Now, a study published in the Cochrane Review says taking zinc might slightly shorten and lessen the severity of colds.
However, it may not be worth the chance of side effects - mostly, the loss of taste and the sense of smell.
Researchers in India reviewed 13 past studies of 1,300 subjects. All of the studies were blinded, but only a few were placebo controlled, meaning users didn't know whether they were taking actual zinc lozenges, or a dummy pill.
And some volunteers may have recognized zinc's distinctive bad flavor.
In the study, users were less likely to have their colds after 7 days, and some who took zinc as a preventive measure were less likely to actually get a cold.
But cutting a cold by one day required taking a zine lozenge every 1 and a half to 2 hours.
Dr. Richard Besser, ABC's chief medical editor, says higher doses come with a much higher risk of unwanted side effects.
His bottom line, "I wouldn't recommend zinc for either the prevention or treatment of colds. If someone wanted to try it I would make sure they were aware of the potential side effects."
He says it's better to focus on prevention: wash your hands, or use an alcohol-based hand sanitizer a lot, especially in the winter, and around young children.