How does your microbiome influence your health and longevity?
Your gut flora changes over the years and is associated with inflammatory processes, immune function and possibly how long you stay healthy. Probiotics may offer modest help with infections and vaccine response in older age, but lifespan extension has not been proven.
As you age, the composition of your gut flora shifts. Beneficial bacterial groups decline, while less desirable species gain ground. This pattern has been found repeatedly, in older adults and even in people aged 105 and above. At the same time, research involving more than 9,000 people shows that healthy individuals over 80 actually develop an increasingly personal, more unique gut flora profile. Those who did not show this and instead retained a gut flora more resembling that of a younger person had a lower chance of survival in the subsequent four years.
A disrupted gut flora appears to contribute to 'inflamm-aging': a smouldering, chronic inflammation associated with age-related conditions such as muscle loss, frailty and neurological disorders. It appears to be a self-reinforcing cycle: the disrupted flora fuels inflammation, and that inflammation further disrupts the flora. Whether the flora is the cause, or whether the inflammation itself disrupts the flora, has not yet been established.
In people of extremely advanced age (105 to 109 years), a relatively higher presence of specific bacterial groups such as Akkermansia and Bifidobacterium was found. In animal research, transplanting gut flora from healthy animals into animals with accelerated ageing extended healthspan and lifespan. The step to humans has not yet been taken; these findings are, for now, no more than preliminary signals.
Probiotics and prebiotics can make a modest contribution in older adults to a better immune response to flu vaccines, fewer respiratory infections and a reduction in constipation. Not all studies are equally strong, but the signals are consistent enough to be worth mentioning. Whether they also extend lifespan is a separate question: that has not been demonstrated and remains speculative for now.
There are also early indications that the gut flora influences skin ageing via the so-called gut-skin axis, and that a shift towards more protein-degrading bacteria is associated with muscle loss. Solid evidence in humans is still lacking here; these are signals from observational research that need to be investigated further.
This answer draws on several reviews and a large study involving more than 9,000 older adults. Many findings come from research in which participants were followed over time without anything being assigned to them, meaning cause and effect cannot be established with certainty. The mouse studies on faecal transplantation are promising but have not yet been confirmed in humans. The researchers themselves point to the limited transferability of animal models and the absence of long-term studies in humans.
Can your microbiome reveal how old you are biologically?
The bacteria in your gut change in recognisable ways with age and are linked to how healthily you grow old. The early evidence is strikingly consistent.
Can your gut microbiome influence how long you live?
There are clear indications that the composition of your gut microbiome is associated with how long and how healthily you age, but whether modifying your microbiome extends your life has not yet been demonstrated in humans.
Does your gut microbiome affect how well you sleep?
Research shows a clear association between a diverse gut microbiome and better sleep, but whether one causes the other remains unknown.
Is fermented food good for your health and your microbiome?
Fermented food, and kefir and yoghurt in particular, likely has beneficial effects on gut flora and several health markers, but the evidence in humans is still limited and does not apply equally to every product.
Can you permanently change your gut microbiome through diet?
Diet does indeed change your gut microbiome, but lasting change requires lasting adjustment of your dietary pattern; a temporary diet has only a temporary effect.
Can your gut microbiome influence your risk of heart disease?
Your gut microbiome influences your heart health through metabolic by-products that can promote arterial hardening, high blood pressure and blood clots. The association is plausible, but how best to modify the gut microbiome to protect your heart has not yet been sufficiently proven: always discuss major interventions with your doctor.