Of 14 studies published over the last 25 years, about half shown benefits. On the positive side, a 2008 study of 50 people in the Journal of Infectious Diseases found that people who took zinc lozenges every few hours within the first 24 hours of a cold had symptoms that lasted half as long as people who sucked on placebo lozenges. With zinc they were also half as miserable.
Compared with the placebo group, those in the zinc group had colds that lasted for an average of four days instead of seven. Coughs lasted for two days instead of five. And runny noses lasted for three days instead of 4-1/2. The lozenges contained 13.3 mg of zinc and people took them five to six times a day while awake.
However, results can depend on the type of zinc lozenge that you use. A chiropractor knowledgeable in nutrition can steer you in the right direction. There are dangers in getting too much and too little zinc. So supplementation should be monitored by a health care professional.
Taking too much zinc or zinc overload could lead to problems like copper deficiency, which can cause anemia, nerve damage, bone loss and other problems. Some studies show that taking 50 mg for more of zinc daily for a few months could lead to copper deficiency. Also, avoid nasal sprays containing zinc, some studies have shown they cause nasal nerve damage and can impair the sense of smell.