Zinc deficiency is more common than you might think! Severe forms may result in delayed growth, loss of appetite, and other potentially serious consequences. Luckily, it’s easy to meet your daily zinc needs with foods and supplements. Read on to learn all about zinc deficiency, sources, side effects, dosage, and more.
Sources of Zinc
Food Sources
In the United States, pulses and cereals provide about 30%, meat about 50%, and dairy products about 20% of dietary zinc [1].
Zinc-rich food include [2, 3, 4]:
- Red meat,
- Poultry
- Seafood (oysters, crab, lobster)
- Eggs
- Beans
- Nuts
- Whole grains
- Fortified cereals
- Dairy products
Although whole-grain breads, cereals, and legumes contain phytates that decrease zinc absorption, they are still good sources of zinc [5].
Supplements
A number of different forms of zinc are available as supplements, including citrate, sulfate, gluconate, orotate, oxide, picolinate, and acetate [6, 7].
The percentage of elemental zinc varies by form. In general, organic zinc salts such as citrate and acetate have better absorption, compared with zinc oxide [6, 7].
Zinc is generally supplemented in:
- proven zinc deficiency and zinc-losing conditions
- acrodermatitis enteropathica and Wilson’s disease [8, 9]
- acute diarrhea in children in developing countries [10]
- pneumonia and malaria [11]
Zinc Daily Needs and Dosage
General doses may not apply to you personally. If your doctor suggests supplementing with zinc, work with them to find the optimal dosage according to your health condition and other factors.
The Recommended Dietary Allowance (RDA) for zinc (according to the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies) [12]:
| Age | Male | Female | Pregnancy | Lactation |
| 0–6 months | 2 mg* | 2 mg* | ||
| 7–12 months | 3 mg | 3 mg | ||
| 1–3 years | 3 mg | 3 mg | ||
| 4–8 years | 5 mg | 5 mg | ||
| 9–13 years | 8 mg | 8 mg | ||
| 14–18 years | 11 mg | 9 mg | 12 mg | 13 mg |
| 19+ years | 11 mg | 8 mg | 11 mg | 12 mg |
Optimal zinc dosage may vary based on the individual. As a general rule, 15 mg a day is considered a preventative dosage, while higher doses up to 30 mg may be needed to correct a deficiency.
The Tolerable Upper Intake Level (UL), the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals, for adults is 40 mg/day.
Zinc Deficiency
Around 10% of persons in the United States have a dietary intake of less than half the RDA of zinc, while over 50% of persons in the third world countries are zinc deficient [13].
1.4% of deaths worldwide are associated with severe zinc deficiency in childhood [14].
Zinc deficiency is characterized by delayed growth, loss of appetite, lethargy, impaired immune function and susceptibility to infection [15, 16, 17].
In more severe cases, zinc deficiency causes hair loss, diarrhea, impaired taste acuity, weight loss, delayed sexual maturation, impotence, testosterone deficiency (hypogonadism) in males, and eye and skin lesions [15, 16, 17].
Groups at risk for zinc deficiency include [18, 19]:
- People with digestive disorders
- Vegetarians
- Pregnant and lactating women
- Alcoholics
- People with sickle cell disease
Causes
1) Inadequate Intake
Zinc deficiency may be caused by an inadequate intake of zinc from the diet [14, 20].
Vegetarians have an increased risk of zinc deficiency because they do not eat meat (high in zinc and may enhance zinc absorption). Their diet is typically rich in legumes and whole grains, but these foods contain phytates that bind zinc and inhibit its absorption [21, 22].
In developing countries, inadequate zinc intake can occur due to malnutrition.
2) Inadequate Absorption
Several diseases of the digestive system could cause inadequate zinc absorption, including:
- acrodermatitis enteropathica [23, 24]
- sprue [25]
- cystic fibrosis [26, 27]
- inflammatory bowel diseases (Crohn’s disease) [28, 29, 30]
- short bowel syndrome [31]
Another cause of low iron absorption in the gut is a high intake of food substances that inhibit zinc absorption, such as:
3) Increased loss
Increased zinc loss may occur due to:
- prolonged diarrhea [14, 20]
- kidney diseases [34]
- liver cirrhosis [35, 36, 37]
- alcoholism [38, 39]
- prolonged bleeding (intestinal parasites and heavy menstrual bleeding) [40]
- chronic inflammatory diseases that increase IL-1 [41, 42]
- hemolytic anemias such as sickle cell disease and thalassemia [43, 44]
- excessive sweating and exercise [45, 46]
- type I and type II diabetics [47, 48, 49]
Zinc Overload
Zinc overload is uncommon but it can occur due to an overdose or toxic overexposure to zinc [50].
Consumption of food or beverages contaminated with zinc released from galvanized containers may also lead to zinc toxicity [51].
Acute adverse effects of high zinc intake (ingesting more than 200 mg/day of zinc) include cramps, nausea, vomiting, diarrhea, loss of appetite, and headaches [52, 53].
“Zinc shakes”, also known as “zinc chills” or “metal fume fever”, are caused by intense inhalation of fresh industrial fumes containing zinc oxide, and presented as fever, chills, cough, chest pain, and abdominal discomfort [54, 55].
Prolonged intake of supplemental zinc at doses of 50-300 mg/day can lead to copper and iron deficiency, reduced immune function, and toxicity to the nervous system [56, 57, 58, 53].
It may also lead to an increase in low-density lipoprotein (LDL) cholesterol and a decline in high-density lipoprotein (HDL) cholesterol, altered heart function, and impaired pancreatic enzymes [55].
Long-term supplementation with doses over 100 mg/day of zinc increased the relative risk of prostate cancer almost 3 fold due to the immunosuppressive effect of zinc [59].
Lab Tests for Zinc Status
Low or high levels of zinc don’t necessarily indicate a problem if there are no symptoms or if your doctor tells you not to worry about it. Discuss your lab results with them.
The assessment of zinc status is difficult and challenging because there are no sensitive and specific biomarkers to detect zinc deficiency in humans.
Dietary and medical history and physical examination may all lead to a proper diagnosis.
Laboratory assays for measurement of zinc status:
1) Blood Zinc
Plasma/serum Zinc Concentrations
Normal values for plasma/serum zinc range from 10.7-23.0 µmol/L [60].
Blood zinc concentration, which represents <0.2% of total body zinc content, is the most frequently measured biomarker of zinc status [61, 62].
Blood zinc is a useful indicator of the size of the exchangeable zinc pool located in the bone, liver, and blood [63].
Reductions in dietary zinc beyond the capacity to maintain balance lead to the utilization of zinc from this pool which leads to the rapid onset of both metabolic and clinical signs of zinc deficiency [63].
Plasma zinc concentration also changes in response to stress, infection, meals, short-term fasting, and the hormonal state [64, 65, 66].
White Blood Cell Zinc Concentration
White blood cell (neutrophil) zinc reflects levels of tissue zinc accurately, and is thus a very useful parameter of zinc status [60, 67].
Zinc in the red cells may also be used for assessment of body zinc but the zinc levels do not reflect recent changes with respect to body zinc stores [60].
Oral Zinc Tolerance Test
The oral zinc tolerance test measures the increase in blood zinc caused by oral ingestion of 25 or 50 mg zinc acetate. The test is quite variable among subjects [60].
This test has also been used to assess the effects of different foods, meals, vitamin and mineral supplements, diseases and medications on zinc absorption [68].
Metallothionein
Metallothionein is a protein found in most tissues, particularly in the liver, pancreas, and kidney, and binds zinc and copper [60].
Metallothionein can also be detected in the plasma and red blood cells, and both clearly indicate whether an individual is zinc-deficient because they reflect recent changes in dietary zinc [63].
Possibly, metallothionein concentrations will also prove to be a useful indicator of changes in dietary zinc [69].
2) Urinary Zinc
Levels of zinc in the urine usually range from 0.3-0.6 mg/day [70].
The measurement of zinc in a 24-hr urine sample is helpful for diagnosing zinc deficiency in healthy individuals. Urinary excretion of zinc is decreased as a result of zinc deficiency [71].
Many diseases such as cirrhosis of the liver, sickle cell disease, chronic kidney disease, burns, and starvation, are characterized by excessive urinary zinc excretion, thus these conditions should be eliminated [70, 72].
3) Hair Zinc
Hair zinc levels of less than 1.07 µmol/g probably reflect a chronic suboptimal zinc status in children. The validity of the hair zinc level as an indicator of chronic suboptimal zinc status in adults remains uncertain [60, 73].
Hair zinc analysis cannot be used in cases of severe zinc deficiency or malnutrition because the rate of hair growth is decreased in malnourished patients. In such cases, hair zinc concentrations may be normal or even high [74, 70].
Hair zinc concentrations vary with hair color, season, sex, age, anatomical site of sampling and rate of hair growth. These factors must be considered when interpreting hair zinc concentrations [70].
4) Taste Acuity
Diminished taste acuity (hypogeusia) is a symptom of zinc deficiency, and it has been used as a functional test of zinc status (75).
In a taste acuity test, solutions of varying concentrations of the four different taste qualities (salt, sweet, bitter, and sour) are used. The test is based on the detection and recognition thresholds for each taste quality [60].
Zinc taste tests should be performed midmorning, at least 2 h after a meal, and by the same person on each occasion [70].
Zinc Side Effects
This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada, you may report side effects to Health Canada at 1-866-234-2345.
Generally, zinc supplements are safe and well tolerated in adequate amounts.
Short term effects of zinc toxicity include nausea, vomiting, diarrhea, headaches, stomach cramps, loss of appetite, and irritability [12].
Long term effects of high zinc intake (150 – 450 mg/day) have been linked to copper deficiency, impaired iron function, depressed immunity, and low levels of high-density lipoproteins (HDL) [12, 76].
Zinc supplements are likely safe for children and pregnant women, too, but they should consult with their doctors before supplementing.
Interactions With Medications
Nutrient-drug interactions can be dangerous and, in rare cases, even life-threatening. Always consult your doctor before supplementing and let him know about all drugs and supplements you are using or considering.
1) Penicillamine
Zinc can reduce the absorption and effectiveness of penicillamine, a drug used to treat rheumatoid arthritis and Wilson’s disease. Zinc and penicillamine should be taken at least 2 hours apart [77].
2) Antibiotics
Both quinolones (Cipro®, Levaquin®) and tetracyclines (Achromycin®, Minocin®) decrease the absorption of zinc in the gut, and vice versa [78].
Taking the antibiotic at least 2 hours before or 4 – 6 hours after taking a zinc supplement minimizes this interaction.
3) Diuretics (Water Pills)
Prolonged use of thiazide diuretics (Hygroton®, Esidrix®, and HydroDIURIL®) could deplete zinc levels by increasing zinc removal in the urine by as much as 60% [79].
Amiloride (Midamor®) can increase the amount of zinc in the body [80].
4) Blood Pressure Medication
ACE inhibitors (Capoten®, Vasotec®, Monopril®) and angiotensin receptor blockers (Edarbi®, Atacand®) used to treat high blood pressure, may decrease the levels of zinc in the blood [81, 82].
5) Cisplatin
Cisplatin, used to treat some types of cancers, increases urinary zinc excretion thus decreasing blood levels of zinc in patients treated with cisplatin [83].
Interactions With Nutrients & Food
1) Iron
High doses of zinc can interfere with the absorption of iron [84].
Iron supplements, taken together with zinc supplements on an empty stomach, may inhibit the absorption of zinc.
When taken with food, supplemental iron does not inhibit zinc absorption [85, 86, 87].
2) Copper
Zinc supplementation can interfere with the absorption of copper, and cause a copper deficiency which has been reported in humans using up to 600 mg elemental zinc daily or excessive usage of zinc-based dental adhesives [88, 89, 90].
3) Alcohol
Alcohol decreases the absorption of zinc and increases urinary zinc excretion [12].
4) Calcium
Excessive dietary calcium decreases zinc absorption [91].
5) Protein
Protein enhances zinc absorption [92].
6) Phytates and Fiber
Phytates and fiber (present in vegetables, whole grains, cereals, and legumes) bind to zinc and inhibit its absorption [32, 33].
7) Chlorogenic Acid
Chlorogenic acid (commonly found in coffee) can decrease zinc absorption [93].
8) Vitamin A
Zinc has been shown to increase Vitamin A levels in the blood [94].
9) Vitamin B6 and Magnesium
Zinc is commonly supplemented with Vitamin B6 and magnesium in the formulation known as ZMA, used primarily by athletes as it is claimed to be a testosterone booster [95].
