Can zinc win the cold war?

How it works

Though they can be caused by any one of several hundred viruses, most colds are caused when the rhinovirus attacks the upper respiratory system (nasal cavity, nose, mouth and throat). When administered properly, zinc is suspected to combat the rhinovirus in at least three ways.

• Zinc may prevent the virus from reproducing itself, thus shortening the length of time you suffer from the cold.
• Zinc is believed to help prevent the rhinovirus from binding to the membranes of the upper respiratory system, thus rendering the existing virus inert and relieving the cold symptoms (running nose, cough, sore throat, etc.).
• Zinc is thought to help in the production of interferon, one of the body's natural disease/illness fighting agents.

Does it work?

Though the degree of effectiveness varies with each person, a number of researchers have shown that zinc can reduce the severity of a cold's symptoms and cut the length of a cold by almost half, especially when taken soon after symptoms begin. One study published in the Annals of Internal Medicine showed that using zinc in lozenge form (Cold-Eeze) reduced colds from an average 7.6 to 4.4 days.

In other studies, zinc lozenges were either less effective or had no effect at all on the symptoms or length of the common cold. However, this ineffectiveness is believed to be the result of the specific manner in which the zinc lozenges used in those studies were prepared.

Researchers believe the key to zinc's effectiveness in fighting colds lies in how it is prepared and administered. Because the rhinovirus that causes the common cold attacks the membrane of the upper respiratory system, zinc must be delivered directly to that site to bind with the virus. As a result, swallowing zinc pills (or even chewing zinc tablets) is not effective in fighting the common cold. Instead, the zinc must be administered in the form of a lozenge which is dissolved rather than chewed in order to effectively deliver zinc's cold-fighting agents to the membranes of the upper respiratory system.

The discovery of zinc as a cold fighter

The need to administer zinc in lozenge form was discovered by accident.

In the late 1970s, the young daughter of George Eby, a Texas mathematics professor, was diagnosed with leukemia and started chemotherapy treatments. At the same time, Mr. Eby began administering large doses of vitamin and mineral supplements to his daughter in the hopes that this might assist her recovery. And, in fact, the young girl's doctors did find that these supplements seemed to improve the effectiveness of her treatments, though they were unsure exactly which of the supplements were having the positive effect, and why.

Although Mr. Eby was not a scientist, he began researching this question, and ultimately came to two conclusions: that the supplements were helping to reduce his daughter's increased susceptibility to bad colds (a common side effect of chemotherapy), thus allowing her to remain stronger and recover more quickly, and that zinc appeared to be the cold-fighting agent.

In response, Mr. Eby increased the dosage of zinc in tablet form, which did not further benefit his daughter. However, several months later, Mr. Eby's daughter developed an especially bad cold, making it very painful for her to swallow anything, including the zinc tablets. As a result, the young girl fell asleep one evening with a zinc tablet in her mouth allowing it to dissolve in her mouth. When she awoke hours later, her cold symptoms had been greatly reduced. This, in turn, led to research into the development of in-mouth dissolving zinc lozenges to fight the common cold. And the rest, as they say, is history.

Researchers have also found that if zinc is to be effective, the lozenges cannot be mixed with compounds that are generally added to most lozenges, including flavorings such as citric acid and sorbitol. Apparently, these compounds themselves bind with the zinc, preventing zinc from binding with the membranes of the upper respiratory system and thus, the rhinovirus. For the same reason, you should avoid taking zinc lozenges with orange or other juices high in citric acid.

The original addition of these flavorings to zinc lozenges led to as noted a number of research studies concluding that zinc had little or no effectiveness in fighting the common cold. This in turn, delayed by a number of years the proof that zinc taken in lozenge form can in fact be quite effective in combating the common cold. But zinc itself has a very sour taste, and needs some sort of flavoring. Ultimately, researchers found that while some flavorings do render the zinc lozenges inert, zinc mixed with other compounds (such as fructose, saccharine and/or dextrose) produced a pleasant-tasting lozenge without interfering with the zinc's ability to effectively combat a cold.

How much is enough?

To be effective, adults should take five to six zinc lozenges containing between 12 and 15 milligrams of zinc (10 milligrams for children) every 24 hours as soon as symptoms of a cold appear and continue this dosage until the cold symptoms completely disappear. A bag of 30 lozenges (five or six day supply) costs about $16.75.

Lozenge therapy should be stopped as soon as the cold ends, since long-term administration of zinc can deplete the body's supply of copper, a mineral necessary to keep your immune system working properly.

As for other side effects, Erin Coffield, a registered dietitian at Boston's Beth Israel Deaconess Medical Center points out that at high dosages, zinc lozenges have been shown to lower HDL (good) cholesterol and can actually suppress the immune system. These effects disappear, however, as soon as you stop taking the zinc lozenges.

Who shouldn't take zinc?

A minority of people will suffer moderate to severe nausea, and/or vomiting or diarrhea from taking zinc. For these people, zinc lozenge therapy is highly impractical, since the cure is worse than the illness.

In addition, the following people shouldn't use zinc lozenges until it has been proven safe for them:

• pregnant women
• children
• people with chronic kidney disease, liver disease or other serious illness

Great medical discovery?

Who knows? As we approach the millennium, maybe zinc lozenges will rank right up there along with penicillin, the polio vaccine, and organ transplantation as one of the great medical discoveries of the 20th century.