Dietary probiotic supplementation enhances natural killer cell activity inthe elderly: An investigation of age-related immunological changes

Many elderly subjects are at increased risk of infectious and noninfectious diseases due to an age-related decline in lymphoid cell activity (immunose nescence). Noninvasive means of enhancing cellular immunity are therefore d esirable in the elderly. Previous reports have suggested that dietary suppl ementation could represent an effective means of enhancing the activity of circulating natural killer (NK) cells in the elderly. In the present study, we have conducted a pre-post intervention trial to determine the impact of dietary supplementation with probiotic lactic acid bacteria (LAB) on perip heral blood NK cell activity in healthy elderly subjects. Twenty-seven volu nteers consumed low-fat/low-lactose milk supplemented with known immunostim ulatory LAB strains (Lactobacillus rhamnosus HN001 or Bifidobacterium lacti s HN019) for a period of 3 weeks. A dietary run-in of milk alone was shown to have no significant effect on NK cells. Irt contrast, the proportion of CD56-positive lymphocytes in peripheral circulation was higher following co nsumption of either LAB strain, and ex vivo PBMC tumoricidal activity again st K562 cells was also increased. Supplementation with HN001 or HN019 incre ased tumoricidal activity by an average of 101 and 62%, respectively; these increases were significantly correlated with age, with subjects older than 70 years experiencing significantly greater improvements than those under 70 years. These results demonstrate that dietary consumption of probiotic L AB in a milk-based diet may offer benefit to elderly consumers to combat so me of the deleterious effects of immunosenescence on cellular immunity.