What is the relationship between gut microbiota and longevity?

More than approximately 30 trillion living microorganisms inhabit the human body, a number equal to all the human cells in a person. These microorganisms, which may be viruses, bacteria or fungi, are called microbiota. The microbiota are most abundant in the gut, followed by the skin. 

A number of changes occur in the microbiota as chronological age advances, that is, as people age in years. However, when discussing age, chronological age alone is not enough. Biological (physiological) age plays an active role in the aging process. Yet aging alone is not sufficient to change gut health. Genetics, diet and lifestyle are among the most fundamental factors affecting gut health.

How does the microbiota change with age?

GRAPHICAL SUMMARY

• The core microbiota that accompany human life decrease with aging.
• In longevity, the age-related diversity of nondominant bacterial species increases.
• The microbiota of long-lived people harbor allochthonous bacteria.
• "Longevity adaptation" appears to involve enrichment of health-associated gut bacteria.

In a study investigating the effects of gut microbiota on longevity, published in Current Biology, age-related microbiota analyses were compared among adults, older adults, centenarians (people aged 99-104) and semi-supercentenarians (people aged 105-109) who participated in the study.

This study, involving a total of 69 participants, was conducted in Italy. The groups comprised 24 semi-supercentenarians, 15 centenarians, as well as 15 older adults and 15 young adult participants.

Daily food intake was recorded to assess participants’ eating habits, while the activities of daily living scale and mini-mental state examination were used to assess the mental health of the semi-supercentenarian and centenarian participants.

Stool samples were examined to assess participants’ gut microbiota. Examination of these samples showed that

• in every age group Bacteroidaceae, Lachnospiraceae and Ruminococcaceae family strains were present.

The total abundance in stool samples, termed “cumulative abuncance” (the combined gut density of the Bacteroidaceae, Lachnospiraceae and Ruminococcaceae families), was examined in detail. Among the groups, the value for the semi-supercentenaria group was 57.7%, for centenarians 58.7%, for older adults 71.1%, and in the adult group 77.8% was recorded.

The age distributions of different bacterial families and strains were also examined to understand which bacterial genera increased or decreased with age.  

• Coprococcus, Roseburia and Faecalibacterium strains belonging to the Lachnospiraceae and Ruminococcaceae families were observed to decline with advancing age . Coprococcus and Faecalibacterium strains are thought to be part of chronological aging, the number of years lived, independently of lifestyle and eating habits.
• Conversely, Oscillospira and Odoribacter and Butyricimonas strains from the Bacteroidales family showed an increase with age. Surprisingly, Eggerthella, Akkermansia, Anaerotruncus, Synergistaceae, Bilophila and Christensenellaceae bacteria also increased with age. This increase was observed particularly in the semi-supercentenaria group.

Figure below: Variations in gut microbiota across age groups

When the data were examined;

• Strains belonging to only 3 bacterial families were seen in the adult group;
• More bacterial families were present in the older group according to the observations.
• In the centenarian group, some of these genera disappeared, while bacterial strains belonging to the unclassified Mogibacteriaceae family appeared.
• Although the centenarian and semi-supercentenarian groups shared similarities, such as Mogibacteriaceae density, there were also major differences, such as the densities of Akkermansia and Phascolarctobacterium.

Although life expectancy varies between countries, we can say that average life expectancy worldwide is 70-80 years. The numbers of participants in the semi-supercentenarian and centenarian groups, who had very long lifespans, increase the value of this research.

Looking at the research details, diversity in the number of bacterial families in the gut is thought to contribute to longevity. For example, recent studies show that Christensenellaceae bacteria found in the semi-supercentenarian and centenarian groups may positively affect BMI (Body Mass Index) and kidney function. Bacteria in the Christensenellaceae family are thought to support longevity, and their abundance in the gut may be an inherited characteristic. The abundance of Akkermansia and Bifidobacterium in the semi-supercentenarian group is also known for inflammation-protective and immune-regulating effects.

Commentary & Summary

The abundance and diversity of beneficial bacteria in the gut have been associated with a healthy microbiota. In particular, the abundance of Akkermansia, Bifidobacterium and Christensenellaceae bacteria found in the semi-supercentenarian and centenarian groups has been linked to positive health effects. However, it is not known whether people in these groups, whose lifespans are much longer than the worldwide average, had these characteristics in their youth. It is also unknown how much their diet and lifestyle in youth contributed to the presence and abundance of these bacteria. Whether these bacteria decline with age or reappear during a long lifespan can be answered only by “long-term” studies, which clearly will not be easy. Based on the available scientific data, you can help support your microbiota through the gut- and beneficial-bacteria-supporting Mediterranean Diet. Regular exercise and lifestyle habits that support your emotional well-being will also contribute to improving gut health.