Zinc is an essential mineral that your body requires in small amounts for many functions. However, overuse of supplements over the long term, or in combination with zinc from other sources, could result in toxicity. Too much zinc in your system can have adverse health effects, including digestive disorders, mineral imbalances, loss of sense of smell or irreversible damage to your nervous system.
Why Your Body Needs Zinc
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- Immune function
- Protein synthesis
- Wound healing
- DNA synthesis
- Proper sense of taste and smell
- Cell division
How Much Do You Need?
Your body cannot store zinc, so you must maintain your requirements through your diet. The recommended daily allowance for zinc differs depending on age and gender.
- Children to 3 years of age, 3 milligrams; 4 to 8 years of age, 5 milligrams; 9 to 13 years of age, 8 milligrams
- Males, ages 14 and over, 11 milligrams
- Women, 14 to 18 years of age, 9 milligrams; age 19 and over, 8 milligrams
- Pregnant and lactating women, 11 to 13 milligrams
These values apply to total zinc intake from food, including fortified foods, water and supplements.
Read more: Maximum Zinc Doses
Risk of Zinc Deficiency
- Poor diet or being a vegan or vegetarian
- Digestive disorders, such as Crohn's, ulcerative colitis. chronic diarrhea or malabsorption syndrome
- Renal disease, sickle cell disease or chronic liver disease
Food Sources of Zinc
There are many food sources of zinc. Oysters contain more zinc than many other foods, with 74 milligrams per 3-ounce serving, supplying 494 percent of your daily value. Other top sources of zinc include:
- Meat: beef, pork, chicken
- Fish and seafood: flounder, crab, lobster
- Fortified foods: breakfast cereals
- Beans and legumes: baked beans, kidney beans, chickpeas, green peas
- Dairy products: yogurt, cheese, milk
- Nuts: almonds, cashews
Causes of Toxicity
Zinc overdose can result from too much zinc intake from the combination of food with various other sources. Overuse of zinc supplements and multivitamins, or high therapeutic doses of prescribed medicines, could cause zinc toxicity symptoms. Over-the-counter medications and homeopathic remedies can contain zinc. Accidental ingestion of household products that contain zinc could also cause zinc toxicity symptoms.
Linus Pauling Institute reports cases of zinc toxicity occurring from eating food or drinking beverages contaminated with zinc released from galvanized containers. Inhaling zinc oxide fumes has been known to cause metal fume fever. Symptoms of weakness, profuse sweating and rapid breathing can develop within eight hours after breathing in the fumes.
Read more: How to Reduce Zinc Toxicity
If you are at risk for a zinc deficiency and feel you could benefit from taking a supplement, use caution with the dosage. Zinc supplements are available in several forms, including gluconate, sulfate and acetate. Each type may have differences in absorption, tolerability and bioavailability.
If you are pregnant or have any medical conditions, consult your doctor before taking products containing zinc. It is not known if zinc will harm your unborn baby or if zinc sulfate passes into breast milk, warns Drugs.com.
The National Institutes of Health lists 40 milligrams of zinc to be the upper daily limit dose for adults. Its experts stress that long-term use above the recommended upper level increases your risk of adverse health effects and zinc toxicity symptoms.
Excess intake of zinc may result in side effects, with symptoms ranging from mild to life-threatening. Intake of 50 to 150 milligrams per day of supplemental zinc can cause minor gastrointestinal distress that may occur within three to 10 hours. Single doses of 225 to 450 milligrams of zinc usually induce vomiting. Other symptoms include:
- Severe dehydration
- A:bdominal cramps
Copper Deficiency and Iron Absorption
Long-term consumption of zinc in excessive amounts — 50 milligrams per day or more — can interfere with copper bioavailability. Zinc has a high affinity for binding with copper, including from food, and competes with copper for similar binding sites. Therefore, excessive zinc decreases uptake of copper into the blood, according to a 2013 study published by Advances in Nutrition. The study concluded that too much zinc can produce a chronic negative copper balance.
- Iron-deficiency anemia: Insufficient healthy red blood cells due to lack of iron in your body
- Neutropenia: A lack of white blood cells in your body due to an interference with their formation
- Leukopenia: A reduced number of white cells in the blood
Copper deficiency can also cause disorders of the nervous system, such as weakness and numbness in the legs and arms, according to Mayo Clinic.
A study published in the Journal of Clinical Pathology in 2015 shows evidence of the potential risk of copper deficiency being inadvertently and unwittingly caused by doctors prescribing too-high doses of zinc. Researchers discovered that 62 percent of patients in the study were prescribed zinc at doses sufficient to cause copper deficiency.
Excessive zinc can also cause a copper deficiency for denture wearers. If you use dental fixatives, be aware that some adhesive creams contain zinc, with levels ranging from 17 to 34 milligrams per gram. If you use excessive amounts of these products — two or more standard-sized tubes per week — zinc toxicity could result. Prolonged usage of these products may cause irreversible neurological damage, as shown in a 2017 Case Report by BMJ.
Loss of Sense of Smell
Some cold medications sold over the counter contain zinc. Although zinc lozenges may help with your sore throat, they can have side effects including nausea and a bad taste in your mouth. Some nasal gels or sprays containing zinc may not be safe and have been reported to cause the loss of your sense of smell. In some cases, this zinc side effect can be long-lasting or permanent. As a result, the FDA recalled many intranasal products from the marketplace to protect consumers from anosmia (loss of smell) associated with their use, according to National Institutes of Health.
Allergic Reaction to Zinc
Get emergency medical help if you have signs of an allergic reaction to zinc supplements, multivitamins, medications or due to accidental ingestion of zinc-containing household products:
- Blistered, red, swollen or peeling skin, with or without fever
- Wheezing or difficulty breathing or swallowing
- Tightness in the chest or throat
- Unusual hoarseness
- Swelling of the throat, mouth, face, lips or tongue
Some prescription drugs may negatively interact with zinc. Be sure to talk to your doctor before taking zinc supplements if you are on medication. Interactions that could have serious consequences when mixed with zinc, according to Drugs.com, include:
Antibiotics: Zinc taken with antibiotics, such as tetracycline or quinolone, can interfere with their ability to fight bacteria. To minimize the effect, take antibiotics two hours before, or four to six hours after, taking zinc.
Rheumatoid Arthritis Drugs: Penicillamine, taken in combination with zinc, can decrease the drug's effectiveness. Take zinc at least two hours before or after taking the drug.
Blood Pressure Drugs: Some blood pressure drugs are diuretics and increase the amount of zinc lost in urine.
- National Institutes of Health: Zinc
- Linus Pauling Institute: Zinc
- NutritionValue: Mollusks, Breaded and Fried, Cooked, Eastern, Oyster
- Drugs.com: Zinc
- Drugs.com: Zinc Side Effects
- Mayo Clinic: Zinc
- BMJ Journals: BMJ Case Reports: Zinc Containing Dental Fixative Causing Copper Deficiency Myelopathy
- University of Virginia: Considerations in the Copper Deficient Patient
- Journal of Clinical Pathology: The Risk of Copper Deficiency in Patients Prescribed Zinc Supplements
- Advances in Nutrition: Discovery of Human Zinc Deficiency: Its Impact on Human Health and Disease