Zinc is one of the most versatile minerals in human biology, involved in over 300 enzymatic processes, yet it's often overlooked in favour of the more-discussed vitamins. In Ireland, inadequate zinc intake is not uncommon, particularly among older adults, vegetarians, and those with digestive conditions. Understanding zinc's wide-ranging roles and how to maintain adequate levels can significantly support your overall wellbeing.
What Does Zinc Do in the Body?
Zinc's influence reaches virtually every body system:
- Immune function: Zinc is essential for the development and function of immune cells, including T-lymphocytes, natural killer cells and neutrophils. Even mild deficiency significantly impairs immune response. Some research suggests that supplementing at the onset of a cold may support shorter duration — though evidence is mixed and strain-specific.
- Skin health: Zinc is concentrated in the skin and plays multiple roles: supporting wound healing, regulating sebum production (relevant for acne), protecting against UV damage, and contributing to the structural integrity of skin cells. Zinc deficiency is associated with poor wound healing, skin lesions and dermatitis.
- Hair health: Hair follicles require zinc for protein synthesis and cell division. Zinc deficiency is a recognised cause of hair loss and can worsen conditions like alopecia. Many hair, skin and nails supplements contain zinc as a core ingredient.
- Hormone regulation: Zinc is needed for the synthesis and regulation of several hormones, including testosterone. It plays a role in male reproductive health and prostate function. It's also involved in insulin signalling and thyroid hormone metabolism.
- Taste and smell: Zinc is required for normal taste and smell. Loss of taste or smell can be a sign of zinc deficiency (and was notably observed in COVID-19 infections, thought to be partly related to zinc).
- Growth and development: Zinc is critical for growth in children and adolescents.
- DNA repair: Zinc plays roles in DNA synthesis and repair, and in protecting cells from oxidative damage.
- Eye health: High concentrations of zinc are found in the retina, where it supports vitamin A metabolism and may have a protective role against age-related macular degeneration.
Signs of Zinc Deficiency
Zinc deficiency can manifest in various ways:
- Frequent infections and slow recovery
- Poor wound healing
- Hair loss or thinning
- Skin problems: acne, eczema, dermatitis
- Loss of taste or smell
- White spots on fingernails (Leukonychia)
- Reduced appetite
- Growth delays in children
- Impaired sense of taste and appetite
- Low mood or irritability
Who May Be at Risk of Low Zinc in Ireland?
- Vegetarians and vegans: Zinc from plant foods is less bioavailable than from animal sources due to phytates in wholegrains and legumes. Vegetarians may need 50% more zinc than meat-eaters to account for reduced absorption.
- Older adults: Both intake and absorption tend to decline with age.
- People with digestive conditions: Inflammatory bowel disease, Crohn's, coeliac disease can impair zinc absorption.
- Alcohol consumers: Alcohol increases urinary zinc excretion and reduces absorption.
- Pregnant and breastfeeding women: Needs increase substantially.
- Those with chronic diarrhoea
Best Food Sources of Zinc
Zinc is found in both animal and plant foods, though bioavailability differs:
High Bioavailability (Animal Sources)
- Oysters — the richest food source of zinc by far
- Red meat (beef, lamb)
- Shellfish (crab, lobster)
- Poultry
- Dairy products
- Eggs
Plant Sources (Lower Bioavailability)
- Pumpkin seeds — one of the best plant sources
- Hemp seeds
- Legumes: chickpeas, lentils, black beans
- Nuts: cashews, almonds
- Wholegrains: oats, quinoa (soaking reduces phytate content and improves zinc absorption)
- Tofu and tempeh
Zinc and Immune Health: What the Research Says
Zinc's role in immune function is well-established. Research suggests:
- Zinc deficiency consistently impairs immune cell function and increases susceptibility to infections
- Zinc lozenges (not capsules or tablets) at specific doses may reduce the duration of common cold symptoms — the lozenge formulation keeps zinc in contact with the throat where rhinoviruses replicate
- Zinc supplementation in elderly people with low zinc status may support immune resilience
- Some research suggests zinc may reduce the risk of age-related macular degeneration when combined with antioxidants
Zinc cannot "prevent" infections or replace other immune support measures, but maintaining adequate status may help the immune system function as intended.
Zinc for Skin and Acne
Zinc's role in skin health has led to its use in treating acne. Topical zinc is used in some skincare formulations, and oral zinc supplementation has been studied for acne management. Some research suggests zinc sulphate or zinc gluconate may reduce acne severity. Zinc's anti-inflammatory and sebum-regulating properties make it a rational choice, though it is typically less effective than antibiotic treatments for severe acne.
Zinc Supplement Forms
- Zinc citrate — good absorption, well-tolerated, gentle on the stomach
- Zinc gluconate — widely used, affordable, reasonable absorption; commonly used in lozenges
- Zinc picolinate — some evidence for superior absorption; popular in quality supplement brands
- Zinc sulphate — older, cheaper form; more likely to cause stomach upset
- Zinc oxide — low bioavailability; primarily used topically in sunscreens and nappy rash creams
Dosage and Safety
- EU Reference Nutrient Intake: 10mg daily for adults
- Typical supplemental dose: 15–25mg daily
- Tolerable Upper Level (EFSA): 25mg daily for adults
Zinc should be taken with food to reduce nausea. Long-term supplementation above 40mg daily can interfere with copper absorption and cause copper deficiency. If supplementing long-term at higher doses, a balanced zinc and copper supplement may be advisable.
Zinc supplements may interact with certain antibiotics (tetracyclines, quinolones) and other medications — take at least 2 hours apart and check with your pharmacist.