Zinc

Medically reviewed by Prof. Giorgi Pkhakadze, MD, MPH, PhD — GMJ Editorial Board

Scientific name: Zn (Chemical symbol)
Category: Essential Trace Mineral
RDA: 8-11 mg/day for adults
UL: 40 mg/day for adults

What is Zinc?

Zinc is an essential trace mineral that plays crucial roles in immune function, protein synthesis, wound healing, and DNA synthesis. As the second most abundant trace mineral in the human body after iron, zinc is involved in the activity of over 300 enzymes and is critical for proper growth and development. The body cannot produce zinc naturally, so it must be obtained through diet or supplements.

Zinc exists in various supplement forms, including zinc gluconate, zinc sulfate, zinc acetate, and zinc picolinate. Each form has different absorption rates and bioavailability, with zinc picolinate and zinc gluconate generally considered among the most easily absorbed.

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Health benefits & uses

Immune function support (Strong evidence): Zinc is essential for immune cell development and function. Clinical trials demonstrate that zinc supplementation can reduce the duration and severity of common cold symptoms when taken within 24 hours of onset.

Wound healing (Strong evidence): Zinc deficiency impairs wound healing, and supplementation in deficient individuals significantly improves healing rates. This mineral is crucial for collagen synthesis and tissue repair processes.

Age-related macular degeneration (Strong evidence): The Age-Related Eye Disease Study (AREDS) showed that zinc supplementation, combined with other antioxidants, can slow the progression of advanced age-related macular degeneration.

Diarrhea in children (Strong evidence): WHO and UNICEF recommend zinc supplementation for treating acute diarrhea in children, as it reduces duration and severity of episodes.

Male fertility (Moderate evidence): Zinc plays a role in testosterone production and sperm quality. Some studies suggest supplementation may improve sperm count and motility in zinc-deficient men.

Acne treatment (Limited evidence): Some research indicates zinc supplementation may help reduce inflammatory acne, though results are inconsistent and more research is needed.

How it works

Zinc functions as a cofactor for numerous enzymes involved in protein synthesis, carbohydrate metabolism, and immune function. It stabilizes cell membranes and plays a structural role in proteins and enzymes through zinc finger domains. In immune function, zinc is essential for T-cell development, natural killer cell activity, and cytokine production.

For wound healing, zinc facilitates collagen synthesis, cell proliferation, and inflammatory response regulation. Its antioxidant properties help protect cells from oxidative damage, while its role in DNA synthesis supports proper cell division and tissue repair.

Dosage

The Recommended Dietary Allowance (RDA) for zinc is 11 mg/day for adult men and 8 mg/day for adult women, with higher requirements during pregnancy (11 mg/day) and lactation (12 mg/day). The Tolerable Upper Intake Level (UL) is set at 40 mg/day for adults.

Typical supplementation ranges vary by purpose:

• General health maintenance: 8-15 mg/day
• Immune support: 15-30 mg/day (short-term)
• Cold treatment: 75-100 mg/day (divided doses, for 1-2 weeks maximum)
• Wound healing: 15-30 mg/day

Always consult with a healthcare provider before starting zinc supplementation, especially at higher doses or for extended periods.

Food sources

Excellent dietary sources of zinc include:

• Animal proteins: Oysters (highest source), beef, lamb, pork, chicken, turkey
• Seafood: Crab, lobster, sardines
• Dairy: Milk, cheese, yogurt
• Plant sources: Pumpkin seeds, hemp seeds, cashews, chickpeas, lentils
• Fortified foods: Breakfast cereals, nutritional yeast

Animal sources provide more bioavailable zinc than plant sources due to the absence of phytates, which can inhibit zinc absorption.

Safety & side effects

Zinc is generally safe when taken within recommended doses. Common side effects of excessive intake include:

• Nausea and vomiting
• Loss of appetite
• Stomach cramps
• Diarrhea
• Headaches

Chronic overconsumption (>40 mg/day long-term) can lead to copper deficiency, reduced immune function, and decreased HDL cholesterol levels. Taking zinc on an empty stomach increases the likelihood of gastrointestinal side effects.

Interactions

Drug interactions:

• Antibiotics: Tetracyclines and quinolones can reduce zinc absorption; separate by 2-3 hours
• Penicillamine: Zinc can reduce drug effectiveness
• Diuretics: May increase zinc losses

Supplement interactions:

• Iron: High doses of either mineral can inhibit absorption of the other
• Copper: Zinc can reduce copper absorption; long-term zinc supplementation may require copper supplementation
• Calcium: May slightly reduce zinc absorption when taken together

Who should be cautious

Certain individuals should exercise caution with zinc supplementation:

• Individuals with hemochromatosis: May have increased risk of zinc toxicity
• People taking immunosuppressive medications: Zinc may counteract intended effects
• Those with kidney disease: May have difficulty excreting excess zinc
• Vegetarians and vegans: Higher risk of deficiency but should monitor copper status with supplementation

Frequently asked questions

Should I take zinc on an empty stomach?

While zinc is best absorbed on an empty stomach, this can cause nausea in some people. If you experience stomach upset, take zinc with a small amount of food to improve tolerance, though this may slightly reduce absorption.

Can zinc help prevent COVID-19?

While zinc is important for immune function, there is currently insufficient evidence to recommend zinc supplementation specifically for COVID-19 prevention. Maintaining adequate zinc status through diet or standard supplementation supports overall immune health.

How do I know if I’m zinc deficient?

Signs of zinc deficiency include frequent infections, slow wound healing, hair loss, loss of taste or smell, and skin problems. However, these symptoms can have many causes. A healthcare provider can assess your zinc status through blood tests and dietary evaluation.

Is it safe to take zinc long-term?

Long-term zinc supplementation at recommended doses (8-15 mg/day) is generally safe for most people. However, prolonged high-dose supplementation can lead to copper deficiency and other complications. Regular monitoring by a healthcare provider is advisable for long-term use.

What’s the best time of day to take zinc?

Zinc can be taken at any time of day, but consistency is important. Taking it 1-2 hours before or after meals optimizes absorption. If taking multiple doses, space them throughout the day to improve tolerance and absorption.