Where is excess zinc stored in the body?

Excess Zinc Storage in the Body

Excess zinc is primarily stored in the liver, bound to metallothionein, and secondarily in bone and skeletal muscle. 1, 2

Distribution of Zinc in the Human Body

Zinc is an essential micronutrient distributed throughout the body in specific patterns:

• Primary storage sites:

  • Liver: The liver is a major site for excess zinc storage, where it binds to metallothionein, a cysteine-rich protein that acts as an endogenous chelator of metals 1
  • Bone: Approximately 85% of the body's zinc is found in muscle and bone 2
  • Skeletal muscle: Contains a significant portion of total body zinc 2

• Secondary locations:

  • Skin: Contains approximately 11% of whole body zinc (along with the liver) 2
  • Other tissues: The remaining zinc is distributed across various tissues and organs 2

Cellular Distribution of Zinc

At the cellular level, zinc is distributed as follows:

• 30-40% in the nucleus
• 50% in the cytoplasm, organelles, and specialized vesicles
• Remainder in cell membranes 2

Zinc Metabolism and Regulation

The body does not have a specialized zinc storage system like it does for iron (ferritin). Instead:

• Zinc cannot be stored in significant amounts, requiring regular dietary intake 3
• Absorption occurs primarily in the duodenum via ZIP4 and ZnT5B transporters 3
• In circulation, approximately 70% of zinc is bound to albumin 3, 2
• Excess zinc intake can inhibit copper and iron absorption 3
• Excretion occurs predominantly through feces, with smaller amounts eliminated via urine, sweat, menstrual flow, and semen 3

Clinical Implications of Zinc Storage

Understanding zinc storage has important clinical implications:

• Wilson's disease treatment: Zinc induces hepatic metallothionein, which binds excess toxic copper to prevent hepatocellular injury 1
• Liver disease: Patients with cirrhosis may have altered zinc metabolism and storage capacity 1
• Inflammation: During acute inflammatory responses, zinc redistributes from plasma albumin to the liver, where it binds to increased metallothionein 1

Monitoring Zinc Status

• Serum/plasma zinc is the most widely used test to assess zinc status, though it fluctuates by up to 20% during a 24-hour period 1
• Interpretation should consider albumin levels and inflammatory markers (CRP) 1
• Zinc levels decrease significantly when CRP exceeds 20 mg/L, complicating interpretation 1

Zinc plays crucial roles in over 300 enzymatic reactions and more than 1000 transcription factors, making proper regulation of its storage and distribution essential for optimal health 4.