Prebiotics vs Probiotics: A Dietitian Answers All Your Questions

What is a probiotic?

• 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. 

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4648921/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4748908/

• 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.

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4748908/

• Probiotic microbes are described by their genus, species and strain designations. Using the example of one well-studied probiotic, Lactobacillus rhamnosus GG – Lactobacillus is the genus, rhamnosus is the species and GG is the strain designation. All three components are necessary to identify a probiotic.
• https://onlinelibrary.wiley.com/doi/pdf/10.1111/nbu.12334%4010.1111/%28ISSN%291467-3010.fashionable_ingredients_the_facts 

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

• Effects of Probiotics, Prebiotics, and Synbiotics on Human Health

• 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.
• https://www.mdpi.com/1422-0067/20/10/2534
• 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.
• https://www.mdpi.com/1422-0067/20/10/2534
• 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.
• https://academic.oup.com/advances/article/10/suppl_1/S49/5307225?itm_medium=sidebar&itm_content=advances&itm_source=trendmd-widget&itm_campaign=trendmd-pilot

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). 
• https://www.nature.com/articles/nrgastro.2014.66.pdf?origin=ppub

Frequently Observed Benefits at the Species Level:

• Creation of vitamins
• Neutralization of cancer-causing compounds
• Bile salt metabolism 
• Alterations of which have been found in certain disease states such as IBD https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-019-0689-3  
• Gut barrier reinforcement 
• Enzymatic activity 
• For example, production of digestive enzymes capable of breaking down lactose. 
• Direct antagonism of pathogens 
• For instance, by production of antimicrobial compounds against pathogenic microbes. 
• https://www.nature.com/articles/nrgastro.2014.66.pdf?origin=ppub

Rare Strain-Specific Benefits

• Neurological effects
• Immune effects
• Endocrine effects
• Production of specific bioactive compounds 
• https://www.nature.com/articles/nrgastro.2014.66.pdf?origin=ppub

Food Sources of Probiotics

• Microorganisms in fermented foods, both live and dead, can have an impact on the microbiota and immune system. Studies are currently limited, but the current data suggests fermented foods may be linked to better health. 
• https://isappscience.org/for-scientists/resources/fermented-foods/
• Fermented foods which retain living cultures include: 
• Fresh kimchi
• Fresh sauerkraut
• Fresh sour dill pickles 
• Water or brine cured olives
• Yogurt
• Kefir
• Some cheeses
• Traditional Salami
• http://4cau4jsaler1zglkq3wnmje1-wpengine.netdna-ssl.com/wp-content/uploads/2019/04/FermentedFoods_outline_rev1029.pdf
• Fermented foods without living cultures include: 
• Tempeh
• Most soy sauce
• Most beer
• Most wine
• Sourdough bread
• Chocolate
• http://4cau4jsaler1zglkq3wnmje1-wpengine.netdna-ssl.com/wp-content/uploads/2019/04/FermentedFoods_outline_rev1029.pdf

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:
• not digested (or only partially digested);
• not absorbed in the small intestine;
• poorly fermented by bacteria in the oral cavity;
• well fermented by seemingly beneficial intestinal bacteria;
• poorly fermented by potential pathogens in the bowel
• Effects of Probiotics, Prebiotics, and Synbiotics on Human Health

Benefits of prebiotics

• Prebiotics may be used as an alternative to probiotics or as an additional support for them. 
• The main aim of prebiotics is to stimulate the growth and activity of beneficial bacteria in the gastrointestinal tract, which confers a health benefit on the host.
• Different prebiotics will stimulate the growth of different indigenous gut bacteria
• Effects of Probiotics, Prebiotics, and Synbiotics on Human Health
• Eating prebiotic compounds is associated with increased abundance of beneficial bacterial families such as Bifidobacterium. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4923077/#!po=0.403226 

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. 
• Effects of Probiotics, Prebiotics, and Synbiotics on Human Health

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.
• Effects of Probiotics, Prebiotics, and Synbiotics on Human Health

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.
• Effects of Probiotics, Prebiotics, and Synbiotics on Human Health

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: