Are Probiotics Necessary?

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Written by Astrid Naranjo (Clean Health Accredited Clinical Dietitian)

Probiotics are a trendy topic when it comes to gut health and there’s a lot of misinformation out there. 

The term probiotic is derived from the Latin preposition “pro,” which means “for” and the Greek word “biotic” meaning “life”.

The Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) defines probiotics as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (1). The modern definition of probiotic was put forward by Havenaar and Huisint Veld (12) as a viable mono or mixed culture of bacteria which, when given to animal or man, affects the host beneficially by improving the properties of the indigenous flora.

Probiotics are commonly consumed as preparations with active live cultures and contain bacteria, such as lactobacilli, lactococci or bifidobacteria that has been isolated from natural environments (11,15).

There are hundreds of different microorganisms in our digestive system, more specifically, the human gut serves as a home to over 100–1000 microbial species, which primarily modulate the an important proportion of the host’s internal environment and thereby, has impact on our health (11). Put into perspective, bacterial cells comprise half of the wet weight of colonic material and their numbers exceed by 10-fold the number of tissue cells forming the human body. Normally, the stomach contains 103 different bacterial species, and the total microbial population of the colon comprises of about 1011–1012 cfu/g (11,13).

The majority of these are bacteria, most of which are friendly. Friendly bacteria produce several important nutrients, including vitamin K and certain B-vitamins, and also help break down fiber, turning it into beneficial short-chain fatty acids like butyrate (2,3).

Research has shown that probiotics can be widely considered as health-promoting microorganisms and could positively impact host physiology and even help treating various diseases through different mechanisms (1-5,11). In addition, probiotics have been shown to be beneficial in the treatment and prevention of gastrointestinal diseases, improving coronary heart disease risk factors such as cholesterol and inflammatory biomarkers, and boosting immune function (6-10). They can even modulate the gastrointestinal hormone release and regulate brain behaviour through bidirectional neuronal signalling, as part of the gut–brain axis (14).

Most probiotic foods which includes fermented foods like sauerkraut, kefir and yogurt, and probiotic supplements contain multiple strains of probiotics (11, 16).

Although probiotics supplements are still in pipeline and requires further studies and development to overcome barriers related to their successful administration and minimal side effects several forms of probiotics are available commercially and are in use in large amount (11). Some of the common commercial microbial strains currently sold as dietary probiotic supplements that generally involve dairy products but can also be incorporated into non-dairy fermented food products, presenting an alternative (11).

However, it is important to note that all probiotics might not be safe for all individuals. Especially, the host factors can be variable, and for a particular milieu under certain clinical conditions, probiotics might be immunogenic and/or pathogenic (18,19).

Source: ScienceDirect (2018)

Probiotics are measured in colony-forming units (CFU). Generally, higher doses have been found to produce the best results in most studies for certain conditions (17). Typical dosages range from 10 to 20 billion colony-forming units per day for adults (17).

However, some probiotics may be effective at dosages of 1–2 billion CFU per day, while others may require at least 20 billion CFU to achieve the desired effects. It doesn’t appear that higher doses provide any additional benefit.

Studies have indicated that many fermented foods contain between 1 to 100 million CFU per mL or gram, although there is considerable variation based on geographical region and sampling time. In general, cultured dairy products consistently contained higher levels of up to 10 billion CFU per mL or gram (17).

However, fermented foods may not be well tolerated by many. Fermented foods may contain biogenic amines (BAs) such as histamine which due to their toxicity, can cause adverse effects on some people (16). Biogenic amines are produced when food ages or is fermented by bacteria. This intolerance may be due to the fact that some people have naturally a weakened function of the DOA enzyme, which is the one that breaks down histamine in the gut, and makes them not be able to tolerate histamine containing foods very well.

For these individuals, and those people who do not consume a lot of probiotic foods, taking a probiotic supplement may be a viable alternative. However, it should be noted that some bacterial strains used in probiotic supplements can also produce histamine inside the digestive tract (17). These include Lactobacillus buchneri, Lactobacillus helveticus, Lactobacillus hilgardii, and Streptococcus thermophilus. Individuals with histamine intolerance should avoid products containing those strains.

In my professional opinion, the term ‘probiotics’ has been marketed in such a manner that everyone has a presumption that the consumption of these products is always beneficial, almost a panacea, with zero risks. Probiotics are not likely to do anything if you are an otherwise “healthy” individual. Probiotics are no ‘magic bullet’, and their administration under the current pretense of microbiota restorative and immunomodulator, might not be universally safe and effective (18,19).

While taking a probiotic is likely not going to cause any harm if you don’t need them, it may just be a waste of money, and it should be best recommended more on a case by case basis. Finally, since probiotics may not be ideal, optimal or safe for everyone (based on current evidence), PREBIOTICS are something that all of us can use to encourage & nurture a “healthy” gut.


  1. Hill C, Guarner F, Reid G, et al. Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-514. doi:10.1038/nrgastro.2014.66
  2. Ríos-Covián D, Ruas-Madiedo P, Margolles A, Gueimonde M, de Los Reyes-Gavilán CG, Salazar N. Intestinal Short Chain Fatty Acids and their Link with Diet and Human Health. Front Microbiol. 2016;7:185. Published 2016 Feb 17. doi:10.3389/fmicb.2016.00185
  3. Baron S (1996). Medical Microbiology (4th edition). Galveston (TX): University of Texas Medical Branch at Galveston; Chapter 95, Microbiology of the Gastrointestinal Tract.
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  5. Dan Cheng, Jingzheng Song, Meizhen Xie, Danfeng Song. The bidirectional relationship between host physiology and microbiota and health benefits of probiotics: A review, Trends in Food Science & Technology, Volume 91, 2019, ISSN 0924-2244,
  6. DiRienzo DB. Effect of probiotics on biomarkers of cardiovascular disease: implications for heart-healthy diets. Nutr Rev. 2014;72(1):18-29. doi:10.1111/nure.12084
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  9. Eckburg PB, Bik EM, Bernstein CN, et al. Diversity of the human intestinal microbial flora. Science. 2005;308(5728):1635-1638. doi:10.1126/science.1110591
  10. Kligler B, Cohrssen A. Probiotics. Am Fam Physician. 2008;78(9):1073-1078.
  11. Rout George Kerry, Jayanta Kumar Patra, Sushanto Gouda, Yooheon Park, Han-Seung Shin, Gitishree Das. Benefaction of probiotics for human health: A review, Journal of Food and Drug Analysis. Volume 26, Issue 3,2018,Pages 927-939. ISSN 1021-9498.
  12. R. Havenaar, J.H.J. Huis in’t Veld. Probiotics: a general view. B.J.B. Wood (Ed.), The lactic acid bacteria in health and disease, Elsevier Applied Science, London (1992), pp. 151-170
  13. Slavin, J. (2013). Fiber and prebiotics: mechanisms and health benefits. Nutrients, 5(4), 1417-1435.
  14. N.B. Kristensen, T. Bryrup, K.H. Allin, T. Nielsen, T.H. Hansen, O. Pedersen Alterations in fecal microbiota composition by probiotic supplementation in healthy adults: a systematic review of randomized controlled trials. Genome Med, 8 (2016), pp. 1-11
  15. G.P.A. Bongaerts, R.S.V.M. Severijnen. A reassessment of the PROPATRIA study and its implications for probiotic therapy. Nature Biotechnol, 34 (2016), pp. 55-63
  16. Rezac S, Kok CR, Heermann M, Hutkins R. Fermented Foods as a Dietary Source of Live Organisms. Front Microbiol. 2018;9:1785. Published 2018 Aug 24. doi:10.3389/fmicb.2018.01785
  17. Gardini F, Özogul Y, Suzzi G, Tabanelli G, Özogul F. Technological Factors Affecting Biogenic Amine Content in Foods: A Review. Front Microbiol. 2016;7:1218. Published 2016 Aug 12. doi:10.3389/fmicb.2016.01218
  18. Damini Kothari, Seema Patel, Soo-Ki Kim. Probiotic supplements might not be universally-effective and safe: A review. Biomedicine & Pharmacotherapy, Volume 111, 2019, Pages 537-547, ISSN 0753-3322.
  19. M.G. Redman, E.J. Ward, R.S. Phillips. The efficacy and safety of probiotics in people with cancer: a systematic review. Annals of Oncology. Volume 25, Issue 10, 2014,Pages 1919-1929. ISSN 0923-7534.

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