What is the role of zinc in the body?

Role of Zinc in the Body

Zinc is an essential micronutrient that serves critical catalytic, structural, and regulatory functions in the body, acting as a cofactor for over 300 enzymes and being required for more than 2000 transcription factors involved in numerous biological processes essential for human health and survival. 1, 2

Key Functions of Zinc in the Body

Enzymatic and Cellular Functions

• Enzyme activation: Zinc serves as a cofactor for more than 300 enzymes involved in metabolism, including:

  • Alkaline phosphatase (important in tissues with high proliferative activity like hair follicles) 1
  • Copper/zinc superoxide dismutase (antioxidant enzyme) 1
  • Numerous other enzymes involved in protein, carbohydrate, and lipid metabolism 2

• Transcriptional regulation: Required for more than 2000 transcription factors that control gene expression 3, 2

• Cellular processes:

  • DNA replication and repair
  • Cell cycle progression
  • Apoptosis (programmed cell death)
  • Aging processes 3

Immune System Function

• Acts as a "second messenger" in immune cells, participating in signaling events 4
• Essential for both innate and adaptive immunity 1
• Affects cells involved in immune function including:
  • Monocytes
  • Polymorphonuclear cells
  • Natural killer cells
  • T-cells
  • B-cells 1
• Acute zinc deficiency causes decreased immunity, while chronic deficiency increases inflammation 1

Antioxidant and Anti-inflammatory Properties

• Part of the body's antioxidant defense system 1
• Stabilizes cytosolic Zn/Cu superoxide dismutase
• Inhibits NADPH oxidase enzyme
• Induces production of cysteine-rich metallothionein (which scavenges heavy metals and protects against stress) 1, 3

Tissue Growth and Repair

• Essential for protein and collagen synthesis 3, 5
• Critical for wound healing through:
  • Supporting zinc-dependent matrix metalloproteinases that aid in autodebridement
  • Facilitating keratinocyte migration during wound repair
  • Providing resistance to epithelial apoptosis
  • Protecting against reactive oxygen species and bacterial toxins 5

Clinical Manifestations of Zinc Deficiency

Zinc deficiency affects approximately 17% of the global population 3 and can manifest as:

• Growth retardation and developmental delays 1, 6
• Skin manifestations:
  • Alopecia (hair loss)
  • Skin rash affecting face, groins, hands, and feet 1, 6
• Impaired wound healing 1, 5
• Immune dysfunction with increased susceptibility to infections 1, 4
• Diarrhea 1, 6
• Blunting of taste and smell 1
• Delayed sexual development and bone maturation 1
• Glossitis and nail dystrophy 6
• Hypogonadism in males 6

High-Risk Populations for Zinc Deficiency

Several conditions increase the risk of zinc deficiency:

• Malnutrition 6
• Malabsorption syndromes 1, 6
• Short bowel syndrome 1
• Bariatric surgery 1
• Inflammatory bowel disease 1, 6
• Chronic renal disease 1
• Liver disease 1, 4
• Sickle cell disease 4
• Alcoholism 1, 6
• Eating disorders (anorexia nervosa, bulimia) 1
• Vegetarian/vegan diets (especially with high phytate content) 1, 4
• Burns, trauma, and sepsis (hypercatabolic states) 1
• Prolonged parenteral nutrition without adequate zinc supplementation 1

Monitoring and Assessment

For patients at risk of zinc deficiency:

• Measure plasma zinc to confirm clinical zinc deficiency 1
• Always interpret results with simultaneous determination of CRP (inflammation marker) and albumin levels 1
• Note that serum zinc decreases significantly when CRP exceeds 20 mg/L, complicating interpretation 1
• In patients on long-term parenteral nutrition, monitor zinc status every 6-12 months 1

Clinical Pitfalls and Caveats

1. Inflammation affects zinc levels: Serum zinc concentrations decrease during inflammation (acute phase response), making interpretation difficult without measuring inflammatory markers 1

2. Zinc supplementation risks: Long-term high-dose zinc supplementation can cause:

   • Suppressed immunity
   • Decreased HDL cholesterol
   • Anemia
   • Copper deficiency 6

3. Special populations: Different populations have varying zinc requirements:

   • Preterm infants: 400-500 μg/kg/day
   • Term infants to 3 months: 250 μg/kg/day
   • Infants 3-12 months: 100 μg/kg/day
   • Children >12 months: 50 μg/kg/day (up to maximum 5 mg/day) 1

4. Increased requirements: Patients with gastrointestinal losses (fistulae, stomas, diarrhea) may need IV doses up to 12 mg per day 1

5. Burns: Patients with major burns >20% BSA have significantly increased requirements (30-35 mg/day IV for 2-3 weeks) 1

Zinc's multifaceted role in human physiology underscores its importance as an essential micronutrient. Maintaining adequate zinc status is critical for optimal health, particularly for immune function, growth, development, and wound healing.