Zinc

What Is Zinc?

Zinc is an essential trace mineral found in every cell of the body. An adult contains approximately 2-3 grams of zinc, concentrated primarily in muscle (60%), bone (30%), skin, liver, kidney, and the prostate gland. Unlike iron, the body has no specialized zinc storage system; adequate daily intake is therefore important for maintaining functional zinc status.

Key Functions

Zinc is a structural and catalytic component of more than 300 enzymes and over 1,000 transcription factors. Its roles span virtually every major metabolic pathway:

• Immune function: Zinc is required for the development and activation of T cells, natural killer cells, and macrophages. Even mild deficiency impairs immune responses and increases susceptibility to infections.
• Wound healing: Zinc participates in collagen synthesis, cell proliferation, and inflammatory regulation — all critical for tissue repair.
• DNA synthesis and cell division: Zinc-finger proteins regulate gene expression. Zinc is essential during periods of rapid growth (infancy, adolescence, pregnancy).
• Taste and smell: Carbonic anhydrase VI in saliva is zinc-dependent; deficiency causes hypogeusia (diminished taste) and hyposmia (diminished smell).
• Antioxidant defense: Zinc is a structural component of copper-zinc superoxide dismutase (Cu/Zn-SOD), a major antioxidant enzyme.

Dietary Reference Values and Food Sources

The RDA for zinc is 11 mg/day for men and 8 mg/day for women. Pregnant women need 11 mg/day and lactating women 12 mg/day. The UL is 40 mg/day. Zinc from animal foods is more bioavailable than from plant foods, where phytates form insoluble complexes that reduce absorption.

• Oysters (3 oz): ~74 mg — the richest food source
• Beef chuck roast (3 oz): ~7 mg
• Alaska king crab (3 oz): ~6.5 mg
• Fortified breakfast cereal (1 serving): ~2.8-15 mg
• Pumpkin seeds (1 oz): ~2.2 mg
• Hemp seeds (3 tbsp): ~3 mg

Deficiency and Toxicity

Zinc deficiency is prevalent in developing countries and among groups with high phytate intake. Symptoms include growth retardation in children, delayed sexual maturation, hair loss, diarrhea, skin lesions, and increased infection rates. Supplementation at doses above 40 mg/day for extended periods can impair copper absorption, leading to copper deficiency and associated neurological complications. Excessive zinc also depresses immune function — the opposite of its essential role at adequate intakes.