Are Probiotics bad for us? Are we getting too much?

Are Probiotics bad for us? Are we getting too much?

Probiotics are huge on the global market nowadays, they bloomed (pun intended) in recent years, and now we see them everywhere. We have spoken about biotics in general prior to now, however, what we wanted to take a deeper look at now is the overuse of probiotics and how they could be affecting your gut.

This is by no means an attack on probiotics, they have their place and are extremely important. A monumental discovery for modern medicine, alas, we always talk about ratios and the crucial importance to keep ratios in mind when eating and supplementing our diet.

Probiotic recap…

When we think about Probiotics, we usually think of lactobacillus off the top of our heads as one we can easily name, or those peculiar tasting probiotics-filled drinks we had in our lunchboxes as children. What are Probiotics though, what are they really?

Probiotics [1] are live cultures (live to be the keyword here as we will get to this later) that can be found in fermented food forms and cultured milk. They support the host's microbiome populations between two main occurring Phyla. These are the categories/classes that our bacteria are placed in. The two main Phyla are:

  • Mostly the clostridium and lactobacillus strains
  • Mostly Bacteroides and Prevotella

    You can supplement with probiotics in your diet if required, usually many will opt for this after a bout of antibiotic use to help restore the beneficial strains that have been lost.

    Firmicutes are Critical

    Firmicutes come in the billions, and there are multiple strains/classes. Currently, there are 7 recognised classes [2], research is always expanding though so this can be subject to change in due time.

    • Erysipelotrichia
    • Negativicutes
    • Limnochordia
    • Tissierellia
    • Thermolithobacteria
    • Clostridia
    • Bacilli

      The role of firmicutes governs how we use fibre, carbohydrates, regulate our immune system and communicate between the brain and gut.

      Bacteroides are beneficial too!

      Bacteroides are a great species for assisting in the breakdown of complex carbohydrates, immune signaling, support of gut-associated lymphoid tissue supporting the health and wellbeing of the gut, and many more benefits…[2]

      The Bacteroides species consists of as we know:

      • B. acidifaciens
      • B. caccae
      • B. coprocola
      • B. coprosuis
      • B. eggerthii
      • B. finegoldii
      • B. fragilis
      • B. helcogenes
      • B. intestinalis
      • B. massiliensis
      • B. nordii
      • B. ovatus
      • B. thetaiotaomicron
      • B. vulgatus
      • B. plebeius
      • B. uniformis
      • B. salyersai
      • B. pyogenes
      • B. goldsteinii
      • B. dorei
      • B. johnsonii

      It’s all about population support!

      Both phyla are incredibly important for balance and function, and overall homeostasis in the body. To achieve this, it comes down to balance, studies are emerging that an abundance of firmicutes in a situation of competitive exclusion of Bacteroides has a higher prevalence in obese individuals [3]. When the subjects of this study were submitted to a calorie restriction environment for 1 year, it showed to not only lose weight (an expected given) but also increase Bacteroides as a result. Balancing the ratios of the two phyla in a parallel effect/benefit to weight loss.

      Firmicutes have been concluded to extract more energy from food than that of their Bacteroides counterparts [4]. Data suggest that alterations of the bacterial composition or diversity of an individual can impact their metabolic profile of the function and influence of the microbiota on the host (us humans) health [5]. This data on the phyla ratios has begun leading the way to be considered as a potential hallmark in obesity.

      Where does this lead us with probiotics?

      Given that probiotics are proponents of the firmicutes species, it's important to keep in mind that throwing these in constantly could lead to a competitive exclusion potentially happening down the track. It is great to include these strains after say a round of antibiotics under the guidance of your doctor, however, constant exposure through probiotic enriched foods which has become very marketable may not be the best thing for us in the long run.

      What should you do?

      If you are absent of specific strains that you should have and know that, definitely work on replenishing these populations by working with your health professional to incorporate suitable live cultures.

      If you are taking probiotics, ensure that they are shelf-stable, a lot of them need to be stored at particular temperatures for the stability of the live cultures. So, ensure that they are shelf-stable or kept with the specific climate they need.

      Ensure you are getting diversity, one well-studied dietary requirement of Polyphenols and fibre rich foods. The complex polysaccharides (complex carbohydrates) and soluble/insoluble fibre components are incredible for supporting the microbiome function [6].


      1. Shi, L. H., Balakrishnan, K., Thiagarajah, K., Mohd Ismail, N. I., & Yin, O. S. (2016). Beneficial Properties of Probiotics. Tropical life sciences research, 27(2), 73–90.
      3. Microbial ecology: human gut microbes associated with obesity. Ley RE, Turnbaugh PJ, Klein S, Gordon JI Nature. 2006 Dec 21; 444(7122):1022-3.
      4. Effects of gut microbes on nutrient absorption and energy regulation. Krajmalnik-Brown R, Ilhan ZE, Kang DW, DiBaise JK Nutr Clin Pract. 2012 Apr; 27(2):201-14.
      5. Metabolic syndrome and altered gut microbiota in mice lacking Toll-like receptor 5. Vijay-Kumar M, Aitken JD, Carvalho FA, Cullender TC, Mwangi S, Srinivasan S, Sitaraman SV, Knight R, Ley RE, Gewirtz AT Science. 2010 Apr 9; 328(5975):228-31.
      6. Kumar Singh, A., Cabral, C., Kumar, R., Ganguly, R., Kumar Rana, H., Gupta, A., Rosaria Lauro, M., Carbone, C., Reis, F., & Pandey, A. K. (2019). Beneficial Effects of Dietary Polyphenols on Gut Microbiota and Strategies to Improve Delivery Efficiency. Nutrients, 11(9), 2216.