Review study finds that zinc supplements may reduce the severity and duration of the common cold

Previously I have written about zinc and vitamin C in relation to the prevention and shortening of the common cold and I would recommend you visit this post for more information.  I have also written about probiotics, elderberry, vitamin D and a healthy diet in relation to the common cold 

Colds are caused by viruses and our susceptibility to these infections is largely dictated by the efficiency of our immune system.  A healthy diet providing our bodies with optimal nutrition may help to keep our immune systems strong and protect us from infection.  The symptoms of a common cold, such as a tickly throat, headache and runny nose, tend to last from a few days to a couple of weeks.  There is mixed evidence with regards prevention and treatment of colds with complementary health methods but a new review study (1) of 15 trials has found that taking zinc supplements in syrup, lozenge or tablet form within a day of symptoms starting can reduce their severity and shorten the length of illness.  Zinc is essential for the efficient functioning of the immune system.  Every cell in our body needs zinc.  This mineral has antioxidant and anti-inflammatory effects in the body which may account for these effects.

The authors of the review study (1) write in their introduction that “the common cold is one of the most widespread illnesses and is a leading cause of visits to the doctor and absenteeism from school and work”.  The review set about looking at all the available information – trials that have occurred since 1984 investigating the role of zinc in the treatment of the common cold symptoms have had mixed results, the review was looking for clarification.

The authors of the study (1) looked for well conducted, randomised, double-blind, placebo-controlled, trials using zinc for at least five consecutive days to treat, or for at least five months to prevent the common cold.   13 therapeutic trials (with 966 participants) and two preventive trials (with 394 participants) were included in the review.  The results showed that the intake of zinc is associated with a significant reduction in the duration and severity of common cold symptoms.  There was also a significant difference between the zinc and control groups (not taking zinc) for the proportion of participants still having symptoms after seven days of treatment .  The incidence rate of developing a cold, school absence and prescription of antibiotics was also found to be lower in the zinc group.

The authors conclude that (1)Zinc administered within 24 hours of onset of symptoms reduces the duration and severity of the common cold in healthy people. When supplemented for at least five months, it reduces cold incidence, school absenteeism and prescription of antibiotics in children. There is potential for zinc lozenges to produce side effects. In view of this and the differences in study populations, dosages, formulations and duration of treatment, it is difficult to make firm recommendations about the dose, formulation and duration that should be used”.

It is important to note that zinc supplements should not be used long-term due to concerns of toxicity.  Excessive amounts of this mineral can lead to nausea, vomiting, abdominal pain and diarrhoea.  Scientists say that more work is needed to determine the exact dose of zinc required to prevent and treat the common cold.

There is no proven treatment for the common cold, but experts believe zinc medications may help prevent and lessen infections by coating the common cold viruses and stopping them from entering the body through the thin lining of the nose.  It also appears to stop the virus from replicating, at least in laboratory tests.   There is also the suggestion that zinc aids the immune system and may dampen down some of the unpleasant reactions the body has to an invading virus.


In a BBC news article the lead researcher of the review, Meenu Singh, said (2)This review strengthens the evidence for zinc as a treatment for the common cold”.  “However, at the moment, it is still difficult to make a general recommendation, because we do not know very much about the optimum dose, formulation or length of treatment.

According to trial results, zinc syrup, lozenges or tablets taken within a day of the onset of cold symptoms reduce the severity and length of illness.   At seven days, more of the patients who took zinc remedies every couple of hours during the daytime had cleared their symptoms compared to those who took placebos.   And children who took 15mg of zinc syrup or zinc lozenges daily for five months or longer caught fewer colds and took less time off school.

Editor in Chief of the Cochrane Library, David Tovey, said (2): “This is a treatment that is showing some promise which, where treating the common cold is concerned, is unusual”.   “Although there are many over-the-counter cold remedies already available, we are not awash with things that can stop cold symptoms or greatly reduce their severity”. “But there is still uncertainty about the best doses, timings and formulations and more studies will be needed to look at this.

Zinc lozenges and dissolvable tablets and drinks often contain vitamin C, another nutrient which some studies suggest may be useful in reducing the severity and duration of cold symptoms.  If you feel a cold coming on it may be useful to try sucking on a lozenge every three hours or so while symptoms persist.  However, more evidence will be needed before firm recommendations about dose and duration of zinc supplementation can be made.  It is important to check with a medical doctor prior to beginning any kind of supplement regiment.  Good food sources of zinc include red meat, poultry, beans, wholegrains, nuts and seeds as well as some seafood such as crab.  The zinc found in plants such as beans and wholegrains is more difficult for the body to absorb since it is bound up with substances known as phytates which reduce its bioavailability in the body.

(1)Singh M & Das RR.  2011.  Intervention Review.  Zinc for the common cold.  Cochrane Database of Systematic Reviews.  2011, Issue 2. Art. No.: CD001364. DOI: 10.1002/14651858.CD001364.pub3.

(2)Michelle Roberts.  2011.  BBC News.  Zinc can be ‘effective treatment’ for common colds.  16 February 2011.

Written by Ani Kowal