Does my gut flora change as I age, and is that a problem?
Your gut flora changes with age, and people who age healthily actually have a richer and more varied flora than the average older person. Centenarians show this most clearly.
Yes, your gut flora changes noticeably as you get older. In healthy ageing, bacterial species such as Akkermansia increase, while Faecalibacterium and Lachnospiraceae decrease. That may sound worrying, but the picture is more nuanced: people who live to a very advanced age (centenarians) actually have a remarkably rich and diverse gut flora, with greater production of short-chain fatty acids such as butyrate. These fatty acids are beneficial for the gut lining and help keep inflammation in check. So how you age matters.
The problem lies mainly in unhealthy ageing. In older people with notable muscle loss, the bacteria that produce those short-chain fatty acids are consistently found in smaller numbers, while bacteria that drive inflammation increase. Across seven studies involving more than 3,000 people in total, this pattern was seen time and again. Whether a disrupted gut flora actually causes muscle loss, or whether muscle loss causes it, has not yet been established in people.
Researchers have looked into whether the gut flora of older people can be steered in a better direction. Animal studies show positive effects of Lactobacillus and Bifidobacterium strains on muscle loss, but studies in people give mixed results: some approaches using probiotics or prebiotics helped, others did not. There is therefore no proven approach that works for everyone.
One specific prebiotic, derived from a substance found in breast milk, increased the amount of Bifidobacterium in the gut in a smaller study of 67-year-olds involving 89 participants. This only worked in people who already had some Bifidobacterium to begin with. The intended goal of that study, namely a better immune response, was not achieved. Rises in insulin, good cholesterol and a hormone were also measured, but what those mean in the longer term is unknown. That study was partly funded by the manufacturer of the product.
The changes in your gut flora as you age are therefore not automatically bad. What matters is the pattern: a richer, more varied flora is associated with healthy ageing. For now, there are no supplements that have been shown to reliably improve that pattern in people.
This answer draws on four review studies that bring together existing research, supplemented by one study in 89 healthy 67-year-olds in which participants were assigned to a treatment. The review studies do not follow people over time but compare age groups at a single point in time, so cause and effect have not been proven. The link between gut flora and muscle loss is consistent but likewise measured only as a snapshot, not as a causal relationship. The study in older adults is small and was partly funded by the manufacturer of the prebiotic being tested, which colours the interpretation of the positive findings somewhat.
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.
What does the menopause do to your gut bacteria?
During the menopause, specific bacterial species in your gut shift and your gut bacteria process oestrogen less actively. Eating a varied diet and taking probiotics are practical ways to support your gut bacteria.
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.
Do your gut bacteria influence how fast your cells age?
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.
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.
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.