Zinc deficiency

Zinc deficiency, as the name suggests, is caused by inadequate zinc in the diet. It can also be due to liver disease, cystic fibrosis or other diseases.

Global prevalence of zinc deficiency

Role of zinc

• Zinc is an essential mineral that is naturally present in some foods, added to others, and available as a dietary supplement.
• Zinc is also found in many cold lozenges and some over-the-counter drugs sold as cold remedies.
• Zinc is involved in numerous aspects of cellular metabolism.

Role in cellular enzymes

It is required for the catalytic activity of approximately 100 enzymes and it plays a role in immune function, protein synthesis, wound healing, DNA synthesis, and cell division.

Role in smell and taste

Zinc also supports normal growth and development during pregnancy, childhood, and adolescence and is required for proper sense of taste and smell.

Recommended daily intake

The RDA varies from 11 mg in normal adult males, to 8mg in adult females. In pregnant women, the RDA is 11mg and in lactating women, it is 12mg of elemental zinc per day.

Rich sources of zinc

Zinc is found in sea food, meats, and some vegetarian items such as seeds, nuts, chickpeas, cereals fortified with zinc etc. Some of the rich sources of zinc include oysters, beef, crab, lobster, pork chop, baked beans, breakfast cereal, chicken, dark meat, pumpkin seeds, cashews, chickpeas, cheese

Zinc Deficiency

• Zinc deficiency is characterized by growth retardation, loss of appetite, and impaired immune function. In more severe cases, zinc deficiency causes hair loss, diarrhea, delayed sexual maturation, impotence, hypogonadism in males, and eye and skin lesions.
• Weight loss, delayed healing of wounds, taste abnormalities, and mental lethargy can also occur.
• Many of these symptoms are non-specific and often associated with other health conditions; therefore, a medical examination is necessary to ascertain whether a zinc deficiency is present.

Role of zinc deficiency in other diseases

Immune function

Severe zinc deficiency depresses immune function, and even mild to moderate degrees of zinc deficiency can impair macrophage and neutrophil functions, natural killer cell activity, and complement activity.

Wound healing

Zinc helps maintain the integrity of skin and mucosal membranes.

Diarrhea

Acute diarrhea is associated with high rates of mortality among children in developing countries The World Health Organization and UNICEF now recommend short-term zinc supplementation (20 mg of zinc per day, or 10 mg for infants under 6 months, for 10–14 days) to treat acute childhood diarrhea.

The common cold

Researchers have hypothesized that zinc could reduce the severity and duration of cold symptoms by directly inhibiting rhinovirus binding and replication in the nasal mucosa and suppressing inflammation In a randomized, double-blind, placebo-controlled clinical trial, the zinc lozenges significantly reduced the duration of cold symptoms (cough, nasal discharge, and muscle aches).

Age-related macular degeneration

Researchers have suggested that both zinc and antioxidants delay the progression of age-related macular degeneration (AMD) and vision loss, possibly by preventing cellular damage in the retina.

Diagnosis

Zinc deficiency is typically diagnosed based on clinical suspicion and a low level of zinc in the blood.

Normal zinc levels

• Any level below 70 mcg/dl (normal 70-120 mcg/dl)is considered as zinc deficiency.
• Zinc deficiency could be also associated with low alkaline phosphatase since it acts a cofactor for this enzyme.

Treatment

Treatment is either with supplements that contain zinc such as zinc gluconate, zinc sulfate, or zinc acetate.

Risk factors

In North America, overt zinc deficiency is uncommon.

People with gastrointestinal and other diseases

• Gastrointestinal surgery and digestive disorders (such as ulcerative colitis, Crohn’s disease, and short bowel syndrome) can decrease zinc absorption and increase endogenous zinc losses primarily from the gastrointestinal tract and, to a lesser extent, from the kidney.
• Other diseases associated with zinc deficiency include malabsorption syndrome, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses [40]. Chronic diarrhea also leads to excessive loss of zinc [27].

Vegetarians

• The bioavailability of zinc from vegetarian diets is lower than from non-vegetarian diets because vegetarians do not eat meat, which is high in bioavailable zinc and may enhance zinc absorption.
• In addition, vegetarians typically eat high levels of legumes and whole grains, which contain phytates that bind zinc and inhibit its absorption/

Pregnant and lactating women

• Pregnant women, particularly those starting their pregnancy with marginal zinc status, are at increased risk of becoming zinc insufficient due, in part, to high fetal requirements for zinc

Older infants who are exclusively breastfed

• Breast milk provides sufficient zinc (2 mg/day) for the first 4–6 months of life but does not provide recommended amounts of zinc for infants aged 7–12 months, who need 3 mg/day

People with sickle cell disease

• Results from a large cross-sectional survey suggest that 44% of children with sickle cell disease have a low plasma zinc concentration, possibly due to increased nutrient requirements and/or poor nutritional status.
• Zinc deficiency also affects approximately 60%–70% of adults with sickle cell disease.
• Zinc supplementation has been shown to improve growth in children with sickle cell disease.

Alcoholics

• Approximately 30%–50% of alcoholics have low zinc status because ethanol consumption decreases intestinal absorption of zinc and increases urinary zinc excretion.

Recommendations to avoid zinc deficiency

• Include a variety of vegetables, fruits, whole grains, fat-free or low-fat milk and milk products, and oils.
• Whole grains and milk products are good sources of zinc. Many ready-to-eat breakfast cereals are fortified with zinc.
• Includes a variety of protein foods, including seafood, lean meats and poultry, eggs, legumes (beans and peas), nuts, seeds, and soy products.
• Oysters, red meat, and poultry are excellent sources of zinc. Baked beans, chickpeas, and nuts (such as cashews and almonds) also contain zinc.
• Reduce alcohol consumption.

External links

• Zinc and health from NIH

Zinc deficiency Resources
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