What is Zinc?
Zinc is a trace mineral and essential for many functions within the body. The pure metal zinc was first discovered in 1746 by German scientist Andreas Marggraf. It was later named as zinc and is derived from the German word “zinke” which means “spiked, prong, point or tooth”. The name was given as a result of spikes forming on the crystals after smelting.
The mineral is essential in trace amounts for plants, animals and humans. It cannot be reproduced by the body and as a result the diet needs to include foods containing zinc and in cases of deficiency will need to be obtained from supplements.
Zinc can be found throughout the body, including various organs and bodily fluids. The body contains up to 2g of the trace mineral. [1]
Zinc is not stored in the body for long periods of time and is excreted through skin cells, urine and faeces. A daily intake of zinc through diet or supplement is required in order to restore zinc levels.
Some of the most important roles that zinc plays in the body include promoting wound healing, improving immune function to fight viruses and aiding in growth and development. It is also involved in gene expression, enzymatic reactions, protein and DNA synthesis. [2] [3]
Health Benefits of Zinc
Zinc serves many functions and is required in sufficient amounts for various biochemical reactions within the body. The following are some of Zinc’s main functions and benefits:
Strengthen immune system and fight colds, viruses
Zinc helps maintain and strengthen the immune system to help the body fight colds, flus, viruses and many other infections such as conjunctivitis, pneumonia etc. [4] [5]
Fights inflammation
Zinc helps to keep inflammation at bay and preventing inflammation related health conditions such as depression, arthritis, heart disease. [6]
Promotes growth
Zinc is essential for growth and development in children and beneficial for pregnant women and fetal growth. One study has shown benefits of supplementing with zinc and vitamin A, reducing infection and improving growth in children. Other studies have revealed beneficial results in underweight children, an increase of height in children after supplementing with a daily dose of 10mg of zinc and increased muscle mass in children. [7] [8] [9] [10] [12] [13]
Promote wound healing
Zinc plays an essential role in wound healing with deficiency of this mineral revealing slow wound healing. Zinc has many roles in the process of wound healing from benefiting the immune system, playing a role in the coagulation of wounds to formations of scar. [14]
Diarrhea treatment and prevention
Zinc has been shown to be effective as a treatment for diarrhoea, decreasing the severity of initial episodes and preventing diarrhea. [15]
Skin health and aging
Many studies are showing the benefits of zinc as oral supplementations and topical use for various skin disorders such as eczema, psoriasis and dandruff (Seborrheic dermatitis). Zinc can be found in topical ointments such as those used for diaper rash, acne remedies and anti-dandruff shampoo. [16] [17] [18] [19]
Needed for vision and improves sense of taste and smell
Zinc has a synergistic regulatory role for vitamin A transport and both nutrients help to maintain eye health. [20] [21]
Researchers from the University of Chicago have identified through one study that the 39% of 3,005 older adults who had impaired or diminished sense of smell died within 5 years. Zinc maintains the sense of smell and taste and a chronic deficiency usually leads to impaired sense of smell and taste. [22] [23]
Improve blood clotting
Studies are showing zinc’s role in blood clot formation revealing the benefits of zinc’s role in blood clotting is dependent on adequate levels of zinc. High or low amounts seem to have adverse effects whereas restoring zinc in a zinc deficiency state normalized platelet aggregation and blood clotting time. [24] [25] [26] [27]
Improve sexual health and balance hormones
Some studies are revealing zincs ability to help balance hormonal health by increasing testosterone levels helping to promote sexual health. Other studies are showing improvements of erectile dysfunction. [28] [29]
Improve Fertility
Zinc helps to boost sperm count and improving fertility. Zinc helps boost fertility in both men and women increasing chances of conceiving.
Supplementing with zinc may improve fertility in women suffering from PCOS as well as reducing various symptoms of PCOS such as acne, hair loss, hirsutism and high levels of testosterone. [30] [31] [32]
Promote thyroid function
Zinc plays an important role in the synthesis of thyroid hormones. Along with various other essential minerals, zinc deficiency has been linked to hypothyroidism. Low levels of zinc impede the production of thyroid stimulating hormone TSH. [33]
Reduce Tinnitus
Some studies are showing the potential of oral zinc reducing symptoms of tinnitus [34]
Agonist / Synergist
Vitamins: A, B3, B6, D, E
Minerals: Cr, K, Mg, Mn, P
Other: Citric acid, picolinic acid, histidine, cysteine, glutathione, tripeptides
Zinc has a synergistic regulatory role for vitamin A transport and both nutrients help to maintain eye health. [35] [36]
Dietary Vitamin B3 (Nicotinic Acid) supplementation improves Zinc uptake in the liver and results in protecting the liver against oxidative stress induced damage.
Antagonist
Vitamins: B1, B6, B10, B12, D, E
Minerals:Ca, Cu, Fe, Mg, P
Metals: Al, Cd, Hg, Ni, Pb
Other: Phytates, oxalates, polyphenols, fibre
Although vitamin B6 works synergistically with zinc high levels of B6 increases the need for zinc and deficiency of vitamin B6 creates an imbalance of zinc and impairs the body’s ability to utilize zinc. [37] [38]
Calcium supplements has shown to reduce zinc absorption [39] [40]
High copper to zinc ratio inhibits zinc absorption leading to a deficiency of zinc and can be a factor in causing a condition known as Pyroluria.
Supplementing with zinc can inhibit non heme iron bioavailability found in plant-based foods.[41]
Regular high doses of zinc can inhibit copper absorption causing a copper deficiency.
Zinc supplements of 142 mg/day can decrease Magnesium absorption [42]
High phosphorus intake can reduce zinc levels.
Food Sources of Zinc
Zinc can be found in high amounts in meat and shellfish. They can also be found in plant based foods such as legumes and wholegrains however these contain high amounts of phytates and may not allow absorption of zinc unless phytate content is reduced which can be done through soaking, sprouting, fermenting.
The following are some of the common foods containing amounts of zinc: lamb, beef, pork, oysters, crab, shrimp, mussels, cheese, milk, eggs, chickpeas, lentils, beans, pumpkin seeds, hemp, flax seeds, sesame, pine nuts, peanuts, almonds, cashews, cocoa / cacao.
Small amounts of zinc can be found in some wholegrains such as wheat, quinoa, oats and rice.
Recommended Dietary Allowance
|
Age |
Zinc: Recommended Dietary Allowance (RDA) in milligrams (mg/d) |
|
CHILDREN |
|
|
0-6 months |
2 mg |
|
7-12 months |
3 mg |
|
1-3 years |
3 mg |
|
4-8 years |
5 mg |
|
|
|
|
Age |
Zinc: Recommended Dietary Allowance (RDA) in milligrams (mg/day) |
||
|
MALES |
|||
|
9-13 years |
8 mg |
|
|
|
14-18 years |
11 mg |
|
|
|
19-30 years |
11 mg |
|
|
|
31-50 years |
11 mg |
|
|
|
|
|
|
|
|
FEMALES |
|||
|
|
|
Pregnancy |
Lactation |
|
9-13 years |
8 mg |
|
|
|
14-18 years |
9 mg |
12 mg |
13 mg |
|
19-30 years |
8 mg |
11 mg |
12 mg |
|
31-50 years |
8 mg |
11 mg |
12 mg |
|
51+ years |
8 mg |
|
|
The upper limit (UL) for zinc intake is set at 40 mg per day for adults and lower for those below 18 years of age. [43] [44]
Zinc Supplementation
Zinc is available in various forms such as capsules, tablets, liquids and lozenges. There are different types of zinc which includes zinc gluconate, zinc picolinate, zinc citrate, zinc sulfate and zinc orotate. Zinc gluconate is commonly used in lozenges and nasal sprays for treating colds.
Some studies have shown that zinc picolinate may be easier for the body to absorb when compared to the other forms. [45]
Deficiency Symptoms of Zinc
Low levels of zinc in the blood is known as Hypozincemia.
Zinc deficiency may be more common as it has been depleted in the soil through agricultural farming. The following are signs and symptoms associated with a zinc deficiency:
- Periodontal disease
- Bleeding gums
- Skin disorders such as:
- Acne
- Eczema
- Dry skin / scaling skin (Xerosis)
- Dandruff (Seborrheic Dermatitis)
- Alopecia(hair loss)
- Impaired wound healing
- Oral ulcers orstomatitis
- White tongue coating
- Angular cheilitis (sores at one or both corners of the mouth)
- Smell and taste disturbances [46]
- Hypogeusia (dysfunction in sense of taste)
- Night blindness
- White spots on fingernails
- Diarrhea
- Loss of appetite
- Anorexia
- Impaired immune function – cause of infections
- Colds and flu
- Behavioral problems
- Impaired cognitive functions – short term memory and spatial learning [47]
- Learning difficulties
- Irritability
- Lethargy
- Depression
- Anhedonia [48]
- ADHD / Hyperactivity
- Schizophrenia
- Delayed growth or stunted growth in children
- Pyroluria
- Vision Degeneration
- Tinnitus
- Loss of libido
- Insomnia
- Impaired sexual health
- Infertility
- Erectile dysfunction
- Irregular periods
- Impaired Adrenal Function
- Oxidative stress
- Anxiety [49]
- Irritable Bowel Syndrome
- Anemia (Non-responsive to Iron intake)
- Pica (eating dirt)
- Anorexia
- Bulimia
- Zinc deficiency issues associated with pregnancy:
Causes of zinc deficiency include:
- Low zinc intake
- Vegan / vegetarian diets
- Use of diuretics
- Diabetes [52]
- Sickle cell disease,
- Chronic kidney disease (CKD)
- Liver disease
- Excessive alcohol consumption
- Poor gut health or malabsorption
- Aging
- Stress / traumatic conditions such as burns, sepsis, head injury [53] [54] [55]
- High intake of antagonistic nutrients such as calcium and phosphorous
Drinking high amounts of milk can inhibit zinc absorption due to the high amounts of calcium and phosphorous which inhibit or reduce zinc.
Pregnant women are at a higher risk of zinc deficiency due to the additional need for the mineral increasing in order to support fetal development. [56]
Usually a treatment of zinc supplementation of 15 to 120mg can help reduce symptoms unless the issue is due to gut impairment in which case this will also need to be addressed.
The Zinc Assay Taste Test which was first reported in The Lancet, a medical journal was devised to measure zinc levels using sense of taste. The Zinc Taste Test (ZTT) is now commonly used by naturopaths to determine zinc levels. The test involves tasting a small amount of zinc sulfate liquid solution. Zinc levels in this test is determined solely by the response to taste. The different tastes reveal the body’s needs for zinc where little or no taste indicates a deficiency and an unpleasant, strong, bitter or metallic taste indicates adequate levels of zinc.
Deficiency of zinc can increase Parathyroid Hormone through decreased serum calcium which can result in poor bone health. [57]
Toxicity Symptoms of Zinc
High levels of zinc in the blood is known as Hyperzincemia.
There are no known cases of zinc toxicity from food which suggests that zinc obtained from food is highly unlikely to produce symptoms of zinc toxicity even with foods that contain high amounts of zinc. This may be because there are other synergistic nutrients in certain foods that balance out the high amounts or they are in forms that the body effectively utilizes.
Excess supplementation of zinc is more likely to produce signs and symptoms of zinc toxicity.
The following are signs and symptoms of zinc toxicity:
- Nausea
- Vomiting
- Stomach pain
- Lethargy
- Fatigue
- Diarrhea
- Low “Good” HDL Cholesterol
- Flu-Like symptoms
- Changes in taste (metallic taste)
- Copper deficiency
- Frequent infections
Treatment options available for excess zinc include counteracting with foods containing high amounts of calcium and phosphorous such as milk or chelating agents. Activated charcoal is also an option.
It is important to seek medical help in case of zinc poisoning.
High dose of zinc is only appropriate for extreme deficiency and for short periods of times as prolonged use can cause a copper deficiency and symptoms of copper deficiency. Due to this many zinc supplements also contain copper.
Precautions and Warnings
Zinc oxide can be found in many sunscreen products which can make the body absorb zinc through the skin although toxic effects of this are currently unknown. Precautionary measures should be taken when using excessive amounts of sunscreen containing zinc oxide in addition to oral supplementation of zinc in order to prevent potential toxicity. [58] [59]
Zinc may reduce the effectiveness of certain antibiotics such as Quinolone and Tetracycline antibiotics. It is important to seek medical advice if taking any drugs when taking zinc supplements. [60]