Most people can’t avoid getting sick this time of year. Cold remedies — or purported remedies — are about as common as the cold itself.

Zinc supplements, taken within 24 hours of the onset of cold symptoms, may reduce the duration of cold by a couple of days and lessen the severity of symptoms, said Dr. Janey Purvis, a family medicine practitioner at Bend Memorial Clinic. However, “It’s still controversial whether it’s effective.”

Whether zinc truly fights the common cold has long been questionable, although evidence suggests that it does. In a 2011 review of 18 high-quality studies, 11 concluded that zinc did reduce the duration and severity of a cold, and seven studies found it did not, Purvis said. The studies used different doses, ages and populations in their research, and none resulted in clear recommendations.

Treating colds

Purvis said the medical community generally believes that 30 milligrams to 150 milligrams a day of zinc may decrease the typical seven-day cold by about two days and can reduce the severity of symptoms. Cold-Eeze over-the-counter zinc lozenges provide the effective dose of about 80 milligrams a day, she said. Users could take six lozenges containing 13 milligrams of zinc each throughout the day.

Consumerlab.com, a New York-based consumer-information company that evaluates products, published a report recently that said most zinc lozenges don’t provide the appropriate dosage to shorten a cold. The only product tested by Consumerlab.com that did was Cold-Eeze, which also happens to be the most expensive lozenge. (The cost per dose from lozenges ranged from 5 to 40 cents, according to the company’s report. See “Cost comparison of popular zinc lozenges,” Page F4.)

That level of supplementation should not be taken for more than a week or so, or else zinc consumption could exceed tolerable levels and create health problems. Long-term supplementation with zinc at high doses, such as 100 milligrams a day, has been associated with a decrease in good cholesterol, reduced immune system function and other risks, according to Consumerlab.com. Excessive intake could interfere with the absorption of copper and suppress the immune system.

Colds are caused by viruses in the upper respiratory system — the nasal passages and throat, Purvis said. How exactly zinc works on colds is unknown, she said. The theory is that zinc has some antiviral properties, but the exact mechanism by which it works isn’t clear. Zinc supplements could stop the virus from replication. Or, she said, it might reduce inflammation in the upper respiratory system.

Studies have shown zinc’s effectiveness on children as well as adults. One concluded that children who took 10 milligrams of zinc a day for five months had reduced cold symptoms, fewer school absences and less need for antibiotics. However, no one is recommending high doses of zinc as a preventive measure, Purvis said.

She noted that research on zinc has studied healthy participants, not people with chronic illnesses, such as asthmatics or diabetics. So someone with an underlying health condition should check with his or her physician before supplementing with zinc.

Zinc

Zinc is an essential mineral that is naturally present in some foods and available as a dietary supplement. Zinc is involved in numerous aspects of cellular metabolism, playing a role in immune function, wound healing, cell division and more, according to the National Institutes of Health.

Foods rich in zinc include red meat, some seafood, legumes, fortified cereals and whole grains, according to the “Dietary Reference Intakes: The Essential Guide to Nutrient Requirements.” Purvis said she wasn’t aware of any studies that showed whether eating foods rich in zinc would help in the treatment of colds.

Serious zinc deficiency is rare, but certain drugs and nutrients can inhibit zinc absorption or increase its excretion. Liquids and pills tend to be used to replenish depleted levels. Zinc supplements have been associated with the reduction of macular degeneration, and may be useful in treating conditions such as acne, depression and anorexia nervosa, according to Consumerlab.com.

But, “If you’re going to do it for colds, (lozenges) seem to be the most effective,” Purvis said.

Side effects

However, some people can’t tolerate the lozenges, she said. Some people experience abdominal pain, constipation or diarrhea, even when consuming the recommended amounts. Lozenges can leave a bad taste in one’s mouth, and can temporarily alter one’s sense of taste.

Syrups and pills, which may be more effective in treating a zinc deficiency than a cold, may have fewer side effects.

Purvis said a nasal spray cold remedy called Zicam was found to permanently destroy users’ sense of smell, so it’s not recommended anymore.

Generally, she said, good nutrition, lots of fluids, general fitness and avoiding smoking are the best tips to staying healthy, without any potential side effects.

“There’s really no treatment for colds,” she said. “Some say chicken soup works as well as anything else.”

Recommended dietary allowance for zinc (mg/day)

Age Males Females

7-12 months 3 3

1-3 years 3 3

4-8 years 5 5

9-13 years 8 8

14-18 years 11 9

19-50 years 11 8

Older than 51 years 11 8

Source: Dietary Reference Intakes