Between the Stratum Corneum and the Lipid Film

Where Zinc Comes Into Play in the Tissue

Before any health-related claim can be used at all in the European Union, the European Food Safety Authority (EFSA) reviews the underlying science and issues its own opinion. Only once that opinion comes back favorable does the European Commission decide whether — and in exactly what wording — the claim gets authorized. For zinc and skin, that authorization exists:

Zinc Transport Proteins Between the Cell Layers

The epidermis consists of several cell layers stacked on top of each other, from the basal layer to the outer stratum corneum. For zinc to reach the places within this tissue where it's needed, specialized transport proteins from the ZIP and ZnT families are required. They actively move the metal ion across the cell membrane and help determine how much of it is available inside each layer.

Without these steps, zinc would still arrive by way of the blood, but not in sufficient amounts at the points within the tissue where it's needed. Which proteins are individually responsible for this is described in the scientific literature; the regulation text itself sticks to a short, general wording.

A Slightly Acidic Film on the Skin's Surface

Under ordinary conditions, the surface of the skin is slightly acidic — an effect that a zinc-dependent enzyme in the sweat glands, carbonic anhydrase, has a part in among other things. This enzyme influences how much the secreted sweat lowers the pH at the surface. The resulting, slightly acidic film is one of the features that set the outermost cell layer apart from its surroundings.

Both of these points sit at different levels of the same tissue. The authorized claim itself doesn't name either the transport proteins or the enzyme — it only records the reviewed end result in a short sentence.