Zinc is an essential mineral that plays many important roles in the body. It is involved in immune function, protein synthesis, DNA synthesis, and cell division. Many people take zinc supplements to prevent or treat colds, boost immunity, improve wound healing, treat diarrhea, or for overall health.
While zinc is safe for most people when taken in recommended dosages, there are some circumstances where zinc supplements should be avoided or used with caution. This article will provide an overview of when zinc supplementation may be inappropriate and the potential risks involved.
If You Have Too Much Zinc in Your System
Getting too much zinc can happen in a few different ways:
Taking High Doses of Zinc Supplements
The recommended daily intake for zinc is 8-11 mg for adults. Doses up to 40 mg per day are considered safe for most adults. However, consistently exceeding 40 mg per day over an extended period can result in zinc toxicity.
Symptoms of zinc toxicity include:
- Nausea
- Vomiting
- Loss of appetite
- Abdominal cramps
- Diarrhea
- Headaches
In severe cases, very high zinc intakes over 150 mg per day can cause anemia, neutropenia (low white blood cell count), copper deficiency, impaired immune function, and potentially permanent nerve damage.
Therefore, zinc supplements should be used cautiously and not exceed 40 mg per day unless under medical supervision. The upper limit is lower for infants and children based on weight.
High Zinc Levels From Other Supplements
Some other supplements like nasal sprays and lozenges may also provide zinc. Multivitamins can contain zinc as well. Consuming these types of zinc-containing products in addition to zinc supplements may lead to excessive zinc intake if total doses are not monitored.
Eating Large Amounts of Foods High in Zinc
It is also possible, although rare, to get excessive zinc from food sources alone. Foods highest in zinc include:
- Oysters
- Red meat
- Poultry
- Beans
- Nuts
- Whole grains
- Dairy products
Eating very large portions of these foods in addition to taking supplements may result in too much zinc. However, this scenario is unlikely, as zinc toxicity from food is very rare.
If You Have Zinc Malabsorption
Certain health conditions can impair the body’s ability to absorb zinc from supplements and food. In these cases, high doses of zinc may build up and cause toxicity.
Conditions linked to zinc malabsorption include:
- Inflammatory bowel disease (IBD)
- Malabsorption syndromes
- Short bowel syndrome
- Gastric bypass surgery
People with these conditions should consult a doctor before taking zinc supplements and follow recommended dosages carefully.
If You Have Liver or Kidney Disease
The liver helps regulate zinc levels in the body. People with liver disease like hepatitis or cirrhosis may not be able to properly metabolize and excrete excess zinc.
Kidney disease can also impair zinc excretion leading to buildup. People with impaired liver or kidney function should avoid zinc supplementation unless approved by a doctor.
If You Have an Immune Disorder
High levels of zinc can suppress the immune system. People with immunodeficiency disorders like HIV/AIDS should avoid zinc doses over 40 mg per day.
If You Are Pregnant or Breastfeeding
Zinc is important for fetal development. However, excessive zinc is linked to adverse effects in pregnancy.
The recommended dosage for pregnant women is 11 mg per day. Doses over 40 mg per day may increase the risk of preterm birth and other complications.
For women who are breastfeeding, up to 40 mg per day is considered safe. High doses may cause deficiency in the infant.
If You Have Cancer
Very high zinc intake may potentially interfere with absorption of copper and iron, which can be problematic for those undergoing chemotherapy or radiation treatments for cancer.
People with cancer should stick to recommended intakes and avoid exceeding 40 mg per day unless approved by their oncologist.
If You Are Taking Certain Medications
Some medications can interact with zinc and increase the risk of excessive buildup and toxicity. Medications that may interact with zinc include:
- ACE inhibitors for blood pressure
- Antibiotics like ciprofloxacin and tetracycline
- Diuretics or “water pills”
- Calcium channel blockers for blood pressure
Check with your pharmacist or doctor about potential zinc interactions with any medications you take.
When Zinc Should be Avoided Entirely
In limited circumstances, zinc supplementation should be avoided entirely:
- With Wilson’s disease, a genetic disorder causing copper toxicity
- If you have had a recent organ transplant
- If you have recurring kidney stones
Zinc can exacerbate copper accumulation in Wilson’s disease. It also suppresses the immune system, which is problematic after organ transplants. High zinc intake is also linked to reduced kidney stone risk in those prone to recurrence.
The Bottom Line
Zinc is an important mineral that plays many roles in supporting health when taken in recommended amounts. However, zinc can build up and become toxic if you:
- Take high supplement doses over 40 mg per day
- Have a condition that impairs zinc absorption or excretion
- Are taking medications that interact with zinc
To avoid negative effects, do not exceed the tolerable upper intake level of 40 mg per day from supplements unless approved by a doctor. Also, consult your physician about zinc if you have liver or kidney disease, an immune disorder, or take medications known to interact with zinc.
While zinc toxicity is rare if supplement dosages are monitored carefully, excess zinc can potentially cause uncomfortable or dangerous side effects. Being aware of the situations where zinc supplementation is inappropriate allows you to maximize the benefits of this mineral while avoiding adverse risks.
References
- National Institutes of Health Office of Dietary Supplements. Zinc Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
- Mayo Clinic. Zinc. https://www.mayoclinic.org/drugs-supplements-zinc/art-20366112
- European Food Safety Authority. Tolerable Upper Intake Levels for Vitamins and Minerals. Parma, Italy: European Food Safety Authority; 2006.
- Roohani N, Hurrell R, Kelishadi R, Schulin R. Zinc and its importance for human health: An integrative review. J Res Med Sci. 2013;18(2):144-157.
- Fosmire GJ. Zinc toxicity. Am J Clin Nutr. 1990;51(2):225-227. doi:10.1093/ajcn/51.2.225
- Willis MS, Monaghan SA, Miller ML, et al. Zinc-induced copper deficiency: a report of three cases initially recognized on bone marrow examination. Am J Clin Pathol. 2005;123(1):125-131. doi:10.1309/V6H7-LYGY-J3RT-RPXB
