Enhancement of immunity in the elderly by dietary supplementation with theprobiotic Bifidobacterium lactis HN019

Background: The aging process can lead to a decline in cellular immunity. T herefore, the elderly could benefit from safe and effective interventions t hat restore cellular immune functions. Objective: We determined whether dietary supplementation with the known imm unostimulating probiotic Bifidobacterium lactis HN019 could enhance aspects of cellular immunity in elderly subjects. Design: Thirty healthy elderly volunteers (age range: 63-84 y; median: 69 y ) participated in a 3-stage dietary supplementation trial lasting 9 wk. Dur ing stage 1 (run-in), subjects consumed low-fat milk (200 mL twice daily fo r 3 wk) as a base-diet control. During stage 2 (intervention), they consume d milk supplemented with B. lactis HN019 in a typical dose (5 X 10(10) or o rganisms/d) or a low dose (5 X 10(9) organisms/d) for 3 wk. During stage 3 (washout), they consumed low-fat milk for 3 wk. Changes in the relative pro portions of leukocyte subsets and ex vivo leukocyte phagocytic and tumor-ce ll-killing activity were determined longitudinally by assaying peripheral b lood samples. Results: Increases in the proportions of total, helper (CD4(+)), and activa ted (CD25(+)) T lymphocytes and natural killer cells were measured in the s ubjects' blood after consumption of B. lactis HN019. The ex vivo phagocytic capacity of-mononuclear and polymorphonuclear phagocytes and the tumoricid al activity of natural killer cells were also elevated after B. lactis HN01 9 consumption. The greatest changes in immunity were found in subjects who had poor pretreatment immune responses. In general, the 2 doses of B. lacti s HN019 had similar effectiveness. Conclusion: B. lactis HN019 could be an effective probiotic dietary supplem ent for enhancing some aspects of cellular immunity in the elderly.