Can You Overdose on Zinc?

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    Zinc is an essential mineral that plays a role in over 300 enzymatic reactions in the body. However, too much zinc can cause adverse effects.

    Zinc is an essential mineral that plays a vital role in over 300 enzymatic reactions in the body, including immune system regulation, digestion, wound healing, and cell division. As a result, many people supplement with zinc to support these various aspects of their health. However, it is possible to have too much of a good thing when it comes to zinc consumption.

    While zinc does have some negative side effects when taken in large doses, it is difficult to overdose on the mineral. In this article, we will take a closer look at what can cause zinc toxicity and what may happen if you consume too much.

    What is Zinc Toxicity?

    Zinc is an essential mineral that performs various functions in the human body, including supporting the immune system, wound healing, and growth and development. The recommended dietary allowance (RDA) for zinc varies depending on age and gender. For instance, adult men need about 11 mg of zinc daily, while women require 8 mg. However, some people may take more than the RDA to reap additional health benefits. For instance, those following plant-based diets, those who are pregnant or breastfeeding, or individuals with malabsorption issues would likely require higher doses.

    Because of zinc’s role in immune system functioning, it is common for this mineral to be included in many supplement formulas including lozenges. The addition of zinc to immune supportive supplements is becoming more and more prevalent, as researchers have hypothesized that zinc could support immune responses by boosting T cells and other cytokines.

    Although zinc is available in many products, it is rare to reach toxicity, as the tolerable upper limit for this mineral is 40 mg. However, taking too much zinc over time can lead to toxicity symptoms such as nausea, vomiting, diarrhea, abdominal cramps, headaches, and loss of appetite.

    It's important to note that not all forms of zinc are created equal; some have higher bioavailability than others. Therefore, taking excessive amounts of supplements that contain highly bioavailable forms of zinc increases your risk of overdose even further. Absorption of zinc from supplements containing zinc citrate or zinc gluconate is around 61%, while absorption from supplements containing zinc oxide is around 50%.

    What Can Cause Zinc Toxicity?

    Zinc toxicity from food sources is highly unlikely and rare. On the other hand, zinc toxicity can occur as a result of excessive consumption of zinc supplements or from exposure to high levels of zinc in the environment, such as in occupational settings. For example, workers in industries such as mining and welding may be at increased risk of zinc toxicity due to frequent exposure to toxic fumes. Additionally, back in the day, zinc was used in denture adhesives, sometimes leading to excessive levels being used.

    However, the most common cause of zinc toxicity today is accidental ingestion of excess supplements. This could occur when individuals take high doses of zinc for an extended period of time. Zinc supplements come in various forms, such as tablets, lozenges, capsules, and syrups, so it is critical to follow the recommended dosage guidelines provided on the label.

    Symptoms of Zinc Toxicity

    Zinc toxicity is not very common and usually occurs as a result of excess supplementation or accidental ingestion of zinc-containing substances. The most common symptoms of zinc toxicity include stomach discomfort, alterations to taste and smell, and abnormal blood work. We will discuss each of these symptoms in more detail.

    Stomach discomfort

    Generally, overt toxicity symptoms of zinc can present mainly as digestive symptoms. Thus the main symptom of zinc toxicity is stomach discomfort. When you consume large amounts of zinc, it can lead to irritation in the digestive tract. This can cause nausea, vomiting, digestive discomfort, lethargy, and fatigue.

    You should always talk to your doctor about any new symptoms or health concerns, as zinc-related symptoms are broad and can be a sign of other underlying health issues, especially if they are persistent.

    Changes to taste

    Zinc is an integral element in the regulation of taste and smell. This is why it is no surprise that the toxicity of this mineral can lead to disruptions in taste. The metallic taste in the mouth is one of the most common symptoms of zinc toxicity. It is often described as a bitter or sour taste that lingers even after eating or drinking something else. If experiencing any chronic changes to taste or smell be sure to talk to your doctor as it may be a sign of other underlying health issues.

    Abnormal blood work

    One of the ways to confirm suspected zinc toxicity is by conducting laboratory tests at the physician's direction. Abnormal blood work can be a reliable indicator of zinc toxicity. Laboratory tests such as serum zinc levels and urine analysis can help confirm suspicions of toxic levels of the mineral in the body. Always be sure to communicate with your doctor and share an up to date list of current supplements and medications you may be taking.

    How Much Zinc is Too Much?

    The RDA for zinc in adults ranges from 8-11 mg per day. Of course, needs may vary from person to person depending on age, gender, and certain health conditions. It is important to remember that the tolerable upper intake level for adults is 40 mg. The Food and Nutrition Board established these upper limits for zinc from food and supplements, as levels ingested beyond this can interfere with the absorption of other important minerals, such as copper and iron.

    Copper and iron are both vital nutrients that play important roles in the body. Copper aids in the production of red blood cells, helps keep your immune system healthy, and supports nerve function. Iron plays a crucial role in oxygen transport throughout the body and supports cognitive function. When excessive levels of zinc are present in the body, they can compete with copper and iron for absorption sites within the intestines.

    This competition may result in reduced absorption rates for copper and iron, which can lead to deficiencies over time. Conversely, supplementing with both zinc and copper together will help maintain the proper balance in the body. Ideally, the ratio of zinc and copper should be 8:1.

    On a final note, many people tend to rely on zinc supplements to fulfill their daily requirement of zinc without realizing that they may not actually need it.

    If you are someone who consumes a balanced diet containing sufficient amounts of zinc-rich foods every day, then you may not need to take zinc supplements, unless there is a clinical deficiency present or your healthcare provider directs you to do so. Some of the highest zinc-containing foods include meat, fish, seafood, legumes, whole grains, and dairy products.

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    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
    Jordana Tobelem, RD
    Freelance Contributor
    Jordana Tobelem is a Registered Dietitian who enjoys helping others become the best versions of themselves through proper nutrition education. Jordana is passionate about promoting lifestyle changes through nutrition, physical activity, and behavior to create a superior quality of life. She uses her experience in the clinical field of dietetics to provide consulting services to an array of healthcare brands and companies. Jordana loves finding the most current research in nutrition to create meaningful content to share with her clients. Jordana has been a member of the Academy of Nutrition and Dietetics since 2018 and also holds certifications in both Personal Training and Health Coaching.