Zinc: Reference and Dietary Sources

Abstract

In this article, we describe:

  • the major purposes of this specific nutrient in the human body, 
  • its experimentally confirmed health uses, 
  • conventional ways to estimate nutrient status,
  • nutrient’s toxicities and deficiencies,
  • experimentally confirmed and approved levels of the nutrient intake for different demographics,
  • dietary sources of the nutrient.

Introduction

Zinc is an essential mineral that is involved in numerous aspects of cellular metabolism. It is required for the catalytic activity of approximately 100 enzymes, and plays a role in immune function, protein synthesis, wound healing, DNA synthesis, and cell division. Zinc also supports normal growth and development during pregnancy, childhood, and adolescence and is 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.

Blood plasma can provide accurate zinc status reading. Other tests for zinc deficiency include a urine test and an analysis of a strand of the hair to measure the zinc content.

Zinc deficiency is characterized by growth retardation, loss of appetite, and impaired immune function. Many of deficiency symptoms are non-specific and are often associated with other health conditions; therefore, a medical examination is necessary to ascertain whether a zinc deficiency is present. 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 for zinc. People at risk of zinc deficiency or inadequacy (those with gastrointestinal and other diseases, vegetarians, pregnant and lactating women, older infants who are exclusively breastfed, people with sickle cell disease, and alcoholics) need to include good sources of zinc in their daily diets. Supplemental zinc might also be appropriate in certain situations.

Severe zinc deficiency depresses immune function, and even mild to moderate degrees of zinc deficiency can impair macrophage and neutrophil functions, natural killer cell activity, and complement activity leading to increased susceptibility to pneumonia and other infections. Individuals 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. Other health conditions affected by in inadequate zinc status are wound healing, diarrhea, common cold, and age-related macular degeneration.

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Higher zinc intakes can inhibit copper absorption, sometimes producing copper deficiency and associated anemia. Fortification of foods with iron does not significantly affect zinc absorption. However, large amounts of supplemental iron (greater than 25 mg) might decrease zinc absorption.

Zinc toxicity can occur in both acute and chronic forms. 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 of approximately 60 mg/day for up to 10 weeks. The doses of zinc 80 mg per day of zinc in the form of zinc oxide for 6.3 years, on average, have been associated with a significant increase in hospitalizations for genitourinary causes, raising the possibility that chronically high intakes of zinc adversely affect some aspects of urinary physiology.

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Recommended Dietary Allowances (RDAs) for Zinc

AgeMaleFemalePregnancyLactation
0–6 months2 mg*2 mg*
7–12 months3 mg3 mg
1–3 years3 mg3 mg
4–8 years5 mg5 mg
9–13 years8 mg8 mg
14–18 years11 mg9 mg12 mg13 mg
19+ years11 mg8 mg11 mg12 mg

* Adequate Intake (AI)

Dietary Sources of Zinc

Red meat and poultry provide the majority of zinc in the Western diet. Oysters contain more zinc per serving than any other food. Other food sources include beans, nuts, certain types of seafood (such as crab and lobster), whole grains, fortified breakfast cereals, and dairy products.

Phytates—which are present in whole-grain breads, cereals, legumes, and other foods—bind zinc and inhibit its absorption. Thus, the bioavailability of zinc from grains and plant foods is lower than that from animal foods, although many grain- and plant-based foods are still good sources of zinc.

Selected Food Sources of Zinc

FoodMilligrams (mg)
per serving
Percent DV*
Fried breaded oysters, 3 ounces74.0673
Braised beef chuck roast, 3 ounces7.064
King Alaska crab, cooked, 3 ounces6.559
Broiled beef patty, 3 ounces5.348
Cooked lobster, 3 ounces3.431
Cooked pork chop (loin), 3 ounces2.926
Canned baked beans, ½ cup2.926
Breakfast cereal, fortified with 25% of the DV for zinc, 1 serving2.825
Cooked chicken (dark meat), 3 ounces2.422
Dried pumpkin seeds, 1 ounce2.220
Fruit yogurt, 8 ounces1.715
Dry roasted cashews, 1 ounce1.615
Cooked chickpeas, ½ cup1.312
Swiss cheese, 1 ounce1.211
Oatmeal cooked with water, 1 packet1.110
Milk, 1 cup1.09
Dry roasted almonds, 1 ounce0.98
Cooked kidney beans, ½ cup0.98
Roasted chicken breast, no skin, ½ breast0.98
Cheese (cheddar or mozzarella), 1 ounce0.98
Green peas, cooked, ½ cup0.55
Cooked fish filet (flounder or sole), 3 ounces0.33
  • DV* = Daily Value.
  • The DV for zinc used here is 11 mg for adults and children age 4 years and older.
  • Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.

References

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