Zinc plays a vital role in fighting infection by preventing the immune system from spinning out of control, research has shown.
The finding may explain the common belief that taking zinc supplements at the start of a cold reduces symptoms.
It also has implications for intensive care treatment. But the scientists say it is too soon to recommend giving zinc to critically ill patients in intensive care units (ICUs).
The laboratory research showed how zinc stems excessive inflammation linked to sepsis, a devastating and potentially fatal reaction to infection.
Mice lacking zinc developed overwhelming inflammation in response to sepsis compared with mice on a normal diet.
When the deficient animals were given zinc supplements their condition improved.
Experiments with human blood cells showed that the calming effect of zinc was due to the way it binds to a specific protein in the inflammation pathway.
The findings are published in the journal Cell Reports.
Lead scientist Professor Daren Knoell, from Ohio State University in the US, said: "If you are deficient in zinc you are at a disadvantage because your defence system is amplified, and inappropriately so.
"The benefit to health is explicit: zinc is beneficial because it stops the action of a protein, ultimately preventing excess inflammation."
He added: "I think the question is whom to give zinc to, if anybody at all. We predict that not everybody in the ICU with sepsis needs zinc, but I anticipate that a proportion of them would.
"Zinc is a critical element that we get from our diet, but we do not think we can give zinc and fix everything. Usually, if there is zinc deficiency, we would expect to see other nutrient deficiencies, too."
Around two billion people worldwide are believed to be deficient in zinc.
Recommended daily allowances for zinc in the UK are 5.5 - 9.5 milligrams for men and four to seven milligrams for women. Taking too much zinc can lead to anaemia and bone weakening.
The Department of Health urges people not to take more than 25 milligrams of zinc a day unless advised to do so by a doctor.
Good sources of zinc include red meat, poultry, dairy products, shellfish, beans, nuts, and whole grains.
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