Probiotics 101: How Probiotics Support Gut, Digestive, and Immune Health

Probiotics are one of the hottest topics in the health industry, and for good reason. Probiotics are widely considered a staple for any daily regimen. These beneficial bacteria work symbiotically with your body to promote digestive health, immune health, neurological health, and emotional wellness (via the gut-brain connection). They are typically identified as a genus (Lactobacillus), species (acidophilus), or strain (LA-14) in research and supplement bottle labels. But what are probiotics exactly, and how do they help you?

Key Takeaways

• Probiotics are live beneficial microorganisms found in the digestive tract.
• The gut hosts trillions of microorganisms critical to digestive and immune health.
• The two primary genera discussed in probiotic research and supplements are Lactobacillus and Bifidobacterium.
• Probiotic supplements list the measurement of active bacteria in colony-forming units (CFU).
• Probiotics are also available from both fermented foods and supplements.

Key Terms

• Probiotic—A term used to refer to any of the many beneficial bacteria species found in the digestive tract.
• Microbiome/gut microbiota—Terms that refer to the ecosystem of the gut and the living microorganisms found there.
• CFU (colony-forming units)—An approximate description of the number of active bacteria in a supplement serving.
• Lactobacillus—A specific genus of beneficial bacteria found in the human digestive tract (among other places in the body such as the urinary tract).
• Bifidobacterium—A specific genus of beneficial bacteria found in the human digestive tract.

What Are Probiotics?

While many people think of bacteria negatively, probiotics are the opposite. But what are they? “Probiotics” is an umbrella term referring to beneficial bacteria and yeasts found along the digestive tract that, when in sufficient numbers, convey certain health benefits.¹ The word probiotic actually translates to “for life”–combining the Latin preposition “pro,” meaning “for” with the Greek word “bios,” meaning “life.”² Each probiotic strain offers unique benefits, providing vital overall wellness support. This can include immune health, digestive health, mood support, and more.

Probiotics in supplements are measured in colony-forming units (CFU), an estimate of the number of viable (live) bacterial cells in each serving.

Why Your Body Needs Them

Digestive Health Support

Probiotics play a central role in promoting proper digestion of food and the absorption of nutrients. They do this by working with enzymes in a symbiotic process of breaking down food. Probiotics break down the indigestible fibers we consume, then release short-chain fatty acids, helping to support a balanced gut microbiome in which natural enzymes can work better.³ This contributes to better overall digestive function and comfort.

Immune System Support

The gut microbiome is a very active space, and home to around 70% of the body’s immune system cells.⁴ Probiotic bacteria communicate with these immune cells in a cross-talk function that helps direct and modulate immune cell activity, thereby promoting overall immune health.⁵ For this reason, ensuring a balanced microbiome in which beneficial bacteria can flourish provides a powerful support to immune function throughout the body.

Beyond Digestion

Emerging research is exploring the ways in which probiotics communicate with other systems in the body through axes such as the gut-brain connection. Scientists are looking into how our gut health and the balance of microorganisms in the gut microbiome can play a direct role in influencing cognitive function and mood.⁶ Read more on this in Understanding the Gut-Brain Connection.

Key Probiotic Species

Lactobacillus

The most populous bacteria found in the small intestine are from the genus Lactobacillus. This type of probiotic bacteria is known for helping to break down lactose and for producing lactic acid.⁷ Common species of Lactobacillus include:

• L. acidophilus: often found in fermented foods, this species supports overall digestion, nutrient absorption, immune health, and other aspects of wellness.⁸
• L. rhamnosus: associated with promoting vaginal health and immune function.⁹ Sometimes popular with travelers for its immune-supporting properties.
• L. fermentum: delivers antioxidant defense and has been linked in preclinical trials to supporting healthy blood glucose response.¹⁰
• L. reuteri: linked in research to powerful immune system support¹¹ and protective benefits along the entire tract.

Bifidobacterium

Like the Lactobacillus species, Bifidobacterium produce lactic acid and help maintain a healthy balance of gut flora to further support immune system function. These include:

• bifidum: associated with promoting homeostasis and immunomodulatory effects on the immune system. Also known to support a strong intestinal barrier.¹²
• lactis: provides powerful immune support by crowding out pathogens, creating acids that defend against pathogens, and by boosting intestinal integrity by bonding to the mucosal layer.¹³
• longum: promotes gut health and comfort in human clinical trials. Displays immunomodulatory and microbiome balancing properties.¹⁴

Saccharomyces Boulardii

A beneficial yeast used as a probiotic agent to support gastrointestinal health¹⁵ and often used by people who travel for its immune support properties.

Food Sources vs. Supplements

Eating fermented foods like yogurt, kefir, or kimchi for probiotic benefits is a very healthy habit, but there are some limitations. For example, it can be very difficult to know exactly which probiotics, and their CFU, are present in a given food or recipe. The number of CFU in a serving of fermented foods can vary by brand and even by batch of product. And while some brands guarantee a certain number of CFU in each package, food labels aren’t required to list the strains of bacteria, so you can’t be quite sure what you’re getting.

Supplements offer precision and consistency for those who want to target specific probiotics or who don’t eat fermented foods regularly. It’s recommended that healthy adults aim for one to two servings of fermented food daily.¹⁶

Both strategies are healthy options, but in the end, it comes down to your own personal goals and lifestyle preferences.

Frequently Asked Questions

• Are probiotic supplements worthwhile?
  Yes! There is an ever-growing body of research exploring the many ways that probiotics can benefit overall health and wellness. Supplements offer the advantage of targeted strains and measurable CFU—useful when you want to support a specific area of wellness or don’t eat fermented foods regularly.
• Are prebiotics the same as probiotics?
  No. Probiotics are live beneficial microorganisms that live in the gut and provide certain health benefits. Prebiotics are types of undigestible dietary fiber that feed beneficial gut bacteria and help them thrive. Probiotics may include species such as L. fermentum or B. lactis, while prebiotic fiber can include inulin or foods like psyllium husk.
• Does the FDA regulate the probiotics?
  While the FDA does not have a standardized definition of “probiotics,” they do regulate probiotic supplements and food ingredients under the Dietary Supplement Health and Education Act (DSHEA), depending on their intended use.¹⁷
• How long does it take for probiotics to work?
  Some people notice digestive changes within a few days; other benefits may take several weeks of consistent use. When first taking a probiotic, you may experience some digestive discomfort. This is completely normal as the gut microbiota shifts and should pass with time. Consult your doctor before using probiotics or prebiotics or if digestive discomfort persists.

Conclusion

Probiotics are among the most well-researched supplements for digestive and immune health support, with new species and benefits being discovered all the time. Adding them to your routine is an excellent way to promote multiple aspects of wellness. Whether you get them through fermented foods or a targeted supplement, consistent use over time can deliver meaningful benefits.

Explore Swanson’s innovative line of probiotics to find a blend that’s right for you and check out Prebiotics vs. Probiotics vs. Postbiotics for more.

About Lindsey Toth, MS, RD

Lindsey is a nationally recognized registered dietitian and nutritionist with a soft spot for ice cream. She empowers people to take charge of their health by finding the balance between the pleasure and nourishment in food. Her philosophy is that you should take care of your body because it’s the only permanent home you have. It’s what inspired her to pursue a career in nutrition.

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

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