Can probiotics improve your health in later life?
Probiotics may offer specific benefits for older adults, such as a better immune response and less constipation, but which strain, dose and person this applies to is not yet precisely known. Discuss it with your doctor if you have chronic complaints that fit the profile.
As you age, the composition of your gut bacteria changes: diversity declines, and bacteria that produce harmful breakdown products gain the upper hand over bacteria that convert fibre into beneficial substances. This pattern is linked to a smouldering, chronic low-grade inflammation in the body, which in turn contributes to conditions such as muscle loss, cancer and brain problems. Multiple reviews confirm this connection, although it is not yet fully clear what is cause and what is effect.
Probiotics appear to improve the immune response in older adults. Reviews report, among other things, a strengthening effect on the response to influenza vaccination. Yet translating this into practice is difficult: which bacterial strains work best for whom, and for how long they need to be taken, has not been well established. For constipation, a common problem in older age, the evidence is somewhat more concrete: both probiotics and prebiotics appear to improve bowel movement, presumably through hormones and short-chain fatty acids.
A systematic review of eight randomised studies found that probiotics, prebiotics or a combination of the two raised blood calcium levels by an average of 0.52 mg/dl. No effect on bone density itself was observed, and other bone markers did not change either. Whether that higher calcium level means anything for fractures in the long term remains unknown.
One small double-blind study in 63 healthy people aged 65 and older showed that twelve weeks of probiotics improved mental flexibility and reduced stress compared with placebo. A protein involved in learning and memory formation also rose significantly in the probiotic group. These are preliminary findings from a single study that need to be confirmed in larger groups.
There is no human evidence whatsoever for direct effects on lifespan. The reasoning that probiotics could extend life by reducing inflammation is purely theoretical. And when it comes to muscle mass: animal research is promising, but in humans there is still barely any indication that probiotics slow muscle loss in later life.
Based on multiple reviews, one systematic review (8 RCTs, 564 participants) and one multicentre RCT (n=63). No large RCTs are available for most outcomes. Direct causality remains uncertain for many effects.