Zinc is an essential micronutrient and Mineral for the human body. It is widely present inside our body systems in the enzymes and
Zinc is liberated from food as free ions during the digestion process. Then, it binds to ligands before it arrives in the small intestine. The absorption of Zinc from the small intestine is dependent on its concentration in foods. Also, studies show that Zinc-deprived humans absorb this element with increased efficiency, while humans on a high-zinc diet show a reduced efficiency of absorption.
When it is absorbed, about 70% of it is bound to albumin protein. So, any disturbance in albumin in blood will affect Zinc. Half of Zinc is excreted in faeces. The remaining is excreted in urine and through skin, hair and sweat.
Importance of Zinc
Zinc is very important for growth and development. It plays an important role in cell growth, differentiation and metabolism.
Over than 300 enzymes are dependent on Zinc. Zinc is important for the structure of proteins and cell membranes. Also, Zinc is important in gene expression.
Also, it is very important for immunity. It stimulates our immune to defend against bacteria and harmful pathogens.
Health Benefits of Zinc
Studies show that supplementation of Zinc in children leads to reduction in the prevalence of pneumonia in developing countries.
Studies show that Zinc might be beneficial in controlling metabolic disorders like obesity and insulin resistance in children.
Studies show that daily administration of Zinc enhances the immunity and reduces the infection with opportunistic bacteria in AIDS patients. However, other studies show that high Zinc intake can increases progression of HIV disease.
Zinc found to be lower in children of parents with premature atherosclerosis. So, administration of Zinc has beneficial effect in the treatment of inflammation and atherosclerosis.
Some studies show that treatment with Zinc gluconate and Zinc acetate lozenges reduce duration of common cold. However, other studies show no effect of these lozenges on common cold.
Age-related macular degeneration
Macular degeneration can lead to blindness in elderly. Macula is part of retina that is responsible for central vision. As age increase, Zinc deficiency occurs thus enzymes dependent on it in the macula are affected.
Studies show that daily administration of Zinc alone (200mg Zinc sulphate which contains Zinc 81mg ) or with mixture of (500 mg of vitamin C, 400 IU of vitamin E, and 15 mg of β-carotene) and high-dose zinc (80 mg of zinc and 2 mg of copper ) reduces the high risk of macular degeneration.
Another study showed that administration of 50 mg/day of zinc monocysteine for six months decrease macular degeneration.
Recommended Dietary Requirement (RDA) for Zinc
|7 – 12 months||3|
|1 – 3 years||3|
|4 – 8 years||5|
|9 – 13 years||8|
|14 – 18 years Male||11|
|14 – 18 years Female||9|
|≥ 19 years Male||11|
|≥ 19 years Female||8|
|Pregnancy ≤ 18 years||12|
|Pregnancy > 19 years||11|
|Lactating woman ≤ 18 years||13|
|Lactating woman > 19 years||12|
Best Zinc Foods for Natural Zinc Supply
- Shellfish, beef, and other red meats are rich sources of zinc.
- Nuts and legumes are relatively good plant sources of zinc.
- Zinc bioavailability (the fraction of zinc retained and used by the body) is relatively high in meat, eggs, and seafood because of the relative absence of compounds that inhibit zinc absorption and the presence of sulfur-containing amino acids (cysteine and methionine) that improve zinc absorption.
- The zinc in whole-grain products and plant proteins is less bioavailable due to their relatively high content of Phytic Acid, a compound that inhibits zinc absorption.
Zinc deficiency can include several organs as the epidermal, gastrointestinal, central nervous, immune, skeletal, and reproductive systems.
Zinc deficiency can affect growth especially in infants and children.
Causes of Zinc Deficiency
- Inadequate dietary intake, as high cereals and legumes intake with less meat intake.
- Malabsorption as in case of inflammatory bowel syndrome.
- Increased fecal excretion of Zinc as in diarrhea.
- Infections can decrease Zinc concentration in blood.
- Genetic disorders as acrodermatitis enteropathica where impaired Zinc absorption and uptake occur. It is characterized by diarrhea.
Symptoms of Zinc Deficiency
In general, clinical manifestations of zinc deficiency vary with age:
- In early infancy, diarrhea is a prominent symptom.
- Zinc deficiency also leads to impaired cognitive function, behavioral problems, impaired memory, learning disability, and neuronal atrophy in babies and children.
- Skin problems become more frequent as the child grows older.
- Alopecia, growth retardation and recurrent infections are common in school-age children.
- Chronic non-healing skin ulcers and also recurrent infections are common among the elderly.
High risk groups for Zinc Deficiency
Infants and children: due to high rate of growth. In the first 5-6 months of life, an infant can get adequate Zinc intake from his mother’s milk if she is well-nourished with Zinc. After this time, introducing of food which is with low Zinc as cereals causes the problem of Zinc deficiency.
Zinc requirement for malnourished children is estimated to be higher than normal children, between 2mg/Kg and 4mg/Kg.
Adolescents: The physiological requirements for zinc peak during adolescence at the time of the pubertal growth spurt, which generally occurs in girls between 10 years and 15 years and in boys between 12 years and 15 years.
Even after the growth spurt has ceased, adolescents may require additional zinc to replenish depleted tissue zinc pools.
Pregnant and Lactating women: need more Zinc demands.
Elderly: as absorption problems occur by age. Also, consumption of red meat is decreased.
Others: Alcoholics and people with chronic renal disease have Zinc deficiency.
Solutions for Zinc deficiency
Supplementation: In cases of diarrhea, supplementation of Zinc for 14 days, 10 mg/day for children under 3 years and 20 mg for older children.
In cases of anemia and other micronutrients deficiency, Zinc supplementation is 5 mg/day for children between 7 months and 3 years and 10 mg/day for older children.
Zinc supplements found in form of sulphate, gluconate and acetate.
Fortification: Zinc is added as Zinc sulphate (which is expensive) or Zinc Oxide. The absorption of both showed to be similar.
Fortification of infants’ milk formula with Zinc as 1mg/Liter
Also, in food as in flour, it is suggested that Zinc can be added in range of 30-70 mg per kg.
Bio–fortification: It differs from fortification as it intends to increase the concentration of Zinc in the growing plants as wheat, maize and rice.
Adding Zinc fertilizers, in the form of Zinc sulphate as it is more soluble and can increase Zinc phytoavailability in the soil, thus increase the cultivation of plants enriched with Zinc. Good results of this bio-fortification were shown in Harvest Zinc Project.
Zinc and other nutrients
Phytic Acid is a major inhibitor of Zinc. Phytic Acid is found in legumes and cereals. Phytic Acid contains high-density negative charge phosphates. It forms insoluble complex with Zinc, so it decreases Zinc absorption.
Some studies suggest consuming calcium is beneficial to prevent this insoluble complex to occur.
Techniques such as soaking, germination, and fermentation promote enzymatic hydrolysis of phytic acid in whole grain cereals and legumes by enhancing the activity of endogenous or exogenous phytase enzyme.
Also, non-enzymatic methods such as milling have been successful in reducing phytic acid content in plant-based staples.
High concentrations of iron in watery solutions can decrease Zinc absorption. Some studies show that iron fortification of solid food as bread does not affect Zinc absorption.
Proteins have a
High Zinc intake (50mg/day) for long period can decrease the absorption of copper as it enhances the synthesis of metallothionein. This protein traps copper and hinders its absorption from small intestine.