Nutritional status was assessed with a 3-day food diary that participants kept at baseline and at 6 months. At randomization, participants were given detailed written and verbal instructions on how to fill out the food diary, and the study nutritionist reviewed each completed diary with the participant. Analysis was performed by using Nutritionist V, version 2.0 (First DataBank, Inc., San Bruno, California). Nutrient deficiency, for the purpose of this study, was defined as intake below the 33rd percentile of the recommended daily allowance (RDA) for zinc; selenium; iron; folic acid; or vitamins A, C, E, or B6. Selection was based on research indicating that even moderate deficiencies of these individual nutrients can impair markers of immune function (3–6, 15–17). Our choice of the 33rd percentile was somewhat arbitrary. There is no standard cut-point for micronutrient deficiency as it relates to impairment of immune function because the role of each micronutrient depends on many other factors, such as age, chronic disease, other nutrient deficiencies, and bioavailability. Because many variables are unique to each individual and sample, previous studies demonstrating an immune function benefit from supplementation have defined deficiency post hoc (11, 16).