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NUTRIDATE

Volume 33, Issue 3 2022

NUTRIDATE

Volume 33, Issue 3 2022

Zinc: a mineral for immunity, skin and DNA

Nicole Murphy, Dietitian, Nutritionist

Despite being a trace mineral, meaning the body only needs it in small amounts, the roles zinc play pack a punch. From supporting a healthy immune system to creating DNA, building proteins, and healing damaged tissue, and zinc is a mighty mineral. In this article, we take a deeper dive into the functions of zinc, where to get it from, and how much you need to consume to avoid deficiency. 

Figure 1: Zinc is one of the essential minerals that we need to get from our diet

What is Zinc?

Zinc is the 24th most abundant element in the earth’s crust and has incredible biological and public health importance. The body doesn’t have a specialised zinc storage system, so we need to consume a little bit of zinc daily. It’s found naturally in, or added to, some foods and is available as a supplement. Some topical medications and lozenges, such as cold and flu lozenges and creams applied to the skin, contain zinc. 

Why is Zinc important?

Zinc is one of the essential minerals for human health as it serves as a co-factor for more than 100 enzymes. A co-factor is a chemical compound attached to a protein. The protein is often an enzyme, and the co-factor or chemical compound is needed to help the enzyme do its work. In its role as a co-factor, zinc helps with many cellular processes, including supporting the formation of DNA through DNA synthesis. Zinc also helps to maintain structural integrity and stabilise the cell membranes of large numbers of proteins. It is critical for normal growth and development and growth and maintenance of connective tissue. 

Figure 2: Zinc is critical for many body functions including healthy growth and development

As well as these critical processes, zinc plays a role in a multitude of other biological functions such as:

  • wound healing
  • taste and smell
  • immune system function
  • proper thyroid function
  • bone mineralisation
  • fetal growth
  • sperm production
  • formulation of collagen to make hair, skin and nails
  • memory and mental development.

 

Common food sources of zinc

Zinc is found in a variety of animal and plant-based foods. Shellfish (such as oysters, crab, and lobster), beef, poultry and pork are rich sources of zinc. Legumes, nuts, seeds and wholegrains are also good sources. They do contain phytates that can bind to zinc and are said to reduce its bioavailability (e.g., its ability to be absorbed by the body). However, the phytates are minimised by cooking, baking, soaking, fermenting and sprouting. Dairy and some breakfast cereals also contain zinc.

Figure 3: Various animal and plant foods contain zinc

Table 1. Food sources and zinc content

FoodZinc content (mg)
3 fresh oysters7mg
1 beef steak 4.5mg
1 chicken breast 1.5mg
2 slices grainy bread 1mg
2 eggs1mg
½ cup cooked white rice 1mg
½ can baked beans 1mg
2 tablespoons pumpkin seeds1mg
2 tablespoons cashews 1mg

Adapted from the Healthy Food Guide

Can I get enough zinc from food?

Most people will be able to meet their zinc needs by consuming various foods from each food group daily. As zinc helps cells to grow and multiply, zinc requirements are higher during developmental periods of rapid growth, such as childhood, adolescence, pregnancy and lactation. 

While the global rate of zinc deficiency has been reported to be as high as 50%, this is mostly due to the higher rates of deficiency seen in developing countries. Zinc deficiency is less common in more developed countries, such as Australia. Zinc deficiency is more common in individuals with digestive disorders who don’t absorb zinc well, such as those with inflammatory bowel diseases and people who have had gastrointestinal surgery.

Figure 4: Consuming a variety of foods from each food group daily should provide adequate zinc for most people, and it is also available in supplements.

Other groups at-risk of deficiency include:

  • Pregnant women: Zinc requirements are higher during pregnancy. Many prenatal supplements consumed by pregnant women contain both zinc and iron (among many other vitamins and minerals). The same transporter molecules transport both zinc and iron and therefore, it’s thought that supplements containing high doses of either mineral may impact the absorption of one of them. 
  • Vegans (and some vegetarians): Zinc found in plant-based foods is less bioavailable, meaning it is not absorbed by the body, as well as zinc from animal sources. 
  • Older adults: Individuals with poor appetite due to chronic diseases or medications are at risk of low zinc intake and subsequent deficiency. According to the 2012 Australian Health Survey, 63% of males over the age of 71 had inadequate intake of zinc compared to only 12% of females of the same age. 
  • Diabetics: Individuals with Type 1 or Type 2 diabetes may be at greater risk of deficiency due to losing higher concentrations of zinc in their urine than those without diabetes. 
  • Children and adults with malnutrition: Micronutrient and mineral deficiencies, including zinc, are major risk factors for malnutrition. Malnutrition affects the immune system, increases the likelihood of infection and can lead to death. Unfortunately, malnutrition is responsible for more than one-third of deaths for children under five in developing countries. 

Signs and symptoms of zinc deficiency

The signs and symptoms of zinc deficiency vary, are often non-specific and could be associated with other medical conditions. It’s important to seek medical and nutritional advice from accredited health professionals to explore whether zinc deficiency is occurring. 

Figure 5: Poor appetite, mental fatigue and hair loss are some symptoms of zinc deficiency.

Common signs and symptoms of deficiency include:

  • impaired growth and development in youth
  • loss of appetite
  • impaired immune function
  • hair loss
  • delayed wound healing
  • mental fatigue
  • hypogonadism in adult males.

Is there such thing as too much zinc?

Too little and too much zinc can be harmful, both in the short and long term. The National Health and Medical Research Council guides the Tolerable Upper Intake Level (UL) – the maximum daily intake of vitamins and minerals that are unlikely to cause harmful effects on health. The UL for zinc is 40 mg daily for all males and females ages 19 years and over. Some of the reported acute adverse effects of high zinc intakes include nausea, vomiting, headaches and diarrhea.

Table 2. Recommended Dietary Intakes (RDI) for Zinc

AgeFemaleMalePregnancyLactation
1-3 yr3 mg/day3 mg/day
4-8 yr4 mg/day4 mg/day
9-13 yr6 mg/day6 mg/day
14-18 yr7 mg/day13 mg/day10 mg/day11mg/day
19-30 yr8 mg/day14 mg/day11mg/day12 mg/day
31-50 yr8 mg/day14 mg/day11 mg/day12 mg/day
51-70 yr8 mg/day14 mg/day
>70 yr8 mg/day14 mg/day
Pregnancy10-11mg/dayN/A

Adapted from Nutrient Reference Values for Australia and New Zealand.

Immunity and inflammation

Zinc is considered critical for a healthy immune system. Zinc is needed for the growth and functioning of immune cells, which means even moderate deficiency can slow the activity of lymphocytes, neutrophils and macrophages that help to protect the body from viruses and bacteria. 

Therefore, maintaining your zinc needs daily through consuming a varied diet from across the food groups can help prevent ill health.  

Evidence suggests that zinc supplements can help prevent and reduce the duration of respiratory tract infections such as colds and the flu., particularly throat and nasal symptoms when taken at the onset of symptoms. It’s still unclear as to the effect of zinc lozenges or supplementation on the severity of symptoms. 

Figure 5: Zinc is needed for healthy immunity and may help prevent and treat symptoms of respiratory tract symptoms.

Skin health and wound healing

Zinc plays a major role in regulating every phase of the wound healing process, including membrane repair, immune defence and scar formation. People with chronic leg ulcers or burns may experience zinc deficiency due to zinc losses through injury or poor appetite. Therefore, zinc therapy, either topical cream or supplement, is often used to support wound healing in individuals with zinc deficiency. 

Student activities

  1. What is your RDI for zinc? 

  2. What foods are high in zinc?

  3. List two factors that can inhibit zinc absorption in the body.
     
  4. Where is zinc found in the body?
     
  5. Write out the foods/meals you need to consume daily to meet your zinc RDI. 

  6. (a) Who is at risk of zinc deficiency? (b) What are some of the signs and symptoms of zinc deficiency? 

  7. What is a co-factor, and what role does zinc play as a cofactor? 

  8. List five biological functions of zinc in the body. 

  9. According to the 2012 Australian Health survey, what percentage of males and females over 71 are not meeting their zinc needs?

    1. 56% for males and 71% for females
    2. 65% for males and 30% for females
    3. 10% for males and 40% for females
    4. 63% for males and 12% for females 

  10. (a) Are zinc supplements effective for preventing colds and flu (Yes/No)?
    (b) Explain your answer.

References and resources

Australian Bureau of Statistics. Australian Health Survey: Usual Nutrient Intakes. Accessed March 2022 https://www.abs.gov.au/statistics/health/health-conditions-and-risks/australian-health-survey-usual-nutrient-intakes/latest-release

Bonaventura, P., Benedetti, G., Albarède, F., & Miossec, P. (2015). Zinc and its role in immunity and inflammation. Autoimmunity reviews14(4), 277-285.

Chasapis, C. T., Loutsidou, A. C., Spiliopoulou, C. A., & Stefanidou, M. E. (2012). Zinc and human health: an update. Archives of toxicology86(4), 521-534 https://doi.org/10.1007/s00204-011-0775-1

Examine. Zinc. Accessed March 2022 https://examine.com/supplements/zinc/research/#safety-and-toxicology 

GI Society: Canadian Society of Intestinal Research. Four myths about food and nutrition. https://badgut.org/information-centre/health-nutrition/4-myths-food-nutrition/

Harvard T.H. Chan School of Public Health. The Nutrition Source, Zinc. Accessed March 2022 https://www.hsph.harvard.edu/nutritionsource/zinc/ 

Harvard School of Public Health. The Nutrition Source: Are anti-nutrients harmful? https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/

Healthline. Zinc: Everything you need to know. Accessed March 2022. https://www.healthline.com/nutrition/zinc 

Healthy Food Guide. A guide to zinc. Access on March 2022. https://www.healthyfood.com/healthy-shopping/a-guide-to-zinc/ 

Lin, P. H., Sermersheim, M., Li, H., Lee, P., Steinberg, S. M., & Ma, J. (2017). Zinc in Wound Healing Modulation. Nutrients10(1), 16. https://doi.org/10.3390/nu10010016

Marreiro, D. D. N., Cruz, K. J. C., Morais, J. B. S., Beserra, J. B., Severo, J. S., & De Oliveira, A. R. S. (2017). Zinc and oxidative stress: current mechanisms. Antioxidants6(2), 24.

National Health and Medical Research Council and Ministry of Health. Nutrient Reference Values Australia and New Zealand. Zinc, nrv.gov.au. Accessed March 2022
https://www.nrv.gov.au/nutrients/zinc

National Institutes of Health, Office of Dietary Supplements. Zinc fact sheet for health professionals, ods.od.nih.gov. Accessed March 2022
https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/

Rangan, A. M., & Samman, S. (2012). Zinc intake and its dietary sources: results of the 2007 Australian National Children’s Nutrition and Physical Activity Survey. Nutrients4(7), 611–624. https://doi.org/10.3390/nu4070611

Singh, M., & Das, R. R. (2013). Zinc for the common cold. Cochrane Database of Systematic Reviews, (6) https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD001364.pub4/abstract

Wilkinson, E. A. J., & Hawke, C. I. (1998). Does oral zinc aid the healing of chronic leg ulcers?: A systematic literature review. Archives of Dermatology134(12), 1556-1560.
https://www.ncbi.nlm.nih.gov/pubmed/9875193

Medical News Today. Zinc may reduce symptoms of cold and flu. https://www.medicalnewstoday.com/articles/zinc-may-reduce-symptoms-of-cold-and-flu

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