The Gut Microbiota Changes with Age: What Supercentenarians Can Teach Us

The gut microbiota is often thought of as a relatively stable ecosystem throughout adult life, rather than something that changes only during infancy and adolescence. In reality, it is a highly dynamic system that continuously adapts in response to diet, lifestyle, medications, infections, and the overall health of the host.

Ageing is also one of the major factors influencing both the composition and the functions of the gut microbiota.

As we grow older, it is not only our organs and tissues that age. The way in which the gut microbiota communicates with the body also changes, progressively reshaping the complex relationship between intestinal microorganisms and their host.

 

What Happens to the Gut Microbiota During Ageing?

Ageing does not cause an abrupt change in the gut microbiota. Instead, it is a gradual process involving both the host and the intestinal ecosystem.

As we age, several factors that directly influence intestinal microorganisms also change. Gastrointestinal motility slows down, the production of saliva and gastric secretions decreases, dietary habits often become less varied, medication use tends to increase, and the immune system gradually loses efficiency. Together, these changes progressively reshape the gut microbiota over time.

From a biological perspective, numerous studies have reported a reduction in microbial diversity, a decline in certain bacteria that produce short-chain fatty acids, alterations of the intestinal barrier, and changes in the production of microbial metabolites.

At the same time, two closely related processes develop: immunosenescence, the progressive decline in immune function, and inflammaging, a state of chronic low-grade inflammation that is considered one of the major contributors to age-related diseases.

These processes are closely interconnected. The gut microbiota influences the immune system through the metabolites it produces, while the immune system, in turn, helps shape the microbial community. This continuous interaction accompanies the entire ageing process.

 

Age Alone Is Not What Matters – Healthy Ageing Does

Over the past few years, researchers have shown that changes in the gut microbiota reflect not only chronological age, but also—and perhaps more importantly—the individual's overall health status.

People of the same age can harbour remarkably different intestinal ecosystems.

Older adults who remain physically independent, consume a varied diet, and maintain an active lifestyle often preserve greater microbial diversity together with a better capacity to produce metabolites involved in maintaining intestinal barrier integrity and regulating immune function.

By contrast, frail older individuals more frequently show a loss of microbial diversity, a reduction in butyrate-producing bacteria, and an increase in opportunistic microorganisms. These changes are commonly associated with higher levels of systemic inflammation and a poorer overall health status.

For this reason, many researchers now consider the gut microbiota to be an indicator of the quality of ageing rather than simply a marker of chronological age.

 

Supercentenarians: A Model of Successful Ageing

Research on supercentenarians has profoundly changed our understanding of the gut microbiota.

Early studies focused on identifying which bacterial species were present in exceptionally long-lived individuals. Today, however, it has become increasingly clear that there is no single "longevity microbiota."

Studies carried out in Sardinian supercentenarians have shown that, during extreme ageing, some bacterial species commonly found in adulthood progressively decline, while other, normally less abundant bacterial groups become more prevalent. Rather than representing a simple sign of deterioration, this reorganisation of the intestinal ecosystem may reflect a biological adaptation that accompanies the body during the most advanced stages of life.

Each supercentenarian possesses a unique microbial community, often substantially different from that of other people of the same age. What many of these individuals appear to share is not a specific combination of bacterial species, but rather the ability of their gut microbiota to maintain efficient metabolic functions.

Several studies have reported a preserved capacity to produce metabolites involved in regulating immune function, inflammation, and energy metabolism, together with increased production of certain secondary bile acids—molecules that may contribute to protecting the host against specific pathogenic microorganisms.

These findings suggest that the gut microbiota of supercentenarians retains a remarkable ability to adapt while maintaining effective communication with the host organism.

The remarkable longevity of these individuals therefore appears to result from decades of mutual adaptation between the host and the gut microbiota, rather than from the presence of specific bacterial species alone.

 

A New Way of Looking at the Gut Microbiota

For many years, research focused primarily on identifying which bacterial species inhabit the human intestine. Today, however, it is becoming increasingly clear that the composition of the gut microbiota alone does not determine whether ageing will be associated with health or disease.

The focus is therefore shifting towards what the gut microbiota is actually capable of doing: which metabolites it produces, how it communicates with the immune system, how it contributes to the host's metabolism, and how effectively it adapts to the physiological changes that accompany ageing.

Supercentenarians seem to perfectly illustrate this new perspective. Rather than preserving the same gut microbiota they had during adulthood, they appear to maintain an intestinal ecosystem that remains adaptable, continues to produce beneficial metabolites, and sustains an effective dialogue with the host.

Healthy longevity may therefore depend not on having the "right" bacteria, but on maintaining a functionally resilient gut microbiota—one that is able to adapt throughout life while continuing to support the body's physiological functions.

This concept represents one of the most important shifts in modern microbiome research. Rather than searching for a single "ideal microbiota," scientists are increasingly investigating the functional capabilities of the microbial ecosystem and its ability to remain resilient despite the profound biological changes associated with ageing.