It remains to be seen whether the latest remedy for the common cold is really any better than chicken soup, a hot toddy by the fire and a few days off, but enthusiasts are seizing on the latest evidence that zinc lozenges may reduce cold misery this sneezing season.
In all, there have been eight studies so far on whether zinc lozenges can shorten the duration of colds, and the score stands at 4-4.
But the latest study, done by Dr. Michael L. Macknin and #F colleagues at the Cleveland Clinic and published several months ago in the Annals of Internal Medicine, is stirring high hopes, not to mention brisk sales of the little zinc candies.
In fact, the manufacturer of COLD-EEZE, the lozenges studied in Cleveland, can't keep its zinc gluconate product -- roughly $5 for a few days' supply -- on the shelves of drug and health food stores around the country.
And by Christmas two more formulations, Fast Dry and ColdFree, both based on a slightly different chemical formulation called zinc acetate, are expected to hit the stores.
For all the buzz, nobody knows quite why zinc might help. In the test tube, zinc does seem to stop some viruses from growing. And if you are deficient in zinc, taking some may boost your immune system, provided you don't take too much. That can have the opposite effect.
In the Cleveland study, 100 volunteers, who all had colds and worked at the clinic, were divided into two groups. Half took a fairly high dose (four to eight 13.3 milligram zinc gluconate lozenges a day). The others took a placebo, which was supposed to taste like the real COLD-EEZE.
Neither the volunteers nor the doctors running the study knew which patients were taking which lozenges.
The zinc lozenges "worked remarkably well," says Macknin, shortening the duration of cold symptoms nearly by half. The folks who sucked on the zinc gluconate candies suffered only 4.4 days of cold symptoms, while the others hung on to their misery for the usual 7.6 days.
And the cold symptoms many people hate most -- coughing, headache, hoarseness, nasal congestion, nasal drainage and sore throat -- went away the quickest.
The only bothersome side effects, says Macknin, were nausea and the bad taste of the candies. The flavor has since been improved -- you still wouldn't confuse it with chocolate, but it's not too bad. During the study, though, some people dropped out because of the taste and others said it ruined their ability to enjoy food.
Still, Macknin says he and his wife and son now swear by the stuff whenever they catch a cold. His 11-year-old daughter, though, says she'd "rather be sick."
Overall, the Cleveland study was "very well done," says Dr. Ananda Prasad, a professor of medicine at Wayne State University School of Medicine who has studied zinc for years.
"Do I recommend that people take it? Yes, based on that study, it's worth trying," he says. And a competing formulation based on zinc acetate "will be better."
So far, zinc acetate has not been studied in clinical trials, but the inventor of both formulations, George Eby, an entrepreneur in Austin, Texas, is convinced that acetate will prevail because it tastes better.
Eby discovered zinc's apparent benefits accidentally when his daughter, who had leukemia, started taking zinc and bounced back unusually quickly from a cold. He believes that zinc acetate may actually cure colds, not just reduce their duration.
Not everyone shares this enthusiasm. Dominick Iacuzio, who heads the influenza and related viral respiratory diseases program at the National Institute of Allergy and Infectious Diseases, cautions that using zinc to fight the common cold is controversial because the data are so 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.
Among other things, this suggests that the zinc in multivitamins, helpful as it may be in offsetting zinc deficiency, probably won't do much for colds because even getting sufficient zinc into the blood didn't combat colds.
Furthermore, Gwaltney says, cold viruses grow mostly in the nose, not the throat, and it's not clear that zinc from lozenges could get up high enough in back of the throat to do any good.
In addition, he believes the Cleveland study was flawed because the placebo may not have tasted enough like the real thing. Macknin counters that only about half of his subjects guessed right about which substance they were taking, a sign that 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 not better.
The 15 milligrams of zinc found in multivitamins 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. And at very high concentrations, he says, zinc can interfere with absorption of another mineral, copper.
Some research also suggests that large doses of zinc can lower levels of "good" cholesterol, or HDL. Given all that, 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 promotional material tells consumers to "break it to Grandma gently" that they're going off chicken soup and switching to zinc, "We say let Grandma (and Grandpa) stay at the stove a while longer."
Pub Date: 12/17/96