TUESDAY, February 15 (Health.com) — As everyone knows, there's no cure for the common cold. So most people simply suffer through two or more colds a year, often missing days of work or school in the process.
Nearly 30 years of research on zinc and colds has had mixed results and has been marred by iffy studies. To get a sound big-picture assessment of zinc's benefits, researchers in India sifted through the evidence and analyzed 15 randomized controlled trials—the "gold standard" in medical research—that compared zinc with placebo for the prevention or treatment of the common cold.
When they compiled the evidence, the researchers found that healthy adults and children who took zinc syrup, lozenges, or tablets within 24 hours of their first cough or sniffle experienced shorter and less severe colds than the participants who took a zinc-free placebo. Taking zinc reduced the odds that a person would still be experiencing symptoms at the seven-day mark by more than half.
Zinc—a mineral that occurs naturally in nuts, seeds, meats, fruits, and vegetables—also appeared to help prevent colds. Study participants who took zinc syrup or lozenges daily for at least five months cut their chances of developing a cold by about one-third, on average. As a result, the children in those studies who took zinc missed fewer days of school and took fewer antibiotics than their peers.
"These findings don't surprise me. We're learning that zinc can be quite helpful," says David Rakel, MD, director of integrative medicine at the University of Wisconsin in Madison, who was not involved in the review. "We know it is an important mineral for immune function and that it can inhibit the replication of some viruses."
Zinc supplements do carry some potential risks. Some of the study participants experienced nausea and a bad taste in their mouths while taking zinc, for instance. And zinc supplements can interfere with the body's uptake of other key minerals such as copper and calcium, Dr. Rakel says.
The authors of the review, which was published in the Cochrane Library, stopped short of recommending over-the-counter zinc supplements. Because the studies included in the review were so varied, they wrote, it wasn't possible to identify an ideal dose, a formulation, or a schedule for taking zinc.
Still, Dr. Rakel says, "zinc looks pretty promising. We need to take precautions, particularly with long-term use, but I'd still recommend it to my patients at the first sign of cold symptoms."