The common cold is more than a mere nuisance. In the United States alone, it prompts up to 100 million doctor's visits, 189 million missed school days and 276 missed work days each year, costing billions of dollars in health care expenses and work losses.
Americans spend $2.9 billion on over-the-counter drugs and another $400 million on prescription drugs to relieve flu symptoms, the authors reported, adding that a medication that is even partially effective could markedly reduce economic losses.
But some experts say evidence for zinc's cold-fighting effects is still lacking.
"I do not recommend zinc, but if asked, I describe the possible benefits and side effects," said Schaffner, adding that the best treatments for a cold are fluids, decongestants and time.
"The current state of the science makes it impossible to say whether zinc works," said Besser. "I am most skeptical of zinc as a means of preventing colds in people who are otherwise well nourished. The evidence is incredibly weak on that question."
Besser said it's also hard to draw conclusions about treating colds with zinc because of the variability in products used across the studies.
"I wouldn't recommend zinc for either the prevention or treatment of colds," Besser said.
For preventing a cold, Besser suggests frequent hand washing or using an alcohol-based hand sanitizer -- especially during cold and flu season and around young children.
For treating a cold, most over-the-counter drugs are ineffective, Besser said. But there are products that can relieve cold symptoms.
"Acetaminophen and ibuprofen are effective pain and fever medications," Besser said. "Some people benefit from a nasal decongestant. And for the uncomfortable nose there are tissues, salt water nose drops and petroleum jelly."
Besser warned against using antibiotics to treat colds, citing the Centers for Disease Control and Prevention motto: "Snort, sniffle, sneeze, no antibiotics please!"
"Colds are caused by viruses and antibiotics treat bacterial infections," Besser said.