Does my gut microbiome change as I get older, and does it matter?
Your gut microbiome certainly changes as you get older, but whether that is harmful depends strongly on which direction that change goes. What you eat has a major influence on this, so that is a concrete area to pay attention to.
Yes, your gut microbiome changes throughout your entire life, and there is no fixed age at which this suddenly happens. Studies involving hundreds to thousands of people consistently confirm this: the changes are gradual and begin early in life.
Notably, the variety of gut bacterial species actually increases in the very oldest people. Those over 80 each develop an increasingly unique microbiome that resembles their peers' less and less. At the same time, bacterial species that are abundant in most people, such as Bacteroides, Lachnospiraceae and Ruminococcaceae, decline with age, while less common species gain more ground.
Whether these changes are harmful depends on which direction they go. In a study of more than 9,000 people, those over 80 who developed a more unique microbiome had a better chance of survival over four years than those in whom Bacteroides remained dominant. In people aged 105 and older, relatively higher levels were also found of bacteria generally associated with good health, such as Akkermansia and Bifidobacterium. Whether this is a cause or a consequence of their advanced age is not known.
Less encouraging is that a shifting gut microbiome in older age is associated with two immune problems that can occur simultaneously: a weakened immune system and chronic low-grade inflammation. This combination increases the risk of age-related diseases. Animal studies also show that an aged gut microbiome may actively contribute to kidney damage, although this has not yet been confirmed in humans.
A diverse gut microbiome containing bacteria that produce anti-inflammatory compounds is linked in multiple studies worldwide to healthier ageing. This pattern appears to be universal. An important caveat: age alone does not determine what your gut microbiome looks like. What you eat and whether you live at home or in a care facility play an equally large role. This makes age difficult to isolate as a cause in its own right.
This answer is based on several large human studies, including one with more than 9,000 participants, supplemented by smaller studies in people aged 105 and older and one animal experiment. The associations between gut microbiome composition and health outcomes have been observed, but no single study can establish cause and effect conclusively. The findings on survival are striking, but have not yet been proven to be causal.
Can your gut microbiome influence how long you live?
There are clear associations between a healthy, diverse gut microbiome and older age, but whether that microbiome promotes longevity or is itself a consequence of being healthy has not yet been proven. For now, a varied diet rich in fibre is the most concrete tool for supporting your gut microbiome.
What does the transition or menopause do to your gut microbiome?
Menopause is accompanied by measurable shifts in the gut microbiome, but how large these are and what they mean in practice has not yet been well established. There is currently nothing concrete you can do with this information, as proven interventions via the gut microbiome are lacking.
Can certain fungi or bacteria in your gut influence your cellular ageing?
Certain gut bacteria produce substances that accelerate cellular ageing, while a diverse microbiome rich in fibre-fermenting bacteria is actually protective. You can already take this into account through a high-fibre diet, but direct interventions in humans have barely been studied.
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 inflammation in your body?
Your gut microbiome can influence inflammatory processes throughout your body via the gut wall. Eating more fibre and exercising regularly are the most well-supported ways to influence this favourably.
What are the signs that your gut flora is out of balance?
There are several recognisable signals, of which abdominal complaints such as persistent pain, diarrhoea, or constipation are the best supported. If you experience prolonged bowel complaints after a course of antibiotics or an infection, discuss this with your GP.