Effects of Prebiotics on the Immune Response to Vaccination in the Elderly*

ABSTRACT. Background: Prebiotics stimulate the growth of bifidogenic bacteria in the gut. The aim of this work was to assess the effects of a prebiotic mixture on the immune response in healthy elderly people. Methods: Healthy free-living elderly people (age, 70 years), receiving a nutritional supplement that provided 1.6 MJ, 15 g of protein, and 50 % of vitamin daily reference values per day, were randomly assigned to receive a prebiotic mixture (6 g/d of a 70% raftilose and 30 % raftiline mixture) or placebo (6 g of malto-dextrin powder) for 28 weeks. At week 2 of the study, all subjects were vaccinated with influenza and pneumococcal vaccines. At weeks 0, 2, and 8 of the study, serum total proteins, albumin, immunoglobulins, saliva secretory immu-noglobulin A (IgA), and serum titers of influenza A and B and pneumococcal antibodies were measured. At week 8, culture