Baby, Toddler, Child
6th Feb 2023

Derived from the Greek language, the word probiotic means ‘for life’.

Probiotics are live bacteria naturally found in the gut, as well as in certain foods and supplements, that when consumed in adequate amounts, provide health benefits the consumer(1).

What are probiotics?

Put simply, the answer to this question is they are the ‘good’ bacteria that work to keep pathogens (or ‘bad’ bacteria) at bay. In addition to maintaining friendly flora within the gut, probiotics have been shown to support gut health and maintain healthy immune system function.

The human body is home to trillions of bacteria and other microorganisms, all of which make up our individual microbiome. In fact, the human body is home to 10x more microbial cells than human cells at any given time(2,3).

What is the microbiome?

Probiotics aren’t only limited to gut and digestive health. They are also found on our skin, in our nose and mouth, as well as in our reproductive and urinary systems.

Together, all the microorganisms living on or in the body make up a child’s microbiome and contribute to their overall health(3).


How does the microbiome develop?

The first thousand days is the period of a child’s life from their conception until their second birthday. It represents a critical window of growth and development and, during this time, trillions of microbes are assembling within the human body to form the microbiome(4).

By the end of the first year of life, a child possesses an individually distinct microbial profile. It was previously believed that the development of a baby’s gut microbiome began at birth, however new research has challenged this notion. It is now clear that the development of the gut microbiota begins while a baby is still inside the womb(5,6).

Research suggests that the colonisation of microbes within a child’s gut plays a critical role in many developmental pathways, and that the disruption of optimal microbial development can influence lifelong health.

The strongest factors influencing the composition and development of the infant gut microbiota are genetics, the maternal microbiome, type of delivery at birth, breast or formula feeding, and antibiotic exposure in both the pre- and post-natal period(7-9).

Are there different kinds of probiotics?

Probiotics have been extensively researched in recent years and, as such, many different strains have been identified. Two of the most widely recognised, and most widely researched probiotics are bifidobacteria and lactobacilli.

Interestingly, not all probiotics are the same. Each probiotic strain is unique and different strains have been shown to have different health benefits.

Research has also shown that age matters. This means that at different stages of life, different bacteria dominate the gut and impact health. During infancy and early childhood, bifidobacteria dominate the gut and play an important role in microbiome development and health. And so, as a child grows, the microbial profile of the gut grows in diversity(8,10).


  1. Fuller, R. (1992). History and development of probiotics. In: Probiotics. Springer, Dordrecht.
  2. Ursell, L, Metcalf, J, Parfrey, L, Knight, R. (2012). Defining the Human Microbiome. Nutr Rev. 70(Suppl 1): S38–S44.
  3. National Institutes of Health (2012). NIH Human Microbiome Project defines normal bacterial makeup of the body. Accessed 12 Aug 2022 <,vital%20role%20in%20human%20health >
  4. Wopereis, H, Oozeer, R, Knipping, K. et al. (2014). The first thousand days–intestinal microbiology of earlylife: establishing a symbiosis. Pediatric Allergy and Immunology, 25. 428-438.
  5. Rodrigues, J, Murphy, K, Stanton, C et al. (2015) The composition of the gut microbiota throughout life, with an emphasis on early life. Microbial Ecology in Health and Disease, 26: 26050. doi: 10.3402/mehd.v26.26050
  6. Voreades, N, Kozil, A & Weir, T. (2014). Diet and the development of the human intestinal microbiome. Frontiers in Microbiology, 5. DOI: 10.3389/fmicb.2014.00494
  7. Roberton, R, Manges, A, Finlay, B, et al. (2019). The Human Microbiome and Child Growth – First 1000 Days and Beyond. Trends in Microbiology, 27 (2). 131-147.
  8. Arrieta, M, Stiemsma, L, Amenyogbe, N, et al. (2014). The intestinal microbiome in early life: health and disease. Frontiers in Immunology, 5. DOI: 10.3389/fimmu.2014.00427
  9. Tamburini, S, Shen, N, Wu, H & Clemente, J. (2016). The microbiome in early life: implications for health outcomes. Nature Medicine, 22 (7). 713-722.
  10. Turroni, F, Peano, C, Pass, D. et al. (2012). Diversity of Bifidobacteria within the Infant Gut Microbiota. PLOS ONE, 7 (5). DOI 10.1371/journal.pone.0036957.