Zinc is being increasingly used nowadays because of its role in boosting immunity against COVID-19 infection. Zinc-rich fruits, vegetables, and supplements are commonly utilized. It is important to know the zinc content of each food so as to avoid toxicity. It is always advisable to avoid zinc tablets and capsules where possible and eat healthy zinc-containing foods.
Zinc is an essential trace mineral. It is required in minimal amounts by the human body. Although it is required in small amounts, it is vital for the body and inadequate amounts of zinc can lead to deficiency symptoms.
The human body does not produce or store zinc, that’s why an adequate amount of zinc should be present in the diet for normal body function and to avoid deficiency symptoms. This article explains everything about the health benefits of zinc, recommended dietary allowance, deficiency symptoms, and zinc-rich foods.
Why zinc is important?
Zinc is involved in numerous functions in the human body:
- It is an important coenzyme for more than 300 enzymes and plays an important role in the functioning of various metabolic pathways. It plays a crucial role in cell metabolism.
- Zinc is required for wound healing. It modulates the inflammatory and immune response that occurs after a trauma or injury. It also affects wound healing by playing a role in the activation and aggregation of platelets. It has been studied in critically ill patients and patients with severe burns, wounds, and injuries [Ref]. Zinc oxide is available as a topical gel formulation and is used for wound healing and treatment of diaper rash.
- Zinc is commonly used to treat respiratory and gastrointestinal infections. It reduces the severity and duration of diarrheal episodes in children. It is an important component of protein synthesis, cell metabolism, differentiation, immune function, and epithelial regeneration [Ref].
- It plays important role in the growth and development during childhood, adolescence, and pregnancy. In males, zinc deficiency has been associated with sexual dysfunction and hypogonadism.
- Zinc is an important co-factor of metalloproteinases which are mostly present in the salivary glands. Zinc supplementation may have a role in the recovery from taste and smell dysfunction that occurs in patients with COVID-19 infection [Ref]. It also stimulates the sense of taste and smell in healthy individuals and those with frequent respiratory infections.
- Zinc is involved in the synthesis of proteins and DNA. The deficiency of zinc is associated with growth retardation.
- Zinc is used in the treatment of various skin conditions. It is required for healthy nails, skin, and hair. Zinc pyrithione is used to treat dandruff (seborrheic dermatitis).
Recommended Dietary Allowance (RDA) for zinc according to different age groups:
Recommended Dietary Allowance (RDA) is the average daily sufficient intake of a nutrient that meets all the requirements of nearly (97%-98%) healthy individuals. The current RDAs for zinc are listed in the table below.
|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|
|19+ years||11 mg||8 mg||12 mg|
Zinc-rich foods (Zinc-rich Fruits, Vegetables, and Supplements)
A variety of foods contain high amounts of zinc. Rich sources of zinc include
- Milk and milk products
- Red meat
- Beans and nuts
Bioavailability of zinc
The bioavailability of zinc from plant food sources is lower than that of animal food sources. This is because of the presence of phytates in plant-based food products. Phytates bind to zinc and inhibit its absorption. This is why vegetarians are at greater risk of zinc deficiency.
Zinc content in different food groups:
- Zinc-rich Bread and Cereals
|Food Item||Serving||Zinc content|
|White Bread||1 slice||1.8 mg|
|Whole Wheat chapatti||1 small||2.0 mg|
|Refined Wheat flour||100 g||2.0 mg|
|Whole wheat flour||100 g||2.9 mg|
|Corn flour||100g||1.7 mg|
|Barley whole grain flour||100g||2.0mg|
|Polished Rice||½ cup||1.2 mg|
|Brown Rice||½ cup||1.4 mg|
- Zinc-rich Vegetables
|Food item||Zinc Content|
- Zinc-rich Fruits
|Food Item||Zinc Content|
- Zinc-rich Milk and Dairy Products
|Food item||Serving||Zinc content|
|Whole milk||1 cup||0.2 mg|
|Yogurt||8 oz||0.6 mg|
|Dry milk powder||1/3 cup||4.1 mg|
- Zinc-rich Meats and Meat substitutes
|Food Item||Zinc content|
|Egg whites||0.01 mg|
|Goat meat||4.5 mg|
|Beef Kidney||1.9 mg|
|Beef liver||1 mg|
- Zinc-rich Beans, peas, and lentils
|Food Item||Zinc Content|
|Kidney beans||3.1 mg|
- Zinc-rich Nuts
|Food item||Serving||Zinc Content|
|Peanuts||16 nuts||1.8 mg|
|Walnuts||4 halves||3.1 mg|
|Pistachio||16 nuts||2.2 mg|
|Cashews||16 nuts||3 mg|
|Almons||16 nuts||3.3 mg|
- Zinc-rich Supplements:
|Zinc Supplements||Elemental Zinc in mg|
|Zinconia||50 mg per tablet|
|Surbex Z||22.5 mg per tablet|
|Polybion Z||22.5 mg per tablet|
|Zincovit||22 mg per tablet|
|Zinklet||20 mg per 5 ml syrup|
|Diazinc||20 mg per 5 ml syrup|
The Daily Value of zinc:
Daily value helps the consumers to know the amount of a nutrient present in food products. It is mentioned on food labels. The daily value for zinc is 11 mg for adults and children aged 4 years and above.
- Food containing 20% or more DV of zinc is considered a high source.
- Foods Providing lower daily values also contribute to a healthful diet.
Diseases associated with Zinc Deficiency:
Zinc deficiency is characterized by
- Growth retardation
- Impaired immune function resulting in frequent gastrointestinal and respiratory infections.
- Hair loss
- Weight loss
- Delayed wound healing
- Eye and skin lesions
- Taste abnormalities
Many of these symptoms are non-specific and also associated with other health conditions. A proper medical examination is necessary to determine the presence of zinc deficiency.
Who is at Risk of Zinc Deficiency?
Zinc deficiency is not very common. When deficiency occurs, it is usually due to inadequate zinc intake, impaired absorption, excessive excretion, or increased requirements by the body. Generally, zinc deficiency is easily covered up by the consumption of a diet rich in zinc. Supplementation might be necessary for the following situations:
Gastrointestinal diseases or digestive disorders (IBS, Ulcerative colitis, and short bowel syndrome) can decrease the absorption of zinc, as a result, there is an increased endogenous loss of zinc. Chronic diarrhea also causes excessive loss of zinc.
The bioavailability of zinc is lower in plant-based food products due to the presence of phytates, which bind to zinc and inhibit its absorption. That’s why vegetarians are at greater risk of zinc deficiency.
Pregnant and lactating women:
Due to high fetal requirements, pregnant and lactating women are at risk of developing zinc deficiency. For these reasons, the RDA of zinc for pregnant and lactating women is higher than other women.
Older infants who are breastfed are at risk of developing zinc deficiency because breast milk provides 2mg/day zinc while the RDA for older infants (7-12 months) is 3 mg/day. Infants should be fed Age-appropriate formula milk along with breast milk to avoid zinc deficiency and to improve growth and development.
Ethanol consumption decreases the absorption of zinc and increases its excretion in urine that’s why alcoholics are at risk of zinc deficiency.
Zinc deficiency in patients with Diabetes and Obesity (Diabesity):
Zinc is an important co-factor in the normal functioning of many enzymes. These enzymes are responsible for the utilization and cellular entry of glucose into the cells and cellular metabolism.
Zinc supplementation is usually required in patients with diabetes as chronic hyperglycemia can result in urinary losses of zinc. It has also been postulated that there is impaired absorption of zinc from the GI tract in diabetic patients.
In one study zinc deficiency was more common in individuals with diabetes especially those who were married, obese, and had long-standing diabetes [Ref].
What are the symptoms of Zinc Toxicity?
Excessive intake of zinc can lead to toxicity. Symptoms for zinc toxicity include:
- Abdominal cramps
Chronic zinc toxicity affects iron function, low copper status, reduces immune function, and decreases the levels of HDL
Tolerable upper intake levels (Uls) for zinc
|0–6 months||4 mg||4 mg|
|7–12 months||5 mg||5 mg|
|1–3 years||7 mg||7 mg|
|4–8 years||12 mg||12 mg|
|9–13 years||23 mg||23 mg|
|14–18 year||34 mg||34 mg||34 mg|
|19+ years||40 mg||40 mg||40 mg|
Beyond these levels, zinc toxicity will occur*
Zinc is present in most food items including fruits, vegetables, meat, nuts, and cereals. It is an important cofactor for many enzymes and its deficiency is associated with many diseases.