Zinc ions inhibit viral replication and spread in vitro across multiple viruses, including those causing the common cold.

Study: Antiviral Activity of the Zinc Ionophores Pyrithione and Hinokitiol against Picornavirus Infections

The study shows that zinc-boosting chemicals can stop cold viruses from multiplying in lab tests, which matches the claim about zinc fighting viruses.

Study: Efficacy of Zinc Against Common Cold Viruses: An Overview

The study shows that zinc, like in lozenges or nasal sprays, can stop cold viruses from spreading by blocking their entry into cells, which supports the idea that zinc helps fight viruses.

Study: Zinc ions inhibit replication of rhinoviruses

The study shows zinc stops cold viruses from growing in lab tests, which supports part of the claim, but it only looked at one type of cold virus, not all viruses mentioned.

Study: PDTC inhibits picornavirus polyprotein processing and RNA replication by transporting zinc ions into cells.

The study shows that a chemical carrying zinc into cells stops cold viruses from copying themselves, which matches the claim that zinc can block viruses like the common cold.