Everything You Need To Know About Zinc

When it comes to micronutrients, you probably haven't given much thought to zinc. However, according to the National Institutes of Health (NIH), the mineral zinc actually plays many important roles in the body. In addition to being a necessary component of at least 100 enzymes, zinc plays a part in immune function, metabolism, protein and DNA synthesis, wound healing, our sense of smell and taste, and cell division. It's particularly critical during times of intense growth such as pregnancy, infancy, and adolescence. 

A 2013 paper published in Nutrients states that zinc is the second most abundant mineral in the body, right after iron. The average adult has about 1.5 to 2.5 grams of zinc distributed throughout every cell in their body. When it comes to zinc, it's important to discuss both how much you're consuming and what your blood's zinc levels are like. Our bodies can't store zinc, so it's important to get enough daily. Luckily, zinc can be found in many foods, as well as supplements and over-the-counter lozenges. 

Zinc deficiency isn't common in the United States, but it can cause serious problems when it does occur. It's also possible to get too much zinc, especially if you're overdoing it on supplements.

How much zinc we need and how much we're getting

The recommended dietary allowances (RDAs) for zinc are based on age and gender. Children's zinc needs aren't substantially smaller than adults, since the mineral is especially important during periods of rapid growth. 

Infants six months and younger require 2 milligrams, while those age seven months to three years need 3 milligrams. The RDA for boys and girls age four to eight is 5 milligrams. Between ages 9 and 13, needs increase to 8 milligrams. Beginning at puberty, zinc requirements for males and females differ. For boys and men age 14 and older, the RDA is 11 milligrams. For teenage girls between 14 and 18, the RDA is 9 milligrams, and then drops to 8 milligrams in adulthood. A woman's zinc needs increase by 3 milligrams during pregnancy and 4 milligrams during breastfeeding. 

National survey data indicate that most Americans meet their RDA for zinc (via the National Institutes of Health). However, research also revealed that approximately 11.7% of Americans age four or older don't meet the estimated average requirement (EAR) for zinc, and are thus at risk of deficiency (per Oregon State University). The EAR indicates how much of a micronutrient is needed to avoid negative health consequences. The EAR for zinc is only 9.4 milligrams for men and 6.8 milligrams for women (via the USDA).

Zinc from food

Our bodies can't store zinc, so it's important to get enough daily. Luckily, zinc can be found in many foods. Oysters are the richest source of zinc. Six medium oysters contain a whopping 32 milligrams — almost three times your daily needs. Other types of shellfish, including crab, shrimp, and mussels, also contain respectable amounts of zinc. Different kinds of meat, particularly red meat, are rich in zinc. For instance, 3.5 ounces of ground beef can provide nearly half of your daily zinc requirement. Dairy products and eggs also contain significant amounts of zinc.

Zinc can also be found in plant foods. Legumes, including chickpeas, lentils, and various types of beans, all contain respectable amounts of this mineral. A 3.5-ounce serving of lentils, for instance, contains about 12% of the zinc you need. Hemp seeds, pumpkin seeds, and sesame seeds are rich in zinc, as are cashews. Whole grains contain zinc as well, but this mineral is largely lost when the grains are refined. And in case you needed one more reason to eat chocolate, a 3.5-ounce serving of dark chocolate (70%–80% cacao) contains 30% of your daily requirement (via Healthline).

Unfortunately, legumes and whole grains also contain phytates, a type of anti-nutrient that inhibits proper zinc absorption. As a 2014 paper published in the Journal of Trace Elements in Medicine and Biology pointed out, one in five people worldwide is at risk for zinc deficiency, largely because of the effects of phytates on zinc absorption.

Zinc supplements

Supplemental zinc is an option for those who don't get enough through their diet or want to up their intake for a particular medical reason. 

Zinc supplements may contain zinc gluconate, zinc sulfate, or zinc acetate, each of which contains a different percentage of elemental zinc. The Supplement Facts panel on a supplement package will list the amount of elemental zinc in the product to avoid potential confusion between the various forms. It's unclear, however, if one form is necessarily better than another in terms of absorption, bioavailability, or likelihood of side effects. In addition to standalone supplements, zinc is found in almost all multivitamins. It is also often combined with other minerals such as calcium and magnesium. Zinc supplements may be tablets, capsules, lozenges, or nasal sprays and gels (via the National Institutes of Health).

Zinc supplements are generally considered safe when taken at recommended doses. In some cases, people taking oral zinc may experience mild side effects such as headache, nausea, indigestion, diarrhea or vomiting. Nasal sprays and gels should be avoided or used with extreme caution, however, as they may cause you to lose your sense of smell, possibly permanently (via the Mayo Clinic).

Zinc can interact with certain medications and other micronutrients

Although zinc supplements are generally considered safe, this mineral can interact negatively with certain medications. Zinc can inhibit absorption of antibiotics (particularly quinolones, tetracyclines, and cephalexin) from the gut, decreasing their effectiveness. To avoid potential issues, it's best to take quinolones or tetracyclines either two hours before or four to six hours after a zinc supplement, and to take cephalexin at least three hours before taking zinc. Taking zinc along with certain cancer drugs and HIV antivirals may also reduce the effectiveness of these medications (via WebMD).

It's also important to note that zinc is intimately connected to two other minerals — iron and copper — and that getting too much zinc can negatively impact the other two. According to the Linus Pauling Institute, taking doses of zinc above 50 milligrams per day over an extended period of time can lead to problems absorbing copper and even copper deficiency. (Interestingly, taking high doses of copper doesn't affect zinc absorption.) 

Large doses of either zinc or iron can also interfere with the absorption of the other mineral. Additionally, high doses of zinc may inhibit folate absorption. Meanwhile, large doses of calcium can negatively affect zinc absorption in animals, but it's not yet clear if this is also true in humans.

Zinc deficiency

According to the Linus Pauling Institute, severe zinc deficiency is quite uncommon, especially in developed nations such as the United States. When it does occur, it can cause "the slowing or cessation of growth and development, delayed sexual maturation, characteristic skin rashes, chronic and severe diarrhea, immune system deficiencies, impaired wound healing, diminished appetite, impaired taste sensation, night blindness, swelling and clouding of the cornea, and behavioral disturbances." 

Milder or marginal zinc deficiency, on the other hand, is estimated to affect more than 2 billion people worldwide. It can impair normal growth and development and make individuals (particularly young children) susceptible to life-threatening infections. In fact, global statistics say that approximately 450,000 children under the age of five die each year because of infections linked to zinc deficiency.

People can become deficient in zinc from not consuming enough of it in their diet. More commonly, however, zinc deficiency is due to problems with absorption or excessive zinc loss (because of prolonged diarrhea or severe burns, for example). In rare cases, severe zinc deficiency can be caused by a genetic disorder called acrodermatitis enteropathica, which impairs the absorption and transport of zinc. Before the nature of acrodermatitis enteropathica was properly understood, individuals with the condition usually died in infancy. Today, regular zinc supplementation can keep people with the condition symptom-free.

Groups at risk for zinc deficiency

In addition to those with the rare genetic condition that impairs zinc absorption, certain groups are at increased risk for zinc deficiency. 

Vegetarians and vegans are more likely than omnivores to be deficient because the zinc from plant-based foods is less bioavailable than that from meat and animal products. The high phytate content in legumes and whole grains inhibits the uptake of zinc, and people who get most of their zinc from these foods may need as much as 50% more than the RDA of zinc in order to actually absorb a sufficient amount. Fortunately, soaking and sprouting legumes, whole grains, and seeds can drastically reduce their phytate content.

Pregnant and lactating women are also at greater risk for zinc deficiency because of increased requirements and the fact that breastfeeding depletes a mother's zinc levels. Infants seven months and older who are exclusively breastfed are also likely to become deficient because breastmilk alone can't provide enough zinc to meet their growing needs. In addition, as many as 50% of alcoholics have low zinc levels because alcohol inhibits absorption of zinc and increases zinc loss in urine. Roughly 44% of those with sickle cell disease also have low zinc levels. Conditions such as ulcerative colitis and Crohn's disease can also impair zinc absorption, leading to deficiency. Finally, one-fifth to one-fourth of elderly Americans don't consume enough zinc from diet and supplements, and are therefore at risk of deficiency symptoms (via the National Institutes of Health).

Zinc toxicity

It's possible to get too much of a good thing when it comes to zinc. Overdoing it on dietary zinc isn't a concern, but excessive use of supplemental zinc can be an issue. Zinc toxicity can be either acute or chronic (via the Linus Pauling Institute). Acute zinc toxicity can occur from taking way too much supplemental zinc at one time or when zinc leaches from galvanized metal containers into food or beverages. A single dose of 225 to 450 milligrams of zinc is usually enough to cause vomiting. Single doses of 50 to 150 milligrams can cause milder gastrointestinal symptoms, including abdominal pain, nausea, and diarrhea.

Chronic ingestion of too much zinc usually doesn't have any direct negative impact, but it can easily lead to copper deficiency, since both metals rely on the same enzyme for absorption and the enzyme binds more easily to zinc than to copper. Copper deficiency has been observed with a zinc intake that's only moderately high — 50 milligrams a day from supplements and 10 milligrams a day from food over the course of just 10 weeks. Because zinc is also found in some denture adhesives, people who use large quantities (two or more tubes a week) may inadvertently be absorbing too much zinc.

To help reduce the chances of getting too much zinc, the Food and Nutrition Board (FNB) has set the tolerable upper intake level (UL) of zinc at 40 milligrams per day (from food and supplements combined) for adults.

Testing zinc levels

Although getting the right amount of zinc is critical for good health, according to the Linus Pauling Institute, it can be surprisingly difficult to ascertain an individual's true zinc levels. 

The best that doctors can do is test to see how much zinc is in a person's blood. But serum (blood) zinc levels don't necessarily correlate to how much zinc is in the body's cells, where it's needed. Serum zinc levels may fluctuate based on time of day, stress, hormone levels, and the presence of inflammation. In addition, a person may have symptoms of mild zinc deficiency but a serum zinc level that falls within the normal range.

Zinc levels usually aren't tested unless a doctor suspects there's a problem (for example, if a child isn't growing normally or if a patient has a condition like ulcerative colitis that might negatively impact zinc levels). Zinc testing is also done to monitor how well zinc therapy is going for those diagnosed with a zinc deficiency and to confirm the presence of acrodermatitis enteropathica, a genetic condition that impairs zinc absorption. You don't need to fast before having blood drawn for this test, but your doctor may ask you to discontinue use of zinc supplements beforehand so that the reading can be more accurate. The normal range for males and females 11 months and older is 44–115 micrograms/deciliter (via Labcorp).

Zinc and the immune system

Vitamin C usually gets all the credit when it comes to maintaining a healthy immune system and fighting off infections, but zinc is also essential for a properly functioning immune system. 

A 2008 paper published in Molecular Medicine noted that in addition to having powerful antioxidant and anti-inflammatory properties (both of which play a role in the body's natural immune response to injury and cellular damage), zinc is essential for many types of immune cells. It's needed for the "normal development and function of cells mediating innate immunity, neutrophils, and NK [natural killer] cells." The authors stated that zinc supplementation "reduced the incidence and duration of ... acute lower respiratory tract infections in infants and children." It also reduced the number of cases of pneumonia and E. coli urinary tract infections. 

Zinc deficiency negatively affects phagocytosis, the engulfing and "eating" of diseased or damaged cells by specialized immune cells called phagocytes. The authors also pointed out that zin deficiency negatively impacts the development and function of both B and T cells. These are specialized immune cells that "remember" pathogens you've been exposed to in the past and produce antibodies to quickly fight off the same pathogens in the future. According to WebMD, zinc lozenges have been shown to shorten the duration of the common cold, though it's unclear if zinc can prevent you from getting sick in the first place.

Zinc and wound healing

Zinc appears to play a major role in wound healing and has been successfully used in the treatment of burns, ulcers, and other skin issues. 

According to a 2018 paper published in Nutrients, about 5% of the zinc in our bodies is located in our skin. Zinc is required any time cells divide to make new cells, such as when new skin tissue must be created to close wounds. It's also needed to create enzymes that oversee the activity of the immune system, which is busy during wound healing clearing away damaged cells. Zinc is needed for collagen production, which in turn is essential for healing wounds. Collagen is a protein that's laid down in a matrix pattern like scaffolding to give skin structure. When wounds heal, a new collagen matrix must be laid down and filled in with skin cells to close the wound. 

Being zinc deficient can significantly impair wound healing, and supplementing with zinc may speed up the process. In a 2017 study published in Wound Repair and Regeneration, researchers divided patients with diabetic foot ulcers into two groups. One group received a zinc sulfate supplement providing 50 milligrams of elemental zinc daily for 12 weeks, while the other group received a placebo. At the end of the study, the ulcers of those who'd been given the zinc were significantly smaller (in terms of length and width) compared to those of the placebo group.

Zinc and metabolism

As WebMD explains, "metabolism refers to all the chemical reactions taking place in the body to convert or use energy." Your metabolism allows you to break down the food you eat into energy your cells can use. It drives the formation of compounds like enzymes and hormones from simple building blocks like amino acids and minerals. 

Getting rid of the waste products created from all these chemical reactions is also the job of your metabolism. While metabolic processes take place in cells throughout your body, the thyroid is the organ that oversees everything. This butterfly-shaped gland located in the neck regulates how quickly or slowly cells use energy. It does this by producing two hormones: T3 (triiodothyronine) and T4 (thyroxine), per Endocrineweb.

Although the thyroid uses iodine to produce the hormones that regulate metabolism, zinc is also required. According to a 2013 paper published in the International Journal of Trichology, zinc is needed to make T3 receptors on body cells active. If T3 receptors aren't active, they can't "accept" T3 and won't metabolize energy correctly. Zinc deficiency has been linked to hypothyroidism (underactive thyroid), which is characterized by weight gain and a number of other unpleasant symptoms. Thyroid hormones are also necessary for the proper absorption of zinc from the diet, so hypothyroidism can exacerbate zinc deficiency, creating a vicious cycle.

Zinc and acne

Unfortunately, acne doesn't always go away after adolescence. According to a paper published in 2014 in The Journal of Clinical and Aesthetic Dermatology, between 12% and 22% of women and 3% of men continue to experience acne into their 20s, 30s, and beyond. The Mayo Clinic called out four underlying causes of acne: excess sebum (oil) production, clogged hair follicles, bacteria, and too many androgens (male sex hormones). Fortunately, zinc can help with many of these factors.

A 2014 paper published in Dermatology Research and Practice noted that both oral and topic zinc were effective against moderate to severe acne. What gives zinc its blemish-busting properties? The researchers explained that zinc's antimicrobial properties can destroy P. acnes, the acne-causing bacteria. Zinc can also fight inflammation and reduce the activity of the oil-producing glands in our skin by reducing androgen levels. Additionally, the authors stated that zinc appears to help with a variety of other skin conditions, including rosacea, eczema, psoriasis, and folliculitis. 

Interestingly, according to a 2014 study published in BioMed Research International, people with acne tend to have lower zinc levels in their blood. The researchers concluded that "zinc levels may be related to the severity and type of acne lesions in patients with acne."

Zinc and eye health

Zinc may play an important role in preventing or slowing the progression of age-related macular degeneration (AMD). As the National Eye Institute explained, AMD is a disease in which central vision becomes blurry because of damage to the macula, a part of the retina that controls sharp, straight-ahead vision. 

AMD is a common cause of vision loss in older adults, though it doesn't lead to total blindness. AMD comes in two forms: the more common dry form and the more severe wet form. In dry AMD, the macula thins gradually over time. In wet AMD, abnormal blood vessels develop in the retina, damaging the macula. It's believed that zinc safeguards against AMD by preventing cellular damage to the macula (via the National Institutes of Health).

In fact, zinc was among the micronutrients included in the now famous AREDS and AREDS2 studies, which confirmed the effectiveness of a specially formulated supplement designed to slow the progression of AMD (via the National Eye Institute). Both the AREDS and AREDS2 supplements included 80 milligrams of zinc, although the number and quantity of other micronutrients varied between the two. But because each supplement contained four to five other micronutrients, it's impossible to know how much credit zinc specifically deserves. While over-the-counter AREDS and AREDS2 supplements are now available, it's important to note that the 80 milligrams of zinc they contain is well above the tolerable upper intake limit (UL) for zinc of 40 milligrams.

Topical zinc

Zinc is one of the most important micronutrients, and it plays many key roles in the body. But topical zinc, in the form of zinc oxide, can also be extremely useful. 

Zinc oxide can be found in ointments and creams used to treat wounds, burns, and minor skin irritations. It's perhaps best known as the active ingredient in diaper rash creams and one of two active ingredients (along with titanium dioxide) in physical-barrier sunscreen (via the Cleveland Clinic). Unlike chemical sunscreens which soak in and alter UV radiation as it hits your skin, physical-barrier sunscreens sit on top of the skin and provide ... well, a physical barrier between your skin and the sun. They reflect back UV light, preventing it from entering and damaging skin cells. 

When it comes to effectiveness, zinc oxide has a slight edge over titanium dioxide because in addition to blocking short-wave UVA waves and UVB rays (which titanium dioxide can also block), zinc oxide can also block long-wave UVA waves (via Livestrong). This means zinc oxide provides a wider spectrum of UV protection. Zinc oxide is also noncomedogenic, meaning it won't clog pores and cause breakouts. Zinc oxide sunscreen may also provide some degree of protection against disease-causing microbes on the skin as well.