Do Zinc Supplements Help Cure Colds?

Q: Do Zinc lozenges or nasal sprays help cure colds faster?

A: With cold season approaching, I get a lot of questions about the effectiveness of popular nutritional supplements marketed as cold remedies, especially Vitamin C, Echinacea, and Zinc.  Since zinc lozenges can be somewhat unpleasant to suck on–often chalky and metallic tasting– it makes sense to question their effectiveness before subjecting yourself to them.

The scientific literature on the effectiveness of zinc lozenges is very split.  There are a few randomized, controlled studies which suggest that people with common colds who sucked on these lozenges once every few hours did experience a significantly shorter duration and severity of symptoms (by a few days) than people who did not.  However, the quality of these studies has subsequently been called into question, and a few systematic reviews have concluded that the bulk of evidence actually does not yet support any benefit from using zinc lozenges for this purpose.  Most of the research also indicates that zinc is most likely to be effective if therapy is started as early as possible in the onset of a cold.  Finally, zinc gluconate is the best-studied form of zinc, and the research that supports a benefit mostly applies to this form of the supplement.

So: to suck on zinc or not to suck on zinc?  While we can’t say conclusively that zinc lozenges work, if you choose to give them a try anyway, follow the dosage instructions on your product and pay attention to possible symptoms of excess intake: upset stomach, nausea, and dizziness.

  • The safe upper limit for extended use of Zinc has been established by the Institute of Medicine at 40mg/day.
  • Side effects may occur if the dose you’re taking over a 24-hour period exceeds about 50-60mg/day in the short-term.
  • Do not use these products at doses exceeding the safe upper limit for more than about 5 days in a row to avoid unintended nutritional consequences, like deficiency of other minerals that compete with zinc for absorption.

As far as nasal sprays and gels, there is some limited evidence to suggest that these products may be beneficial in shortening the duration of a cold.  However, I urge you to think twice before using such products!  In 2009, the FDA issued a warning against the use of 3 popular products marketed under the “Zicam®” brand: Nasal Gel, Gel Swabs, and Cold Remedy Swabs.  According to the warning, use of these products was associated with a potentially permanent loss of the sense of smell in over 100 consumers. (As far as I can tell, all three products continue to be sold on the market.)  While the risk of having this adverse effect appears low, it’s a severe enough consequence to give pause and consider whether shortening a cold for a few days is worth it!


Tamara Duker Freuman, R.D.

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