Zinc may shorten common colds

As autumn and winter draw on, many of us are blighted by the common cold.  While there is still no cure for the virus, a new literature review indicates that a common supplement can reduce its duration.

Zinc may help the immune system
Studies have found that zinc and zinc lozenges may shorten the duration of the common cold by 40% (3)

The study, published in the Open Respiratory Medicine Journal, found that when given in higher doses, zinc and zinc lozenges may shorten the duration of the common cold by 40%.

There have been many studies on the effectiveness of zinc lozenges in treating colds, and results have not been consistent.  This new meta-analysis assessed 13 placebo-controlled trials in order to get a better picture of the effectiveness of the supplement.

Of the 13 trial studies, 5 used a total daily zinc dose of less than 75mg.  Each of these studies found no beneficial effect on cold duration.

Three trials used zinc acetate in daily doses of more than 75mg.  Each of these 3 studies found zinc to be beneficial, with an average of a 42% reduction in the duration of colds.

Five further trials used other forms of zinc in daily doses of more than 75mg.  Again, these trials showed benefit, with an average 20% decrease in the duration of colds.

While some studies recorded adverse effects such as unpleasant taste, no evidence was found that zinc lozenges might cause long term harm.  The study leader Dr Hemia concluded that “since a large proportion of trial participants have remained without adverse effects, zinc lozenges might be useful for them as a treatment option for the common cold.”

The therapeutic properties of zinc are thought to be due to this mineral’s ability to affect the immune response, as well as its antioxidant and anti-inflammatory properties.  In addition, zinc may actually inhibit the common cold virus (rhinovirus) (3).

For the common cold, zinc lozenges and sublingual zinc do appear to be a better option than zinc tablets or capsules.  This is because zinc lozenges dissolve in the mouth allowing the mucus membranes in the throat (and any cold virus there) to be acted on directly by the zinc.  Swallowing a capsule or tablet would not allow the zinc to work in the same way.

The trials that Dr Hemlia reviewed were each based on small numbers of participants, indicating that more research is needed in this area.  I would also add as a caveat that zinc is known to compete with other minerals in the body.  These minerals include copper and iron.  Long term intakes of high levels of any one mineral can reduce levels of another, a process called ‘competitive inhibition’.  Nevertheless, the study indicates that short-term intakes of high amounts of zinc should pose no harm, and may provide welcome relief for those suffering with winter colds.

Written by Nadia Mason, BSc MBANT NTCC CNHC


1. Harri Harri. Zinc Lozenges May Shorten the Duration of Colds: A Systematic Review. The Open Respiratory Medicine Journal, 2011; 5 (1): 51 DOI: 10.2174/1874306401105010051.

2. Korant BD, et al. Inhibition by zinc of rhinovirus protein cleavage: interaction of zinc with capsid polypeptides. J Virol. 1976;18(1):298-306.

3.  Image courtesy of Ambro.