Zinc

Educational overview

Dietary supplement; chronic high intake can cause copper deficiency and neurologic problems and can interact with some antibiotics.

Zinc is an essential trace mineral that serves as a structural or catalytic component of several hundred enzymes and of the zinc-finger proteins that regulate gene transcription. It is required for protein synthesis, wound healing, immune cell function, taste and smell, and normal growth. The body has no dedicated store, so intake and intestinal absorption regulate status day to day, and absorption falls when phytate-rich plant foods, iron, or calcium are consumed at the same time. Supplements supply zinc as gluconate, sulfate, acetate, citrate, or picolinate salts, and the elemental zinc content differs between them. Zinc also appears in cold lozenges, most multivitamins, denture adhesives, and topical products.

Deficiency biology is well established, and zinc supplementation in deficient children in low-income settings reduces diarrhoea and respiratory illness. In well-nourished adults the main clinical literature concerns the common cold: a 2024 Cochrane review found low-certainty evidence that zinc lozenges or sprays shorten cold duration by about two days without preventing colds, at the cost of taste disturbance and nausea; an earlier Cochrane review was withdrawn in 2015 over data errors. Chronic excess causes copper deficiency, presenting as anaemia, neutropenia, and a myeloneuropathy that can be mistaken for myelodysplasia or B12 deficiency. Intranasal zinc gels were linked to permanent loss of smell in a 2006 case series and in laboratory studies of nasal tissue.

In the United States, oral zinc is a dietary supplement, and the NIH Office of Dietary Supplements publishes an RDA and a tolerable upper level. Zinc sulfate injection is an FDA-approved prescription product for adding to parenteral nutrition, and zinc oxide is an over-the-counter skin protectant, so the mineral spans three regulatory categories. Intranasal zinc products are the cautionary example: in 2009 the FDA warned consumers about Zicam zinc gluconate nasal gel and swabs after more than 130 reports of anosmia, the products were withdrawn, and the agency has since cited the episode in its guidance on drugs labelled as homeopathic. Zinc lozenges continue to be sold as supplements or homeopathic drugs. In the European Union and United Kingdom, oral zinc is a food supplement.

Zinc supplements are stable at room temperature in a closed container away from moisture; lozenges and liquids follow their labels. For a record, the salt and its elemental zinc content matter more than the tablet strength, because products with the same milligram figure can deliver very different amounts of zinc. Duration is the second key field, since copper deficiency develops over months of sustained high intake, and the total across a multivitamin, a cold remedy, and a standalone tablet is easily overlooked. Zinc taken close to quinolone or tetracycline antibiotics, penicillamine, or oral iron reduces absorption of one or both, so timing entries relative to those medicines are useful. Any change in taste or smell dated against product changes is worth noting.

Category

Mineral

Routes represented

Oral

Storage context

Follow the product label; store in the original container away from excess heat and moisture.