From anti-wrinkle concoctions to fad diets and detoxes, humans throughout history have gone to great lengths to ward off the most inescapable of afflictions; old age. The secret to longevity has eluded scientists since time immemorial. However, current research into the microbiome has shed new light on the ageing process; could the little microbes dwelling in our gut be the key to healthy ageing?

How Our Microbiome Changes As We Age

Microbes are predominantly acquired at birth, on our skin and in our mouths as we descend the birth canal, through the breast milk we consume and via contact with our carers’ skins during those first cuddles. It’s during the first three years of life that our microbiota is the most dynamic. Sources of bacteria now include sloppy kisses from grandma, premasticated potatoes, compost heap frolics, and playtime with the pet pig. These first three years are crucial to early development in terms of immunity, metabolism and cognition.

After the age of three, the microbiome is fairly stable and it’s difficult to discern between the gut of a toddler and that of an adult. That being said, changes in the gut microbiome of adults do occur, much of which can be attributed to the environments we live in, the medications we take and our diets.

Moving into the golden years, as a person approaches 80, microbiome diversity diminishes; an undesirable occurrence given that low diversity has been linked to negative health outcomes. Not only do bacterial species start to dwindle, but older people have more of the types of bacteria known to cause disease in humans than their younger counterparts (1).

According to research (8), centenarians have more beneficial microbes than the general elderly population. However, these successfully ageing people are not necessarily immune to dysbiosis; beneficial bacteria in centenarians start having to share space with the increased populations of disease-causing bacteria that come with age.

Gut Microbial Changes And Their Implications On Ageing

While many studies have already linked age-associated illnesses such as cardiovascular disease and type 2 diabetes with a disturbed microbiota (4), what’s really exciting is that for the first time, ageing itself, separate from disease or medication use, has been associated with changes to the microbiome (1). The big idea is that these microbial alterations could be guiding the ageing process, and if true, the secret to a longer and healthier life could be protecting your microbes.

While it’s not yet known if or how exactly changes to the microbiome might guide the ageing process, various studies have paved the way for understanding how it may occur. Research in rodents (2) showed that the ability for intestinal stem cells to regenerate is made more difficult when the bacteria in our guts are disturbed. This dysbiosis has the potential to affect metabolism as well as the health of the gut lining; the deterioration of which has already been linked to ageing as well as age-related diseases (3).

Also, chronic inflammation is one of the key drivers of ageing, and recent evidence suggests that the gut microbiome may play a significant role in age-related inflammation (4). Young germ-free mice, when administered gut microbes from older mice, develop age-related inflammation according to a study (5), indicating the possible involvement of bacteria in the ageing process.

Another experiment (6) looking into the link between microbiota and the ageing process was carried out by Dr Damien Rei, who found that when gut bacteria were transferred from older mice to young adult mice, there was reduction in learning and memory. Interestingly, the opposite was true when older mice received microbiota from younger mice, their cognitive abilities returned to their original normal. While conclusions about the microbiome’s influence on age can’t be drawn solely on this experiment due to differences in the physiology of mice and humans, the results give yet another reason to forge ahead with research into the mechanisms behind age-related microbiota changes.

Slowing down the ageing process

It’s important to note that while research into the link between the gut microbiome and ageing shows promise, currently only associations have been found. Do changes in gut bacteria occur because people age or do we age because of these changes? The jury is still out.

If it does turn out that the secret to longevity lies in our guts, protecting the bacteria that reside will be vitally important. Lifestyle choices such as eating a varied diet rich in fibre, exercising more and using antibiotics prudently have already been shown to positively impact the microbiome. One study (7) has even shown that probiotic supplements can help improve cognitive function and memory in patients with Alzheimer’s – a disease of the elderly – hinting that the microbiome may have a role in ageing and age-related disease.

Conclusion

Thanks to new and exciting research being conducted into the microbiome and its link to the ageing process, humans have yet another incentive to treat their gut microbes like the magnificent creatures they are; the hope of a long and healthy life.

Brigid xx

References

(1) Leite G, Pimentel M, Barlow GM, Chang C, Hosseini A, Wang J, Parodi G, Sedighi R, Rezaie A, Mathur R. Age and the aging process significantly alter the small bowel microbiome. Cell Rep. 2021 Sep 28;36(13):109765. doi: 10.1016/j.celrep.2021.109765. PMID: 34592155.

(2) Peck BCE, Shanahan MT, Singh AP, Sethupathy P. Gut Microbial Influences on the Mammalian Intestinal Stem Cell Niche. Stem Cells Int. 2017;2017:5604727. doi: 10.1155/2017/5604727. Epub 2017 Aug 22. PMID: 28904533; PMCID: PMC5585682.

(3) Funk MC, Zhou J, Boutros M. Ageing, metabolism and the intestine. EMBO Rep. 2020 Jul 3;21(7):e50047. doi: 10.15252/embr.202050047. Epub 2020 Jun 21. PMID: 32567155; PMCID: PMC7332987.

(4) Buford, T.W. (Dis)Trust your gut: the gut microbiome in age-related inflammation, health, and disease. Microbiome 5, ****80 (2017). https://doi.org/10.1186/s40168-017-0296-0

(5) Fransen F, van Beek AA, Borghuis T, Aidy SE, Hugenholtz F, van der Gaast-de Jongh C, Savelkoul HFJ, De Jonge MI, Boekschoten MV, Smidt H, Faas MM, de Vos P. Aged Gut Microbiota Contributes to Systemical Inflammaging after Transfer to Germ-Free Mice. Front Immunol. 2017 Nov 2;8:1385. doi: 10.3389/fimmu.2017.01385. PMID: 29163474; PMCID: PMC5674680.

(6) Damien Rei. Age-associated gut microbiota impairs hippocampus-dependent memory in a vagus-dependent manner. bioRxiv 2021.01.28.428594; doi: https://doi.org/10.1101/2021.01.28.428594

(7) Akbari, Elmira et al. “Effect of Probiotic Supplementation on Cognitive Function and Metabolic Status in Alzheimer’s Disease: A Randomized, Double-Blind and Controlled Trial.” Frontiers in aging neuroscience vol. 8 256. 10 Nov. 2016, doi:10.3389/fnagi.2016.00256

(8) Biagi E, Franceschi C, Rampelli S, Severgnini M, Ostan R, Turroni S, Consolandi C, Quercia S, Scurti M, Monti D, Capri M, Brigidi P, Candela M. Gut Microbiota and Extreme Longevity. Curr Biol. 2016 Jun 6;26(11):1480-5. doi: 10.1016/j.cub.2016.04.016. Epub 2016 May 12. PMID: 27185560.