Can Zinc Lozenges Treat the Common Cold?
As winter approaches people look to protect themselves from the common cold. Numerous products on the shelves claim to offer such protection; among them are various types of zinc lozenges. Do they work? First a bit about zinc. It is an essential mineral to health. We cannot live without it. But we don’t need very much. About 15 mgs a day will do. Zinc is important in wound healing, the functioning of our immune system, eyesight, brain development, the proper functioning of sperm and the synthesis of testosterone. The high zinc content of oysters may thus explain the traditional belief that they possess aphrodisiac properties. Even our senses of smell and taste depend on enzymes that include zinc in their molecular structure. The zinc-cold relationship was first noted in 1980 when more on a lark than anything else, although with the knowledge that zinc played a role in immunity, doctors gave a 3 year old girl a 50 mg Zn gluconate tablet to try to boost her immune system because of chronic colds. She refused to swallow the tablet but did suck on it as if it were candy. Her symptoms resolved! This prompted a number of studies on the value of zinc supplements in alleviating the common cold. The trials have been split down the middle, with some showing an improvement in symptoms and some not. One study, however, published in the Annals of Internal Medicine seemed to shift the playing field in favor of the supplements.
In a controlled trial, 50 volunteers took about 13 mg of zinc in the form of zinc acetate or placebo every 2-3 hours as long as they had cold symptoms. The results were statistically significant. The zinc group had a shorter average duration of colds, 4.5 days versus 8 days. The total zinc taken was about 80 mg a day which although well above the daily requirement should not cause any problems over such a short period. Exactly how the zinc works is not known. One theory is that it prevents the virus from entering cells by binding with a protein that normally facilitates such entry. Another possibility is that zinc decreases the levels of inflammatory substances in the blood called cytokines. The form of zinc supplement seems to be important. In one study, the duration of illness was significantly lower in the group receiving zinc gluconate lozenges (providing 13.3 mg zinc) but not in the group receiving zinc acetate lozenges (providing 5 or 11.5 mg zinc). None of the zinc preparations affected the severity of cold symptoms in the first 3 days of treatment. The bottom line then is that zinc is not a cold cure, but if you can get over the metallic taste and dry mouth, it may be worth a try to shorten the duration of a cold. The number of days lost from work due to the common cold annually is a burden on the economy. And one last thing: Low levels of zinc in the blood have been associated with cognitive impairment. So maybe, by taking zinc, we’ll be better able to judge whether we should be taking zinc or not!