How do zinc and biotin relate to hair, nails and skin?

Hair, nails and skin are grouped together in the annex because several of the same nutrients carry maintenance statements for all three.

What statements are recognised?

Under the annex to Thai Ministry of Public Health Notification No. 447 (B.E. 2566):

Zinc contributes to the maintenance of normal hair, nails and skin, to normal protein synthesis, and to the protection of cells from oxidative stress.

Biotin contributes to the maintenance of normal hair, skin and mucous membranes, and to normal energy-yielding metabolism.

What does "maintenance of normal" mean?

It means the nutrient is involved in the tissue working normally.

How much zinc per day?

Recommended intakes set by the US National Academies' Food and Nutrition Board, as published by the NIH Office of Dietary Supplements, are 11 mg a day for adult men and 8 mg for adult women. The tolerable upper intake level for adults is 40 mg a day from all sources combined.

Taking large amounts of zinc over long periods interferes with copper absorption, so long-term high intake is not a self-managed decision.

Where do they come from in food?

Zinc: oysters, red meat, poultry, crab, shrimp, dried beans, pumpkin seeds, wholegrains, eggs and milk.

Biotin: egg yolk, liver, nuts, seeds and wholegrains.

Is plant-source zinc absorbed as well?

Less so, because phytate in beans and grains binds it. Soaking, sprouting and fermenting reduce phytate.

When should it be taken?

Zinc on an empty stomach makes some people nauseated, so with food is the more comfortable default, and it is usually spaced apart from large amounts of iron and calcium.

Dietary supplements are not intended to prevent, treat or cure any disease.