Preparations containing zinc can shorten and alleviate the symptoms caused by colds by at least one day. However, they must be taken within 24 hours of the first symptoms, such as a runny nose and sore throat, reports the Cochrane Database of Systemic Reviews.
Zinc is useful for both treating and preventing colds. You just need to take it regularly. Prophylactically administered to children reduces their absenteeism at school. And even if they catch a cold, the infection rarely lasts more than a week. They also have to take less antibiotics – we read in a report by Cochrane, an independent organization that studies, among others, the effectiveness of drugs and therapy.
However, Cochrane Library makes no recommendations. It does not specify in what doses zinc should be taken or for how long. It also does not specify which preparations available on the pharmacy market are most useful in the treatment of colds. We could not do it, because there is no consensus on this matter yet – admits prof. Meenu Singh, pediatrician at the Postgraduate Institute of Medical Education and Research in Chandigarh, India, who led the report.
Difficulties in determining the effectiveness of zinc result, among others, from of the fact that it is often found in various types of preparations in tablets and syrups also containing other ingredients that hinder its absorption and reduce its effectiveness. Many people use the wrong doses and start treatment 24 hours after the first symptoms appear, says Prof. Ananda Prasad, oncologist at Wayne State University School of Medicine in Detroit, co-author of the Cochrane report.
The first studies suggesting that zinc may be useful in the treatment of colds appeared in 1984. However, they were not accepted because they did not meet basic scientific requirements. First of all, it does not use the so-called a blind test, in which the participants in the studies do not know whether they are taking a drug or a placebo.
Since then, 18 studies have been conducted on the subject. Eleven of them indicated that zinc helps in treating the common cold, but the remaining seven denied it.
One of the most optimistic studies was published in 2008 in The Journal of Infectious Diseases. It showed that the zinc-containing lozenge preparation (also available in Poland in lozenges) accelerates the treatment of cold symptoms from an average of seven to four days. It was also supposed to shorten the struggle with a cold from five to just two days.
The Cochrane report included 15 studies in which 1 people participated. Only those that met at least some methodological criteria were selected. Unfortunately, some of the participants guessed that they were taking zinc (they could sense it from the characteristic taste of the preparation). They were given various types of agents, including, among others, Zinc sulfate in syrup and a form of zinc aspartate.
The doses of this zinc used ranged from 30 to 160 mg. Lozenge was taken every 3-4 hours for four days, i.e. at a dose of 50 to 65 mg per day.
Cochrane has not studied Zicam nasal preparations containing zinc gluconate, which can irritate the olfactory nerves in some people when taken. This can result in impaired or even complete loss of smell (known as anosmia). At least such warnings were issued in 2009 by the US Food and Drug Administration. Since then, zinc gluconate has generally been taken in the form of lozenges or swallows.
Asthma patients were not included in the Cochrane report. All the above-mentioned studies were conducted only on healthy people. It is not known, therefore, whether preparations with zinc relieve the symptoms caused by asthma, which usually worsen due to colds.
It is also unknown how zinc works against colds. It is only suspected that it limits the penetration of the viruses causing this infection into the nasal mucosa, and also inhibits their multiplication after entering the body. Perhaps it also supports the immune system in the fight against these germs.
All doubts as to the validity of the use of zinc in the treatment of colds have not been dispelled. Prof. Ronald Eccles, dir. Common Cold Center at Cardiff University. The scientist in a statement for the BBC warns that if taken for too long, it can be toxic to the body. It is also noted that the research was conducted in less affluent countries, where deficiencies of this micronutrient occur more often.
Zbigniew Wojtasiński (PAP)