Zinc may slightly shorten duration of common cold symptoms

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Rest is important when recovering from cold symptoms. JulPo/Getty Images
  • Zinc supplements might help shorten cold symptoms but are not likely to prevent them, a new analysis suggests.
  • Existing studies on zinc’s effectiveness are somewhat inconclusive due to different designs, different drug delivery systems, and lack of a single definition of which cold viruses are being targeted.
  • Experts say people can still take zinc as long as they’re aware of side effects and should consult their physician before doing so.

Taking zinc when you have the sniffles could reduce cold symptoms by a couple of days, but it’s no sure thing, a new systematic review of existing studies finds.

The review looked at more than 30 studies that examined people who took zinc as either a preventive measure to ward off colds or as a treatment for cold symptoms.

Breaking these studies down, the review authors said they found no evidence that zinc was useful for preventing colds, but a review of eight studies of nearly 1,000 participants for zinc as a treatment for a cold symptoms found “low-certainty” evidence the nutrient could shorten cold duration by a couple of days.

The theory behind zinc as a cold treatment is that it might interrupt the replication of the cold virus, similar to how an antiviral drug works.

However, while zinc is widely marketed in a variety of forms with claims to help treat or prevent colds — from pills to sprays to syrups and lozenges — there’s no consensus on whether zinc is effective or if one form is better than another.

“The timing of zinc supplementation in relation to the onset of cold symptoms may impact its effectiveness, adding complexity to study designs,” said Dr. Monica Amin, PharmD, a pharmacist with the pharmaceutical companies Marley Drug and Medicure who was not involved the study.

“Variations in individuals’ immune responses and genetic factors can influence their reactions to treatments, contributing to variability in study findings,” Amin told Medical News Today. “These factors collectively contribute to the challenge of determining whether zinc is an effective remedy for colds.”

However, experts say this review should help point the way toward better future studies on zinc to determine its efficacy once and for all.

“The evidence on zinc is far from settled: We need more research before we can be confident in its effects,” Dr. Susan Wieland of the University of Maryland School of Medicine and a senior author of the review, said in a press release. “Future studies should adopt standardized methods for administering and reporting treatments and defining and reporting outcomes. Additional studies focusing on the most promising types and doses of zinc products and using appropriate statistical methods to assess outcomes that are important to patients will enable us to understand whether zinc may have a place in the treatment of the common cold.”

Then, there’s the question of even defining a “cold” in the context of a clinical trial.

“There is no consistency to the definition of who has a common cold. And even people who have classic cold symptoms with fever, runny nose, and sore throat, might be infected with one of many viruses: adenovirus, rhinovirus, metapneumovirus, influenza, RSV, or even COVID,” said Dr. David Cutler, a family medicine physician at Providence Saint John’s Health Center in California who was not involved in the study.

“So, without knowing what we are treating and including patients with many different illnesses, it is difficult to conclude that a specific treatment is alleviating a specific illness,” Cutler told Medical News Today.

So, whether you should take a nutrient supplement that might work (or might not) to combat a cold is ultimately up to the individual, but experts say there are some factors to consider, including side effects.

“It is certainly possible that zinc may at times improve the course of a viral cold illness, but its potential benefits must be weighed against its potential risks,” Cutler said. “Zinc can be a stomach irritant causing nausea, abdominal pain, and sometimes vomiting. The chemical similarity between zinc and copper can lead to zinc blocking copper absorption, resulting in copper deficiency. Copper deficiency may manifest as neuropathy, anemia or immune dysfunction.”

In addition, the federal Food and Drug Administration has also warned against the use of zinc nasal sprays due to a risk of decrease or loss of sense of smell.

“If a patient can start taking zinc at the onset of cold symptoms without experiencing an upset stomach, it’s likely safe for them to use,” Amin said. “To ensure safety, patients should consult with their healthcare provider before starting any new supplement regimen, as supplements can potentially have side effects and interact with medications.”

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