Zinc and the Common Cold

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Some research shows it can shorten your misery. But don't toss the tissues just yet

The first time I heard about using zinc to ward off colds was in a Manhattan taxi, riding uptown with an inebriated bond trader at two in the morning. He explained to me that cold viruses couldn't grow in the presence of zinc, whether in a laboratory, a throat, or a nose. All you had to do was suck on a zinc lozenge as soon as you felt the first scratch of a cold, and you'd banish the virus. I ignored him on principle.

The second time was a year later, while I was talking with a widely respected Harvard biochemist. In passing he mentioned that he would suck on zinc lozenges whenever he noticed a cold stirring. This time I paid attention.

So it was that I started religiously popping zinc the moment I sensed a cold in the wings. And it seemed to work. For two years I was virtually cold-free, although I went through zinc lozenges like they were M&M's.

In the summer of 1996 science lent support to my habit. Researchers at the Cleveland Clinic published a study showing that when subjects began taking zinc within 24 hours of the appearance of symptoms, they reduced the severity and duration of their colds by nearly half.

The study made zinc one of the hottest alternative remedies of the year. TV news shows reported that the humble element had beaten the heretofore invincible cold. Hundreds of thousands, if not millions, of people started putting zinc tablets on their tongues every time they felt a flutter in their throats.

But as a new cold season arrives and drugstores struggle to keep zinc lozenges on their shelves, here are the sorry facts: The scientific jury is still out, and a look at the zinc studies of the past decade indicates that the supposed cure may not do a thing.

The first suggestion that zinc might undermine a cold appeared in a 1984 scientific journal article coauthored by George Eby, a self-taught scientist whose daughter had been treated for leukemia. While ill she was continually afflicted with colds. Eby noticed that when she sucked on zinc lozenges, one of the supplements she was prescribed, the colds seemed to abate.

Eby recruited researchers at the University of Texas at Austin to test the idea that zinc dispatched his daughter's colds. His study involved 65 people in the first stages of a cold; 37 were given zinc lozenges, 28 a placebo. The zinc-treated colds averaged four days, while subjects on the placebo sniffled on for 11.

The Eby results spurred a number of pharmaceutical companies to look into the possibilities of zinc as a cold-virus killer. By the end of the decade one more study had reported that zinc worked, but four others had reached the opposite conclusion. Scientists, not to mention drug companies, lost interest.

All was pretty quiet on the zinc front until the Cleveland Clinic results came out in 1996. That study was initiated by a chemist named John Godfrey, who believed he knew why zinc had so far failed to fulfill its promise. Because sucking on zinc is about as pleasant and tasty as sucking on a nickel, many of the studies had combined zinc with other compounds to make it more palatable. Godfrey speculated that these substances interfered with the metal's ability to fight a cold virus. "My contribution was to make the taste of zinc more acceptable and still release free zinc ions in the mouth," he says.

Godfrey and his wife patented a formulation (one now sold as Cold-Eeze) and, after testing it out on students at Dartmouth College, approached Mike Macknin, head of pediatrics at the Cleveland Clinic. Macknin was skeptical of zinc, making him an ideal researcher.

Macknin and his colleagues gave either zinc or a placebo to 83 clinic employees within 24 hours of the first signs of a cold; the volunteers were told to dissolve a lozenge in their mouths every two waking hours until their symptoms resolved. The results: Colds lasted about seven days for those on the placebo and about four for the zinc users. This seemed to be proof of zinc's cold-beating powers.

But is the common cold really on the brink of extinction? Not according to many veteran cold researchers, among them Jack Gwaltney, chief of epidemiology and virology at the University of Virginia's medical school. Gwaltney has been studying colds and other respiratory infections for 30 years, and he's far from convinced that zinc is an effective cold treatment.

Gwaltney believes that the Cleveland Clinic study and Eby's study both suffer from a fundamental flaw: failure to take into account the importance of placebos. Studies have shown that the nastier a remedy is, the more apt people are to believe in its potency. Zinc isn't merely distasteful; sucking on it can actually be sickening. "Zinc is one of the most unpleasant-tasting compounds I've encountered in three decades," says Gwaltney. "The Cleveland Clinic's placebo was relatively tasteless. A credible study would use a placebo that has the same taste, aftertaste, and side effects as zinc."

The problem was compounded, says Gwaltney, by Macknin and his colleagues' allowing the participants to quit the treatment once they felt their colds had cleared. "If something nauseates you, and you have to take it every two hours, you're highly motivated to tell the researchers you feel better just so you can stop using it," he says. Having subjects take the substance for a predetermined period would have been preferable.

Macknin concedes that Gwaltney's point about placebos is well taken. The Godfreys' flavor-improvement efforts notwithstanding, 80 percent of the zinc group complained about bad taste compared to 30 percent of the placebo group, and 20 percent of the zinc takers reported nausea compared to 4 percent of those who took the placebo. "I by no means consider my study definitive and flawless," says Macknin. "I think our placebo was adequate. A significant number of our subjects couldn't correctly determine what they were on. But as Gwaltney says, a better placebo would be indistinguishable from the real thing."

Still, Macknin points out, his subjects got better faster on zinc, whatever they thought they were taking. And as for the criticism that participants were allowed to stop taking lozenges as soon as they felt they were better, he notes that the study nurse examined each subject within one day of the reported recovery and observed no cold symptoms.

The study's findings are cast into doubt by one test that did address the placebo problem head-on: Gwaltney's own. Shortly after Eby published his results in 1984, Gwaltney designed a study in which both placebo and zinc were equally distasteful and nauseating. "We ended up with the stuff they use to keep children from sucking their fingers," he says.

With a placebo as unsavory as the alleged remedy, Gwaltney found no salubrious effect from the zinc: No matter what his volunteers took, their colds lasted a week, as colds usually do. Blood tests showed that the zinc subjects were downing their medicine, but by all measures--from the amount of cold virus in the nose to the weight of nasal mucus--there was no difference between the two groups. "Zinc is actually an extremely weak antiviral," says Gwaltney.

Macknin, who describes himself as "no zinc zealot," has another study in the works and plans on doing a third. "A lot of drug manufacturers are going to get into zinc this cold season because they see a market," he says. "I just wish it were better proven before everybody jumps on the bandwagon."

Is there any harm in sucking along with the crowd? For most of us, probably not. But some researchers urge caution for people with hemochromatosis, a disorder in which the body absorbs abnormally large quantities of iron and other metals, including zinc. "We know of no metal that isn't toxic when it accumulates, and it's hard to imagine zinc being any different," says James Barton, a physician and researcher at the Southern Iron Disorders Center in Birmingham, Alabama. Barton, who specializes in the disease, suggests that the I million Americans with hemochromatosis and their family members (who may also be at risk) find other cold remedies.

As for me, I've given up zinc. Even before I looked into the studies, I had decided the lozenges were of dubious benefit. I found myself obsessively monitoring my throat and nose, reaching for zinc whenever I felt the slightest hint of a cold. Hypersensitized, I sucked on zinc daily, if not hourly, through the winter. My colds seemed fewer and milder, but was it the zinc, coincidence, or my imagination? Regardless, I seemed to feel slightly nauseated from November through April. Finally I decided I'd rather just sneeze, sniffle, be miserable, and be done with it.

Cold Treatments That Work
No one has figured out how to kill a cold virus, but you can make its presence more bearable. A number of remedies have loyal adherents.

Vitamin C Some studies report that vitamin C can shorten the duration of a cold, but most research indicates that it merely lightens symptoms. If you choose this route, don't go too far: The body can absorb about 200 milligrams a day at most, and doses above 1,000 mg may lead to kidney stones. Steer clear of chewables, which can eat away tooth enamel.

Echinacea This herb has been shown to increase the activity of white blood cells, bolstering the body's attack on the cold virus. The liquid extract may work better than capsules; add a dropperful to your water, tea, or juice three times a day as soon as you sense a cold lurking.

Chicken soup Chicken contains an amino acid called cystine that's chemically similar to a drug prescribed for bronchitis and respiratory infections. Adding plenty of garlic and hot peppers to the soup will boost the decongestant effect.

Over-the-counter cold products Avoid multisymptom remedies; they're overkill. For congestion, nasal sprays work faster than pills and are less likely to cause side effects. You can take a cough suppressant to hold down a dry hack, but don't try to stopper a cough that's bringing up mucus. Throat sprays or lozenges can temporarily ease a sore throat.

--Kate Lee

PHOTO (COLOR): Tablets

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By Gary Taubes and Kate Lee

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