Zinc

Zinc2018-06-14T08:01:55+00:00

Are You Getting Enough Zinc?

Zinc is a trace element and an essential micronutrient for humans. Essential micronutrients are vitamins and minerals that are required in small amounts by the body for optimal health. Since the body is unable to synthesize these micronutrients, a dietary source is necessary.

Early during digestion, zinc ions present in food release and then are absorbed in the small intestine. About 70% of zinc in circulation is bound to the blood protein albumin. Any conditions that alter the albumin concentration, therefore, have a secondary effect on the body’s zinc levels.1 Low albumin levels occur in conditions in which the body does not properly absorb and digest protein, such as Crohn’s disease or celiac disease, or in diseases where large volumes of protein are lost through diarrhea. The liver synthesizes albumin, so any form of liver inflammation or disease can also negatively affect zinc levels.

Approximately half of all the zinc eliminated from the body occurs through the gastrointestinal tract.1 Some pancreatic secretions are high in zinc, including insulin. Certain gastrointestinal diseases and disorders such as ulcerative colitis, Crohn’s disease, and short bowel syndrome can increase the likelihood of zinc deficiency. Symptoms of both ulcerative colitis and Crohn’s disease usually involve diarrhea and abdominal pain. Because increased motility decreases the success of digestion and absorption, severe diarrhea can result in malabsorption of all nutrients, including zinc. Attempting to avoid disease symptoms associated with eating might also influence the quantity of food individuals are willing to consume, which further increases their risk of deficiencies.

Researchers have found that zinc-deficient animals require 50% more food to obtain the same weight gain as an animal with adequate amounts of zinc.2 They suggest that humans might react to zinc deficiency in a similar way.

What Does Zinc Do?3

  • assists in the activity of numerous enzymes
  • essential to immune function and wound healing
  • aids in DNA synthesis and reproductive development
  • maintains sense of taste and smell
  • regulates insulin production, storage, and release
  • helps produce the active form of vitamin A
  • assists in thyroid function

Zinc in the Body

Zinc is present in all organs, tissues, fluids, and secretions in the body, but the majority of zinc (83%) is present in skeletal muscle and bone.4 When zinc intake is insufficient, levels within skeletal muscle, skin, and heart are maintained, while zinc levels in bone, liver, testes, and plasma decline. More than 100 specific enzymes require zinc for their catalytic function.2 The body is not able to store excess zinc, so continuous dietary intake is required.

Deficiency Diagnosis

It is difficult to measure a person’s zinc status accurately because of the element’s distribution throughout the body. Before making a diagnosis, clinicians consider the person’s risk factors (such as inadequate caloric intake and the presence of digestive diseases), the presenting symptoms of zinc deficiency, and the results of specific laboratory tests (blood and/or urine) to determine zinc status. Depending on the severity of the deficiency, a health professional may recommend zinc supplementation at levels higher than the recommended dietary allowance. All individuals should consult with his or her own physician before taking any new supplements.

Signs of Zinc Deficiency2,5

  • loss of appetite
  • impaired immune function
  • hair loss
  • delayed sexual maturation
  • weight loss
  • delayed healing of wounds
  • taste abnormalities
  • mental lethargy
  • impaired growth and development of infants, children and adolescents
  • increased prevalence and incidence of childhood infections, such as diarrhea and pneumonia, which may result in increased rates of mortality
  • impaired maternal health and pregnancy outcomes

Sources of Zinc

Diet: Zinc occurs in different concentrations in a wide variety of foods. Animal-based foods have especially high concentrations, particularly in the organs and flesh of beef, pork, poultry, fish and shellfish (oysters contain more zinc per serving than any other food!), and lesser amounts in eggs and dairy products.5 Beans, nuts, and fortified breakfast cereals are other common sources of zinc in the North American diet.

Supplements: Zinc is also available as a dietary supplement on its own or as part of a multivitamin. Different forms commonly found in supplements include zinc gluconate, zinc sulfate, and zinc acetate, which vary in the quantity of elemental zinc. The standard ingredient labels for dietary supplements provide the name of the form of zinc in the product (e.g., zinc [as zinc sulfate]) and the amount of elemental zinc in milligrams.6

Medicinal Products: Zinc is a common ingredient in many over-the-counter products, including throat lozenges, lotions, and nasal sprays.

Zinc Content in Foods4

Food Zinc mg/100 g
Liver, kidney (beef, poultry) 4.2-6.1
Meat (beef, pork) 2.9-4.7
Poultry (chicken, duck, etc.) 1.8-3.0
Seafood (fish, etc.) 0.5-5.2
Eggs (chicken, duck) 1.1-1.4
Dairy (milk, cheese) 0.4-3.1
Beans, lentils (soy, kidney bean, chickpea, etc.) 1.0-2.0
Whole-grain cereal (wheat, maize, brown rice, etc.) 0.5-3.2
Vegetables 0.1-0.8
Fruits 0-0.2

 

Overt human zinc deficiency in North America is not common. The Recommended Dietary Allowance (RDA) for adults set by Health Canada is 8mg/day for women and 11mg/day for men.7

 


First published in the Inside Tract® newsletter issue 177 – 2011
Image credit:  © Dan Tera | iStockphoto.com
1. Saper R. Zinc: An Essential Micronutrient. American Family Physician. 2009;79(9): 768-772.
2. Jackson MJ et al. Tissue zinc levels as an index of body zinc status. Clin Physiol. 1982;2:333-43.
3. Nutrition 101: Zinc page. Healthcastle. Available at: http://www.healthcastle.com/nutrition101_zinc.shtml. Accessed 2011-03-28.
4. Chapter 1 Overview of Zinc Nutrition. Food and Nutrition Bulletin. The United Nations University. 2004; 25(1):S99-S129.
5. Zinc: Health Professional Fact Sheet page. National Institute of Health Office of Dietary Supplements. Available at http://ods.od.nih.gov/factsheets/Zinc_pf.asp. Accessed 2011-03-28.
6. Saper R. Zinc: An Essential Micronutrient. American Family Physician. 2009;79(9): 768-772.
7. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. The National Academies Press. Available at: http://www.nap.edu/catalog.php?record_id=10026. Accessed 2011-03-28.