Zinc: everything you need to know about this vital mineral

Zinc is the second most abundant mineral in the body after iron, with over 300 enzymes and 1000 transcription factors dependant on this essential micronutrient. It is involved in many cellular processes such as cell proliferation and differentiation, protein synthesis, gene transcription, nucleic acid metabolism and DNA synthesis.¹

Zinc deficiency is common, with an estimated one quarter of the world’s population being deficient, often caused by poor dietary intake, low absorption and increased zinc loss.¹ The best food sources of zinc can be found in meat, eggs and fish alongside plant-based options such as pumpkin seeds, legumes, cashew nuts, mushrooms and spinach.

In this article we take a closer look at zinc and explore its many benefits to health, including research findings, supplement forms and how to improve absorption.

What are the benefits of zinc to health?

Immune function

Zinc affects multiple aspects of the immune system, from maintaining macrophage and neutrophil function, to supporting natural killer cell activity. As zinc is required for protein synthesis, it is needed for the production of immune antibodies. ^2,3

Sufficient zinc levels are needed for adequate functioning of the immune system due to its role in regulating intracellular signalling pathways of the innate and adaptive immune cells,² alongside it’s influence on inflammatory signalling and antibody production.¹

Zinc is a cofactor for over 200 enzymes involved in the bodies antioxidant defence system. It is involved in maintaining macrophage and neutrophil function, supporting NK cell activity, modulating cytokine release, cell growth and differentiation of immune cells and developing and activating T-lymphocytes.³ Zinc deficiency has been linked to low T-cell and B-cell function and the dampening down of other immune markers, alongside increasing the production of pro-inflammatory cytokines, such as IL-1ϐ, IL-6 and TNF-a, highlighting the importance of zinc intake and supporting the reputation of zinc as an antiviral mineral.² 

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Histamine and the allergic response

Zinc can inhibit the release of histamine from basophils and mast cells, which can help reduce symptoms caused by histamine excess, such as itchy eyes and a runny nose.⁴

Research has discussed the involvement of zinc in the development of allergic disease, noting its deficiency as a risk factor for allergic eosinophilic inflammation such as asthma, which is associated with a Th2 mediated eosinophilic airway inflammation. Research has also found lower zinc levels in those with atopic asthma compared to controls, with supplementation being found in some studies to provide a benefit.⁵

Zinc and skin health

The skin is the third most zinc abundant tissue in the body, so it is not surprising then that suboptimal zinc concentrations have been indicated in a number of common skin disorders such as acne, rosacea, psoriasis and eczema.⁸

In one study, patients suffering with acne had significantly lower zinc levels than those in the control group, with zinc treatment leading to significant improvements in inflammatory papules.⁹

Zinc inhibits the activation of integrins by keratinocytes, the cells that produce keratin, an overproduction of which can cause the walls of a skin pore to clog together, leading to acne. This inhibition also modulates the production of TNF-a and IL-6 and reduces the production of inflammatory mediators such as nitric oxide.8 As an antibacterial agent, zinc has been found to kill cutibacterium acnes; the bacteria associated with acne. The common medical treatment prescribed for acne is often antibiotics, due to the potential of bacteria becoming antibiotic resistant; zinc may offer a natural alternative.⁶

Studies also report lower levels of zinc in those with atopic dermatitis in serum, erythrocyte and hair testing, alongside decreased zinc transporter and zinc dependent enzymes in atopic lesions.⁷

Furthermore, zinc has demonstrated a clear ability to prevent UV-induced damage, thus reducing the incidence of malignancies. For this reason, zinc oxide is still widely used as a topical sunscreen.⁸

Hair

Zinc supports the hair follicle cycle by reducing follicle regression and supporting follicle recovery.  Studies have found that supplementing zinc had a clinically therapeutic effect in those with alopecia areata.^10,11

Digestive health

The intestinal tract is protected by a layer of specialised epithelial cells held together by proteins called tight junctions that control what can pass between the bloodstream and the digestive system. If these proteins fail, intestinal permeability or ‘leaky gut’ is increased, which has been indicated in many gastrointestinal disorders.

Zinc homeostasis is vital for the intestinal mucosal barrier and deficiency can lead to alterations, hyperpermeability and reduced tight junction barrier function. A recent meta-analysis highlighted the link between low zinc levels from increased excretion and reduced absorption in Crohn’s disease; a key characteristic of this disease is damaged intestinal mucosa.15  Overall, zinc is often a prominent nutrient in gut healing and repair programmes due to its ability to support the repair and regeneration of the mucosa.¹⁶

Zinc and sleep

Evidence suggests that zinc may play a role in sleep regulation due to its central role in the production and regulation of the hormone melatonin, higher serum concentrations of zinc were found in those who slept over 7 hours a night, compared to those who slept fewer than 7. Other research found that zinc supplementation improved sleep onset latency and sleep efficiency compared to controls.^12,13

Hormonal health and fertility

Zinc plays a crucial role in hormonal and reproductive health and without adequate zinc the ability to convert cholesterol and lipid precursors into sex hormones is impaired. Zinc plays a role in epithelial barrier integrity and is also needed to support the healthy lining of the reproductive organs.¹⁷ A deficiency has been noted to cause abnormal or failed development of germ cells in both males and females which can result in infertility.^18,19

• Males:  Zinc has been found to positively correlate with testosterone levels²⁰ and play a significant role in the male reproductive system, with lower levels of zinc being found in infertility cases and higher levels being found in fertile males. Deficiency has been linked with changes in testis volume and testicular weight, alongside spermatogenesis failure and low sperm count and quality. Furthermore, zinc is needed in adequate concentration in the seminal plasma for normal sperm function and fertilization, however, excessive levels of zinc can also negatively affect sperm quality.²¹
• Females:  Zinc plays a role in a number of processes that regulate fertility and pregnancy. Deficiency during pregnancy can increase the risk of miscarriage, impaired growth and development and placental dysfunction and insufficient levels have been linked to the risk of pre-eclampsia.²² 

Child growth and development

Zinc has become well-recognised as an essential micronutrient for infant growth and development and is a standard component of parenteral nutrition for infants with gastrointestinal dysfunction or low birth weight. Zinc is a vital nutrient to support healthy growth and development and supplementation has been found to improve growth outcomes in children.^20,23 

Cognition

Zinc plays a role in brain and central nervous system development, with deficiency increasing the risks of pathological conditions, cognitive impairment and ageing.²⁴ Zinc is required for the proliferation, differentiation and death of neurons throughout human life.²⁵ Zinc is abundant in the brain, accumulating in the synaptic vesicles, where it plays a role in memory and learning.²⁶

Zinc may play an important role in the progression of Alzheimer’s disease (AD), with research finding those with AD have lower serum zinc levels. Supplementation has been associated with slowing cognitive decline.²⁷

Zinc and attention disorders

Zinc is very important for healthy neurological function and studies have found zinc deficiency in those with hyperactivity. One systematic review of randomized clinical trials found that low zinc (and iron) levels were linked to increased ADHD severity, while supplementation led to significantly better outcomes compared to controls.¹⁴ 

Mood and emotional health

Dysregulation of zinc in the amygdala, hippocampus and cerebral cortex may be linked to the pathophysiology of depression. Research has found that patients with depression appear to have lower levels of circulating zinc²⁸, while supporting research found that supplementation significantly lowered depressive symptom scores.²⁹

MRI research looking at depression has found reduced hippocampal volume, while studies have found an association between zinc and decreased hippocampal neurogenesis. Other studies have found reduced levels of brain-derived neurotrophic factor (BDNF) in those with depression, with zinc being studied in its ability to increase BDNF gene expression in the hippocampus or cortex.³⁰

Signs of zinc deficiency

Mild	Severe
·         Diminished smell or taste ·         Poor vision and/or night blindness ·         Slow wound healing ·         Loss of appetite ·         Weight loss ·         White spots of finger nails ·         Apathy or low mood	·         Hair loss ·         Behavioural changes ·         Skin lesions ·         Delayed sexual and bone maturation ·         Increased susceptibility to infections

Who is most at risk for zinc deficiency?

There are certain factors which may lead to an increased risk of deficiency:

• Dietary insufficiency can quickly lead to low circulating zinc.
• Alcoholism is linked to poor absorption of zinc in the body.³¹
• Elderly individuals may have lower levels of serum zinc.
• Diabetic have been found to have lower levels of zinc. Poor glycaemic control is also linked to zinc deficiency. ³²
• Pregnant and breastfeeding women have increased zinc requirements.
• Vegetarians/vegans or any group who have a high intake of foods rich in phytic acid such as grains and legumes and low zinc intake.
• Increased sweating can reduce zinc levels i.e. athletes or menopausal women experiencing night sweats

Common forms of supplemental zinc

There are many forms of zinc compounds available:

• Zinc carbonate
• Zinc chloride
• Zinc citrate
• Zinc bisglycinate
• Zinc sulphate
• Zinc picolinate
• Zinc ascorbate
• Zinc gluconate

Research regarding the efficacy of one form of zinc over another is limited and may be subject to many individual variables. Absorption of zinc citrate and gluconate has been found to be significantly better than zinc oxide, with authors concluding that zinc citrate is well absorbed by healthy adults.³³ Research has looked the bioavailability of zinc in the bisglycinate form being better than gluconate by up to 43%.³⁴

Dietary factors that influence zinc absorption

As with certain nutrients, fractional absorption of zinc appears to decrease with increasing total amounts in food. Other factors such as phytic acid and protein content also appear to impact absorption and so should be considered when designing meals for boosting zinc levels:

• Phytic acid: phytate or phytic acid found in many plant foods such as corn, rice, legumes and spinach can have an inhibitory effect on zinc absorption. Phytic acid can bind to minerals such as zinc and form insoluble complexes. As the human gastrointestinal tract has limited phytase activity (the enzyme which breaks down phytic acid), this can have a significant impact on absorption. Fermentation, soaking and/or sprouting and cooking of foods prior to consumption can lower the levels of phytic acid present.³⁵
• Chlorogenic acid: is mostly found in caffeine and may decrease the absorption of zinc. This is why we would recommend that to take zinc supplements away from caffeinated beverages.³⁵

How much zinc should I supplement?

Researchers have recommended that women get 17mg and men 20mg of zinc daily for optimal health; however, the UK Recommended Nutrient Intake (RNI) is 9.5mg per day for men and 7mg for women. The National Diet and Nutrition Survey (NDNS) found that in the UK population the average zinc intake fell between 4.18 mg a day to 10.56 mg a day, meaning people are often falling short of not just the RNI intakes proposed, but may not be having adequate zinc to support optimal health.³⁶ 

Nutrient-nutrient interactions

• Iron: Zinc deficiency may induce iron deficiency by mechanisms that block either mobilization of iron from tissues or reduced intestinal absorption. It is theorised that low zinc status leads to reduces pancreatic zinc which then reduces iron absorption in the intestines via a decrease in divalent metal transporter (DMT1) and Ferroportin 1 (FPN1) expression. Therefore, supplemental iron causes a dose-dependent decrease in zinc absorption, while zinc supplementation also has an inhibitory effect on iron absorption.³⁷
• Copper: Copper and zinc homeostasis is tightly controlled by a system of transporters and transport proteins and a ratio between the two is important in many areas of health. An excess of zinc can affect the bioavailability of copper as it competes with copper to bind to the protein metallothionein, which transports these minerals to the intestinal cells.³⁸ The ratio between zinc and copper may have a greater impact on health outcomes than copper concentration itself.³⁹
• Calcium: intake of calcium also appears to affect the absorption of zinc. Doses of calcium between 600-1200mg reduced zinc absorption by as much as 50%.⁴⁰

Precautions when taking zinc

• Diabetics: zinc has beneficial effects on glycaemic control.³² Therefore, high dose zinc-containing products should be used with caution in people taking medication for diabetes.
• Drug interactions: zinc may reduce the efficacy of certain antibiotics and medications. Those who are currently receiving drug therapy should speak with a qualified practitioner before taking zinc at levels higher than in a multivitamin and mineral supplement.

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Last updated on 10th April 2024 by cytoffice