RESUMO
OBJECTIVES: To assess whether an experimental nutritional formula (EXP) supports immune function in seniors living in long-term care facilities. DESIGN: Prospective, randomized, double-blind, controlled trial conducted September 2002 through January 2003. SETTING: North central Florida nursing homes. PARTICIPANTS: Subjects aged 65 and older (n = 157). INTERVENTION: Subjects received 240 mL/d of EXP or standard liquid nutrition (CON) for 4 weeks before and 6 weeks after an influenza vaccination. MEASUREMENTS: Influenza vaccine antibody responses, immunophenotyping, lymphocyte activation, cytokines, and clinical measures (fever, number of prescribed antibiotics). RESULTS: Ninety-two subjects (n = 40, CON; n = 52, EXP) completed the study. Geometric mean antibody titers were similar between groups, yet the percentage of subjects with H1N1 antibody titers greater than 100 postvaccination was higher in the EXP group than in the CON group (43% vs 23%, P=.047). Similar trends were found for the percentage of subjects (intent to treat) with fourfold increases against the B/Hong Kong component (64% vs 46%, P = .09) or with H3N2 antibody titers of 40 or more (97% vs 89%, P=.06). EXP subjects had higher levels of influenza-activated lymphocytes (CD69+ and CD25+). Cytokine production after mitogen activation was lower in EXP than CON subjects (interleukin (IL)-6: 20+/-3 vs 29+/-3 ng/mL, P = .045; IL-10: 310+/-60 vs 603+/-140 pg/mL, P = .06). Fewer EXP subjects were treated for fever (5% vs 16%, P = .02) or prescribed antibiotics (7 vs 11 new antibiotics/100 days of study, P = .06). CONCLUSION: Seniors consuming the EXP formula demonstrated enhanced immune function, indicated by increased influenza vaccine response and lymphocyte activation, less fever, and fewer newly prescribed antibiotics than those consuming a standard ready-to-drink nutritional supplement.