Correcting zinc deficiency in nursing home residents: a randomized trial comparing 30 and 60 mg/day elemental zinc supplementation

INTRODUCTION: Low serum zinc is associated with higher pneumonia incidence and illness duration compared to individuals with adequate serum zinc levels. However, the optimal and safe zinc supplementation dose to correct deficiency has not been established. This study aimed to determine the optimal and safe dose of elemental zinc supplementation to correct deficiency in older adults residing in nursing homes. METHODS: Methods: We conducted a 12-month randomized, placebo-controlled, double-blind clinical trial in zinc-deficient nursing home residents, comparing supplementation of 30 and 60 mg/day elemental zinc versus placebo on zinc status and potential adverse effects (n = 26-35/group). RESULTS: Both the 30 and 60 mg/day groups significantly increased serum zinc levels compared to placebo (p < 0.001). All participants in the 60 mg/day group reached the target threshold (> 70 μg/dL), with 100% achieving zinc adequacy by month 8. In contrast, only 46.4% (13 of 28) of participants in the 30 mg/day group reached this threshold, with the proportion plateauing at month 8. No participant in the placebo group reached zinc adequacy. No impact on copper status was detected. Although not powered for clinical outcomes, exploratory analyses showed participants in the placebo group reported significantly more coughing episodes, fevers, and chills throughout the study compared to those in 30 and 60 mg/d supplemented groups. DISCUSSION: In zinc deficient older adults, 60 mg/day of elemental zinc effectively corrected deficiency with no adverse effects. These findings inform the dosing protocol for a fully powered randomized trial testing the effect of zinc supplementation on pneumonia incidence and outcomes in this population. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/, identifier NCT05527899.