Clinical Effects of Probiotic Bifidobacterium longum BB536 on Immune Function and Intestinal Microbiota in Elderly Patients Receiving Enteral Tube Feeding

Background : Immune system function declines with age. We evaluated the effects of supplementation with the probiotic Bifidobacterium longum BB536 on immune function and intestinal microbiota in the elderly. Materials and Methods : In a double‐blind study, 45 elderly patients fed by enteral tube feeding (mean [SD] age 81.7 [8.7] years) were given BB536 (n = 23) or a placebo powder (n = 22) for 12 weeks and were observed for an additional 4 weeks posttreatment. At week 4, all patients received an influenza vaccination (A/H1N1, A/H3N2, and B). Clinical data were assessed, including body temperature, bowel movements, fecal microbiota, and immunological biomarkers in blood. Results : BB536 intake significantly increased cell numbers of bifidobacteria in fecal microbiota. There was a tendency toward an increase ( P = .085 at week 4 and P = .070 at week 16) of serum IgA in the BB536 group compared with the placebo group. BB536 intake did not significantly affect hemagglutination inhibition (HI) titers in response to the influenza vaccine. Natural killer (NK) cell activity decreased significantly in the placebo group during the intervention but not in the BB536 group. Among those subjects with low NK cell activity (<55%, n = 10 for each group), a significant intergroup difference ( P < .05) was observed in the changed values from baseline of NK cell activity at weeks 8 and 12. Conclusions : These results shed new light on the potential of long‐term ingestion of BB536 in increasing the cell number of bifidobacteria in intestinal microbiota and modulating immune function in the elderly.