Zinc is an essential trace element present in almost every cell of the human body, regulating cellular metabolism. Zinc interacts with thousands of different molecules, regulating a wide range of cellular functions throughout the body.
Functions of zinc depend on an unstable equilibrium. Both insufficient and excess levels of zinc can disturb the zinc-mediated equilibrium of physiological functions.
Daily zinc requirements are best covered by a healthy diet including 5 portions of fruit or vegetables per day. Zinc deposits stored in the body can be depleted during times of increased demand, such as during pregnancy, infection, inflammation, trauma or stress. These situations can lead to a zinc deficiency, which can be reversed by timely increased zinc supplementations.
What are the functions of zinc?
Zinc deficiency – what causes it and what are the symptoms?
Zinc belongs to the group of type 2 micronutrients. These are present in all parts of the body and are involved in fundamental cellular processes. Moderate deficiency in type 2 micronutrients often triggers unspecific symptoms that may initially remain undiagnosed.
- Face rash
- Rash in the genital area
- Sore, dry or tickly throat
- Mouth ulcers and sores
- Sores in the nose
- Skin lesions and cracked skin, particularly in the genital region
- Fungal infections
- Athlete’s foot
- Increased susceptibility to infections and inflammations
- Impaired wound healing
- Reduced vaccination efficiency
- Attention disorder
- Impaired memory
- Mood swings
- Loss of appetite and weight loss
- Developmental disorders (in children)
- Growth disorders (in children)
Zinc dosage recommendations
The daily intake of zinc as recommended by the German society for nutrition (DGE) depends on age and weight, and is different for men and women.
The following recommendations are provided in milligram (mg) per day:
- New-borns up to 4 months: 1 mg
- Babies from 4 to 12 months: 2 mg
- Children from 1 to 3 years: 3 mg
- Children from 4 to 6 years: 5 mg
- Children from 7 to 9 years: 7 mg
- Children from 10 to 12 years: Boys: 9 mg; Girls: 7 mg
- Children:13 to 14 years: Boys: 9,5 mg; Girls: 7 mg
- Adolescents 15 years and over, and adults: Men: 10 mg; Women: 7 mg
- Pregnant women from the 4th months of pregnancy: 10 mg
- Lactation: 11 mg
Who needs zinc?
Zinc is an essential micronutrient necessary for normal functioning of almost every cell in the body. Daily uptake of an adequate amount of zinc is therefore important to maintain cellular homeostasis.
Sufficient supply of zinc is crucial for normal development of babies and children, as well as during pregnancy and lactation.
Elderly people are also at increased risk of zinc deficiency, which can negatively impact immune function and cognitive abilities.
In case of suspected zinc deficiency, additional intake of zinc is recommended, eg using zinc supplements. Zinc infusions may be indicated in the case of acute severe zinc deficiency.
Caution is advised however, as excess intake of zinc can negatively affect the physiological balance of the body.
Zinc supports the immune response
The immune system is constantly reacting to invading pathogens such as viruses and bacteria, and is responsible for the removal of damaged cells. A weakened immune system is unable to promote optimal communication between the different immune cells, making the immune response less efficient. Zinc increases the activity of T helper cells, which are recruiting antibody producing B cells. In the case of a zinc deficiency, this communication pathway is delayed.
The same effect is observed in the ageing immune system. Zinc supplementation therefore supports the optimal functioning of the immune system, and has the potential to rejuvenate the immune response of older people.
Evidence for the direct action of zinc on the immune system has been provided by several studies with persons suffering from common cold. Zinc supplementation reduced the duration of the cold on average by 33%.
Zinc improves mental capacity
A major part of the zinc taken up with the diet is delivered to the brain, where it is required for the building of the neuronal networks. Zinc deficiency, especially during the developmental phase of the brain, can therefore disturb the mental development. Babies born from mothers with a zinc deficiency during pregnancy show reduced attention spans and activity, are slower learners and have lower motor skills.
Furthermore, studies are no showing that zinc also contributes to the preservation of mental capacity. Zinc supplementation positively impacts on the cognitive and emotional capacities of older women. Several lines of evidence also demonstrate that zinc can alleviate the symptoms of depression, especially in patients considered to be therapy resistant.
Zinc helps a healthy digestion
Dietary zinc is taken up via the gastrointestinal system, where the nutrients are absorbed through the intestinal epithelial layer to the cells. The development of this epithelial layer follows a complex process of cell division, cell specification and removal of excess cells. Zinc plays a crucial part in this procedure.
Zinc deficiency during the development of the gastrointestinal system can therefore have serious consequences for the digestion, and lead to severe diarrhoea.
A holistic approach to homeostasis (the physiological balance of the entire body) led scientists to propose that digestive problems due to zinc deficiencies can affect the immune system as well as cognitive abilities.
Zinc preserves the skin’s protective properties
As zinc is an important catalyst of cell renewal, zinc deficiencies have a particular effect on the skin. Insufficient zinc supply rapidly causes rashes, ulcers and lesions. The skin is losing its protective properties, opening the door to fungal infections and inflammations. Adequate zinc supply is also critical for wound healing. Long-term zinc deficiency can cause severe dermatitis.
Zinc as an antioxidant
Antioxidants reduce the amount of free radicals that are formed in the body due to environmental factors. Zinc belongs to the group of micronutrients acting as antioxidants. Neutralizing free radicals reduces oxidative stress, which can potentially cause cell damage.
Cancer cells on the other hand benefit from oxidative stress. The effect of zinc can therefore influence the activity of cancer cells. Zinc greatly contributes to cancer cell death, and has the potential to enhance the effect of chemotherapy.
Zinc in food
Zinc is present in a variety of foodstuffs. High amounts of zinc are found in beef, pork, and chicken, as well as in oysters, crabs and lobster. Other animal products that are excellent sources of zinc include cheese, yoghurt and milk. Pulses such as beans or chickpeas, as well as cashew and other nuts also contain high amounts of zinc.
Zinc side effects
Zinc belongs to the group of metals, and can therefore be toxic if taken up in high amounts. The recommended upper limit for intake of zinc has been set at 40 mg for adults. Possible symptoms for acute zinc poisoning include nausea and vomiting, loss of appetite, diarrhoea, stomach cramps and headaches.
Chronic overdoses of zinc (more than 150 mg/day) can modify the iron and copper deposits in the body, and have detrimental effects on the immune system. The recommended upper limit for the uptake of zinc should therefore not be exceeded.
Zinc can interact with several prescription drugs:
- Antibiotics: Concomitant use of zinc supplements and quinolone or tetracycline can impair the uptake of zinc as well as of the antibiotics.
- Penicillamine is a used for the treatment of rheumatoid arthritis. Simultaneous use of zinc prevents the uptake of penicillamine.
- Diuretics can increase the excretion of zinc via the urine, potentially leading to a depletion of endogenous zinc deposits.
- Micronutrients: Excess intake of iron can reduce the uptake of zinc, while excess intake of zinc impairs the uptake of copper.
In the case of concurrent use of zinc and prescription medications, careful study of the package information leaflet is advised, and the intake should be spaced at least 2 hours apart where appropriate. Homeostasis of micronutrients need to be monitored in case of supplementation.
Zinc Studies and references
- King JC. Zinc: an essential but elusive nutrient. A J Clin Nutr. 2011;94(2):679S-684S.
- Shenkin A. Micronutrients in health and disease. Postgrad Med J. 2006;82(971):559-567.
- Hemilä H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open. 2017;8(5):2054270417694291.
- Haase H, Mocchegiani E, Rink L. Correlation between zinc status and immune function in the elderly. Biogerontology. 2006 Oct-Dec;7(5-6):421-8.
- Lomagno KA, Hu F, Riddell LJ. Increasing iron and zinc in pre-menopausal women and its effects on mood and cognition: a systematic review. Nutrients. 2014 Nov 14;6(11):5117-41
- Prasad AS. Impact of the discovery of human zinc deficiency on health. J Am Coll Nutr. 2009 Jun;28(3):257-65.
- Schwartz JR, Marsh RG, Draelos ZD. Zinc and skin health: overview of physiology and pharmacology. Dermatol. Surg. 2005;31:837-47.
- Kocdor H, Ates H, Aydin S. Zinc supplementation induces apoptosis and enhances antitumor efficacy of docetaxel in non-small-cell lung cancer. Drug Des Devel Ther. 2015 Jul 27;9:3899-909.
- Deutsche Gesellschaft für Ernährung Zink - empfohlene Zufuhr
- Bhatnagar S, Taneja S. Zinc and cognitive development. Br J Nutr. 2001 May;85 Suppl 2:S139-45.
- Vela G, Stark P, Socha M, Sauer AK. Zinc in Gut-Brain Interaction in Autism and Neurological Disorders. Neural Plast. 2015;2015:972791.
- National Institutes of Health. Zinc: Fact Sheets for Health Professionals.