Objective: to evaluate whether oral supplementation with zinc or zinc/arginine increases the antibody response to influenza vaccine or modulates the lymphocyte phenotype in elderly subjects.
Design: a randomized controlled trial with two supplemented groups and one control group.
Setting: a community nursing home.
Participants: 384 subjects aged 64-100 (mean age 82 years) examined in three separate studies.
Intervention: oral supplementation with zinc (400 mg/day) or zinc plus arginine (4 g/day) for 60 days starting 15 days before influenza vaccination. The control groups received vaccine only.
Measurements: haematological and nutritional indices, antibody titre against influenza viral antigens, lymphocyte phenotype.
Results: supplementation with zinc or zinc plus arginine increased zinc plasma concentrations restoring the age-related impairment in zinc concentrations to values found in younger people. The antibody titre against influenza viral antigens was not increased in zinc or zinc/arginine supplemented groups in comparison with subjects receiving vaccine alone. The number of CD3, CD4 or CD8 lymphocytes was not affected by zinc or zinc/arginine supplementation.
Conclusion: prolonged supplementation with zinc or zinc/arginine restores zinc plasma concentrations but is ineffective in inducing or ameliorating the antibody response after influenza vaccination in elderly subjects.