Objective: Physical age, energy restriction (ER), and weight loss have been reported to suppress indices of innate immunity, which may increase the risk of illness. To evaluate these interactions, we recruited older, postmenopausal women (50 to 80 years) to fill one of the following 9-week ER (1250 kcal/d) groups: beef [n = 14; reported intakes 46% carbohydrate (CHO):24% protein (PRO):30% fat], chicken (n = 15; 51% CHO:25% PRO:24% fat), or CHO (n = 14; 59% CHO:17% PRO:24% fat), or a non-intervention control (n = 11).
Research methods and procedures: Fasting blood was collected before and after ER to determine leukocyte phenotype, neutrophil oxidative burst capacity, natural killer cell activity, stimulated interleukin-2 and interferon-gamma production, and blood zinc and iron concentrations.
Results: No significant effects of ER (8.6% weight loss) or PRO quantity and source were found for the majority of indices of innate immunity. Small but significant (p < 0.05) declines in interleukin-2 production were found in the chicken and CHO groups only; however, the clinical significance of this finding is not known.
Discussion: In the present study, 9 weeks of moderate ER did not suppress immunity in postmenopausal women. Also, contrary to our hypothesis, differential zinc and iron intakes did not significantly alter immunity.