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

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

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

Postbiotics

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

Synbiotics

Synbiotics are a combination of prebiotics and probiotics¹¹.

Why is the gut microbiome important?

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 immunity^13,14.

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.

How does the gut microbiome affect immunity?

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 immunity^17,18.

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.

What is gut dysbiosis?

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:

allergies^22,23
asthma^24,25
autism spectrum disorder²⁶
diabetes^27,28
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: