Essential trace element important for immunity, growth and development.
Deficiency associated with impaired immunity, increased risk of infections, pneumonia and diarrhea.
Supplementation for children in third world countries reduces incidence and severity of diarrhea and pneumonia.
Acquired zinc deficiency can occur as a result of low nutritional intake, malabsorption, excessive loss of zinc, or a combination of these factors.
An essential mineral that is naturally present in some foods, added to others, and available as a dietary supplement.
Also found in many cold lozenges and some over-the-counter drugs sold as cold remedies.
Involved in numerous aspects of cellular metabolism.
It is required for the catalytic activity of approximately 100 enzymes.
Has a role in immune function, protein synthesis, wound healing, DNA synthesis, cell division.
Zinc supports normal growth and development during pregnancy, childhood, and adolescence.
Required for proper sense of taste and smell.
A daily intake of zinc is required to maintain a steady state because the body has no specialized zinc storage system.
Intake recommendations for zinc vary by age and gender.
Recommended Dietary Allowances (RDAs) for Zinc:
0–6 months 2 mg
7–12 months 3 mg
1–3 years 3 mg
4–8 years 5 mg
9–13 years 8 mg
14–18 years 11 mg-13 mg
19+ years 11 mg-12 mg
Oysters contain more zinc per serving than any other food.
Red meat and poultry provide the majority of zinc in the American diet.
Good sources of zinc in foods include: beans, nuts, crab and lobster, whole grains, fortified breakfast cereals, and dairy products.
Phytates present in whole-grain breads, cereals, legumes bind zinc and inhibit its absorption.
While bioavailability of zinc from grains and plant foods is lower than that from animal foods, many grain- and plant-based foods are still good sources of zinc.
The Daily Value for zinc is 15 mg for adults and children age 4 and older.
Food labels are not required to list zinc content unless a food has been fortified with this nutrient.
Foods providing 20% or more of the Daily Value are considered to be high sources of a nutrient.
Zinc supplements contain several forms of zinc, including zinc gluconate, zinc sulfate, and zinc acetate, and the percentage of elemental zinc varies by form.
Approximately 23% of zinc sulfate consists of elemental zinc.
It has not been determined whether differences exist among forms of zinc in absorption, bioavailability, or tolerability.
Zinc is present in several products, including homeopathic medications, sold over the counter for the treatment and prevention of colds.
Reports of anosmia associated with the use of zinc-containing nasal gels or sprays, but these safety concerns have not been found to be associated with cold lozenges containing zinc.
Zinc is present in some denture adhesive creams at levels ranging from 17–34 mg/g .
Use of dental adhesive excessively, of greater than 1.5 gm/d,
can lead to zinc toxicity, resulting in copper deficiency and neurologic disease.
As a result, many denture creams have now been reformulated to eliminate zinc.
Most infants, children, and adults in the United States consume recommended amounts of zinc.
NHANES III data found that 35%–45% of adults aged 60 years or older had zinc intakes below the estimated average requirement of 6.8 mg/day for elderly females and 9.4 mg/day for elderly males.
20%–25% of older adults have inadequate zinc intakes.
Intake is low in elderly in U.S. households that are food insufficient.
Zinc deficiency is characterized by: growth retardation, loss of appetite, impaired immune function, hair loss, diarrhea, delayed sexual maturation, impotence, hypogonadism in males, and eye and skin lesions, weight loss, delayed healing of wounds, taste abnormalities, and lethargy.
Many symptoms of zinc deficiency are non-specific.
Zinc status is difficult to measure as it is distributed throughout the body as a component of various proteins and nucleic acids.
Plasma or serum zinc levels are used for evaluating zinc deficiency.
Zinc levels do not necessarily reflect cellular zinc status due to homeostatic control mechanisms, so that
clinical effects of zinc deficiency can be present in the absence of abnormal laboratory indices.
Uncommon process in Western societies, and when zinc deficiency does occur, it is usually due to inadequate zinc intake or absorption, increased losses of zinc from the body, or increased requirements.
Gastrointestinal surgery and digestive disorders such as ulcerative colitis, Crohn’s disease, and short bowel syndrome can decrease zinc absorption and increase endogenous zinc losses primarily from the gastrointestinal tract.
Other diseases associated with zinc deficiency include malabsorption syndrome, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and chronic diarrhea.
The bioavailability of zinc from vegetarian diets is lower than from non-vegetarian diets.
Meat, which is high in bioavailable zinc and may enhance zinc absorption.
Vegetarians typically eat high levels of legumes and whole grains, which contain phytates that bind zinc and inhibit its absorption, so that they sometimes require as much as 50% more of the RDA for zinc than non-vegetarians.
Techniques to increase zinc bioavailability include soaking beans, grains, and seeds in water for several hours before cooking them .
Vegetarians can also increase their zinc intake by consuming more leavened grain products than unleavened products because leavening partially breaks down the phytate.
The body absorbs more zinc from leavened grains than unleavened grains.
Pregnant women are at increased risk of becoming zinc insufficient due, in part, to high fetal requirements for zinc.
Lactation can also deplete maternal zinc stores
Breast milk provides sufficient zinc at 2 mg/day for the first 4–6 months of life.
Breast milk does not provide recommended amounts of zinc for infants aged 7–12 months, who need 3 mg/day.
Infants aged 7–12 months should consume age-appropriate foods or formula containing zinc in addition to breast milk.
Approximately 44% of children with sickle cell disease have a low plasma zinc concentrations possibly due to increased nutrient requirements and/or poor nutritional status.
Zinc deficiency affects approximately 60%–70% of adults with sickle cell disease.
Zinc supplementation may improve growth in children with sickle cell disease.
Approximately 30%–50% of alcoholics have low zinc levels.
Ethanol consumption decreases intestinal absorption of zinc and increases its urinary zinc excretion.
The types of food consumed by many alcoholics is limited, leading to inadequate zinc intake.
Severe zinc deficiency depresses immune function.
Mild to moderate zinc deficiency can impair macrophage and neutrophil functions, natural killer cell activity, and complement activity.
Zinc is required to develop and activate T-lymphocytes.
Patients with low zinc levels have shown reduced lymphocyte proliferation response to mitogens and other adverse alterations in immunity that can be corrected by zinc supplementation.
Low zinc status has been associated with increased susceptibility to pneumonia and other infections in children in developing countries and the elderly.
Zinc helps maintain the integrity of skin and mucosal membranes.
Patients with chronic leg ulcers have abnormal zinc metabolism and low serum zinc levels.
Skin ulcers often treated with zinc supplements, although
it has not been shown that the general use of zinc sulfate in patients with chronic leg ulcers or arterial or venous ulcers is effective.
Zinc deficiency causes alterations in immune response that contribute to increased susceptibility to infections, such as those that cause diarrhea, especially in children.
Malnourished children experience shorter courses of infectious diarrhea after taking zinc supplements.
The World Health Organization and UNICEF recommend short-term zinc supplementation (20 mg of zinc per day, or 10 mg for infants under 6 months, for 10–14 days) to treat acute childhood diarrhea.
In a randomized, double-blind, placebo-controlled clinical trial, 50 subjects developing the common cold took a zinc acetate lozenge (13.3 mg zinc) or placebo every 2–3 wakeful hours: the zinc lozenges significantly reduced the duration of cold symptoms including cough, nasal discharge, and muscle aches.
In another trial involving 273 participants with experimentally induced colds, zinc gluconate lozenges significantly reduced the duration of illness compared with placebo but had no effect on symptom severity.
Treatment with zinc acetate lozenges which provides 5 or 11.5 mg zinc, had no effect on either cold duration or severity.
Neither zinc gluconate nor zinc acetate lozenges affected the duration or severity of cold symptoms in 281 subjects with natural colds in another trial.
Caruso and colleagues published a structured review of the effects of zinc lozenges, nasal sprays, and nasal gels on the common cold: Of the 14 randomized, placebo-controlled studies included, 7 had a beneficial effect and 7 showed no effect.
A Cochrane review concluded that zinc is beneficial in reducing the duration and severity of the common cold in healthy people, when taken within 24 hours of onset of symptoms.
The safety of intranasal zinc has been called into question because reports of anosmia, in some cases long-lasting or permanent, from the use of zinc-containing nasal gels or sprays.
In a population-based cohort study in the Netherlands, high dietary intake of zinc as well as beta carotene, vitamin C, and vitamin E was associated with reduced risk of age-related macular degeneration in elderly subjects.
However, a systematic review and meta-analysis published concluded that zinc is not effective for the primary prevention of early AMD, although it might reduce the risk of progression to advanced disease.
Supplementation with antioxidants plus zinc significantly reduce age-related macular degeneration.
Visual acuity loss is not significantly affected by zinc supplementation alone.
Large amounts of supplemental iron might decrease zinc absorption.
High zinc intakes can inhibit copper absorption, sometimes producing copper deficiency and associated anemia.
Zinc toxicity can occur in both acute and chronic forms.
Acute adverse effects of high zinc intake include nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, and headaches.
Intakes of 150–450 mg of zinc per day have been associated with such chronic effects as low copper status, altered iron function, reduced immune function, and reduced levels of high-density lipoproteins.
Reductions in a copper-containing enzyme, a marker of copper status, have been reported with even moderately high zinc intakes.
Possible that chronically high intakes adversely affect some aspects of urinary physiology.
Tolerable upper intake levels for Zinc
0–6 months 4 mg
7–12 months 5 mg
1–3 years 7 mg
4–8 years 12 mg
9–13 years 23 mg
14–18 years 34 mg
19+ years 40 mg
Zinc supplements interact with several types of medications:
Both quinolone antibiotics and tetracycline antibiotics interact with zinc in the gastrointestinal tract, inhibiting the absorption of both zinc and the antibiotic.
Zinc can reduce the absorption and action of penicillamine.
Thiazide diuretics such as chlorthalidone and hydrochlorothiazide increase urinary zinc excretion by as much as 60%, and prolonged use could deplete zinc tissue levels.
Whole grains and milk products are good sources of zinc.
Many breakfast cereals are fortified with zinc.
Dietary sources of zinc include: lean meats, poultry, fish, beans, eggs, and nuts, oysters, red meat, and poultry..
Baked beans, chickpeas, and nuts also contain zinc.