The second most common trace mineral in the body, zinc, is essential for healthy human functioning. However, it's estimated that between 15 and 50% of the United States population does not have sufficient zinc levels. This article will discuss what zinc is, its function in the body, how to test for zinc, and how to ensure proper zinc levels.
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What is Zinc?
Zinc is the 23rd most abundant element in the earth's crust and is the world's fourth most produced metal, only behind aluminum, copper, and iron. Zinc has been used industrially to create rubber, brass, bronze, chemicals, paint, steel coatings, and more. Zinc is also essential for all forms of life.
What is Zinc's Role in The Body?
Zinc is required for many physiological functions. Zinc has the ability to affect growth and development, reproduction, and neurological, intestinal, and immune functioning. These effects result from zinc's catalytic, structural, and regulatory functions.
Catalytic Function
Zinc is required for the proper functioning of over 50 different enzymes.
Structural Role
Zinc is required to maintain the structure of receptors for hormones, such as estrogen and thyroid hormones, and vitamins, such as vitamin D and vitamin A. Without proper receptors, the actions that result from these hormones and vitamins would be non-existent.
Zinc is also required for the formation of the copper-zinc superoxide dismutase enzyme, a potent antioxidant. Improper formation of this enzyme has been implicated in hereditary amyotrophic lateral sclerosis (ALS).
Regulatory Functions
Through its actions on gene expression, zinc plays a role in the release of hormones and nerve cell communication.
Due to these cellular functions, zinc may be beneficial for depression and cognition, immunological functioning, type II diabetes, painful menstruation, acne, and age-related macular degeneration.
How to Test Zinc Levels
Zinc levels can be measured in the blood. Different lab companies offer a serum zinc test with normal levels ranging from 60-106 micrograms per deciliter (mcg/dL) in adults. High inflammation and high albumin levels, a protein tested for in a comprehensive metabolic panel (CMP), may affect serum zinc levels leading to an inaccurate measurement.
Access Medical Laboratory offers a zinc red blood cell (RBC) test, with levels ranging from 9.0 to 14.7 milligrams per liter (mg/L). An RBC zinc test may be more appropriate in suspected cases of chronic zinc deficiencies.
Since zinc and copper work so closely together, checking zinc and copper levels simultaneously may be advisable. Great Plains Laboratory offers a zinc and copper profile.
Additionally, zinc is a part of many micronutrient panels.
Zinc at 50mg or higher can inhibit the absorption of copper, leading to a copper deficiency and also causing lower HDL cholesterol levels and suppressed immune function. Extremely high intakes of zinc (142 mg per day) can lower magnesium absorption. Symptoms of high zinc intake include nausea, vomiting, stomach distress, headaches, dizziness, and loss of appetite. Dietary intake of zinc at these levels is rare. Rather, zinc supplementation and denture cream containing zinc is often the culprit of high zinc levels.
Zinc deficiency can manifest in various organs since it is so widely used, and symptoms seem to vary by age. In infants and children, zinc deficiency can cause low appetite, diarrhea, and slowed growth, leading to reproductive challenges in adulthood. Older children also experience hair loss and frequent illnesses. In countries with low animal protein intake, pregnant women are at an increased risk of maternal morbidity, and their children are at greater risk of morbidity and mortality. In older adults, zinc deficiency may impact cognitive and psychological functioning and cause a delay in wound healing. In all populations, zinc deficiency alters the senses of smell and taste. People with gastrointestinal disorders, those who have had bariatric surgery, pregnant and lactating women, people with alcoholism, and those who do not consume animal meat or products are at a greater risk of zinc deficiency. Additionally, infants six months or older who are exclusively breastfed are also at risk for a zinc deficiency due to a decline in zinc levels in breast milk.
How to Make Sure You Are Getting Enough Zinc
The National Academies of Science, Engineering, and Medicine created a Food and Nutrition Board that created Dietary Reference Intakes (DRI) for vitamin and mineral intake. The Recommended Dietary Allowance (RDA) is a DRI defined as the average daily intake required to reach nutritional adequacy in most healthy people. Adequate Intake (AI) is a DRI that is created when there is an insufficient amount of evidence to form an RDA. The AI measurement is defined as an amount assumed to reach nutritional adequacy.
RDA for Zinc
RDAs for pregnant and lactating women may differ since their nutritional needs are often higher. The RDA for pregnant women aged 14-18 is 12 mg and 11 mg for women aged 19+. The RDA for lactating women aged 14-18 is 13 mg and 12 mg for those aged 19+.
A 2 mg AI was established for male and female infants from birth to 6 months old.
Zinc sources include food, supplements, over-the-counter medicines, and denture creams.
Foods containing a Daily Value of 20% or more are considered to be high sources of zinc. Although zinc can be found in animal and plant products, animal products are superior for zinc absorption and utilization, as plant sources often contain phytates, which are structures that inhibit nutrient absorption.
Foods Containing 10% or more of the Daily Value of Zinc
Zinc Supplements
Zinc is found in most multivitamins and as a stand-alone vitamin. Zinc in supplements comes in many forms, including zinc citrate, zinc gluconate, and zinc oxide. The absorption rate of zinc citrate and gluconate is around 61%, whereas zinc oxide is around 50%. Zinc taken with 25 mg or more of elemental iron will lower zinc absorption.
Zinc Over-the-Counter Medicines
Zinc is found in nasal sprays, cold medicines, and lozenges.
Denture Creams
Denture adhesive cream products can contain anywhere from 17-34 mg/g, although the dose per use is around 0.5-1.5 g. However, these products can lead to excessive zinc levels if not used properly. This has led some manufacturers to produce zinc-free denture creams.
Personal Care Products
Personal care products such as sunscreens, cosmetics, and diaper creams may contain zinc, as it functions as a skin protectant or barrier. However, zinc in these products is in the form of zinc oxide, and the topical application of zinc is not readily absorbed and thus does not affect systemic levels.
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Summary
Zinc is an essential mineral for numerous processes in the body, ranging from hormones to immune function to inflammatory processes. Zinc testing can be useful to ensure proper levels of zinc, as both high and low amounts can lead to detrimental outcomes. Zinc sources are numerous, including food, supplements, healthcare products, and more. Knowing zinc levels can help utilize these sources to avoid over or under-nourishment of the mineral.
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