Zinc | Supplementopedia

Overview

Zinc (Zn²⁺) is an essential trace mineral crucial for over 300 enzymes and the structural integrity of numerous proteins.
Its primary function is as a catalytic, structural, and regulatory cofactor supporting cellular metabolism, immune function, and DNA/RNA synthesis.

Immune Support: Enhances innate immunity (neutrophil chemotaxis, NK-cell activity) and shortens common cold duration at doses ≥15 mg/day (meta-analyses of 17 RCTs).
Wound Healing: Accelerates re-epithelialization and collagen synthesis, particularly in pressure and diabetic ulcers.
Cognitive Function: Adequate zinc levels correlate with improved memory and executive function in older adults; deficiency links to neurodegeneration and ADHD-like behaviors.
Hormonal & Reproductive Health: Essential for testosterone synthesis, spermatogenesis, and menstrual cycle hormone balance modulation.
Metabolic Health: Contributes to insulin storage and signaling; supplementation modestly improves glycemic control in type-2 diabetes when combined with lifestyle interventions.
Antioxidant Defense: As a Cu/Zn-SOD component, it reduces oxidative stress in cardiovascular and neuroprotective contexts.

Zinc (Zn²⁺) coordinates with cysteine-histidine “zinc-finger” motifs, enabling transcription factor binding (e.g., p53, NF-κB) and gene expression regulation.
It acts as a Lewis acid in enzyme catalytic sites (e.g., carbonic anhydrase, alkaline phosphatase), stabilizing transition states and facilitating substrate binding.
In immune cells, it modulates signaling pathways (MAPK and JAK/STAT), influencing cytokine production.
Zn²⁺ stabilizes cell membrane structures, influencing ion channel function (e.g., NMDA receptor modulation).
Its antioxidant role stems from Cu/Zn-superoxide dismutase, converting superoxide radicals to H₂O₂, limiting oxidative damage.

General Adult Maintenance: 8 mg (women) – 11 mg (men) per day (RDA).
Therapeutic (e.g., colds, deficiency): 15–30 mg elemental zinc daily for 5–10 days; 30 mg may be used short-term under medical supervision.
Timing: Take with food to reduce gastric irritation; avoid high-dose (>50 mg) on an empty stomach.
Special Cases:
- Pregnancy/Lactation: Up to 12 mg/day (no >20 mg).
- Athletes: 20–30 mg/day may support recovery, but should not exceed 40 mg total daily intake.

Common Adverse Effects: Nausea, metallic taste, and mild diarrhea, usually mitigated by food intake.
Contraindications: Copper deficiency (high zinc impairs copper absorption), leading to anemia, neutropenia, and neurological symptoms.
Drug Interactions: Reduces absorption of quinolones, tetracyclines, and penicillamine; may increase systemic exposure to diuretics (thiazide) and ACE inhibitors.
Upper Limit: 40 mg/day for adults; excess can cause copper deficiency, dyslipidemia, and impaired immune response.
Vulnerable Groups: Infants <6 months, patients with chronic kidney disease, and individuals with hereditary hemochromatosis should avoid high-dose supplementation without clinician guidance.

Element: Zinc (Zn), atomic number 30, atomic weight 65.38 g·mol⁻¹.
Oxidation State: +2 in biologically active forms (e.g., Zn²⁺).
IUPAC Name: Zinc(II).
Typical Supplement Forms: Zinc gluconate (C₁₂H₂₂O₁₄Zn), zinc citrate (C₆H₆O₇Zn), zinc picolinate (C₁₀H₈NO₂Zn), and zinc oxide (ZnO).
Physical Properties: Metallic, bluish-white, malleable, low-melting (419 °C). Insoluble in water as elemental Zn; soluble as salts (e.g., ZnCl₂) with high aqueous solubility, facilitating absorption.

Natural Sources: Red meat, oysters, crab, pumpkin seeds, legumes, nuts, and whole-grain cereals provide biologically bound zinc.
Supplement Production: Zinc metal is purified by electro-refining; salts are synthesized via reaction of metallic zinc with appropriate acids (e.g., sulfuric acid → ZnSO₄) or by neutralizing zinc oxide with organic acids (e.g., gluconic acid).
Quality Considerations: Good Manufacturing Practice (GMP) compliance, USP or NSF verification, and low heavy-metal contamination (<10 ppb lead) are essential for safe supplementation. Organic-acid salts (e.g., zinc picolinate) often show higher bioavailability than inorganic salts (e.g., zinc sulfate).