Not everyone shares his zeal.
Dominick Iacuzio, who heads the influenza and related diseases program at the National Institute of Allergy and Infectious Diseases, cautions that zinc ``is controversial,'' in part because the data is inconsistent.
And Dr. Jack Gwaltney, a virologist and epidemiologist at the University of Virginia Health Sciences Center, is even more critical.
In studies he did of zinc and cold germs half a dozen years ago, Gwaltney measured both virus and zinc levels in volunteers' blood -- something the Cleveland team did not do -- and found that high zinc levels did not make colds go away faster.
This suggests that the zinc in multi-vitamins, helpful as it may be in offsetting zinc deficiency, probably won't do much for colds.
Furthermore, Gwaltney says, cold viruses grow mostly in the nose, not the throat, and it's not clear that zinc from lozenges can get to where it might do any good.
In addition, he believes the Cleveland study was flawed because the placebo may not taste enough like the real thing. Macknin counters that only about half of his subjects guessed right about which substance they were taking, so the taste difference could not have been huge.
Jeff Blumberg, associate director of the Tufts University nutrition research center, warns against excessive enthusiasm for zinc, because more is distinctly not better.
The 15 milligrams of zinc found in multi-vitamins is fine, he says. But older people who take zinc as pills start to have immunosuppression at 50 milligrams a day; it probably takes higher doses of zinc from lozenges to induce immunosuppression.
Some research also suggests that large doses of zinc can lower levels of ``good'' cholesterol, or HDL.
Given all that, perhaps it's not surprising that two prestigious health newsletters -- the University of California at Berkeley's Wellness Letter and Health News, put out by the Massachusetts Medical Society -- view zinc lozenges differently.
The Massachusetts group cautiously endorses the lozenges. But the Berkeley folks say that while COLD-EEZE's ads tell consumers to ``break it to Grandma gently'' that they're going off chicken soup, ``We say let Grandma [and Grandpa] stay at the stove a while longer.''
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