zinc

Zinc is an indispensable trace mineral that plays a foundational role in human health. As an essential nutrient, zinc must be obtained through diet because the body cannot synthesize it on its own. Chemically, zinc exists in ionic form (Zn2+) in biological systems and participates as a catalytic and structural cofactor in hundreds of enzymes and transcription factors. These zinc-dependent enzymes are involved in processes ranging from DNA synthesis, protein production, and cellular signaling to antioxidant defense and cell division. Zinc was first recognized as an essential micronutrient in the early 20th century when researchers observed growth failure in animals deprived of dietary zinc, leading to the identification of its critical biological roles. Today, zinc remains one of the most researched trace minerals due to its extensive involvement in biochemical pathways and its influence on human health. At the cellular level, zinc helps stabilize the structure of proteins and cell membranes and assists in gene expression by regulating transcription. Throughout the body, zinc contributes to organ system integrity, immune cell function, sensory perception, and metabolic homeostasis. Despite being present only in trace amounts, the biological consequences of inadequate zinc are profound, affecting growth, immunity, skin health, neurological function, and reproductive health. Because it is involved in so many pathways, zinc deficiency can present in a wide range of clinical manifestations, which will be discussed later in this article. For most healthy adults, dietary intake following recommended levels supports the maintenance of adequate zinc status, but certain populations and conditions may increase requirements or impair zinc utilization.

Zinc’s primary physiologic functions revolve around its roles as a catalytic cofactor and structural component of numerous proteins and enzymes. One of its most widely recognized functions is supporting immune competence; zinc is crucial for the development, differentiation, and function of innate and adaptive immune cells. Zinc deficiency impairs neutrophil function, macrophage activity, and lymphocyte proliferation, increasing susceptibility to infections and prolonging recovery from illness. Mechanistically, zinc modulates signaling pathways involved in inflammation and immune cell recruitment. A 2021 systematic review and meta-analysis found that zinc supplementation in adults led to significant reductions in inflammatory markers such as C-reactive protein and interleukin-6 and improved antioxidant capacity, demonstrating its potential immunomodulatory effects. Other systematic analyses show zinc’s effects on inflammatory cytokines, with decreases in IL-6 observed in multiple controlled trials of supplementation, reinforcing its role in immune regulation. Beyond immunity, zinc has well-established functions in wound healing. Zinc participates in all phases of wound repair, including hemostasis, inflammation, cellular proliferation, and tissue remodeling. Recent meta-analyses of clinical trials indicate that supplemental zinc may improve healing of chronic wounds and ulcers, perhaps by enhancing fibroblast proliferation and collagen synthesis and reducing local inflammation. At the molecular level, zinc-dependent enzymes facilitate DNA and RNA polymerization, making zinc essential for growth and development. This is particularly critical during periods of rapid cell division, such as infancy, childhood, adolescence, and pregnancy. Zinc is also involved in hormone metabolism, including thyroid and sex hormones, contributing to fertility and reproductive health. Additional evidence suggests zinc’s involvement in improving digestive health by bolstering mucosal integrity and reducing the duration and severity of diarrheal episodes in children. Overall, zinc’s health benefits stem from its multifaceted biochemical actions, and although evidence varies across conditions, adequate intake is foundational to human health.

Daily zinc requirements vary by age, sex, and physiologic status. In infants, adequate intake levels are established based on average consumption from breastmilk or formula. Children and adolescents have increasing requirements that reflect growth needs, while adult males and females have distinct Recommended Dietary Allowances (RDAs) to support metabolic functions. According to the NIH Office of Dietary Supplements, infants 0–6 months typically require about 2 mg, increasing to approximately 3 mg by 7–12 months. Children aged 1–3 years require around 3 mg, 4–8 years 5 mg, and 9–13 years 8 mg. In adolescence, males require about 11 mg per day, whereas females require 9 mg. Adult males require 11 mg daily and adult females 8 mg. Pregnancy and lactation increase zinc needs to 11–12 mg to support fetal growth and milk production. These RDAs are devised to meet the nutritional needs of nearly all healthy individuals in each demographic. It is important to distinguish minimal intake from optimal intake; certain conditions, such as malabsorption, chronic illness, or dietary restrictions (e.g., strict vegan diets), may necessitate higher zinc intakes or supplementation to maintain adequacy. Conversely, intakes that exceed established upper limits can pose health risks, as discussed in later sections. Health professionals consider individual factors, including dietary pattern, digestive health, and specific life stages when advising on zinc intake. For practical dietary planning, foods naturally rich in zinc or fortified with zinc, such as oysters, lean meats, seeds, and fortified cereals, can help individuals achieve recommended amounts.

Zinc deficiency occurs when intake or absorption fails to meet physiologic needs. Mild deficiency may be subtle, while more severe deficiency produces overt clinical signs. Common early symptoms include reduced immune competence, frequent infections, prolonged wound healing, hair loss, and dermatologic manifestations such as rashes or lesions. Individuals may also experience changes in taste and smell, decreased appetite, poor growth in children, and delayed sexual maturation. In infants and children, deficiency can present as growth retardation and increased susceptibility to diarrhea and pneumonia. Dermatologic signs include acne-like eruptions, xerosis (dry skin), and nail changes. Neurologic and psychological features such as irritability and lethargy may also occur. Because zinc is essential for mucosal integrity, deficiency might also lead to gastrointestinal symptoms such as diarrhea. Diagnosing zinc deficiency is challenging because plasma or serum zinc levels can be affected by inflammation, albumin levels, and other factors, and mild deficiencies often evade detection on routine blood tests. Typical reference ranges for plasma zinc are approximately 70–120 µg/dL, but interpretation must consider clinical context. At-risk populations include individuals with malabsorptive disorders (e.g., celiac disease, Crohn’s disease), chronic liver or kidney disease, older adults, those consuming diets high in phytates (which hinder zinc absorption), and individuals with chronic diarrhea or alcohol use disorder. In the U.S. population, dietary surveys suggest that a notable minority have intakes below recommended levels, although overt deficiency is uncommon in healthy individuals consuming balanced diets. Clinical diagnosis often relies on a combination of symptom assessment, dietary history, and, when available, biochemical markers, with therapeutic response to zinc supplementation often confirming deficiency.

Zinc is found in a variety of animal and plant foods, with some sources providing exceptionally high amounts. Shellfish, particularly oysters, are among the richest natural sources; cooked eastern oysters can supply more than 50 mg of zinc per 3-ounce serving. Red meats such as beef and lamb and poultry like turkey and chicken also provide substantial zinc, with typical 3-ounce servings delivering several milligrams. Fortified breakfast cereals are important sources, especially for vegetarians and vegans, contributing meaningful percentages of daily needs. Plant-based foods including legumes (such as beans and lentils), seeds (e.g., pumpkin, sesame), and nuts (such as cashews) offer additional zinc, though phytates in these foods can reduce absorption. Dairy products contribute modest amounts. This diversity of food sources allows individuals to meet zinc needs through varied dietary patterns. Additionally, fortified foods can bridge gaps, especially in populations with increased requirements or limited animal product intake. Practical dietary planning involves combining high-zinc foods with enhancers of absorption (e.g., animal proteins) and reducing inhibitors (e.g., high-phytate foods consumed without preparation techniques such as soaking or fermenting).

The bioavailability of zinc from food depends on the food matrix and the presence of dietary enhancers and inhibitors. Animal proteins enhance zinc absorption, whereas phytates found in whole grains, legumes, and seeds bind zinc and reduce its bioavailability. Soaking, fermenting, or sprouting high-phytate foods can reduce phytate content and improve zinc absorption. Zinc competes with other divalent minerals, such as iron and copper, for absorption, and excessive supplemental doses of one can impair the uptake of others.

Supplementation may be appropriate for individuals at risk of deficiency, including those with malabsorptive conditions, older adults, strict vegetarians, and pregnant or breastfeeding women. When dietary intake is insufficient or absorption is impaired, supplements can help meet recommended needs.

While zinc is essential, excessive intake—especially from supplements—can cause adverse effects, including nausea, vomiting, headaches, and interference with copper absorption.

Zinc supplements can interact with certain medications. Quinolone and tetracycline antibiotics may have reduced absorption when taken with zinc, and zinc can reduce the effectiveness of penicillamine. Thiazide diuretics increase zinc loss in urine and may necessitate monitoring zinc status.

Common Forms: Zinc gluconate, Zinc sulfate, Zinc acetate, Zinc picolinate

Typical Doses: 8–11 mg daily for maintenance; higher doses under medical supervision

When to Take: On an empty stomach or with food to reduce GI upset

Best Form: Zinc picolinate

⚠️ Interactions: Quinolone antibiotics, Tetracycline antibiotics, Penicillamine