Probiotic (pro-by-otik);
noun
1. A usually dairy food or a dietary supplement containing live bacteria that replace or add to the beneficial bacteria normally present in the gastrointestinal tract.
2. a bacterium in such a food or dietary supplement.
Prebiotic (pree-by-otik);
noun
a non-digestible food ingredient that promotes the growth of beneficial microorganisms in the intestines.
Both of these are required for good health and get mentioned a lot in any facebook group with many "crunchy" or healthy living people, but why do we need them? How do they work? How much do we need them? At the end of this article I'll give a link to a file I have composed for additional studies going as far back as the year 2000. Due to the rapidly changing landscape of the literature on this topic I have endeavored to only use studies published in the last 10yrs directly in this piece.
After writing that catchy intro I had to go to bed because my darling child can't sleep if I'm not there. That means when I came back to finish writing this a few days later and I spent some time staring at the screen blankly.... Let's just go through those questions and use that as our format today shall we?
First question; Why do we need them?
To answer this lets break that down into categories based on a known effect. Based on current research we know that probiotic balance influences digestion and nutrient absorption, immunity, and hormone production with implications towards mental health. For the sake of my readers I will only quote 1 study per category mentioned with the remainder appearing in the document mentioned previously.
This study requires you to sign up (for free) to the website if you wish to read the whole thing.
Fermented foods, neuroticism, and social anxiety.
Abstract:
"Animal models and clinical trials in humans suggest that probiotics can have an anxiolytic effect. However, no studies have examined the relationship between probiotics and social anxiety. Here we employ a cross-sectional approach to determine whether consumption of fermented foods likely to contain probiotics interacts with neuroticism to predict social anxiety symptoms. A sample of young adults (N=710, 445 female) completed self-report measures of fermented food consumption, neuroticism, and social anxiety. An interaction model, controlling for demographics, general consumption of healthful foods, and exercise frequency, showed that exercise frequency, neuroticism, and fermented food consumption significantly and independently predicted social anxiety. Moreover, fermented food consumption also interacted with neuroticism in predicting social anxiety. Specifically, for those high in neuroticism, higher frequency of fermented food consumption was associated with fewer symptoms of social anxiety. Taken together with previous studies, the results suggest that fermented foods that contain probiotics may have a protective effect against social anxiety symptoms for those at higher genetic risk, as indexed by trait neuroticism. While additional research is necessary to determine the direction of causality, these results suggest that consumption of fermented foods that contain probiotics may serve as a low-risk intervention for reducing social anxiety."
Effects of gut microbes on nutrient absorption and energy regulation.
Abstract
"Malnutrition may manifest as either obesity or undernutrition. Accumulating evidence suggests that the gut microbiota plays an important role in the harvest, storage, and expenditure of energy obtained from the diet. The composition of the gut microbiota has been shown to differ between lean and obese humans and mice; however, the specific roles that individual gut microbes play in energy harvest remain uncertain. The gut microbiota may also influence the development of conditions characterized by chronic low-level inflammation, such as obesity, through systemic exposure to bacterial lipopolysaccharide derived from the gut microbiota. In this review, the role of the gut microbiota in energy harvest and fat storage is explored, as well as differences in the microbiota in obesity and undernutrition. (Nutr Clin Pract. 2012;27:201-214)"
Conclusion
"Malnutrition may manifest as either obesity or undernutrition. Microorganisms play an important role in nutrient and energy extraction and energy regulation. To date, the specific roles that individual gut microbes play in energy harvest remain uncertain. A better understanding of host-microbe and microbe-microbe interactions may lead to the development of novel adjunctive treatment strategies for obesity and undernutrition. This will undoubtedly be an important area of nutrition research in the years to come."
Abstract
"Lactobacilli strains with probiotic traits were tested for their ability to survive to the digestion process modelled during this study. These strains managed to sustain the harsh conditions of the gastric and duodenal phases and showed good adhesion capacities to human Caco-2 cell line. These probiotic microorganisms have survived during these steps, exposed to low pH, high concentration of bile salts and enzymes occurring in the digestion and virtually reached the duodenal compartment in sufficient amount with limited population loss. These lactobacilli strains appeared to be non-cytotoxic after contact with Caco-2 cells for 24 h. Importantly, some of these strains showed immunomodulatory effect, lowering the pro-inflammatory cytokine IL-8 and promoting secretion of the anti-inflammatory IL-10. Besides, Lactobacillus gasseriCMUL34 and Lactobacillus acidophilus CMUL67 strains were able to modulate secretion and expression of two intestinal hormones: the Glucagon-Like Peptide 1 (GLP-1) and the cholecystokinin (CCK) in STC-1 cells."
Translation:
Specific probiotic strains were tested in a laboratory created digestion process. The strains survived the different stages and did well with the specific human cell line we chose. The bacteria was not toxic to the human cells even with prolonged contact. Some of the types of bacteria boosted immune function of the cells and helped lower inflammation. 2 of the strains changed the expression of two intestinal hormones.
I did not provide a translation for the other 2 abstracts because they are not filled with excess information (for the layperson). The above studies merely support the assertions I made regarding immune function, hormones, nutrient absorption, ect... As for how they work this is only going to get more technical but I'll do my best to provide plain language explanation with studies.
If you paid attention in basic high-school biology then you know that we chew food to start the digestion process, swallow, acid turns it into a gross soup known as chyme, and then the stomach empties into the deodenum where bile will be added to the mix before entering the small intestine. The small intestine is where the real work begins. Everything before getting there was just prepping it for the bacteria in your small intestine. The reason we need to consume sources for certain micronutrients is because we cannot synthesize them ourselves so how do we get them from our food?Your bacteria and friends break down that food and synthesize the vitamins or simplify the minerals so our gut can absorb them.
Bacteria as vitamin suppliers to their host: a gut microbiota perspective
Abstract:
"Food-related lactic acid bacteria (LAB) as well as human gut commensals such as bifidobacteria can de novo synthesize and supply vitamins. This is important since humans lack the biosynthetic capacity for most vitamins and these must thus be provided exogenously. Although vitamins are present in a variety of foods, deficiencies still occur, mainly due to malnutrition as a result of insufficient food intake and because of poor eating habits. Fermented milks with high levels of B-group vitamins (such as folate and riboflavin) can be produced by LAB-promoted and possibly bifidobacteria-promoted biosynthesis. Moreover, certain strains of LAB produce the complex vitamin cobalamin (or vitamin B12). In this review, fermented foods with elevated levels of B-group vitamins produced by LAB used as starter cultures will be covered. In addition, genetic abilities for vitamin biosynthesis by selected human gut commensals will be discussed."
Commensal bacteria at the interface of host metabolism and the immune system
Abstract:
"The mammalian gastrointestinal tract, the site of digestion and nutrient absorption, harbors trillions of beneficial commensal microbes from all three domains of life. Commensal bacteria, in particular, are key participants in the digestion of food, and are responsible for the extraction and synthesis of nutrients and other metabolites that are essential for the maintenance of mammalian health. Many of these nutrients and metabolites derived from commensal bacteria have been implicated in the development, homeostasis and function of the immune system, suggesting that commensal bacteria may influence host immunity via nutrient- and metabolite-dependent mechanisms. Here we review the current knowledge of how commensal bacteria regulate the production and bioavailability of immunomodulatory, diet-dependent nutrients and metabolites and discuss how these commensal bacteria–derived products may regulate the development and function of the mammalian immune system."
I've already shown you studies that show the implications for immune function, mental health, and some hormone regulation. As for how it works I'll spare you the confusing studies that require very specific knowledge to read, rather I will just explain it plainly. The residents of your gut send off chemical signals to each other but also to the cells lining the intestine, think of it like text messages. Some of those messages will tell the body or other bacteria to produce different hormones for different functions. The ones explicitly mentioned signal the "I'm full and therefor not hungry" feeling to your brain. You can learn about the known hormones produced in the gut here: Overview of Gastrointestinal Hormones I really hope that the "how much do we need them?" question has been answered already for you. If not I urge you to go back and read again.
As for Prebiotics, the function and purpose of them is to feed that bacteria. Prebiotics do more than just provide food for your microbiome, they also help keep your bowel movements regular and exfoliate your gut which keeps it functioning well. But where do you find these magical prebiotics? Eat your fibre. No seriously, it's that easy.
That only leaves us with one more major question. Fermented foods or supplement? Which is better? To which the answer is neither is better, they each have their place. For example hand made fermented foods will have far greater probiotic counts and diversity, however they are also high histamine foods. If an individual suffers from allergies, reactive skin diseases such as psoriasis or eczema, or autoimmune issues then the histamines could make things worse. In such cases a store bought supplement may be preferable. However it is important to make sure you get a good quality one, believe it or not the price does not indicate quality.
There are some people who can experience negative side effects other than a normal adjustment period (up to 2 weeks) and shouldn't take any probiotics. ProbioticsCenter.org gives a really good write up of normal side effects and examples of people who likely shouldn't take probiotics for safety reasons. If you find you are someone who shouldn't be taking them then just make sure you eat a clean diet and get plenty of fibre to get your microbiome in a good balance. The results take longer but you will get them.
While doing the research for this article I stumbled across this funky tool that lets you create visual maps of different nutrient interaction pathways. If you have the knowledge on how to read it you may find this kinda fun to play with http://pathways.embl.de/
https://probiotics.org/ is an excellent resource to continue learning this topic in far greater depth than I can provide with a single article. You can see the rest of the studies I used for researching this article in the document Probiotics and prebiotics study collection.
When I originally wrote this article I only had native english speakers who were reading my work. If you feel overwhelmed or confused about anything any reader can ask for clarification and I will take as much time as needed to answer you properly. This is true for anything I write.
Full studies can be accessed by putting the url into sci-hub.
Image is from pixabay and edited in canva by me.