Probiotics are well known for their health benefits, especially their role in maintaining a healthy gut microbiome and aiding healthy digestive function. According to the National Center for Complementary and Integrative Health, the use of probiotics quadrupled between 2007 and 2012, and a 2022 global survey including 16,000 participants found that 48% of respondents consume supplemental or dietary probiotics daily.

Prebiotics and postbiotics are less well-known but equally important for gastrointestinal and systemic health. Working synergistically, prebiotics, probiotics, and postbiotics all hold distinct responsibilities for maintaining a healthy intestinal environment and providing extraintestinal benefits to the person taking them.

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What are Prebiotics?

Prebiotics are a group of selectively fermentable nutrients by the gastrointestinal microbiota, resulting in specific compositional changes and activity of the gut microbiome and health benefits to the human host. Simply stated, prebiotics are bacteria food.

The terms "fiber" and "prebiotics" are often used interchangeably but should not be. While all prebiotics are fibrous carbohydrates, not all fibers can be classified as prebiotic substances. A nutrient must meet the following criteria to be classified as a prebiotic (1):

• It is resistant to the acidic pH of the stomach and cannot be degraded by human digestive enzymes or absorbed in the gastrointestinal tract
• It can be fermented by the intestinal microbiota
• It can stimulate the growth and activity of the intestinal microbiome to improve human health

Inulin, fructooligosaccharides (FOS), and galactooligosaccharides (GOS) are well-established prebiotics. Other compounds demonstrating prebiotic potential include fructans, lactulose, resistant starch, polydextrose, pectin, arabino-oligosaccharides, xylooligosaccharides, beta-glucans, and guar gum. (1, 2)

Dietary prebiotic sources include beans and legumes, garlic, onion, under-ripe bananas, Jerusalem artichokes, chicory, tomatoes, whole grains, raw honey, and breast milk (3).

What are Probiotics?

Probiotics are live microorganisms that give health benefits to the host taking them when administered in adequate amounts. Probiotics are administered to support the human microbiome, the community of microorganisms that live on and in the human body. Probiotics communicate with the nervous system; inhibit the growth of pathogenic organisms; colonize the gut microbiome; modulate immune function; synthesize vitamins, enzymes, and short-chain fatty acids (SCFAs); and regulate digestion and metabolism (4, 5).

Probiotics can be taken in supplemental form, but are also found naturally in fermented foods like yogurt, kefir, sauerkraut, and kombucha. There are three main types of probiotic supplements: Lactobacillus and Bifidobacterium blends, Saccharomyces boulardii, and soil-based probiotic blends. Specific probiotic strains are known to confer specific health benefits, so choosing the appropriate probiotic strains is important when selecting a probiotic supplement (4).

What are Postbiotics?

The concept of postbiotics is the newest emerging concept in the field of "-biotics." Postbiotics are the bioactive products of bacterial fermentation of prebiotics, including bacterial metabolites, SCFAs, microbial cell fractions, functional proteins, and extracellular polysaccharides (EPS). Postbiotics are a separate entity from, but dependent on, the adequate consumption of prebiotics and probiotics. Postbiotics are technically considered dead; they are non-living compounds without a shelf life but continue to exhibit positive health benefits to the host. (6, 7)

Benefits of Prebiotics vs. Probiotics vs. Postbiotics

Probiotics have been studied extensively for their ability to modulate and treat human disease processes. The biological activity of probiotics is specific to the individual probiotic strain, meaning that health effects observed from one strain cannot necessarily be applied to others. Probiotics are most notoriously known for their ability to support and treat gastrointestinal disorders, including irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), infectious diarrhea, and constipation. However, emerging research also supports using probiotics to treat cardiovascular and metabolic diseases, allergies, autoimmune diseases, mood disorders, cognitive decline, and urogenital infections. (5, 8-11)

Prebiotics act as a fuel source for commensal intestinal microbes, promoting a healthy microbiome composition and providing many associated health benefits related to digestive health and function, the immune system, the central nervous system, and cardiovascular health (3). Additionally, prebiotics are often combined with probiotics, called synbiotics, to create synergistic health benefits that include supporting fat metabolism, mineral absorption, healthy immune responses, and regular bowel movements (12).

Because postbiotics are a more recent and emerging concept, more research is needed to comprehend the spectrum of health benefits postbiotics fully may provide. Postbiotics have been shown to support gastrointestinal health, reducing inflammation in conditions like IBD and improving IBS-related digestive symptoms. Because 70-80% of the immune system is located in the gut, a healthy intestinal barrier is imperative for healthy immune responses. Postbiotic supplementation has been shown to reduce the rate of the common cold in elderly adults, reduce diarrhea and respiratory infections in children, and offer symptom relief for those suffering from allergic diseases (13, 14).

When to Not Use Prebiotics vs. Probiotics vs. Postbiotics

Generally, prebiotics, probiotics, and postbiotics are considered safe for most of the population. There has been mention in the literature of interactions between warfarin and probiotics; therefore, patients taking warfarin should consult with their doctors before starting probiotic therapy. Probiotics should also be used cautiously in patients who are critically ill, severely immunocompromised, or have central venous catheters (15).

Prebiotics, probiotics, and postbiotics may exacerbate gastrointestinal symptoms in patients with small or large intestinal bacterial overgrowth. If dietary or supplemental biotic therapy continuously exacerbates symptoms, testing to rule out bacterial overgrowth is indicated, and supplementation should be postponed until the dysbiosis is corrected.

Functional Medicine Labs to Test Whether Prebiotics, Probiotics, or Postbiotics Would Be Beneficial for Patients

Substantial evidence supports that the efficacy of probiotic therapy is both strain- and disease-specific. This should be considered when recommending appropriate probiotic therapy for a patient. Functional medicine labs can help practitioners personalize appropriate treatment options for their patients.

Comprehensive Stool Test

A comprehensive stool test is an excellent place to start when assessing gastrointestinal health and determining whether prebiotic, probiotic, or postbiotic therapy would benefit patients.

This type of stool test analyzes the pathogenic and commensal microbes living in the large intestine, screening for dysbiosis and infection that could indicate the need for probiotic support. In addition, these results can guide specific probiotic recommendations based on the concentration of specific bacterial strains measured through PCR testing. Comprehensive stool tests also measure the total amount of SCFAs present in stool and a breakdown of specific SCFA types. SCFA deficiencies, especially in conjunction with intestinal inflammation and dysbiotic microfloral patterns, indicate the need for prebiotic, probiotic, and postbiotic interventions.

SIBO Breath Test

While a comprehensive stool test can diagnose large intestinal bacterial overgrowth, it cannot definitively diagnose small intestinal bacterial overgrowth (SIBO). For patients experiencing prolonged adverse side effects with prebiotic, probiotic, or postbiotic therapy, a SIBO breath test can be helpful to screen for SIBO as an underlying reason for therapy intolerance.

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Summary

Prebiotics, probiotics, and postbiotics are fermentable nutrients, live microorganisms, and metabolic byproducts, respectively, that confer a multitude of benefits to human health. Probiotics can restore balance and maintain a healthy composition within the gut microbiome. Prebiotics reinforce a healthy microbiome by feeding live microorganisms. Postbiotics are natural fermentation byproducts produced by the microbiome that continue to enhance gut and immune function.

For the general population, prebiotics, probiotics, and postbiotics are safe to use. Comprehensive stool testing to analyze the microbiome can help refine a probiotic regimen and guide recommendations on when biotic therapy may or may not be of value.