The human microbiota consists of the 10-100 trillion symbiotic microbial cells harboured by each person, primarily bacteria in the gut; the human microbiome consists of the genes these cells harbour.2Ursell LK, et al. Defining the human microbiome. Nutr Rev 2012;70(1):S38-S44. A typical digestive tract contains a vast collection of microbial communities, including:3Sender R, et al. Revised estimates for the number of human and bacteria cells in the body. PLOS Biology 2016;14(8):e1002533.
The gut contains more than 1000 bacterial species. And that’s a good thing, because a diversity of bacteria in the gut is associated with stability and resilience, which is a reliable indicator of gut health.4McBurney MI, et al. Establishing what constitutes a healthy human gut microbiome: state of the science, regulatory considerations, and future directions. J Nutrition 2019;149(11):1882-1895. And, interestingly, research has shown that the composition of the gut microbiome can change with dietary intervention,5So D, et al. Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis. Am J Clin Nutrition 2018;107(6):965-983. stress levels6Conlon MA and Bird AR. The impact of diet and lifestyle on gut microbiota and human health. Nutrients 2015;7(1):17-44. and quality of sleep.7Benedict C, et al. Gut microbiota and glucometabolic alterations in response to recurrent partial sleep deprivation in normal-weight young individuals. Mol Metab 2016;5(12):1175-1186.
Gut microbiota are unique to each individual. Their composition is influenced by various factors – some of which we can control, and others we can’t.
For example, when a baby is born, the delivery method can influence maternal-offspring exchanges of microbiota. In the womb, if the unborn baby is exposed to antibiotics, this can also affect their gut microbiome.10Mueller NT, et al. The infant microbiome development: mom matters. Trends Mol Med 2015;21(2):109-117.
Throughout life, people can support the balance of their gut microbiome by making healthy lifestyle choices, such as the food they eat and how much exercise they get.11Quigley E. Gut microbiome as a clinical tool in gastrointestinal disease management: are we there yet? Nat Rev Gastroenterol Hepatol 2017;14:315-320.
For more information about factors that influence the balance of the gut microbiome, please download our gut microbiome factsheet.
In healthy bodies, the gut microbiota perform a number of key functions:
| Metabolism |
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| Fermenting non-digestible food components (mainly dietary fibre) to produce short-chain fatty acids that are important for maintaining a healthy colon12Gill PA, et al. Review article: short chain fatty acids as potential therapeutic agents in human gastrointestinal and inflammatory disorders. Aliment Pharmacol Ther 2018;48(1):15-34. |
| Synthesis of essential nutrients, including B vitamins13Magnusdottir S, et al. Systematic genome assessment of B-vitamin biosynthesis suggests co-operation among gut microbes. Front Genet 2015;6:148. |
| Release/stimulation of important neurotransmitters, such as dopamine and serotonin14Cryan JF, et al. The microbiota-gut-brain axis. Physiol Rev 2019;99(4):1877-2013. |
| Immunity |
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| Gut-associated lymphoid tissue is highly specialised and is the main entity of mucosal-associated lymphoid tissue, representing ~70% of the entire immune system |
| Gut microbiota inform the immune system in establishing a balance between tolerating/responding to potential threats14Cryan JF, et al. The microbiota-gut-brain axis. Physiol Rev 2019;99(4):1877-2013. |
| Protection |
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| The microbiota act as a structural barrier, preventing pathogen adhesion and subsequent colonisation15Iacob S, et al. Intestinal Microbiota as a Host Defense Mechanism to Infectious Threats. Front Microbiol 2018;9:3328. |
When the microbiome becomes imbalanced, this is known as ‘dysbiosis’ and can be defined as:16Petersen C and Round JL. Defining dysbiosis and its influence on host immunity and disease. Cellular Microbiol 2014;16(7):1024-1033.
Dysbiosis can be implicated in the pathophysiology of gastrointestinal disorders17Pittayanon R, et al. Gut microbiota in patients with irritable bowel syndrome – a systematic review. Gastroenterology 2019;57(1):97-108.,18Nishida A, et al. Gut microbiota in the pathogenesis of inflammatory bowel disease. Clin J Gastroenterol 2018;11(1):1-10. and other metabolic conditions.19Vallianou N, et al. Understanding the role of the gut microbiome and microbial metabolites in obesity and obesity-associated metabolic disorders: current evidence and perspectives. Current Obesity Reports 2019;8(3):317-332.
Dysbiosis may be caused by medication (e.g. antibiotics),20Maier L, et al. Extensive impact of non-antibiotic drugs on human gut bacteria. Nature 2018;555(7698):623-628.,21Lange et al. Effects of Antibiotics on Gut Microbiota. Digestive Diseases. 2016;34:260-268.bacterial infections (e.g. gastritis),22Iacob S and Iacob DG. Infectious threats, the intestinal barrier, and its Trojan horse: dysbiosis. Front Microbiol 2019;10:1676. stress,23Clapp M, et al. Gut microbiota’s effect on mental health: the gut-brain axis. Clin Pract 2017;7(4):987.and lack of sleep.24Parkar SG, et al. Potential role for the gut microbiota in modulating host circadian rhythms and metabolic health. Microorganisms 2019;7(2):41.
To find out more, please download our factsheet about how the gut microbiome affects health, including links to key review papers.
Unlike with other organs of the body, communication between the gut and the brain appears to be a two-way affair. This two-way communication is believed to occur via various routes.25Liang S, et al. Gut-brain psychology: rethinking psychology from the microbiota-gut-brain axis. Front Integr Neurosci 2018;12:33.
Vagus nerve and spinal cord
HPA axis
Production of cytokines
Short-chain fatty acids interact with enteroendocrine cells to produce neuropeptides
There are various lifestyle factors that can influence the health of the gut microbiome. These include:
In terms of diet, variety and diversity are key. The focus should be on plant-based nutrition, and should include polyunsaturated and monounsaturated fats, and proteins from foods such as fish, poultry, beans and nuts. Artificial sweeteners and alcohol should be consumed in moderation. Experimenting with fermented foods is recommended, for example cultured milk products and yogurt.26Singh RK, et al. [Influence of diet on the gut microbiome and implications for human health. J Transl Med 2017;15:73. Food supplements containing live bacteria are also a popular way of supporting the microbiome. For more information on what to recommend to your patients, download our nutrition and the microbiome article – written by registered dietitian Laura Tilt.
Lack of exercise may have an important influence on shifts in microbial populations. A study showed that professional athletes had an increase in the diversity of their gut microbial populations in response to exercise and diet.6Conlon MA and Bird AR. The impact of diet and lifestyle on gut microbiota and human health. Nutrients 2015;7(1):17-44.
Stress has an impact on colonic motor activity via the gut-brain axis, which can alter gut microbiota profiles.6Conlon MA and Bird AR. The impact of diet and lifestyle on gut microbiota and human health. Nutrients 2015;7(1):17-44. Activities such as yoga and meditation have been demonstrated to reduce the effects of stress on the body.27Pascoe MC, et al. Yoga, mindfulness-based stress reduction and stress-related physiological measures: a meta-analysis. Psychoneuoroendocrinology 2017;86:152-168.,28Cahn BR, et al. Yoga, meditation and mind-body health: Increased BDNF, cortisol awakening response, and altered inflammatory marker expression after a 3-month yoga and meditation retreat. Front Hum Neurosci 2017;11:315. People who wish to help promote a healthy balance of their gut microbiome may find using techniques such as yoga and meditation to reduce their stress levels beneficial.
A study has shown that short-term sleep loss induces subtle effects on the human microbiota.10Mueller NT, et al. The infant microbiome development: mom matters. Trends Mol Med 2015;21(2):109-117. This points to the role of sleep in gut health. Good quality sleep is an integral part of a healthy lifestyle. And a healthy diet, regular exercise and techniques to reduce stress all contribute to enjoying a better quality of sleep.
Smoking has a significant negative influence on gut microbiota composition.6 Conlon MA and Bird AR. The impact of diet and lifestyle on gut microbiota and human health. Nutrients 2015;7(1):17-44. Therefore, alongside all the other known health reasons to quit, the best advice is to aim to give up smoking as soon as possible to help promote a healthy gut microbiome. People should consult their doctor if they need assistance in quitting.
Alongside recommending a healthy diet and lifestyle, food supplements can be used to help promote a healthy balance of bacteria in the gut.
| Has it demonstrated a benefit in clinical trials and in the population of interest? |
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| Does it provide an effective dose, as shown by research studies that have used the product? |
| Is it adequately labelled with: |
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Has it demonstrated a benefit in clinical trials and in the population of interest?
Does it provide an effective dose, as shown by research studies that have used the product?
Is it adequately labelled with:
| Is the strain level fully characterised? |
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| Has its viability and functionality through the gut been established? |
| Does it contain any ingredients that may be unsuitable for certain people, such as: |
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Is the strain level fully characterised?
Has its viability and functionality through the gut been established?
Does it contain any ingredients that may be unsuitable for certain people, such as:
Symprove Ltd
Sandy Farm Business Centre
Sands Road
The Sands
Farnham
GU10 1PX
Symprove Ltd
Sandy Farm Business Centre
Sands Road
The Sands
Farnham
GU10 1PX
Symprove Ltd
Sandy Farm Business Centre
Sands Road
The Sands
Farnham
GU10 1PX