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Prebiotics vs Probiotics: A Dietitian Answers All Your Questions

Researched and Written by:
Bailey Franzen MS, RDN Bailey Franzen MS, RDN

What is the difference between these two similar sounding gut superheroes?  And which one is most important for our health?  Let's find out.

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Table of Contents

    What is a probiotic?

    Although there can be many characteristics of probiotic microbes, it’s useful to remember what the ISAPP consensus statement stipulates about probiotics: 
    • A probiotic must be alive when administered
    • Have sufficient evidence of a health benefit 
    • Be safe for the intended use
    • Be delivered at an effective dose at the time of administration (not time of manufacture) 
    • Must be a defined entity allowing for appropriate identification at the strain level. 

  • The most commonly used probiotics are Lactobacillus, Bifidobacterium, Bacillus coagulans, Escherichia coli strain Nissle 1917, Enterococcus faeciumSF68, and the yeast Saccharomyces boulardii.

          • Lactobacillus includes several individual species, the most notable of which include L acidophilus, L rhamnosus, L bulgaricus, L reuteri, and L casei. Similarly, the Bifidobacterium species that are most commonly used in probiotics include B animalis, B infanti, B lactis, and B longum.

          Benefits of Probiotics 

          Four mechanisms in which probiotics are beneficial: 

          1. Antagonism through the production of antimicrobial substances
          2. Competition with pathogens for adhesion to the epithelium and for nutrients
          3. Immunomodulation of the host
          4. Inhibition of bacterial toxin production
          • Among the main effects of probiotics at the intestinal level, the following are noteworthy: Balancing and restoration of the gut microbiota, protection against pathogens, immunomodulation, and maintenance of intestinal barrier integrity.
          • Probiotics are widely used in dietary supplements, food, infant formula formulations, and medical devices. They have demonstrated significant potential as therapeutic options for a variety of diseases, mainly gastrointestinal diseases (including acute infectious diarrhea, antibiotic-associated diarrhea, ulcerative colitis, irritable bowel syndrome, functional gastrointestinal disorders, or necrotizing enterocolitis), but also extra-intestinal disorders, such as hepatic encephalopathy.
          • Help allergic disorders such as eczema and allergic rhinitis in infants. In addition, probiotics may be helpful when combined with traditional treatments for metabolic disorders, including obesity, metabolic syndrome, nonalcoholic fatty liver disease, and type 2 diabetes.


          Widespread Benefits Among Studied Probiotics

          • Commonly studied probiotics confer the following benefits:
            • Resistance of
            •  colonization and competitive exclusion of pathogenic microbes.  
            • Normalizing the perturbed microbiota 
            • Increased turnover of the intestinal absorptive cells (Enterocytes)
            • Regulating intestinal transit 
            • Production of acid and beneficial short chain fatty acids (SCFAs). 


          Frequently Observed Benefits at the Species Level:


          Rare Strain-Specific Benefits

          Food Sources of Probiotics

          What are Prebiotics?

          • Current definition of prebiotics by FAO/WHO experts: a nonviable food component that confers a health benefit on the host associated with modulation of the microbiota.
          • Prebiotics may be a dietary fiber, but dietary fiber is not always a prebiotic. Types of soluble fiber tend to have more prebiotic properties than insoluble fiber.
          • Prebiotics may be classified as: 
            • Disaccharides
            • Oligosaccharides (3–10 monomers): fructooligosaccharides (FOS), galactooligosaccharides (GOS), isomaltooligosaccharides (IMO), xylooligosaccharides (XOS), transgalactooligosaccharides (TOS), and soybean oligosaccharides (SBOS).
            • Polysaccharides: inulin, reflux starch, cellulose, hemicellulose, or pectin may potentially be prebiotics. 
          • Prebiotics properties:

          Benefits of prebiotics

          Widespread Benefits:

          • Inulin and oligofructose may lead to numerous health benefits for colorectal cancer, may also help reduce LDL cholesterol, stimulate the immunological system, increase absorbability of calcium and magnesium, maintain the correct intestinal pH value, lower caloric value, alleviate symptoms of peptic ulcers and vaginal mycosis, prevent carcinogenesis, as well as alleviate lactose intolerance or dental caries. 
          • Numerous studies have shown that prebiotics are helpful to mitigate the infection from pathogenic microorganisms and bacteria. Rat studies have shown that a prebiotic-enriched diet leads to significantly reduced indexes of carcinogenesis. Scientific research demonstrated that butyric acid may be a chemopreventive factor in carcinogenesis. 

          Immune system:

          • Increased production of short-chain fatty acids (SCFAs), such as propionic acid or butyric acid.
          • The production of SCFAs (especially of butyric acid) as a result of fermentation was identified as a modulator of histone acetylation, thus increasing the availability of numerous genes for transcription factors.
          • The modulation of mucin production.
          • It was demonstrated that FOS and several other prebiotics cause an increased count of lymphocytes and/or leukocytes in gut-associated lymphoid tissues (GALTs) and in peripheral blood.

          Food Sources of prebiotics

          • Sources of prebiotics: Fruit, vegetables, cereals, and other edible plants. More specifically, potential sources include: tomatoes, artichokes, bananas, asparagus, berries, garlic, onions, chicory, green vegetables, legumes, as well as oats, linseed, barley, and wheat. 
          • Prebiotics can be artificially produced: lactulose, galactooligosaccharides, fructooligosaccharides, maltooligosaccharides, cyclodextrins, and lactosaccharose.
            • Lactulose constitutes a significant part of produced oligosaccharides (as much as 40%). Fructans, such as inulin and oligofructose, are believed to be the most used and effective in relation to many species of probiotics
          • Prebiotics that get added to food to improve their nutritional and health value: inulin, fructooligosaccharides, lactulose, and derivatives of galactose and β-glucans.

          Which one is more important: prebiotics v probiotics?

          We may be biased on this one from all of our time spent reading about fiber, but we'd say prebiotics win.

          The thing about prebiotics is that they can bolster the number of beneficial microbes transiently, and also possibly cause more global microbiome shifts with long term consumption.

          More importantly though, they’re changing the behavior of the entire microbiota when they’re consumed. That’s really powerful because you’re not just taking a small dose of beneficial microbes, but rather, you’re mobilizing the benefits of the trillions of microbes you already have in your gut.

          Prebiotics may also help pathogens to behave more like neutral commensal microbes instead, (e.g. shifting away from mucus layer consumption etc.).

          Likewise, you have the benefit of producing more beneficial metabolites such as SCFAs, which probiotics may support as well, but the shift towards fiber metabolism in a more general sense is a two for one as far as maintaining gut barrier defenses goes.

          That, and we discovered recently that certain fiber structures may also beneficially interact with various immune regulatory mechanisms in the gut (e.g. toll like receptors and so forth) in a way that’s not all that dissimilar to how probiotics might also interact with the immune system.

          So in that way, even if the good microbes aren’t there to be “fed”, some beneficial immune regulation might happen regardless with the right fibers/prebiotics on board.

          What about synbiotics?

          • Synbiotics are a combination of probiotics and prebiotics and should exert a positive effect on the host’s health when used separately. 
            • Probiotics are active in the small and large intestine where prebiotics are observed in the large intestines. 
            • It is thought that when combined, they have a synergistic effect.
            • Improve survival of beneficial microorganisms added to food or feed
            • Stimulate the proliferation of specific native bacterial strains present in GIT. 
            • The effect of synbiotics on metabolic health remains unclear. Considering a huge number of possible combinations, the application of synbiotics for the modulation of intestinal microbiota in humans seems promising.
          • A combination of Bifidobacterium or Lactobacillus genus bacteria with fructooligosaccharides in synbiotic products seems to be the most popular. Other examples in the table below:


          Evidence Based

          An evidence hierarchy is followed to ensure conclusions are formed off of the most up-to-date and well-designed studies available. We aim to reference studies conducted within the past five years when possible.

          • Systematic review or meta-analysis of randomized controlled trials
          • Randomized controlled trials
          • Controlled trials without randomization
          • Case-control (retrospective) and cohort (prospective) studies
          • A systematic review of descriptive, qualitative, or mixed-method studies
          • A single descriptive, qualitative, or mixed-method study
          • Studies without controls, case reports, and case series
          • Animal research
          • In vitro research

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