There is no guarantee that zinc will help you feel better faster.

In some studies, zinc did nothing to shorten how long people with colds felt bad. In other studies, zinc may have shortened symptoms by a few days. But the side effects from taking zinc can be uncomfortable or serious in some cases.

No one enjoys the tiredness, scratchy or sore throat, drippy nose, headache, and cough of a cold.

Viruses are the most common causes of colds, in particular viruses called rhinoviruses. There are more than 100 strains of rhinoviruses, and they are very good at growing in the nose and throat.

The idea behind using zinc to stop cold symptoms is based on lab experiments. Scientists found that zinc blocked the rhinovirus from getting into cells.

To test the idea, a study in 1984 used zinc as a tablet that dissolves in the mouth, called a lozenge. It compared people taking zinc with those taking a lozenge without zinc. The study found that zinc shortened the time people felt sick from their colds. It also reported a lot of side effects.

Compared with people who didn't take zinc, those who did commonly complained of upset stomach, problems with taste and mouth irritation. Other side effects of taking zinc can be serious. Some people who used zinc nasal sprays had permanent loss of smell.

Taken all together, research shows mixed results for zinc and colds. For that reason, zinc can't be recommended to shorten your cold symptoms.

Researchers can't say why zinc works in some studies and not others. There are still questions about which type of zinc works best. Research also doesn't show what amount of zinc is the best. And researchers don't know how people can avoid the side effects of taking zinc. As a result, it's not clear what the best dose or treatment plan would be.

The limit of zinc for adults is less than 40 mg a day unless their health care providers say otherwise.

The safest option is to talk to your provider before using zinc when you have a cold.