Ranjan Sinha

April 14, 2021

The advantages of a changing gut microbiome as you age

Some people grow more versatile with age...both inside and out!

A recent study has shown that changes in the gut microbiome composition that occur with age are a major element in determining healthy aging processes. A dynamic gut microbiome appears to confer a better aging advantage than a static one. The greater the change, the stronger the advantage. In other words, the gut microbiome you had at 20 may not serve you all that well at 80!

Gut microbiomes diversify with age (and they should)

By studying individuals ranging in age from 18 to 101, it was observed that in healthy individuals, the gut microbial populations that are dominant in early adulthood tend to dwindle over the years, giving way to the rise of other, formerly less prevalent bacterial species. The precise opposite happens in less healthy individuals: the gut microbiome does not change all that much. The adult microbiome, which begins to develop around 40 years of age, continues to evolve in healthy individuals, but not in unhealthy ones. A relatively unchanged gut microbiome is seen to be associated not only with an unhealthy aging trajectory but also a significantly shorter life span.

In an effort to identify distinct signatures in the gut microbiome that are linked to either healthy or unhealthy aging journeys, scientists may have found a way of predicting longevity or long-term survival in humans. The “microbial drift,” i.e. the tendency to build a more divergent microbiome starting around mid-to-late adulthood, was spotted in healthier aged individuals but was found to be missing in less healthy older people. Moreover, the microbiome of healthier aged individuals was found to be depleted of core gut bacterial species typical to humans such as Bacteroides. Where high levels of core gut bacterial species were present in old age, they were associated with reduced survival.

The gut-protective effects of a more divergent microbiome in old age

The researchers also discovered that higher levels of health-promoting compounds of gut microbial origin, including those that are important to fight chronic diseases, were also present in the blood of those whose microbiome developed a unique signature as they aged. Notable among these are indoles, which reduce inflammation and protects against “leaky gut” by helping maintain the integrity of the protective mucus barrier that lines the gut. In addition, individuals with a more divergent microbiome had higher levels of vitamin D, lower levels of “bad” cholesterol and triglycerides. They were physically more active and needed fewer medications.

The study is in tune with previous observations that leaner, fitter older people have a gut microbial composition that is different from those in poorer shape or ill health. Diminished gut microbial diversity has also been seen in those who show early signs of frailty.

These findings have significant clinical implications towards monitoring the gut microbial composition of an individual throughout their life as a marker of health and modifying it to promote better health or alleviate disease states. As our understanding of the gut microbiome grows, particularly in the context of aging, it could lead to the development of interventions and treatments to alter it to promote better health and quality of life alongside extending the human life span.

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