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Baby having a check up
Baby having a check up

The Gut Microbiome: Our partner in Infant Health and Immunity

What is the gut microbiome?

Microbes are found on every external surface in the body including the skin and the gut1.

The gut is the area with the highest levels of bacteria in the body7, with 1,000 different species of known bacteria present1, and it is thought we have 10-100 times more bacterial cells than human cells on our body2. The combination of all the genetic information of these gut bacteria is termed the ‘gut microbiome’1.

The gut microbiome can be influenced by a range of environmental factors including mode of delivery, diet and gestational age at birth8. A healthy gut microbiome has implications for overall health and can be influenced by nutrition.

What are Prebiotics, Probiotics, Postbiotics and Synbiotics?


Prebiotics are substrates that pass to the gut where they stimulate the growth or activity of beneficial bacteria9.

Human milk oligosaccharides (HMOs) are the third most abundant component of human milk10. They are a group of structurally diverse oligosaccharides with prebiotic effects, amongst other benefits.

Fructooligosaccharides & galactooligosaccharides (FOS & GOS) also known as prebiotic fibres. Prebiotic fibres promote the growth of beneficial bacteria in the large intestine. 


Probiotics are beneficial bacteria that affect the host gut microbiome when ingested in adequate amounts11.


Postbiotics are bioactive compounds produced by beneficial bacteria, which have biological activity in the host11.


Synbiotics are a combination of prebiotics and probiotics11.

The gut microbiome has been increasingly researched over recent years, with over 30,000 scientific papers on the topic12, showing links to overall health, particularly in the areas of digestion and absorption of nutrients, gut-brain interactions and immunity13,14.

Bacteria digest fibres, in the large intestine, and this leads to production of important metabolites e.g. short chain fatty acids (SCFA)15. SCFAs are estimated to contribute 10% of energy requirement16, highlighting the microbiome’s important role in extracting nutrients from our diet.

70-80% of the body’s immune cells are in the gut and the bacteria in the gut communicate with these cells. The gut microbiome, therefore, provides the most important stimulation source for developing immunity17,18.

In relation to immunity, studies have found links between gut microbiome and allergy incidence. For example, caesarean infants, who had a different microbiome composition to vaginal delivered infants, were found to have increased cytokine IL-13 production suggesting higher asthma incidence19.

Dysbiosis is an imbalance of bacteria in the microbiome, involving the loss of health promoting bacteria, the increase of pathogenic bacteria20 or a reduction in microbial diversity21.


Dysbiosis and implications for health

There are associations between dysbiosis and different health conditions and the science in this area is growing. At present, correlations with dysbiosis have been found with the following conditions, and it should be noted this does not prove cause and effect but does indicate an important relationship between dysbiosis and the conditions:

  • allergies22,23
  • asthma24,25
  • autism spectrum disorder26
  • diabetes27,28
  • inflammatory bowel diseases29
  • obesity and metabolic disorder30

What can be done to prevent Dysbiosis?

Whilst there is generally a lack of randomised controlled trials in this area, taking simple actions will help to look after the microbiota and prevent dysbiosis:




Eating a wide range of healthy foods and consuming pre- and probiotics30


Breastfeeding can help support the developing microbiome31



Exercise and maintain a healthy weight33

  • Helps the body to digest certain foods e.g. dietary fibre34, 35
  • Supports the production of some vitamins e.g. B12, folate, K34
  • Regulated energy metabolism34,35
  • Defends against pathogens34,35
  • Provides signals for the development of the immune system34,35
  • Influences gut-brain communication for optimal gut and brain functions34,35
  • Sets up metabolic homeostasis in early life36

Learn more about the Gut Microbiome in your area of interest

You may also be interested in

  1. Gerritsen J et al. Genes Nutr. 2011;6:209–240. 
  2. Lozupone CA, et al. Nature, 2012;489(7415):220-230. 
  3. Hawrelak JA, Myers SP. Altern. Med. Rev. 2004;9:180–197.
  4. Vangay P, et al. Cell.2018;175(4):962-972.e10.
  5. Dominguez-Bello MG, et al. Proc. Natl. Acad. Sci. USA. 2010;107:11971–11975.
  6. Zoetendal EG, et al. Microb. Ecol.Health Dis. 2001;13:129–134.
  7. Lee KN, Lee, OY. World J Gastroenterol. 2014;20:8886–8897. 
  8. WHO. The optimal duration of exclusive breastfeeding: report of an expert consultation, 2015. 
  9. Gibson GR, et al. Nat Rev Gastroenterol Hepatol 2017;14(8): 491–502. 
  10. Bode L. Glycobiology. 2012;22:1147–6212). 
  11. Schrezenmeir J, et al. Am J Clin Nutr. 2001;73(Suppl 2):361S–364S.
  12. Ncbi.nlm.nih.gov. (2021). gut microbiome - PubMed - NCBI. [online] Available at: https://www.ncbi.nlm.nih.gov/pubmed/?term=gut+microbiome [Accessed 07 May 2021].
  13. Forsythe, P., Sudo, N., Dinan, T., Taylor, V. and Bienenstock, J. (2010). Mood and gut feelings. Brain, Behavior, and Immunity, 24(1), pp.9-16.
  14. Rook & Stanford,  Immunol Today.1998;19(3):113-6.
  15. Wong JM, de Souza R, Kendall CW, Emam A, Jenkins DJ (2006) Colonic health: fermentation and short chain fatty acids. J Clin Gastroenterol 40(3):235–243.
  16. Wopereis H, et al. The first thousand days—intestinal microbiology of early life: establishing a symbiosis. Pediatric Allergy and Immunology, 2014;25(5):428-438Furness JB, et al. Nutrient Tasting and Signaling Mechanisms in the Gut Am J Physiol, 1999; 277(5 Pt 1):G922-8.
  17. Koenig, J. et al. Proc Natl Acad Sci U S A, 2010;108(Suppl 1)4578-4585. 
  18. Furness JB, et al. Gut Am J Physiol, 1999;277(5 Pt 1):G922–8.
  19. Martin, R. et al. Benef Microbes, 2010 ;1(4):367-382.
  20. Wilkins LJ, et al. Sci Rep 2019;9:12918.
  21. Petersen C, Round JL. Cell Microbiol. 2014;16(7):1024–1033.
  22. Canani RB, etal. ISME J. 2016;10(3):742–750.
  23. Thompson-Chagoyan OC, et al. Pediatr Allergy Immunol. 2010;21(2p2):e394–e400.
  24. Abrahamsson TR, et al. Clin Exp Allergy. 2013.
  25. Sokolowska, M, etal. asthma res and pract 2018:4,1.
  26. Fattorusso A, et al. Nutrients. 2019 Feb 28;11(3):521.
  27. Karlsson FH, et al. Nature. 2013;498:99–103.
  28. Giongo A, et al. ISME J. 2011;5:82–91.
  29. FrankDN. Proc Natl Acad Sci USA. 2007;104:13780–13785.
  30. Arslan N.World Journal of Gastroenterology. 2014;20(44):16452–63.
  31. van den Elsen LWJ, et al. Front Pediatr. 2019;7:47.
  32. Valdes A M, et al. BMJ 2018;361:k2179.
  33. Aoun A,et al. Prev Nutr Food Sci. 2020;25(2):113-123.
  34. Shamir R, van Elbur_ R, Knol J, Dupont C. Gut Health in Early Life: Significance of the Gut Microbiota and Nutrition for Development and Future Health.Essential Knowledge Briefing, Wiley, Chichester (2015).
  35. Van de Wiele T et al. Nature Reviews Rheumatology, 12:398–411, 2016.
  36. Nash MJ, Frank DN, Friedman JE. Early Microbes Modify Immune System Development and Metabolic Homeostasis—The “Restaurant” Hypothesis Revisited. Front Endocrinol 2017; 8: 349.

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