Zinc
Zinc is a structural component of over 3,000 proteins and a cofactor for hundreds of enzymes involved in cell division, immune function, wound healing, DNA synthesis, and protein synthesis. Marginal deficiency is common; overt deficiency is a real problem in low-income countries and in specific medical conditions.
Daily requirements
- Adult men: 11 mg/day.
- Adult women: 8 mg/day.
- Pregnancy: 11 mg.
- Lactation: 12 mg.
- Vegetarians / vegans: up to 50% higher due to phytate-related absorption inhibition.
- Tolerable Upper Intake Level: 40 mg/day — chronic excess causes copper deficiency and immunosuppression.
Deficiency signs
- Impaired wound healing
- Recurrent infections
- Hair loss (alopecia)
- Loss of taste and smell (hypogeusia, hyposmia)
- Diarrhoea
- Delayed growth and sexual maturation (in children)
- Skin rash (acrodermatitis)
Common cold and immunity
Cochrane meta-analysis (Singh & Das 2013) of zinc lozenges (75+ mg/day started within 24 hours of cold onset) shows ~33% reduction in cold duration. The effect is form-specific: zinc acetate and zinc gluconate lozenges are effective; syrups and nasal sprays are not. Nasal zinc has been withdrawn due to permanent anosmia risk. Don't use it.
Testosterone
Zinc deficiency lowers serum testosterone and correction restores it. Supplementation does not raise testosterone above normal in men with sufficient baseline zinc. See our testosterone page for the same pattern with vitamin D. If your libido is low, test zinc, vitamin D, and morning testosterone together.
Wet macular degeneration (AREDS)
The AREDS and AREDS-2 formulations include 25–80 mg zinc plus copper 2 mg (to prevent zinc-induced copper deficiency). Slows progression of intermediate-to-late age-related macular degeneration.
Food sources
- Oysters (3 oz): 32 mg — by far the highest natural source
- Beef, chuck (3 oz): 7 mg
- Crab (3 oz): 6.5 mg
- Pumpkin seeds (1 oz): 2.2 mg
- Cashews (1 oz): 1.6 mg
- Yogurt (1 cup): 1.7 mg
- Chickpeas (½ cup): 1.3 mg
Supplement forms
- Zinc picolinate — well absorbed; commonly recommended.
- Zinc gluconate — used in lozenges for colds.
- Zinc citrate — well absorbed; gentle.
- Zinc sulphate — cheapest; can be harsh on the stomach.
- Take on an empty stomach for best absorption, or with food if it causes nausea.
- Long-term supplementation > 40 mg/day: pair with 1–2 mg copper to prevent copper deficiency.