Zinc Functions

Zinc is an essential trace element required by almost every biological process in the human body including growth and development, immune function, wound healing, protein and DNA synthesis, and cell division. It is used in over 300 enzymatic reactions, serves as an anti-inflammatory and an antioxidant, and is important for sight, hearing, and taste.

The system-wide ubiquity of zinc increases the clinical importance of detecting and supporting a deficiency when present. Unfortunately, it is frequently underutilized in clinical practice. Gaining a deeper understanding of the many roles zinc plays in human health, learning the appropriate methods for assessing deficiency, reviewing which conditions may benefit from supplementation with zinc, along with supplementation guidelines and recommendations will increase the clinician’s confidence in the appropriate use of zinc with patients.

Zinc Select

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Causes of Zinc Deficiency

The most common reasons for a zinc deficiency are increased losses of zinc, increased requirements for zinc, inadequate dietary intake, or reduced bioavailability/absorption of zinc. Increased losses can come from gastrointestinal diseases, surgery, trauma, oral contraceptives, and zinc lost in ejaculate with excessive sex. The requirement for zinc increases during periods of rapid growth, pregnancy, and lactation. Common examples of inadequate dietary intake include teenagers and college students as well as individuals following plant-based diets. Diets high in fiber are also rich in phytates which inhibit absorption.

Dietary factors, such as the consumption of alcohol or following a vegetarian/vegan diet, can impair zinc absorption. Decreased absorption increases the risk for deficiency. Plant-based diets and diets high in seeds, legumes, and unprocessed whole grains contain phytates that bind with zinc, inhibiting its absorption. Soaking, sprouting, and/or fermenting can reduce the phytic acid content of these foods, increasing the bioavailability of zinc. It has been shown that the process of sour leavening to make sourdough bread reduced the phytate content by ~ 25% and increased the rate of zinc absorption by 30-50%.

Other dietary factors that reduce the absorption rate include coffee, calcium in dairy products, increased fiber intake from fruits and vegetables, and a high fat diet (> 100g/day) in those with fat malabsorption issues. Deficiency can also be present in those with gastrointestinal issues that impair absorption such as Celiac disease, Crohn’s disease, or bypass surgery, and in those with hypochlorhydria (commonly seen with aging).

Assessment of Zinc Status

Laboratory Assessment

A zinc deficiency is not always easy to recognize. It can manifest as a variety of symptoms and routine laboratory testing does not provide a reliable indicator of zinc status. Low plasma stores of zinc (~0.1%) cause the standard blood test for plasma zinc concentrations to lack sensitivity and specificity, making it unreliable as a marker of deficiency. Therefore, an assessment of zinc status and a diagnosis of deficiency is largely based on clinical findings.

Clinical Zinc Assessment

Zinc homeostasis is primarily regulated by the amount of zinc in the diet. Clinical evaluation should include a detailed review of the patient’s dietary eating patterns to determine if a deficiency is likely. The physical examination may reveal white spots on their fingernails and/or patches of dry skin. The patient history should be reviewed for associated conditions or medications known to cause impaired zinc absorption and a therapeutic trial of zinc may be recommended in those instances.

A Zinc Taste Test provides a quick and inexpensive evaluation of zinc levels that can be conducted during the office visit. This test is not completely reliable due to the dependence on individual variances in self...