Zinc runs your immune defence, wound healing, and sense of taste and smell, among many other roles. When intake stays low over time, that's associated with more frequent infections, slower healing, and sometimes a dulled sense of taste, signs that are easy to pin on something else.
It's also one of the most widespread gaps in the world: global estimates put the number of people with inadequate intake at more than 2 billion. Zinc isn't stored in large amounts, so a regular supply matters more than the occasional big hit.
Adults need around 11 mg a day for men and 8 mg for women. Good sources include red meat, shellfish (especially oysters), poultry, chickpeas, lentils, and nuts and seeds. There's a firm limit worth respecting: it's best not to exceed 40 mg a day, since too much zinc can interfere with how your body absorbs other minerals like copper.