Zinc

Zinc serves three main roles: (1) enzymatic cofactor — zinc is required by over 300 enzymes involved in carbohydrate metabolism, protein synthesis, nucleic acid metabolism, and fatty acid synthesis; (2) structural role — zinc stabilises approximately 2,000 transcription factors that regulate gene expression across the genome; (3) signalling molecule — zinc participates in cell signalling, immune activation, and apoptosis. Functionally, zinc is essential for immune function (T-cell development, thymus gland maturation, natural killer cell activity), wound healing (cell proliferation and collagen synthesis), taste and smell perception, male reproductive health (testosterone biosynthesis, sperm production), hair and skin integrity (keratin synthesis), and vision (retinal enzyme component).

Slow-healing wounds are the hallmark and earliest sign, appearing weeks to months before other symptoms. Classic signs include hair loss or thinning, acne and eczematous skin lesions (particularly around the eyes, nose, mouth, and genitals), loss or distortion of taste and smell (sometimes metallic taste), reduced appetite and weight loss, frequent infections (bacterial, viral, fungal), growth retardation in children, male infertility and sexual dysfunction, night blindness, and white spots on fingernails. In severe, prolonged deficiency, mental fog, depression, and immune collapse can occur. At-risk groups include vegans/vegetarians, older adults, those with chronic diarrhoea or malabsorption disorders, and individuals on long-term diuretics or immunosuppressive therapy.

The FDA Daily Value is 11 mg. The Recommended Dietary Allowance (RDA) is 11 mg/day for adult men, 8 mg/day for adult women, 11 mg/day for pregnant women, and 12 mg/day for breastfeeding women. The Tolerable Upper Intake Level (UL) is 40 mg/day for adults. Vegetarians and vegans require approximately 50% more — roughly 16–17 mg/day for men and 12–13 mg/day for women — due to phytate inhibition of plant-based zinc. Long-term supplementation above 40 mg/day is contraindicated without medical supervision because it depletes copper, causing neurological and immune problems. High-dose zinc (75+ mg/day as lozenges) for cold duration reduction should only be used for short periods (under 7 days).

Oysters are by far the richest source: 32 mg per 85 g (3 oz) cooked serving — far exceeding any other food. Other excellent animal sources include beef chuck roast (7 mg per 85 g), Alaska king crab (6.5 mg per 85 g), pork chop (2.9 mg per 85 g), and eggs. Plant sources are modest: baked beans (2.9 mg per 172 g / 1 cup cooked), chickpeas (2.5 mg per 164 g / 1 cup cooked), pumpkin seeds (2.2 mg per 28 g / 1 oz), and cashews (1.6 mg per 28 g / 1 oz). Because plant zinc is less bioavailable (inhibited by phytates), vegetarians and vegans should consume larger quantities or combine with vitamin C to enhance absorption.

Yes, but with important caveats: zinc is absolutely essential for baseline immune function, and severe deficiency dramatically impairs immunity. However, supplementation above the RDA in zinc-replete individuals does NOT improve baseline immunity. For cold duration reduction, zinc lozenges (not tablets or capsules) containing acetate or gluconate formulations at 75+ mg/day, started within 24 hours of symptom onset, reduce cold duration by approximately 33% (Cochrane 2015). Lozenges work because they dissolve slowly in the mouth/throat, reaching mucous membranes where the virus replicates. Oral supplements and food do not provide this local effect. Short-term use (1 week) is safe; long-term daily lozenges >40 mg/day risk copper deficiency.

Yes, particularly if deficient: zinc regulates sebum production, has anti-inflammatory properties, and is required for skin barrier integrity and wound healing. Topical zinc oxide accelerates wound closure and reduces inflammation. For acne, zinc acetate and erythromycin combination therapy is standard in many countries and supported by clinical trials. Oral zinc supplementation (15–30 mg/day) modestly improves acne in some studies, particularly in deficient or low-normal individuals. However, the effect is moderate, and high-dose supplementation provides no additional benefit and risks copper deficiency. If considering supplementation, first test zinc levels.

Only in deficiency: zinc is required for hair follicle growth and differentiation, and deficiency causes alopecia. In deficient individuals, zinc repletion restores hair growth. However, in people with normal zinc status, supplementation does not improve hair growth or prevent androgenetic alopecia (male/female pattern baldness). Hair loss is multifactorial — common causes include iron deficiency (check ferritin), vitamin D deficiency, thyroid dysfunction, and genetic factors. Before supplementing zinc for hair loss, rule out these other deficiencies and confirm low zinc status via serum zinc testing.

Yes — the Tolerable Upper Intake Level (UL) is 40 mg/day. Acute excess (single very high doses) causes nausea, vomiting, loss of appetite, and abdominal cramps. Chronic excess (long-term supplementation >50 mg/day) causes copper deficiency — zinc competes with copper for intestinal absorption — leading to neurological symptoms (ataxia, peripheral neuropathy), microcytic anaemia, immune impairment, and impaired wound healing (ironically, despite being on zinc). The copper-to-zinc ratio should remain approximately 10:1. People taking therapeutic zinc long-term (>40 mg/day) must also take a copper supplement (2–4 mg/day) and have copper levels monitored. Zinc from food sources alone very rarely reaches toxic levels.