A 'resilient' Gut Microbiota may be a critical factor in healthy ageing

Our gastrointestinal tract (GIT) is home to trillions of microorganisms that constitute the human gut microbiota (GM). These microorganisms and especially the bacteria, help us extract energy and nutrients from our diet. They contribute key metabolites to our organisms such as the short-chain fatty acids (SCFA) acetate, propionate and butyrate. The GM is also vital for a robust immune system and helps us fight off gut infections.[1]

Research has revealed the importance of the GM in human health. It has also shown how changes in the population of the GM microorganisms may lead to disease. This phenomenon is called 'dysbiosis'. Our life choices such as dietary habits, smoking, exercise, antibiotic overuse may affect the GM composition and lead to dysbiosis. Conditions that may be associated with dysbiosis range from heart diseases, GIT disorders, cognitive issues, and even cancer. The 'healthy' GM is stable throughout adulthood, but with ageing, there is a decline in this stability. A series of factors may impact the composition and diversity of the GM explained below.[2]

How age affects our microbiota

During ageing, the functionality of our body declines- organs and cells throughout the body and in the GIT age. The immune system is not so efficient in responding to challenges. Notably, there is low-grade systemic inflammation observed in older people called 'inflammageing', which is associated with age-related conditions.

Older populations show altered patterns of food consumption and altered motility in their GIT. Usually, the ability to chew and to swallow deteriorate with age. We still lack conclusive data from human studies that demonstrate what if any hormonal and enzyme alterations in older age lead to these changes.[3]

Other factors that impact the GM composition are changes in the socioeconomic status of older people that lead to lifestyle changes (e.g. less physical activity) and poor diet (e.g. less variety in food). Also, increased poly-medication, recurrent antibiotic use and increased incidents of admission to long-term care units are a challenge for the 'healthy' GM.

Older populations show a higher prevalence of diabetes, cardiological issues, cognitive decline, 'sarcopenia' and 'frailty. Such conditions are often associated with GM alterations. Sarcopenia refers to significant muscle loss and weakness. Sarcopenia leads to a general state of diminished functionality and increased dependability. The two syndromes are gaining medical interest because of their potential severe outcomes in the elderly.[4]

The 'aged' GM is often characterised by a low diversity of species and the loss or low proportions of certain beneficial microorganisms that are more abundant in younger adults. In a simple scheme, there are beneficial GM bacteria that thrive with a healthy diet and are responsible for breaking down complex sugars and carbohydrates from food. This activity results in the production of SCFA, such as butyrate. According to the latest Science, it may be involved in anti-inflammatory responses. This decline in beneficial bacteria gives a chance to potentially harmful species to increase. An alarming example of this is the increased incidents of the life-threatening infection with Clostridium difficile among hospitalised older people.[5]

As we age our microbiota's diversity is reduced, further accelerating the progressive decline associated with age. Maintaining your microbiota diversity can help you curb biological ageing.

Dietary habits for a diverse aging microbiota

But it is not all gloomy for the ageing population. Based on science, we can improve the dysbiosis that comes with ageing and therefore manage healthier ageing. Diet plays a crucial role in the maintenance of a 'resilient' and 'healthy' GM throughout our lives and during ageing. A plant-based diet with a plethora of vegetables and fruits can maintain and improve diversity in the GM by nourishing the beneficial microorganisms in our gut. Potentially the following can play a role in ageing management:

  • Prebiotics: those are dietary fibres found in fruits and vegetables that when consumed nourish certain GM microorganisms.

  • Probiotics: those are beneficial microorganisms found naturally in fermented foodstuffs such as yoghurt or as dietary supplements.

  • Postbiotics: those are products derived from beneficial microorganisms that may confer the benefits of a probiotic without the use of the actual live microorganisms. For safety and regulatory reasons, but also due to potentially easier formulation, the use of postbiotics may be a good alternative to probiotics.[12]

[1] Donaldson, G.P.; Lee, S.M.; Mazmanian, S.K. Gut biogeography of the bacterial microbiota. Nat. Rev. Microbiol. 2015, 14, 20–32.

[2] Levy, M.; Kolodziejczyk, A.A.; Thaiss, C.A.; Elinav, E. Dysbiosis and the immune system. Nat. Rev. Immunol. 2017, 17, 219–232.

[3] Lloyd-Price, J.; Abu-Ali, G.; Huttenhower, C. The healthy human microbiome. Genome Med. 2016, 8, 51.

[4] An, R.; Wilms, E.; Masclee, A.A.M.; Smidt, H.; Zoetendal, E.G.; Jonkers, D. Age-dependent changes in GI physiology and microbiota: Time to reconsider? Gut 2018, 67, 2213–2222.

[5] López-Otín, C.; Blasco, M. a; Partridge, L.; Serrano, M.; Kroemer, G. The hallmarks of aging. Cell 2013, 153, 1194–217.

[6] An, R.; Wilms, E.; Masclee, A.A.M.; Smidt, H.; Zoetendal, E.G.; Jonkers, D. Age-dependent changes in GI physiology and microbiota: Time to reconsider? Gut 2018, 67, 2213–2222.

[7] Keevil, V.L.; Romero-Ortuno, R. Ageing well: a review of sarcopenia and frailty. Proc. Nutr. Soc. 2015, 44, 1–11.

[8] Levy, M.; Kolodziejczyk, A.A.; Thaiss, C.A.; Elinav, E. Dysbiosis and the immune system. Nat. Rev. Immunol. 2017, 17, 219–232.

[9] Salazar, N.; Valdés-Varela, L.; González, S.; Gueimonde, M.; de los Reyes-Gavilán, C.G. Nutrition and the gut microbiome in the elderly. Gut Microbes 2017, 8, 82–97.

[10] Rea, M.C.; O’Sullivan, O.; Shanahan, F.; O’Toole, P.W.; Stanton, C.; Ross, R.P.; Hill, C. Clostridium difficile carriage in elderly subjects and associated changes in the intestinal microbiota. J. Clin. Microbiol. 2012, 50, 867–875.

[11] Duncan, S.H.; Flint, H.J. Probiotics and prebiotics and health in ageing populations. Maturitas 2013, 75, 44–50.

[12] Aguilar-Toalá, J.E.; Garcia-Varela, R.; Garcia, H.S.; Mata-Haro, V.; González-Córdova, A.F.; Vallejo-Cordoba, B.; Hernández-Mendoza, A. Postbiotics: An evolving term within the functional foods field. Trends Food Sci. Technol. 2018, 75, 105–114.

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