There are many theories for the mechanism of action that causes the results seen with the use of zinc products. Among them, is the suggestion that zinc, when in contact with the cellular sructure of the mouth of throat, deactivates the cold virus. It has been submitted that zinc might initiate some form of action that inhibits the replication of the rhinovirus, the causative agent in most colds. It is also though that zinc affects cell membrane protection and the activation and regulation of T-cells.
Some theorists go so far as implying zinc can interfere with the intracellular adhesion molecule, the very place on the nasal epithelial cell where a rhinovirus fixes itself. If this is the case, the virus cell cannot infect the nasal tissue cells thus, no replication. The end result of this action is an interruption of the infection process and a shortening of the duration of a cold.
Some studies have indicated the possibility of zinc stimulating interferon production. Others offer the possibility that zinc may inhibit prostaglandin metabolism thus allowing the mineral to relieve cold symptoms.
A major consideration, however, is how can zinc, when used as a lozenge, reach and have an effect on the nasal mucosa - the actual site of the viral infection we call a cold?
In the pages of a 1997 issue of the Archives of Internal Medicine, an analysis of 8 clinical trials of zinc containing products was done. The studies were randomized, double-blind, and placebo controlled. Six of the eight studies were analyzed and the results showed three with positive results for zinc and three where the results were no better than a placebo. Of the two not included, one showed zinc in a positive light, the other, negative. Based on these studies, the conclusion drawn was that zinc was not more effective than a placebo in treating the common cold.
But, what of these studies? There were different formulations used in each study which immediately brings qualifying questions into play. In the four studies that showed zinc in a better light has preparations that gave up a higher concentration of zinc ions. There was the question of the forms of zinc used, the doses varied, etc. This makes for a questionable result.
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