Nutritional formula enhanced immune function and reduced days of symptoms of upper respiratory tract infection in seniors.

OBJECTIVES: To assess whether an experimental nutritional formula, given as a supplement, would reduce days of symptoms of upper respiratory tract infection (URTI) and affect antibody and lymphocyte proliferative responses to influenza vaccine. DESIGN: A prospective, randomized, double-blind, controlled trial was conducted between October 1999 and April 2000. SETTING: Assisted- and independent-living facilities in North Central Florida. PARTICIPANTS: Sixty-six individuals, aged 65 and older. INTERVENTION: Subjects received 8 oz/d of an experimental formula containing antioxidants, zinc, selenium, fermentable oligosaccharides, and structured triacylglycerol or an isoenergetic, isonitrogenous control formula for 183 days. MEASUREMENTS: Subjects recorded daily symptoms of URTI. Antibody titers and lymphocyte proliferation to three influenza vaccine components were measured on Days 57 and 183. RESULTS: Eighteen subjects in the control group and 16 subjects in the experimental group consumed an average of 7 ounces of formula daily and completed the 183-day study. Median days of symptoms of URTI were 3 (range 0-69, total days=156) and 0 (range 0-49, total days=78) for the control and experimental groups, respectively (P=.049). On Day 57, seven of 17 (41%) subjects in the control group and 13 of 15 (87%) subjects in the experimental group achieved a fourfold or greater increase in serum antibody titer to A/Beijing (P=.012). Lymphocyte proliferation to influenza vaccine components was greater in the experimental (median=1,365 cpm, range=0-14,955 cpm) than the control group (median=136 cpm, range=0-4,270 cpm) (P=.013). CONCLUSION: Subjects consuming an experimental nutritional formula experienced enhanced immune function and fewer days of URTI symptoms.