contain probiotics and prebiotics, making it easy to include them in your diet.

A vibrant probiotic and prebiotic-rich parfait showcasing Greek yogurt, chia seeds, kiwi, and berries.

Before We Dive In: Key Terms to Know

Before exploring how probiotics, prebiotics—and other “biotics”—impact health and how to include them in your diet, let’s clarify what these terms mean:

• Microbiome: Your large intestine is home to trillions of “friendly” microbes, primarily bacteria, along with beneficial viruses and fungi. Together, these tiny organisms form the microbiome. Everyone’s microbiome is unique from birth and shaped by factors such as diet and supplements.

• Probiotics: These are live microorganisms that provide health benefits when consumed. The term comes from the Greek words pro and bios, meaning “for life.”

• Prebiotics: These are non-digestible food components that feed beneficial microbes in your gut, helping them grow and maintain a diverse, thriving microbiome.

• Psychobiotics - Psychobiotics are “probiotics that confer mental health benefits” (6).

Health benefits of a Balanced Gut

Keeping your gut microbes in balance offers a wide range of health benefits—and research in this area continues to grow every day. A healthy gut microbiome supports digestion, produces essential nutrients, strengthens the immune system, and even plays a role in mood and mental well-being. It can also help reduce inflammation and limit the effects of harmful, toxin-producing microbes. In this article, we’ll focus on two key areas where gut health makes a big impact: digestive health and mental health.

Gut health

Your gut microbiome plays a vital role in maintaining digestive health. It supports normal bowel function and may even help manage conditions like colitis. Research also suggests that probiotics can ease issues such as diarrhea and constipation, particularly when these problems stem from an imbalance in gut bacteria.

How does a healthy microbiome achieve this? In several ways. Certain microbes produce beneficial compounds like short-chain fatty acids and B vitamins, which your body absorbs and uses throughout its systems. Other substances help lower gut pH and strengthen the intestinal lining. A balanced microbiome can also reduce inflammation, neutralize toxins, and improve the absorption of essential minerals—key factors for overall gut health.

Mood, mental health, and psychobiotics

Research in nutritional psychiatry—the study of how diet impacts mental and emotional well-being—is growing rapidly. Studies consistently show a strong connection between what we eat and how we feel. For example, a nutrient-rich diet supports brain health, reduces inflammation, and promotes more stable moods.

Interestingly, many chronic gut conditions are linked to mood disorders such as anxiety and depression. This connection has led to the discovery of psychobiotics, a special class of probiotics that may offer mental health benefits. In fact, a recent review of seven clinical trials published in BMJ Nutrition, Prevention & Health found that certain probiotic supplements, with or without prebiotics, were associated with measurable reductions in depression symptoms.

So, how does gut health influence the mind? Through the gut-brain axis—a complex communication network between your digestive system and brain. Key components include:

• Neurotransmitter production: About 90–95% of the body’s serotonin—critical for mood, sleep, and appetite—is produced in the gut.

• Nerve and immune connections: The digestive system contains roughly 100 million nerve cells and serves as a major hub for immune activity.

• Stress and inflammation regulation: A healthy microbiome helps manage stress responses and reduce inflammation throughout the body.

  
  

All of these processes are influenced by the gut microbiome—and by probiotics and psychobiotics that support it.

How to get enough probiotics and prebiotics

Pro- and prebiotics can be found in both foods and supplements.

Probiotic foods

Many fermented foods are naturally rich in probiotics thanks to the beneficial bacteria used in their production. Popular options include yogurt, kefir, sauerkraut, miso, pickles, and kombucha.

However, not all fermented foods retain live cultures by the time they reach store shelves. To ensure you’re getting the benefits, choose products from the refrigerated section and check labels for phrases like “contains live active cultures.”

Additionally, some companies now fortify non-fermented foods—such as cereals and juices—with probiotics. As always, read the label to confirm these added benefits.

Prebiotic (fiber-rich) foods

Prebiotics are found in many fiber-rich foods that help nourish the beneficial microbes in your gut. Great sources include:

• Whole grains: Oatmeal, whole-grain breads, and pastas

• Vegetables: Asparagus, leeks, onions

• Starchy vegetables: Sweet potatoes, corn

• Fruits: Bananas

• Legumes: Beans, lentils, peas

  
  

Including a variety of these foods in your diet can naturally boost the health and diversity of your microbiome.

Along with adding probiotic and prebiotic foods, it’s equally important to limit foods that can harm your gut microbes—such as highly processed items high in sugar, artificial sweeteners, and saturated fats.

Probiotic supplements

Probiotic supplements come in many forms, each containing different strains of beneficial microbes with unique effects. Common strains include Lactobacillus, Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, Escherichia, and Bacillus. Many of these are similar to those naturally found in the gut microbiome, though not all. Manufacturers often combine multiple strains in varying amounts to create specialized formulas.

Unlike foods, probiotic supplements are not closely regulated in the U.S., and some products may contain fewer or different strains than listed on the label. For this reason, it’s important to choose a high-quality, reputable brand whenever possible, and consult with a Registered Dietitian with any questions.

Prebiotic supplements

Prebiotic supplements provide the fibers and starches that nourish beneficial gut microbes, helping them produce health-promoting compounds. Common types include inulin, GOS (galactooligosaccharides), FOS (fructooligosaccharides), and lactulose. These supplements can be a helpful option when dietary intake of prebiotic-rich foods is limited.

Bottom Line

Gut health is about more than digestion—it plays a vital role in both physical and mental well-being. One of the most effective ways to support a healthy gut is by nourishing your microbiome. This means enjoying a variety of probiotic-rich foods (like fermented products) and prebiotic foods (rich in fiber). When needed, high-quality probiotic and prebiotic supplements can also help fill the gaps.

Looking for personalized guidance to optimize your gut health and overall wellness? As a Registered Dietitian, I’d be happy to help you create a plan that works for you.

References

(1) National Center for Complementary and Integrative Health. (2019, August). Probiotics: What You Need To Know. https://www.nccih.nih.gov/health/probiotics-what-you-need-to-know

(2) Harvard Health Publishing. (2024, June 3). Probiotics and prebiotics: what’s really important? https://www.health.harvard.edu/nutrition/are-you-getting-essential-nutrients-from-your-diet

(3) Corliss, J. (2023, November 1). How a healthy gut helps your heart. Harvard Health Publishing. https://www.health.harvard.edu/heart-health/how-a-healthy-gut-helps-your-heart

(4) Ji, J., Jin, W., Liu, S. J., Jiao, Z., & Li, X. (2023). Probiotics, prebiotics, and postbiotics in health and disease. MedComm, 4(6), e420. https://doi.org/10.1002/mco2.420https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10625129/

(5) Golen, T & Ricciotti, H. (2021, November 1). What are postbiotics? Harvard Health Publishing. https://www.health.harvard.edu/nutrition/what-are-postbiotics

(6) Del Toro-Barbosa, M., Hurtado-Romero, A., Garcia-Amezquita, L. E., & García-Cayuela, T. (2020). Psychobiotics: Mechanisms of Action, Evaluation Methods and Effectiveness in Applications with Food Products. Nutrients, 12(12), 3896. https://doi.org/10.3390/nu12123896https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7767237/

(7) Selhub, E. (2022, September 18). Nutritional psychiatry: Your brain on food. Harvard Health Blog. https://www.health.harvard.edu/blog/nutritional-psychiatry-your-brain-on-food-201511168626

(8) Harvard Health Publishing. (2022, February 2). Should you take probiotics? https://www.health.harvard.edu/staying-healthy/should-you-take-probiotics

(9) Office of Dietary Supplements. (2023, March 25). Probiotics: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Probiotics-HealthProfessional/

(10) British Medical Journal. (2020, July). Probiotics alone or combined with prebiotics may help ease depression. https://www.bmj.com/company/newsroom/probiotics-alone-or-combined-with-prebiotics-may-help-ease-depression/