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Martina M. Cartwright

Martina M. Cartwright Ph.D., R.D.

Zinc and the Common Cold: Just the Facts

How taking the right zinc supplement may zap your cold

Perhaps you are one of millions of cold sufferers who tried a zinc supplement to rid yourself of pesky symptoms like runny nose and cough only to find disappointment. After a week of slamming zinc lozenges every two hours, maybe you are still plagued by a cough that won't quit and nasal congestion that makes your nose run so often that you could compete with Rudolph the Red Nose reindeer. So what happened? Maybe it's the type of zinc used, maybe it's the way you took it, maybe it was the dose. For the past week or so, I've been peppered with questions about zinc and the common cold..does it work? If so, how?

The "common" cold affects an estimated 62 million Americans each year and is the number one reason for work and/or school absences. Although over 200 viruses can cause a cold, most colds are typically caused by rhinoviruses, a family of 99 viruses that cause symptoms like sore throat, runny nose, nasal congestion and sneezing. "Rhino" is derived from the Greek word for nose and it is here that the virus likes to live and breed. The average cold lasts about 7 days but lingering symptoms like a retched cough may persist for days. Since colds spread by respiratory droplets or by person-to-person contact, its best to stay home during the first few days in order to avoid contaminating your colleagues..unless you really don't like them, then you may want to share.
Most people would do just about anything to shorten the duration of a cold. Colds symptoms are inconvenient; the constant nasal drip, sore throat and sneezing interfere with activities, sleep and energy levels, so the idea of getting back to a normal routine sooner rather than later is appealing. Enter zinc, a common mineral that if taken "correctly" may help zap a cold in its tracks.

Zinc is an essential mineral required for wound healing, vision, reproduction, and immune function. Red meat, nuts, and whole wheat flour are great sources of zinc. As a dietary supplement, zinc is found in many forms including zinc gluconate, zinc acetate, zinc citrate, zinc sulfate, zinc carbonate, and zinc picolanate to name a few. Not all of these forms of zinc are effective in reducing cold symptoms. The type of zinc (eg: the form) as well as the delivery (eg: oral pill vs. topical lozenge) is critical to achieving cold fighting effectiveness.
A few days ago, the Cochrane Library, an international group of experts that regularly reviews the scientific evidence for a number of medical therapies, evaluated 15 scientific studies, including 1360 people of all ages, to see if zinc actually squelched cold symptoms. The answer was promising. Zinc taken as a lozenge (adults) or syrup (children) was beneficial in reducing the duration and severity of the common cold in healthy folks if taken within 24 hours of the first sign of symptoms.

Zinc lozenges and nasal gels directly interfere with the rhinovirus' ability to breed in the moist environment of the throat or nose. Zinc gluconate and zinc acetate have shown the greatest anti-viral effectiveness if delivered in this manner. However, certain flavorings added to the lozenges may interfere with the virus busting ability; these include citric acid and tartaric acid...avoid these by perusing the ingredient label. Flavorings are a must as zinc on its own tastes nasty. Upset stomach and bad taste are common side effects with the lozenges. In order for the zinc to zap the rhinovirus, the lozenge must completely dissolve in the throat where the virus lives and the typical dose required is 13.3 to 23 mg of zinc given every 2 hours while awake as symptoms persist. This amount of zinc appears to be safe for most adults but should NOT be used for longer than a week or two. Excessive zinc can be toxic and interferes with copper absorption, which can lead to copper deficiency and associated anemia and heart problems. Recommended upper limits (UL) of zinc for all age groups are available on-line.

Lozenge use in kids is strongly discouraged as it is a choking hazard. For children, a study showed that zinc sulfate syrup in a dose of 15 mg of zinc per day may help prevent colds while 30 mg of zinc per day at the first onset of symptoms may help treat a cold, although the benefits were modest. Use caution and contact a pediatrician before starting zinc therapy in kids. I'm repeating myself here, but zinc is toxic.
When considering a zinc lozenge, check the label for flavorings, type of zinc (eg: gluconate or acetate) AND zinc amounts. The average lozenge only contains about 5 mg of zinc, well below the suggested amount required to kill the virus. So you may have to endure more lozenges to get the right amount. When using zinc nasal gels, do not deeply inhale as this can be painful. There have been some reports of loss of smell with zinc gels and effectiveness has been debatable.

Zinc can also be taken as a supplement and may help improve immune function in some. People who took zinc supplements regularly for at least five months suffered from fewer colds and absences. Again, zinc is toxic, so watch the dose and consult with a dietitian or physician for your optimal dose. Several drugs, including oral contraceptives, stomach acid reducers and ACE inhibitors, and nutrients, like calcium and fiber, can reduce oral zinc absorption. Be sure to mention all drugs and supplements to your healthcare provider.

The take home message about zinc and the common cold is that zinc lozenges if taken in the right dose, at the right time (first 24 hours) and in the right formulation, may reduce cold symptom duration by a day or two. Side effects include bad taste and nausea. No studies have been conducted looking at individuals with asthma, HIV or chronic illness, so no recommendations were made in the Cochrane report for these groups. Further, given the differences in the folks included in the study, as well as the wide variations in formulation, dose, duration of use etc, a general recommendation for the use of zinc for treatment of the common cold has yet to be made. However, one thing is for sure: if you have a cold and want to try zinc, start taking it as soon as cold symptoms appear. Timing is key to success. Have I mentioned that zinc in excess can be toxic??


About the Author

Martina M. Cartwright

Martina M. Cartwright, Ph.D., R.D., is an adjunct professor of Nutritional Sciences at the University of Arizona and an independent biomedical consultant.


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