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What are probiotics?

Your gut is filled by trillions of bacteria, but there is no reason to be freaked out by it

Bacteria usually get bad rep, and perhaps for good reasons. Many bacteria strains can be harmful to our health and should therefore be avoided.  However, did you also know that there are a large set of bacterial strains that support our basic bodily functions? In fact, we might become sluggish or even sick when we lack these bacteria. Many fermented foods such as yoghurt, Korean kimchi, or saurkraut contain these beneficial bacteria, which are also called probiotics.

Support and protect

According to the general picture, beneficial bacteria are located in the guts. However, this is only partially true. The human microbiome includes both the internal and the external bodily environment such as your mouth and skin. These bacteria support several bodily processes such as digestion, the production of vitamins such as B12 and folate, and protect against pathogens. The species of bacteria might reach up to several hundreds.

Number and scope

Moreover, the number of bacteria in our microbiota ranges between approximately ten-fold and one-fold according to the literature. However, in both cases the bacterial presence indicates an omnipresence in our bodies. In fact, while humans have 26 thousand genes (compared to 46 thousand genes in rice plants), our “gut bugs” consist of 100 thousand genes. So yes, only together do we beat the rice plant. These numbers do not necessarily mean much in terms of health outcomes, but  they can help to shift our focus more firmly to somewhere that has gained increasing prominence in the last few decades: our microbiota.

Mechanisms of effect

There are several ways in which probiotics can exert positive health outcomes. Micriobiotics can

  • Stop potential pathogens before they can affect you negatively.
  • Improve the barrier function in the body.
  • Modulate the immune system for the better.
  • Help to produce neurotransmitters

Balance of the bacteria

Under healthy circumstances, the good bacteria triumph over the bad ones. However, some factors can deteriorate this balance: diet, stress, disease and antibiotics use. When this happens, certain niches in your gut can make place for harmful bacteria. In order to prevent this, supplements and cultivated foods can come into play and could support human health.

Treatment effectiveness of supplements

One 2017 review states that probiotic supplements could actually treat at least six gut-related disorders:

  • Irritable bowel syndrome (IBS)
  • Helicobacter pylori infection
  • Lactose intolerance
  • Infectious diarrhea
  • Antiobiotic-associated diarrhea (AAD)
  • Inflammatory bowel disease (IBD)

Side effects

In most cases, the side effects of probiotic supplements are easily manageable and include symptoms such as upset stomach and bloating. However, in immunosuppressed individuals, probiotics might cause a more severe adverse risk. Allergic reactions are also possible. In any of these cases, it is recommended to get advice from your doctor prior or during use.

Food and supplemental sources

Not all probiotic sources are made equal. According to one study, the bacteria derived from probiotic supplements were less diverse than beneficial bacteria from fermented foods. In fact, when these bacteria were placed on petri dishes they formed neat circles or “colourful and disorderly splotches” respectively.

References and further reading
  • Harvard Health Publishing, “The Growing Role of Probiotics,” Harvard Health, accessed May 11, 2018 (link)
  • Michael A. Conlon and Anthony R. Bird, “The Impact of Diet and Lifestyle on Gut Microbiota and Human Health,” Nutrients 7, no. 1 (January 2015): 17–44 (link)
  • Borja Sanchez et al., “Probiotics, Gut Microbiota, and Their Influence on Host Health and Disease,” Molecular Nutrition & Food Research 61, no. 1 (January 2017) (link)
  • Sender, Ron, Shai Fuchs, and Ron Milo. “Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans.” Cell 164, no. 3 (January 28, 2016): 337–40 (link)
  • “Gut Check: Do Probiotics Work?,” accessed May 11, 2018 (link)
  • Harvard Health Publishing, “The Benefits of Probiotics Bacteria,” Harvard Health, accessed May 11, 2018 (link)
  •  Conlon and Bird, “The Impact of Diet and Lifestyle on Gut Microbiota and Human Health.” (link)
  • Sanchez et al., “Probiotics, Gut Microbiota, and Their Influence on Host Health and Disease.” (link)
  • Harvard Health Publishing, “Benefit of Probiotics: Should You Take a Daily Dose of Bacteria?,” Harvard Health, accessed May 11, 2018 (link)
  • “What Are Probiotics?,” WebMD, accessed May 11, 2018 (link)
  • “Which Probiotic Is Right for You?,” WebMD, accessed May 11, 2018 (link)
  • TEDx Talks. Microbiome: Gut Bugs and You | Warren Peters | TEDxLaSierraUniversity. Accessed June 1, 2018 (link)