Nursing home residents low in zinc took 30 or 60 mg a day for a year. Only the higher dose fixed it for everyone

Zinc helps the immune system work, and older people living in nursing homes often have too little of it. A Boston research group at Tufts University has spent years linking low blood zinc in nursing home residents to more pneumonia and longer illness. Before they can test whether topping up zinc actually prevents pneumonia, they needed to answer a simpler question: how much zinc does it take to bring a deficient older person back to a normal level, safely? Their answer was published in Frontiers in Nutrition on 30 September 2026.

The team screened 275 long-stay residents aged 65 and over in nursing homes around Boston between 2022 and 2024. About 38% had serum zinc below 70 micrograms per decilitre, the cut-off the study used for deficiency. The 105 deficient residents (average age about 78; 43% women; around 85% Black) were randomly given one capsule a day for 12 months, without them or the researchers knowing which: a control capsule with half the daily allowance of all essential vitamins and minerals, including 5 mg of zinc, or the same capsule with 30 mg or 60 mg of zinc as zinc gluconate. Nurses handed the capsules out with residents' morning medicines.

Blood zinc barely moved in the control group (57.2 at the start, 54.2 at 12 months). On 30 mg it rose from 55.4 to 72.4, and on 60 mg from 56.3 to 83.1. The study's main measure was how many residents reached at least 70. By month 8 all 30 residents still taking 60 mg had, against 13 of 28 (46%) on 30 mg and none on the control capsule, and the numbers stayed the same at 12 months. Zinc can block the uptake of copper, so every capsule included 0.8 mg of copper; blood copper stayed normal in all groups and its changes did not track the zinc changes. No moderate or severe side effects were reported. Two residents on 30 mg stopped because of the pill's size or taste.

The trial was a dose-finding pilot, not a test of whether zinc prevents illness. Residents on the control capsule reported cough, fever and chills more often than those on zinc at a number of the fortnightly check-ins, but these were self-reports, the trial was not designed to measure infections, and 21 residents dropped out early, most when COVID-19 restrictions shut nursing homes to visitors. Serum zinc is also an imperfect marker of the body's zinc stores. The 60 mg dose is above the 40 mg a day upper limit set for the general population; the authors say that limit was based on people with normal zinc levels and was never meant for treating deficiency under medical supervision. The group plans a larger trial to see whether correcting zinc deficiency cuts pneumonia in nursing homes.