Zinc — Benefits, Dietary Sources, Deficiency, and Supplements

by Victoria Mazmanyan | Last updated on March 25, 2024

Medically reviewed by Arpi Gasparyan

Introduction

Zinc is an essential trace element that plays a vital role in numerous physiological processes throughout the human body. It is involved in various biochemical reactions and serves as a cofactor for over 300 enzymes, contributing to metabolism, immune function, DNA synthesis, and wound healing.

As a micronutrient, zinc is crucial for maintaining overall health and well-being. It is particularly important during periods of growth, development, and reproduction. Zinc deficiency can lead to a variety of health problems, including impaired immune function, growth retardation, delayed wound healing, and cognitive dysfunction.

In this article, we will discuss the properties of zinc in detail and delve into the topics of absorption, metabolism, zinc sources, and more.

Absorption, Metabolism, and Regulation

Despite being a trace element, zinc is the second most abundant element in the body, second only to iron. On average, the human body contains approximately 2.6g of zinc. Most of this zinc is located in the muscles and bone; some is stored in the skin and liver. Smaller amounts are found in most tissues and organs, such as the brain, eyes, heart, lungs, stomach, pancreas, kidneys, and more (1).

The primary mechanism of zinc regulation is through absorption. On average, 33% of dietary zinc is absorbed from the diet; however, depending on the zinc concentration in the food and the physiological need, the absorption rate can increase (2). Increased physiological need will increase zinc absorption, while meals high in zinc will have the opposite effect.

Another important factor for zinc absorption is the availability of soluble zinc from the food components in the diet.

Almost half of the zinc lost is excreted in the gastrointestinal system through intestinal and biliary secretions. However, most of it is later reabsorbed. Additionally, the body loses zinc daily through feces, urine, and sweat, as well as in smaller amounts through menstrual blood, semen, hair and nail loss, and skin flaking.

Factors Affecting Zinc Absorption

Phytic acid significantly limits zinc absorption by binding to the mineral. Foods high in phytic acid include certain grains (especially whole grains), legumes, nuts, and seeds. Food treatments, such as soaking, fermentation, and thermal processing, can decrease phytic acid levels and increase zinc bioavailability (2).

Inversely, protein intake improves zinc absorption. Consuming animal protein, such as meat and dairy, along with plant foods high in phytic acid, helps somewhat neutralize its negative effect.

At the same time, casein from milk may negatively impact zinc absorption (3).

As mentioned above, increased amounts of zinc in a meal reduce zinc absorption. However, this does not apply to zinc supplements, as the mineral in these is water-soluble (3).

Definitive interactions have not been found between zinc absorption and minerals, such as calcium and iron.

Recommended Intakes

As there isn't a specific storage in the human body for zinc, the body relies on continuous replenishment through dietary intake to maintain adequate levels. Thus, daily zinc intake is necessary to maintain its balance in the body.

The required amount or recommended daily allowance (RDA) for zinc is presented below for different sex and age groups (4).

	2-3	4-8	9-13	14-18	19+
Female	3mg	5mg	8mg	9mg	8mg
Male	3mg	5mg	8mg	11	11

The RDA of zinc for pregnant women is naturally higher—11mg for women over 18 in all trimesters. This value for lactating women is 12mg (2).

Food Sources

Zinc is found in various foods, such as meat, seafood, legumes, nuts and seeds, dairy, and fortified foods.

The table below lists foods high in zinc, along with their zinc content based on average serving sizes.

Food Name	Zinc Content	Serving Size
Beef (tenderloin, roasted)	3.1mg	85g or 3 ounces
Pork (loin, broiled)	2mg	85g or 3 ounces
Oyster (eastern, cooked)	66.8mg	85mg or 3 ounces
Beans (baked, canned)	0.9mg	63g or ¼ cup
Chickpeas (boiled)	1.2mg	82g or ½ cup
Pumpkin seed (roasted)	2.9mg	28.35g or 1 ounce or 85 seeds
Cashew (raw)	1.6mg	28.35g or 1 ounce
Cheddar cheese	1mg	28g or 1 ounce or 1 slice
Tofu (raw)	1.3mg	81g or ¼ block
Cereal	2.2mg	29g or 1 cup

You can also find a list of foods high in zinc on our website.

Health Benefits and Functions of Zinc

Zinc is a cofactor for over 300 enzymes involved in various biochemical reactions, supporting metabolism, digestion, and cellular function. This mineral plays an important role in basic physiological functions in the human body, such as immune system support, wound healing, growth and development, sensory function, reproductive health, and antioxidant defense.

The Immune System

Zinc is recognized for its pivotal role in the immune system, and individuals with zinc deficiency are more prone to various infections. For many years, researchers have investigated the immunological mechanisms through which zinc modulates susceptibility to infections (5).

Furthermore, scientists have proposed that zinc may lessen the severity and duration of cold symptoms by directly blocking the binding and replication of rhinovirus in the nasal mucosa and reducing inflammation (6).

Low zinc levels are also associated with increased vulnerability to pneumonia and a more severe disease course (6).

Allergy

Zinc has anti-inflammatory and antioxidant qualities. Thus, zinc deficiency has been found to increase inflammation and inflammatory markers (7). Zinc deficiency also poses a risk factor for asthma, especially among children with allergic conditions (8).

Zinc supplementation may help relieve the allergic state (8).

Skin and Acne

Research involving 77 people with acne found that only 5% had slightly low zinc levels. However, oral zinc supplements (220mg, twice per day) had positive effects on acne, reducing the severity of inflammatory lesions by 60% and comedones by 23% (9).

Overall, it has been concluded that increased zinc levels improve acne, particularly inflammatory lesions (9, 10).

Vision

Zinc is essential for maintaining normal ocular function and is found in high concentrations in ocular tissues, especially in the retina and choroid. It is thought to interact with taurine and vitamin A in these tissues. Zinc deficiency has been suggested to impact the onset and advancement of various chronic eye conditions (11).

Age-related macular degeneration is the primary cause of notable vision impairment among the elderly. Studies indicate that supplements containing zinc and antioxidants could potentially slow down the advancement of this disease and vision loss. This effect may be attributed to the prevention of cellular damage within the retina (6).

Gastrointestinal System

Zinc is involved in essential processes in the intestines. It is a cofactor for various digestive enzymes, helps maintain the integrity of the intestinal barrier, and supports gut microbiota balance.

Thus, zinc supplementation has been demonstrated to offer protective effects on the epithelial barrier across various studies involving cell lines, animal models, and human subjects. These effects have been observed in a range of conditions, such as chronic alcohol exposure, heat stress, diarrhea, chronic fatigue syndrome, colitis, other gastrointestinal disorders, and certain neurological conditions (12).

Zinc can also help manage infectious diarrhea. Zinc supplementation has been shown to decrease the duration and severity of diarrhea episodes and the risk of subsequent infections in the following 2 to 3 months (13).

Zinc and Testosterone

Severe and moderate zinc deficiency in men has been linked to hypogonadism or decreased functional activity of the reproductive gland. When healthy young men undergo dietary zinc restriction, serum testosterone concentrations decrease significantly (14).

Research has found a positive correlation between serum zinc levels and total testosterone. Thus, zinc may have a significant role in regulating serum testosterone levels in men with normal health (14, 15).

Type 2 Diabetes

Low zinc levels are commonly observed in individuals with type 2 diabetes. This has led researchers to suggest that zinc depletion could contribute to the progression of diabetes (6).

Zinc deficiency is more prevalent in diabetic people than in individuals without diabetes, and inadequate blood sugar control is linked to lower zinc levels (16).

As zinc has antioxidant properties, its deficiency is also known to elevate oxidative stress levels, particularly in individuals with diabetes (16).

Body Weight and Obesity

Research suggests that zinc supplementation alongside a calorie-restricted diet has beneficial effects on reducing body weight and circumference, inflammatory markers, insulin resistance, and appetite in individuals with obesity (17).

Overall, studies suggest that zinc deficiency is a risk factor for obesity (20).

Zinc Deficiency

Zinc deficiency poses a significant global health concern, particularly in developing nations with prevalent malnutrition. Approximately one in every five individuals worldwide experiences zinc deficiency, with the prevalence of deficiency increasing as individuals age (18).

Zinc deficiency in developing countries is often accompanied by iron deficiency. This is said to be due to the large consumption of bread made from whole wheat flour, which is high in phytates and decreases the absorption of both iron and zinc (19).

Regions with zinc-deficient soil may also produce crops with lower zinc content, leading to dietary deficiency in affected populations.

The average zinc level in the plasma for healthy adults falls in the range of 70 to 250µg/dL. Clinical manifestations of mild zinc deficiency may appear when zinc levels decrease to 40 to 60 μg/dL (20).

Infants, children, adolescents, and pregnant and lactating women have higher zinc requirements than others, putting them at greater risk of zinc deficiency.

Vegetarians and vegans are also at higher risk for zinc deficiency, as their diets are higher in phytates and lower in available zinc.

Causes

Zinc deficiency in humans can result from decreased dietary intake, impaired absorption, excessive loss, or increased utilization by the body. Inadequate dietary intake is the most common cause worldwide.

Impaired absorption can result from various diseases that cause malabsorption, such as celiac disease, Crohn’s disease, ulcerative colitis, bariatric and other gastrointestinal surgeries, as well as chronic pancreatitis.

Chronic diseases such as diabetes, alcoholic cirrhosis, chronic kidney disease, and people with sickle cell disease who exhibit hyperzincuria (excess zinc in the urine) due to persistent destruction of red blood cells (hemolysis) can also lead to zinc deficiency (19).

Excessive zinc loss can occur through various means, including burns, hemodialysis, hemolysis, diarrhea, or urinary excretion due to alcohol consumption or diuretic use (20). Chronic alcohol consumption not only increases urinary zinc excretion but also can impair zinc absorption.

Pregnancy, lactation, growth spurts during childhood and adolescence, and certain medical conditions can increase the body's need for zinc.

Symptoms

Some symptoms of zinc deficiency are discussed in the “Health Benefits and Functions” section.

Zinc deficiency commonly manifests with symptoms related to infection, inflammation, gastrointestinal issues, or skin problems (20).

Extended and severe zinc deficiency can result in various complications, growth failure, hypogonadism, recurrent infections - both acute and chronic, diarrhea, delayed wound healing, low bone mineral density, and skin conditions like acrodermatitis enteropathica, cheilitis, and dermatitis (20).

Zinc Supplements

Zinc supplements can be used to treat zinc deficiency or improve zinc intake. As mentioned above, zinc supplementation can have various beneficial effects on health.

Zinc deficiency treatment typically starts with oral replacement therapy. In adults, a daily dose of 20 to 40 mg often resolves all clinical symptoms within 1 to 2 weeks (20).

Zinc supplements come in various forms, including:

zinc gluconate
zinc acetate
zinc sulfate
zinc picolinate
zinc citrate
zinc oxide

These supplements are available in different formulations, such as tablets, capsules, lozenges, and liquid solutions.

Zinc Toxicity

Zinc toxicity or zinc overdose can happen due to ingesting high doses of zinc supplements or prolonged exposure to zinc-containing materials.

When zinc intake exceeds 50mg a day, gastrointestinal symptoms like nausea, abdominal discomfort, and diarrhea are common. Moreover, doses surpassing 150 mg/day can negatively impact immune status and lipid profile. Higher doses may decrease iron and copper absorption, potentially causing genitourinary issues (20).

When using zinc supplements for prolonged periods, it is crucial to monitor blood copper levels (20).

Treatment typically involves stopping zinc intake and supportive care to manage symptoms.

Interactions With Medications

Certain medications, such as penicillamine, specific diuretics, certain antibiotics, and sodium valproate, can interfere with the body's absorption of zinc (20).

Interactions with antibiotics, such as quinolones (Cipro) and tetracyclines (Achromycin, Sumycin), may inhibit both zinc and antibiotic absorption. To avoid this interaction, it is recommended to take the antibiotic 2 hours before or 4 to 6 hours after zinc supplements (6).

Penicillamine is used to treat diseases such as Wilson’s and rheumatoid arthritis. This medication and zinc supplements should be taken an hour apart (6).

Thiazide diuretics, such as chlorthalidone and hydrochlorothiazide, interact with zinc by increasing zinc loss through urine (6).

Summary

Zinc is a trace mineral essential for the immune system, wound healing, growth and development, sensory function, reproductive health, and antioxidant defense.

Zinc levels are regulated through absorption. Increased physiological need increases zinc absorption, while meals high in zinc have the opposite effect.

Phytates found in certain whole grains, legumes, nuts, and seeds inhibit zinc absorption, whereas animal protein increases absorption.

Zinc is high in meat, seafood, legumes, nuts and seeds, dairy, and fortified foods.

Zinc supplements can lessen the severity and duration of cold symptoms, relieve the allergic state, slow down age-related macular degeneration, decrease the duration and severity of diarrhea episodes, and more.

Zinc deficiency commonly manifests with symptoms related to infection, inflammation, gastrointestinal issues, or skin problems.

References

Author name: Victoria Mazmanyan

Education: General Medicine at YSMU

Last updated: March 25, 2024

Medically reviewed by Arpi Gasparyan