Immune Ageing

Two linked processes, both tied to the gut

Ageing brings two related immune changes: immunosenescence, a general decline in immune cell function that increases infection risk and weakens vaccine responses, and inflammageing, a low-grade, chronic inflammation that persists even without an active infection. Both are increasingly linked to age-related changes in gut bacteria, including reduced diversity and lower levels of beneficial, butyrate-producing species.

A large, honest trial with limited results

A randomised controlled trial gave older adults living in UK care homes, aged 67 to 97, a combination of two well-studied probiotic strains, Lacticaseibacillus rhamnosus GG and Bifidobacterium animalis subsp. lactis BB-12, or placebo for up to 12 months. The trial measured a wide range of immune markers, including blood cell counts, phagocytosis, and vaccine response, and found the probiotic combination had only a limited effect overall. This is a genuinely useful, honest result from a well-designed, long trial in exactly the population most likely to benefit, rather than a clear win.

Source: Combination of the Probiotics Lacticaseibacillus rhamnosus GG and Bifidobacterium animalis subsp. lactis, BB-12 Has Limited Effect on Biomarkers of Immunity and Inflammation in Older People

Other trials have found more specific, modest effects

Not every study has been null. Separate research found that a specific strain, Bifidobacterium lactis Bi-07, improved the phagocytic activity of certain immune cells, a more specific cellular function rather than an overall clinical outcome. A broader systematic review of probiotic trials in healthy older adults concluded that effects on immune function tend to be modest and inconsistent across studies, while effects on gut bacteria composition itself are far more reliable.

Source: The Effect of Probiotics on Health Outcomes in the Elderly: A Systematic Review of Randomized, Placebo-Controlled Studies

What this means for you

Older adults remain more vulnerable to infection and benefit most from established measures, including staying up to date with vaccinations, good nutrition, and prompt treatment of infections, none of which a probiotic replaces. Given how mixed the direct evidence is, a specific probiotic strain is a reasonable, low-risk thing to try for general gut support in older age, but it's worth being realistic that the trial evidence for a genuine immune boost specifically is modest at best. A varied, plant-rich diet remains a well-evidenced way to support the gut bacteria this research consistently shows shift with age, regardless of whether a specific probiotic changes immune markers. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.