By Mary Ellen Posthauer RDN, CD, LD, FAND
Function/Recommended Dietary Allowance:
Zinc is an essential trace mineral for DNA synthesis, cell division, collagen formation, protein synthesis, and immune function - all necessary processes for tissue regeneration and wound repair. Zinc is necessary to develop and activate T-lymphocytes, which are important for the immune system. Alterations in immune function increase the risk of infection, especially in the elderly and the very young.
The current Recommended Dietary Allowance (RDA) of zinc for healthy adults is 11 mg for males and 8 mg for females. Zinc is abundant in protein-rich foods such as red meat, shellfish, dairy products, nuts, cereals, and whole grains. The bioavailability of zinc from plant foods, such as grains and legumes, is lower than in animal foods, due to the phytates in grains that bind zinc, inhibiting its absorption. Food product labels list the Daily Value (DV) of nutrients to assist consumers in comparing the nutritional content of products. If a food product has 20% or more of the DV for zinc, it will be listed on the label. The DV for zinc is 15 mg, so if the label on an eight-ounce commercial supplement lists 25% of the DV for zinc, it contains 4 mg.. Some protein supplements, ordered as part of a wound care treatment plan, have the milligrams of zinc listed on the labels (i.e. 10 mg zinc).
Symptoms of zinc deficiency include growth retardation, loss of appetite, and impaired immune function. Loss of hair, eye and skin lesions, diarrhea, weight loss, and changes in taste and smell may also be apparent. These symptoms are also noted in other disease states, making it difficult to link the symptoms to zinc deficiency.
Overt zinc deficiency is not common in North America, but there are certain conditions that increase the risk such as absorption problems, increased zinc losses from the body, or inadequate zinc intake. Individuals with digestive disorders, such as Crohn’s disease or short bowel syndrome, have decreased zinc absorption and increased loss in the GI tract. Zinc losses can occur with alcoholism, chronic liver and chronic renal disease, malabsorption problems, malignancies, and diabetes. Chronic diarrhea, large draining wounds, and chest tubes can also lead to zinc losses.
NHanes III data indicated that 35-45% of adults 60 and older have a below average intake of zinc. Factors such as the inability to purchase nutritious food, coupled with the inability to chew meat leads to low zinc intake in this population.
While zinc has been hypothesized to promote wound healing, the research to support daily doses of elemental zinc without a confirmed deficiency is lacking. Plasma and serum zinc are the commonly used laboratory tests to assess zinc status. Due to the wide distribution of zinc throughout the body (as a component of protein and nucleic acid), these tests don’t reflect zinc status. Hence, zinc deficiency is difficult to diagnose. Some wound care protocols recommend a daily zinc supplement with elemental zinc, such as zinc sulfate or zinc gluconate, to accelerate wound healing. 220 mg of zinc sulfate has 50 mg of elemental zinc. The Tolerable Upper Intake Level (UL), defined as the maximum daily intake unlikely to cause adverse health effects, is 40 mg. 220 mg of zinc sulfate bid provides 100 mg of elemental zinc, which is 60 mg over the UL for the mineral. Copper is responsible for collagen cross-linking, and high zinc levels may inhibit copper metabolism - resulting in copper deficiency and anemia. The 2009 NPUAP/EPUAP nutrition treatment guidelines for pressure ulcers recommends consumption of a balanced diet and offering a multivitamin/minerals when an individual has a poor appetite, or suspected/confirmed zinc deficiency. If zinc supplements are considered, the order should include a time limit for administration, and tolerance should be monitored. Nausea, vomiting, diarrhea, headaches, and cramps are some symptoms of zinc toxicity.
- Assessment by the healthcare team should include consultation and collaboration with the registered dietitian (RD)
- RD should evaluate approximate zinc intake from meals and oral nutritional supplements
- Honor individuals’ food choices and preference to improve intake
- Recommend a vitamin/mineral supplement when oral intake is poor or deficiency is suspected
- Monitor acceptance of oral nutritional supplements
Wintergrest E S, Maggini S, Horning DH; Contribution of selected vitamins and trace elements to immune function. Ann Nutr Metab 2007; 51: 301-23
Institute of Medicine, Food and Nutrition Board Daily Reference Intakes for: Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, D.C. National Academy Press. 2001.
National Pressure Ulcer Advisory Panel and European Pressure Ulcer Advisory Panel. Prevention and treatment of pressure ulcers: clinical practice guideline. Washington DC: NPUAP; 2009.
About The Author
Mary Ellen Posthauer RDN, CD, LD, FAND is an award winning dietitian, consultant for MEP Healthcare Dietary Services, published author, and member of the Purdue University Hall of Fame, Department of Foods and Nutrition, having held positions on numerous boards and panels including the National Pressure Ulcer Panel and the American Dietetic Association’s Unintentional Weight Loss work group.
The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, Kestrel Health Information, Inc., its affiliates, or subsidiary companies.