Nutrition

What is Zinc: Benefits, Deficiency, Sources, and Risk

Written by Adeel Asghar Ph.D.

What is Zinc?

Zinc is one of the most important elements in the human body. An adult human contains about 2-3g of total zinc (1).

Zinc is the 6th most abundant metal in the body (2). Although present in all body cells, about 85% of total zinc is present in muscles and bones (3).

Zinc binds with approximately 3000 types of proteins. It also interacts with more than 300 different enzymes. It is involved in several cellular functions including cell division, proliferation, and growth which are required for human growth and development (4,5).

Zinc plays a role as an antioxidant, anti-inflammatory agent, immunomodulator, and antiviral agent.

This article explains zinc benefits, daily zinc requirement, zinc deficiency, treatment, and zinc risks.

Zinc Benefits

1. Zinc has antioxidant potential and reduces inflammation

Zinc is part of many enzymes, including antioxidant enzymes. It is an integral part of superoxide dismutase (SOD).

SOD is one of the most important antioxidant enzymes. Low zinc levels or deficiency can lead to a severe reduction in SOD, which may cause increased oxidative stress (6). Thus, zinc is essential for antioxidant function.

Zinc can also minimize inflammation. Zinc supplementation is shown to reduce inflammation indicators including C reactive protein(CRP), MCP-1, and IL-6 levels in humans (7).

2. Zinc is recommended for the treatment of pediatric diarrhea

Zinc as a supplement is an effective treatment of diarrhea in developing countries (8).

Both the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) recommended zinc supplementation for the treatment of diarrhea in children (9).

3. Zinc is essential for growth and development

Zinc is important for growth and development. Its deficiency can lead to stunted growth in children and development issues (10).

First reported cases of zinc deficiency found retarded growth in individuals with zinc deficiency. So far, many studies have shown that zinc supplementation is essential for the growth and development of children (11).

4. Zinc can help improve male fertility

Zinc is important for male fertility. Fertile males have higher levels of seminal plasma zinc compared to infertile men. Also, higher zinc levels are associated with better sperm quality (12).

More zinc is not always better. Optimum zinc levels are crucial for healthy sperm production. Very high or very low zinc levels are detrimental to male fertility (13).

Zinc may promote good sperm parameters via its antioxidant activity (14).

5. Zinc is important for the immune system

Zinc is essential for the immune system. Its deficiency is associated with reduced immune system function.

Both higher or lower than normal zinc levels are associated with a dysfunctional immune system (15).

Zinc deficiency causes a reduction in the function of T-lymphocytes and B cells (16).

A high level of zinc can impair T cell function (17).

Balanced zinc levels are required for a fully functional immune system.

6. Zinc is required for mental health

Zinc is vital for brain health as well. Zinc deficiency causes growth retardation as well as brain dysfunctions. Zinc is found in the brain where it is part of many biological complexes (18).

Zinc deficiency is associated with a higher risk of Parkinson’s disease, Alzheimer’s disease, attention-deficit hyperactivity disorder (ADHD), schizophrenia, multiple sclerosis, and other brain disorders (19,20,21,22).

Therefore, adequate amounts of zinc are required for good brain health.

7. Zinc can be useful in diabetes management

Zinc is vital for glucose regulation because it is required for the synthesis, storage, and secretion of insulin. Moderate to mild deficiency of zinc can affect the ability of insulin production and secretion (23).

The use of supplementation is beneficial for improving glycemic control in type 2 diabetes conditions (24).

8. Zinc reduces common cold symptoms and duration

Several studies have shown that the use of zinc supplements is effective in reducing the symptoms and duration of the common cold (25).

Zinc acetate lozenges significantly reduced symptoms such as nasal congestion, sneezing, sore throat, hoarseness, and cough (26).

9. Zinc is essential for bone health

Zinc is required to maintain a balance between bone damage and repair. A large portion of zinc is distributed in bones (27).

Fetus skeletal development is affected by a mild deficiency of zinc (28).

Zinc deficiency decreases new bone-cell formation thereby affecting bone health (29).

10. Zinc is useful in wound healing

Zinc is present in high quantities in the skin. Zinc deficiency is associated with delayed wound healing. Oral supplementation is beneficial in improving wound healing (30).

11. Zinc is important for healthy skin

Zinc is useful in maintaining healthy skin. Topical use of zinc creams can minimize the adverse symptoms of various skin conditions including acne, psoriasis, and eczema (31,32,33).

12. Can Zinc treat Covid-19 infection?

Zinc has an important role in immunity. It also has antiviral properties. Some studies have suggested that it may be useful against Covid-19. Zinc supplementation as a prophylactic or adjuvant therapy may provide benefits (34,35).

Research shows that zinc inhibits Covid-19 viral growth by inhibiting its viral replication (36).

But currently, no clear evidence of the zinc supplement for the prevention or treatment of Covid-19 infection exists.

How much zinc per day?

Small amounts of daily zinc intake are necessary for body growth and function.

The recommended daily allowance (RDA) of zinc for adult men is 11 mg, and for adult women is 8 mg. The lower body weight of infants and children allows them to consume lower amounts of zinc per day.

The following table describes RDA according to age and gender in more detail. The zinc amount is given in milligrams (37).

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

Zinc Deficiency and Symptoms

It is estimated that 20% of the world population is at risk of zinc deficiency (38). The elderly population is most vulnerable. Statistics show that more than half of the elderly population (over 71) don’t meet the daily zinc intake requirements (39).

Since zinc is important for human health, deficiency can lead to severe consequences.

Zinc deficiency can be severe or moderate.

Severe zinc deficiency symptoms include dysfunctional growth, anemia, and neurological problems, whereas mild zinc deficiency is associated with chronic diseases such as cardiovascular diseases (40).

In humans, zinc deficiency can occur due to:

Poor dietary intake
Poor absorption

The most common cause of zinc deficiency is poor dietary intake. The first cases of severe zinc deficiency were reported in Iran (41).

Later, several studies showed zinc deficiency as a worldwide problem.

Zinc deficiency due to poor absorption can be caused by genetics.

A severe zinc deficiency caused by genetics is called Acrodermatitis enteropathica (42).

The symptoms of Acrodermatitis enteropathica include:

Growth retardation
Compromised immune systems
Alopecia
Dermatitis
Diarrhea
Risk of mental disorders

Causes of moderate zinc deficiency include alcohol abuse, malabsorption, chronic kidney failure, and chronic weakness (43).

The moderate zinc deficiency symptoms include:

Growth retardation
Hypogonadism (low sex hormone production) in men
Rough skin
Poor appetite,
Mental lethargy
Delayed wound healing
Taste abnormalities
Abnormal dark adaptation
Poor immunity

Poor absorption of zinc can also be caused by the source of food. Phytate which is naturally present in plants is one of the widespread inhibitors of zinc absorption (44). Therefore, plant-based zinc may not be absorbed efficiently in the body.

Germination and fermentation of a plant-based diet reduce phytate and may improve zinc absorption (45).

Thus, intake of a fermented plant diet could be useful in a vegetarian diet.

Zinc from high protein sources increases bioavailability and improves absorption (46). High protein sources such as red meat and poultry are good sources of bioavailable zinc.

How to prevent or treat zinc deficiency

Food sources of zinc
Zinc supplements
Zinc fortified foods

1. Food sources of zinc

Diet improvement is one of the best methods to eliminate zinc deficiency. Adequate intake of food sources high in zinc can reduce the risk of zinc deficiency. It can also improve zinc levels in the body.

High protein food sources, especially red meat, have higher zinc content compared to carbohydrate foods. As carbohydrate-heavy foods are a poor source of zinc, vegetarians are at risk of developing zinc deficiency (47).

Dairy products provide a great option for vegetarians to reduce the risk of zinc deficiency. Dairy products including milk and cheese provide readily absorbed zinc (48).

Different food groups provide a certain range of zinc given below.

Food group	Zinc mg per 100g of food group
Meat	0.40 to 6.77 mg
Grains	0.30 to 2.54 mg
Dairy products	0.36 to 0.49 mg
Vegetables	0.12 to 0.60 mg
Fruits	0.02 to 0.26 mg

Foods high in zinc are listed below as per the NIH.

Food	Serving Size	Zinc Amount in milligrams	The daily value (%)
Oysters, cooked, breaded, and fried	3 ounces	74.0 mg	673
Beef chuck roast, braised,	3 ounces	7.0 mg	64
Crab, Alaska king, cooked	3 ounces	6.5 mg	59
Beef patty, broiled	3 ounces	5.3 mg	48
Lobster, cooked	3 ounces	3.4 mg	31
Porkchop, loin, cooked	3 ounces	2.9 mg	26
Baked beans, canned, plain, or vegetarian	½ cup	2.9 mg	26
Breakfast cereal, fortified with 25% of the DV for zinc	1 serving	2.8 mg	25
Chicken, dark meat, cooked	3 ounces	2.4 mg	22
Pumpkin seeds, dried	1 ounce	2.2 mg	20
Yogurt, fruit, low fat	8 ounces	1.7 mg	15
Cashews, dry roasted	1 ounce	1.6 mg	15
Chickpeas, cooked	½ cup	1.3 mg	12
Cheese, Swiss	1 ounce	1.2 mg	11
Oatmeal, instant, plain, prepared with water	1 packet	1.1 mg	10
Milk, low-fat or non-fat	1 cup	1.0 mg	9
Almonds, dry roasted	1 ounce	0.9 mg	8
Kidney beans, cooked	½ cup	0.9 mg	8
Chicken breast, roasted, skin removed	½ breast	0.9 mg	8
Cheese, cheddar, or mozzarella	1 ounce	0.9 mg	8
Peas, green, frozen, cooked	½ cup	0.5 mg	5
Flounder or sole, cooked	3 ounces	0.3 mg	3

2. Zinc Supplements

Zinc Supplements are recommended for individuals who are clinically zinc deficient. Zinc supplements are an easy and cheap way to quickly improve zinc levels in the body (49).

The best zinc supplements are the ones with readily absorbable zinc compounds (50).

Readily absorbed zinc compounds include:

Zinc Sulfate (ZnSO4)
Zinc Gluconate
Zinc Acetate

If you suffer from any medical condition, always consult a physician before taking zinc supplements.

3. Zinc fortified foods

Another method to overcome zinc deficiency is to consume zinc-fortified foods. Foods fortified with zinc and other mineral/trace elements are easily available in the market. Food packaging provides zinc amount per serving.

Some examples of food fortified with zinc include ready-to-eat cereal breakfasts and mineral fortified bread, etc.

Two more common zinc compounds used in the food industry for zinc fortification are zinc oxide and zinc sulfate (ZnSO4). Research shows that both compounds are readily absorbed in the body (51).

Bread fortified with zinc sulfate is shown to decrease zinc deficiency (52).

Zinc Risks

Although zinc is well-tolerated, a long-term high intake of zinc is detrimental to health.

Long-term high zinc intake is associated with copper deficiency (53).

Long-term high zinc is also associated with an increased risk of prostate cancer due to the detrimental effects of high zinc on the immune system (54).

High doses of zinc may also cause general cell death. It may also cause nerve cell death (55,56).

In humans, the lethal dose (LD50) of zinc is 29 g per day (57).

High amounts of zinc cause several adverse effects (58).

These include:

Vomiting
Abdominal pain
Nausea
Lethargy
Anemia
Dizziness

Considering, high zinc intake may cause more harm than benefit, taking zinc supplements within the recommended daily amount (11 mg for men, 8 mg for women) should be ideal for optimal health.