Zinc is an essential trace mineral vital for maintaining human health across multiple physiological systems. As a cofactor for over 300 enzymes, zinc participates in critical processes including immune function, wound healing, growth and development, and sensory perception. Unlike some nutrients, the body cannot synthesise or store large quantities of zinc, making regular dietary intake crucial. Understanding what zinc does for the body helps explain why adequate intake supports optimal health, whilst deficiency can lead to widespread consequences affecting immunity, growth, skin integrity, and cognitive function. This article explores zinc's essential roles, dietary requirements, and when supplementation may be appropriate.

What Does Zinc Do for the Body

Zinc is an essential trace mineral that plays a fundamental role in maintaining human health. Unlike some nutrients that the body can store in large quantities, zinc must be obtained regularly through diet or supplementation, as the body has limited storage capacity. This micronutrient is involved in numerous physiological processes, making it indispensable for normal growth, development, and overall wellbeing.

As a cofactor for over 300 enzymes, zinc participates in critical biochemical reactions throughout the body. These enzymes are involved in diverse functions including DNA synthesis, protein production, cell division, and wound healing. Zinc also acts as a structural component of certain proteins and transcription factors, which regulate gene expression and cellular function. The mineral supports antioxidant defence systems through its role in enzymes such as superoxide dismutase and metallothionein, helping protect cells from oxidative damage.

The body contains approximately 2–3 grams of zinc distributed across various tissues, with the highest concentrations found in muscle, bone, skin, and the prostate gland. Zinc cannot be synthesised by the body, making dietary intake crucial. The mineral is absorbed primarily in the small intestine, with absorption rates varying depending on dietary factors and individual zinc status. Understanding zinc's multifaceted roles helps explain why deficiency can lead to widespread health consequences, whilst adequate intake supports optimal physiological function across multiple organ systems.

Essential Functions of Zinc in Human Health

Immune System Support

Zinc is vital for proper immune function, influencing both innate and adaptive immunity. The mineral is required for the development and function of immune cells including neutrophils, natural killer cells, and T-lymphocytes. Zinc deficiency can impair immune responses, increasing susceptibility to infections. Some research suggests that zinc may help reduce the duration and severity of common cold symptoms when taken within 24 hours of onset, though evidence remains mixed and routine prophylactic supplementation is not recommended by UK health authorities.

Growth and Development

During periods of rapid growth—pregnancy, infancy, childhood, and adolescence—zinc requirements are particularly important. The mineral is essential for cell division and protein synthesis, processes fundamental to physical growth and development. Zinc plays a particularly important role in foetal development, supporting proper formation of organs and tissues. Inadequate zinc status during pregnancy may be associated with adverse outcomes including low birth weight and preterm delivery.

Wound Healing and Skin Health

Zinc contributes significantly to maintaining skin integrity and supporting wound repair. The mineral is involved in collagen synthesis, inflammatory response modulation, and epithelial tissue regeneration. Topical and oral zinc preparations are sometimes used therapeutically for wound management, though clinical evidence for routine supplementation in wound healing varies, and treatment should be guided by healthcare professionals.

Sensory Function and Cognition

Zinc is concentrated in areas of the brain involved in learning and memory, particularly the hippocampus. The mineral influences neurotransmitter function and neuronal signalling. Additionally, zinc is essential for normal taste and smell perception, with deficiency potentially causing taste abnormalities (dysgeusia) or reduced sense of smell (hyposmia). These sensory changes can affect appetite and nutritional intake, particularly in older adults.

Daily Zinc Requirements and Dietary Sources

Recommended Daily Intake

The UK Department of Health provides Reference Nutrient Intakes (RNIs) for zinc, which vary by age, sex, and life stage. Adult men require 9.5 mg daily, whilst adult women need 7.0 mg daily. There is no increase in the RNI during pregnancy (remains 7.0 mg). During lactation, requirements increase to 13.0 mg daily for the first four months, then 9.5 mg thereafter. Children's requirements range from 5.0 mg for ages 1–3 years, 6.5 mg for ages 4–6 years, 7.0 mg for ages 7–10 years, increasing progressively to adult levels by adolescence. These recommendations assume normal absorption and no significant losses.

Dietary Sources of Zinc

Zinc is widely available in both animal and plant-based foods, though bioavailability differs considerably between sources. Animal sources provide highly bioavailable zinc and include:

• Oysters and shellfish (exceptionally rich sources)

• Red meat, particularly beef and lamb

• Poultry, especially dark meat

• Fish and seafood

• Dairy products including cheese and milk

• Eggs

Plant-based sources contain zinc but also phytates, which can reduce absorption:

• Whole grains, particularly wheat germ

• Legumes including chickpeas, lentils, and beans

• Nuts and seeds, especially pumpkin seeds and cashews

• Fortified breakfast cereals

Factors Affecting Absorption

Zinc absorption typically ranges from 20–40% of dietary intake, depending on various factors. Phytates, found in whole grains and legumes, form complexes with zinc that reduce bioavailability. Conversely, animal protein enhances zinc absorption. Those following vegetarian or vegan diets may need to pay particular attention to zinc intake due to lower bioavailability from plant sources. Food preparation methods such as soaking, sprouting, or fermenting grains and legumes can reduce phytate content and improve zinc absorption.

Signs of Zinc Deficiency and Excess

Zinc Deficiency

Zinc deficiency can be classified as mild, moderate, or severe, with symptoms varying accordingly. In the UK, severe deficiency is uncommon, but marginal deficiency may affect certain population groups including older adults, pregnant women, and individuals with malabsorption disorders.

Common signs of zinc deficiency include:

• Impaired immune function with increased infection susceptibility

• Delayed wound healing

• Hair loss (alopecia)

• Skin lesions, particularly around body orifices

• Loss of appetite

• Altered taste or smell perception

• Growth retardation in children

• Hypogonadism and delayed sexual maturation in adolescents

• Diarrhoea

• Mental lethargy and mood disturbances

Seek medical advice if you experience persistent symptoms such as unexplained taste or smell changes, severe skin lesions, persistent diarrhoea, or failure to thrive in children. Note that blood tests for zinc can be affected by inflammation and should be interpreted by healthcare professionals in clinical context.

Risk Factors for Deficiency

Certain conditions and circumstances increase deficiency risk. Gastrointestinal disorders such as Crohn's disease, ulcerative colitis, and coeliac disease impair zinc absorption. Chronic kidney disease increases urinary zinc losses. Alcoholism interferes with zinc absorption and increases excretion. Strict vegetarian or vegan diets without careful planning may provide insufficient bioavailable zinc. Older adults face increased risk due to reduced dietary intake, decreased absorption, and medication interactions.

Zinc Excess and Toxicity

Whilst zinc deficiency poses health risks, excessive intake can also cause adverse effects. The UK Safe Upper Level for supplemental zinc is 25 mg daily for adults. Acute toxicity from single large doses (typically >200 mg) can cause nausea, vomiting, abdominal pain, and diarrhoea. Chronic excessive intake may lead to copper deficiency (as zinc interferes with copper absorption), impaired immune function, and reduced HDL cholesterol levels. Long-term supplementation above recommended levels should only occur under medical supervision. If you experience symptoms potentially related to zinc imbalance, contact your GP for appropriate assessment and guidance. Report any suspected adverse reactions to zinc supplements via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

When to Consider Zinc Supplementation

Clinical Indications

Zinc supplementation may be appropriate in specific clinical situations, though routine supplementation is unnecessary for most people consuming a balanced diet. UK public health guidance does not routinely recommend zinc supplementation for the general population, but recognises its role in managing certain conditions.

Confirmed deficiency represents the primary indication for supplementation. Diagnosis typically involves clinical assessment combined with serum zinc measurement, though interpreting zinc levels can be challenging as they don't always reflect total body stores and can be affected by inflammation and hypoalbuminaemia. Supplementation doses for treating deficiency are usually higher than maintenance doses and should be prescribed by a healthcare professional.

Specific Population Groups

Pregnant and lactating women with inadequate dietary intake may benefit from supplementation, particularly if dietary assessment suggests insufficient zinc consumption. However, most prenatal vitamins contain adequate zinc. Exclusively breastfed infants born prematurely or with low birth weight may require supplementation, as determined by paediatric assessment.

Individuals with malabsorption disorders including inflammatory bowel disease, short bowel syndrome, or chronic diarrhoeal conditions often require supplementation due to impaired absorption or increased losses. Those following strict vegetarian or vegan diets should ensure adequate intake through careful food selection or consider supplementation if dietary intake appears insufficient.

Older adults with poor nutritional intake, multiple medications, or chronic health conditions may benefit from assessment and possible supplementation.

Important Considerations

Before starting zinc supplements, consult your GP or a registered dietitian. Self-supplementation without professional guidance risks excessive intake and potential interactions with medications. Zinc can interact with several medicines including antibiotics (particularly tetracyclines and quinolones), penicillamine, and diuretics. According to the British National Formulary, zinc supplements should be taken at least 2 hours apart from tetracyclines, at least 2 hours before or 4–6 hours after quinolones, and at least 2 hours apart from penicillamine. Always check specific timing with your pharmacist or doctor.

Supplementation is available in various forms including zinc gluconate, zinc sulphate, and zinc acetate, with bioavailability varying between preparations. For age-related macular degeneration (AMD), NICE guidance (NG82) indicates that specific formulations containing zinc may be beneficial for those with existing disease, following ophthalmological assessment. However, there is no evidence supporting zinc supplementation for preventing AMD in individuals without existing eye disease. Always inform healthcare providers about any supplements you're taking to ensure safe, coordinated care.

Frequently Asked Questions