Probiotic supplementation may help support the immune systems of elderly adults, while animal studies hint at more intriguing potential benefits in aging. Where is the research headed next? Find out here.
Probiotics & Healthy Aging: Insufficient Evidence
When we age, the composition of our gut flora shifts, and our immune response declines. Are these connected? Some researchers think they might be. This post will explore the relationship between probiotics and immune function in elderly people.
Because immune function is less robust in older adults than in young people, it’s especially important to consult your doctor before taking probiotics to stave off the effects of aging.
Note that probiotics’ benefits to aging are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of probiotics for this purpose. Remember to speak with a doctor before taking probiotic supplements, and never use it in place of something your doctor recommends or prescribes.
Human Studies
Levels of Bifidobacteria decrease as we age [1].
B. animalis spp. lactis beneficially modified gut microbiota in the elderly, increasing Bifidobacteria, Lactobacilli, and Enterococci and reducing Enterobacteria [2].
B. animalis spp. lactis enhanced natural immunity in healthy elderly subjects [3]. B. animalis spp. lactis increased leukocyte phagocytic and NK cell tumor-cell-killing activity in the elderly and increases the proportions of total, helper (CD4(+)), and activated (CD25(+)) T lymphocytes and natural killer cells [4, 5, 6].
B. longum stimulated the immune functions in the elderly [7].
B. bifidum and L. acidophilus positively modulated the immunological and inflammatory responses in elderly subjects [8].
Some researchers believe that L. delbrueckii ssp. bulgaricus may favor the maintenance of an adequate immune response in the elderly, possibly by slowing the aging of the T-cell subpopulations and increasing the number of immature T cells which are potential responders to new antigens [9].
L. acidophilus increased Bifidobacteria levels and beneficially changed microbiota in elderly subjects [10].
Heat-killed L. gasseri enhanced immunity in the elderly. This probiotic increased the number of CD8(+) T cells and reduced CD28 expression loss in CD8(+) T cells [11].
Animal Studies
Feeding of probiotic bacteria (L. reuteri) to aged mice induced integumentary changes mimicking peak health and reproductive fitness characteristic of much younger animals [12].
A probiotic fermented milk drink called Dahi with L. lactis, L. acidophilus and B. bifidum reversed age-related decline in expression of biomarkers of aging, PPAR-α, SMP-30, and Klotho in hepatic and kidney tissues in mice [13].
L. lactis along with L. acidophilus or combined with L. acidophilus and B. bifidum reversed age-related decline in immune functions and improve lymphocyte functions in aging mice [14].
Heat-killed L. gasseri increased natural killer cell (NK cell) activities and enhanced cell-mediated immunity in aged host animals, thereby altering age-related immunosenescence [15].
Dahi containing L. acidophilus was effective in reversing age-related immune function decline in mice [16], where this probiotic also combated oxidative stress and molecular alterations associated with aging [17].
L. fermentum alleviated immunosenescence, possibly by enhancing antioxidant enzyme activities and was shown to reduce E. coli infection in aging mice [18].
L. johnsonii helped recover nutritional status and systemic immune responses in aged mice [19].
Long-term oral intake of L. lactis suppressed the reduction of bone density and body weight in senescence-accelerated mice [20].
B. bifidum delayed immunosenescence in mice by enhancing the anti-oxidation activity in thymus and spleen and by improving immune function [21].
Intake of heat-killed L. lactis altered the intestinal flora, affected plasma metabolite levels, including fatty acid levels, and slowed down age-related hearing loss in mice. Researchers have suggested that this probiotic may have inhibited the loss of neurons and hair cells in mouse inner ear [22].
In mice, L. reuteri increased thyroid size and activity (increasing T4 levels), lessening fatigue and weight gain associated with aging and resulting in a more youthful physical appearance [23].
Antioxidant Action
L. casei, L. helveticus, L. fermentum, B. bifidum and B. subtilis exhibit antioxidant properties [24, 25, 26, 27, 28, 29].
Similarly, B. animalis and L. lactis effectively scavenge free radicals and significantly enhance the activity of antioxidative enzymes in mice [30, 31].
A B. subtilis signal molecule induces the heat shock protein Hsp27 in mammalian cells; this protein protects intestinal cells against oxidant-mediated tissue damage [32].
Takeaway
Probiotic supplementation stimulated immune function in multiple clinical trials of elderly people. In mice and rats, meanwhile, probiotics have shown the potential to restore energy levels, hearing, and reproductive function to the levels of much younger animals.
Some of these benefits could potentially be attributed to the antioxidant activity of probiotic bacteria.
Further Reading
We’ve compiled deep dives into each potential benefit of probiotics. Check them out here:
