Zinc (Zn) is an essential trace element for all forms of life, found in nearly 100 specific enzymes. Next to iron, zinc is the most common trace mineral in the body and is found in every cell.

 

The human body contains two to four grams of zinc with the highest concentrations in the prostate and parts of the eye.

 

Zinc insufficiency has been recognized by a number of experts as an important public health issue, especially in developing countries.

A sufficient intake of zinc is important as it supports the body in

 

• immune function
• protein synthesis
• wound healing
• DNA synthesis
• cell division
• normal growth and development during pregnancy, childhood, and adolescence
• tasting and smelling

 

The European Food Safety Authority (EFSA), which provides scientific advice to assist policy makers, has confirmed that clear health benefits have been established for the dietary intake of zinc in contributing to:

 

• a normal function of the immune system;
• normal DNA synthesis and cell division;
• the protection of cell constituents from oxidative damage;
• the maintenance of normal bone;
• normal cognitive function;
• normal fertility and reproduction;
• normal metabolism of fatty acids;
• normal acid-base metabolism;
• normal metabolism of vitamin A;
• the maintenance of normal vision;
• normal protein synthesis;
• the maintenance of normal serum testosterone concentrations;
• normal carbohydrate metabolism;
• normal macronutrient metabolism;
• the maintenance of normal skin;
• the maintenance of normal hair;
• the maintenance of normal nails.

Delay in growth and development
Significant delays in growth and weight gain ('growth retardation') are common features of mild zinc deficiency in children, occurring especially in developing countries.

 

Low zinc nutritional status in pregnant women has been associated with diminished attention in newborn infants and poorer movement function at six months of age.

 

Zinc supplementation has been associated with improved movement coordination in very low birth weight infants, and more vigorous activity in infants and toddlers.

 

A sufficient zinc intake is essential for normal growth and development during pregnancy, childhood, and adolescence.

 

Impaired immune system function
Adequate zinc intake is essential in maintaining a proper working immune system; thus, zinc-deficient individuals can experience increased susceptibility to a variety of infectious diseases, such as diarrhea, pneumonia, and malaria in children.

 

In a number of studies, zinc supplementation in combination with oral replenishment of water ('rehydration') has been shown to significantly reduce the duration and severity of acute and persistent childhood diarrhea and to increase survival.

 

Studies in developing countries demonstrated a substantial reduction in the total number of cases with pneumonia in children supplemented with zinc.

 

Some studies have indicated that zinc supplementation may reduce the incidence of clinical attacks of malaria in children, while other studies did not find such effect *.

 

Age-related declines in immune function have been associated with the vulnerability of the elderly to mild zinc deficiency. In some studies, levels of immune cells have been found to improve with zinc supplementation, while other studies have reported zinc supplementation does not improve immune function.

 

More research is required before any recommendations can be made regarding zinc and immune system response in the elderly *.

 

Pregnancy complications
Poor zinc nutritional status in pregnant women has been associated with a number of adverse outcomes of pregnancy, including low birth weight, premature delivery, labor and delivery complications, and anomalies in developing fetuses.

 

The results of maternal zinc supplementation trials have been mixed: while some studies have found that zinc supplementation increases birth weight and decreases the likelihood of premature delivery, other studies found that zinc supplementation did not affect these pregnancy complications *.

 

More research is needed to clarify the effects of zinc supplementation in this field.

 

* see also Principles – The complexity of micronutrient research

Please note:
Any dietary or drug treatment with high-dosed micronutrients needs medical supervision. 

 

Common cold
Many people believe that taking zinc lozenges or using zinc nasal spray when they first show signs of a cold can reduce the duration and severity of symptoms, but the evidence is decidedly mixed *.

 

More and better studies are needed that examine which kinds of zinc may be effective and against which kinds of cold pathogens.

 

Age-related macular degeneration

Zinc is found in the retina at high concentrations declining with age; thus, zinc is hypothesized to play a role in the development of age-related macular degeneration (AMD), an eye disease that occurs when the macula, the part of the retina that is responsible for central vision, starts to deteriorate.

 

A major clinical trial found that people who had AMD could slow its progression by taking zinc, vitamin C, vitamin E, beta-carotene, and copper. However, not all studies have found zinc to be helpful *.

 

At present, there is little evidence that zinc supplementation would be beneficial to people with early signs of macular degeneration, but further studies are warranted.

 

Diabetes

Moderate zinc deficiency may be relatively common in individuals with diabetes.

 

However, the influence of zinc on glucose metabolism is not clear at present and requires further study before high-dose zinc supplementation can be recommended for diabetics *.

 

HIV infection / AIDS

Sufficient zinc is essential in maintaining immune system function and HIV-infected individuals are particularly susceptible to zinc deficiency. In HIV-infected patients, low blood levels of zinc have been linked with a more advanced stage of the disease and also with increased risk of death.

 

Further research is necessary to determine optimal zinc intakes for HIV-infected individuals *.

 

* see also Principles – The complexity of micronutrient research

European health authorities recommend zinc intakes for adults of 9.5 mg per day for males and 7 mg/day for females.

 

In the U.S., the recommended intake for adults has been set at 11 mg/day for men and 8 mg/day for women.

 

The requirement for dietary zinc may be as much as 50% greater for strict vegetarians whose major food staples are grains and legumes.

 

A strong relationship exists between zinc and copper. Too much of one can cause a deficiency in the other. Long-term use of zinc should be accompanied by copper.

Dietary surveys in Europe and the U.S. estimated that the average zinc intake for adult men most often meets the recommended values.

 

On the other hand, it has been estimated that 82% of pregnant women worldwide are likely to have inadequate zinc intakes. In addition, infants, children, and breast-feeding women have been found to have an increased risk of zinc deficiency.

It is rare for people in industrialized countries to be seriously deficient in zinc.

 

Infants, children, and pregnant and breast-feeding women are at increased risk of zinc deficiency.

 

Low zinc levels are sometimes seen in the elderly, alcoholics, people with anorexia, and people on very restricted diets. People who have malabsorption syndromes, such as Crohn's disease or celiac disease, may also be deficient in zinc.

 

Symptoms of zinc deficiency include loss of appetite, poor growth, weight loss, lack of taste or smell, poor wound healing, skin problems (such as acne and psoriasis), hair loss, lack of menstrual periods, night blindness, white spots on the fingernails, and depression.

The best sources of zinc are oysters, red meats, poultry, cheese (e.g., ricotta, Swiss, Gouda), shrimp, crab, and other shellfish.

 

Other good, though less easily absorbed, sources of zinc include legumes (especially beans, peas, soybeans, and peanuts), whole grains, tofu, brewer's yeast, cooked greens, mushrooms, green beans, pumpkin, and sunflower seeds.

 

Only 20–40% of the zinc present in food is absorbed by the body. Zinc from animal foods like red meat, fish, and poultry is more readily absorbed by the body than zinc from plant foods.

 

Zinc is best absorbed when taken with a meal that contains protein.

Isolated outbreaks of acute zinc toxicity have occurred as a result of the consumption of food or beverages contaminated with zinc released from galvanized containers.

 

Signs of acute zinc toxicity are abdominal pain, diarrhea, nausea, and vomiting.

 

The major consequence of long-term consumption of excessive zinc is copper deficiency.

 

Tolerable upper intake level
European health authorities have defined safe upper intake levels of 25 mg zinc per day for adults, as well as pregnant and breast-feeding women.

 

In the U.S., the tolerable upper intake level for zinc intake has been set at 40 mg/day for adults.

 

Drug interactions
Please note:

Because of the potential for interactions, dietary supplements should not be taken with medication without first talking to an experienced healthcare provider.