What Is Zinc?
Zinc is an essential trace element required for more than 300 enzymatic reactions. It is involved in DNA repair, protein synthesis, cell division, immune defence, and the activity of antioxidant enzymes (superoxide dismutase).
In the context of healthy ageing, zinc is particularly relevant because it systematically declines with age — a phenomenon that contributes to immunosenescence (ageing of the immune system).
Who Is at Risk for Deficiency?
| At-risk group | Cause |
|---|---|
| Older adults (>65 years) | Reduced absorption, less meat consumption |
| Vegans / vegetarians | Phytates in legumes inhibit zinc absorption |
| PPI users | Gastric acid required for zinc absorption |
| Regular alcohol consumers | Increased renal excretion |
| Endurance athletes | Increased loss through sweat |
What Do the Studies Actually Show?
Clearly established (EFSA-approved)
- Immune function: T-cell proliferation, NK cell activity, antibody production
- DNA synthesis and cell protection: cofactor for DNA polymerases and repair enzymes
- Wound healing: collagen synthesis and epithelial regeneration
- Testosterone: in deficiency, supplementation normalises levels
Comparatively well studied
- Reduction in cold duration (~33% shorter with zinc lozenges within 24 hours of symptom onset)
- Investigated in the context of age-related macular changes (AREDS2 study: zinc + antioxidants)
Important: No effect in adequately nourished individuals
Testosterone effects, immune boosts, and hormone improvements occur only in genuine deficiency. For adequately nourished people, additional intake provides no benefit and carries risks.
Overdose: The Copper Problem
Zinc displaces copper during intestinal absorption. Chronically high zinc doses (>40 mg/day) can cause copper deficiency — with consequences for nerve health, immune function, and anaemia. This is the most common mistake in self-supplementation with zinc.
Recommendation: Never supplement more than 25–40 mg/day and with long-term intake above 15 mg: add 1–2 mg copper.
Which Form?
| Form | Bioavailability |
|---|---|
| Zinc picolinate | Very good (well chelated) |
| Zinc gluconate | Good (common in lozenges) |
| Zinc citrate | Good, stomach-friendly |
| Zinc oxide | Poor — common in cheap products |
Zinc oxide is inexpensive but barely bioavailable. When buying: check the compound form.
Is Zinc Safe?
At 8–25 mg/day from food and supplements combined: likely safe. EFSA’s tolerable upper level (UL) is 25 mg/day for adults.