Microbiome = the microscopic ecosystem on and within your body.
This ecosystem contains trillions of microorganisms that are in continuous communication with your body, and perform many functions crucial to your health and wellbeing.
It may be surprising that your immune system allows some microbes to live and thrive within your body whilst simultaneously fighting off other disease-causing microbes. However, this co-dependency between your immune system and your microbiome has evolved over millions of years and is fundamental to your survival. Ever since you were born your immune system and your natural microbial flora have been continually communicating with one another.
Your microbiome bacteria release molecules that ‘speak to’ and regulate your immune cell responses, enabling your “good” bacteria to live happily whilst inhibiting the colonisation and growth of invading pathogens.(2-4) This back-and-forth communication is critical for efficient and effective immune function ensuring swift and effective immune response against harmful pathogens, whilst allowing beneficial microbes to remain.
Short chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, are an example of important immunity-affecting molecules that are secreted in high amounts by your microbiome bacteria. Other examples include taurine, histamine, spermine, and niacin. They perform crucial immune functions such as supressing inflammation (5-8), maintaining the intestinal mucus layer, promoting viral recognition, and generating downstream production of important immune factors(9-10).
~ When your immune cells identifies a threatening microbe, a series of immune responses are triggered.
~ Your immune system ‘memorises’ this interaction, so your immune system is better equipped to respond rapidly next time.
~ A faster immune response can mean a reduction in the severity of symptoms, a shorter period of feeling unwell, or it may prevent you from becoming unwell completely.
~ Microbiome bacteria communicate with your immune system by releasing molecules that promote immune responses, resulting in a more efficient, healthy immune system.
Sometimes, abnormal interactions between the immune system and the microbiome can lead to the development of immune disorders. This occurs when the microbiome is in a state of imbalance or 'dysbiosis'. For example, in Inflammatory Bowel Disease (IBD), alterations to bacterial communities in the gut have led to impacted immune responses in the gut mucosa (the mucus lining of the gut) which leads to chronic intestinal inflammation and tissue injury in the gut. (11)
Consumption of Bacteria with Immune Benefits
There are a number of bacterial species that produce a range of immune-regulating signals, such as SCFAs. These bacteria have also been found to provide many health benefits arising from the interaction with the immune system. For example, clinical studies have shown that ingesting Lactobacillus strains can:
~ reduce the duration and severity of common colds, flu, and other respiratory illnesses (12-14).
~ significantly reduce the symptoms of hay fever (14)
~ improve immune cell activity and reduce symptoms of chronic inflammation (15)
~ reduce the incidence of side-effects, such as diarrhoea and urinary tract infections, that can occur following a course of broad-spectrum antibiotics (16-19).
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(5) Zeng et al. (2017) Butyrate Inhibits Cancerous HCT116 Colon Cell Proliferation but to a Lesser Extent in Noncancerous NCM460 Colon Cells. Nutrients. 9(1): 25.
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(20) Adnan et al. (2020). Probiotics as Promising Immunomodulatory Agents to Prevent COVID-19 Infection:
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