Gut Microbiota

Although the bacterial community resident in the human gut has evolved over millions of years, research into the functions of those bacteria has developed exponentially only in the last decade or so.^1,2  Early life has been identified as a significant period for the establishment of the gut microbiota with a number of key factors at this time influencing the nature of that development.^1-3  Disturbances in the gut microbiota, sometimes referred to as dysbiosis, has been linked to numerous diseases and conditions in infancy and childhood including allergy, obesity, diabetes, coeliac disease and asthma.²

One significant early life event that has been repeatedly linked to differences in the infant gut microbiome is the mode of delivery, that is, Caesarean section versus vaginal delivery.^4-6  Such differences may be important as a recent publication from a longitudinal study in 150 countries revealed that the number of births by Caesarean section had increased from 6.7% in 1990 to 19.1% in 2014.⁷

Intestinal bacterial colonisation with Lactobacillus, Bifidobacterium and Bacteroides has been reported to be delayed in children born via Caesarean section when compared to infants born vaginally.⁸ A delay in Bacteroidetes colonisation has been reported up to 1 year after Caesarean section delivery.⁹

Another important factor is antibiotic use in early life.  Whilst, of course, antibiotics are a treatment option in infectious diseases, their use in early life can cause dysbiosis affecting both beneficial and harmful bacteria.¹⁰ The effect of antibiotics on the microbiota is influenced by many factors including the age at the time of treatment as well as the duration of use, frequency and dosage.¹¹ Antibiotic use has been shown to reduce the abundance of beneficial Bifidobacterium as well increasing the ratio of Firmicutes to Bacteriodetes^12-13 which in some, but not all studies, has been associated with obesity.^14-16

One of the most powerful factors that impacts upon the gut microbiota is breastfeeding.^17,18  It has been reported that the breastfed infant has significant quantities of Bifidobacterium longum that are able to metabolise human milk oligosaccharides in the colon.²  The short-chain fatty acids produced by this metabolism have been associated with gut epithelial integrity, differentiation of T cells and anti-inflammatory responses.¹⁹

In summary, the gut microbiota has a significant role in the infants developing immune system which, in turn, can influence short term and long term health and disease risk.²  It has been suggested that the next stage of development in this area will be targeted microbial therapy although before that can occur more research and information is required relating to the complex gut microbiota.²

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