Zinc

In its pure form, zinc is a heavy metal with a bluish sheen that is relatively brittle under normal conditions and therefore difficult to work with. It has the atomic number 30 in the periodic table of elements and its chemical symbol is Zn. However, when heated above 120° C, it can be processed very easily, e.g. rolled into sheet metal. It does not occur in nature in elemental form. The main ores in which it occurs are zinc blende (zinc sulphide) and zinc spar (zinc carbonate). It was first described in detail in our culture in 1740 by the physician Johann Friedrich Henckel (1678-1744). It was first produced in 1746 by the Berlin chemist Andreas Sigismund Marggraf (1709-1782). Zinc is used in technology as brass (copper-zinc alloy), for galvanizing iron sheets and for the production of dry batteries (carbon zinc element, carbon manganese element). It is also used as zinc dust in paints as a rust inhibitor and in the form of zinc oxide as a white pigment.

Zinc is used medicinally in the form of zinc oxide or zinc sulphate in ointments, pastes or shaking mixtures to treat wounds or damaged skin areas (especially diaper rash). The astringent effect of the zinc compounds mentioned is utilized here. By precipitating or fixing proteins, astringents lead to the formation of a membrane and thus have an anti-inflammatory, drying, hemostatic and bacteriostatic effect.

Functions in the body

Zinc is an essential trace element for most living organisms and, along with iron, is the most common trace element in the human body. Higher concentrations of zinc are found in the red blood cells, eyes, skin and hair, as well as in the prostate and liver. Zinc is a cofactor of numerous enzyme systems and plays a role in vitamin A, carbohydrate and lipid metabolism. Zinc is also essential for the function of various hormones, such as insulin, thyroid hormones, sex hormones and growth hormones.

Zinc also plays an important role in the metabolism of nucleic acids (carriers of genetic material) and proteins. For example, it serves to stabilize the DNA and RNA structure, but is also a component of key enzymes in nucleic acid synthesis (e.g. DNA polymerases).

Zinc is involved in cell growth and cell differentiation. Zinc is also required for a functioning immune defense, namely for the cellular and humoral immune response, as well as for T cell differentiation. Zinc also plays a role in taste perception, although the factors involved are not known in detail.

Foods containing zinc

As the various foods sometimes contain very different amounts of zinc, a varied diet should be ensured for an optimal supply of the trace element.

Animal foods, including fish and seafood, often contain higher amounts of zinc than plant foods, with offal in particular being very rich in zinc. Of the marine animals, oysters are interestingly characterized by very high amounts of zinc. Cow's milk contains relatively small amounts of zinc, whereas some dairy products, such as Camembert, processed cheese or Emmental, contain quite high amounts. From the group of cereal products, oat flakes, millet, cornflakes, whole wheat flour and wheat germ are very good sources of zinc. Although many vegetables are not as rich in zinc, the consumption of green peas, dried lentils and soybeans also provides relatively high levels of zinc. Brewer's yeast, cocoa and most nuts also contain a lot of zinc. It should also be mentioned that some kitchen spices are very rich in zinc, including basil, tarragon, caraway, cloves, ginger, marjoram, thyme, rosemary and sage.

Potential health benefits of zinc

Zinc is vital to many aspects of health and is associated with a number of health benefits, which we will briefly discuss below.

Zinc can improve immune function

Many over-the-counter medications and natural remedies contain zinc due to its ability to improve immune function and fight inflammation.

Zinc can alleviate oxidative stress and improve immune function by increasing the activity of T cells and natural killer cells, which help protect the body from infection (20).

In fact, a study review showed that zinc lozenges containing 80 to 92 mg of zinc could reduce the duration of a common cold by up to 33% (1). A study of 50 older adults concluded that 45 mg of zinc gluconate per day over a one-year period could reduce several markers of inflammation and lower the incidence of infections (4).

Zinc could promote blood sugar control

Zinc is known for its role in blood sugar control and insulin secretion (5). Insulin is the hormone responsible for transporting sugar from the bloodstream into the body's tissues.

Some research suggests that zinc may help keep blood sugar levels stable and improve the body's sensitivity to insulin.

One study review concluded that zinc supplements are effective in improving short-term and long-term glycemic control in diabetics (6). Another study showed that zinc may help reduce existing insulin resistance, which can improve the body's ability to use insulin efficiently to maintain normal blood sugar levels (7, 8).

Zinc can help fight acne

Zinc supplements are often used to promote skin health and treat skin conditions such as acne (9). Zinc sulphate has been shown to be particularly effective in reducing the symptoms of severe acne (10). A three-month study of 332 people found that 30 mg of elemental zinc - a term that refers to the actual amount of zinc contained in a supplement - was effective in treating inflammatory acne (11).

Zinc supplements are often preferred over other treatments because they are inexpensive and effective, and are also associated with fewer side effects (12).

Zinc could improve heart health

Heart disease is responsible for around 33% of all deaths worldwide (13). Some research shows that taking zinc could reduce several risk factors for heart disease and even lower triglyceride levels and blood cholesterol levels. A review of 24 studies found that zinc supplements helped lower levels of "bad" LDL cholesterol and triglyceride levels in the blood, which could potentially help prevent heart disease (14).

Another study conducted with 40 young women showed that higher zinc intake was associated with lower systolic blood pressure levels (the upper value) (15). Overall, however, there is little research on the effects of supplements on blood pressure. Another study suggests that low serum zinc levels may be associated with a higher risk of coronary heart disease, but these results are inconclusive (16).

Zinc can reduce inflammation

Zinc can act as an antioxidant, helping to reduce inflammation and protect against chronic diseases such as heart disease, cancer and diabetes (2, 3). Zinc reduces oxidative stress and reduces the levels of certain pro-inflammatory proteins in the body (17).

Oxidative stress leads to chronic inflammation, a contributing factor in a wide range of chronic diseases such as heart disease, cancer and mental decline (18). In a study of 40 older adults, those who took 45 mg of zinc per day experienced greater reductions in inflammatory markers than those who received only a placebo (19).

Zinc could reduce the risk of certain age-related diseases

Zinc may reduce the risk of certain age-related diseases such as pneumonia, infections and age-related macular degeneration.

Older adults who supplement zinc show a better response to flu vaccination, a reduced risk of pneumonia and increased mental performance (21, 22, 23).

In fact, one study found that 45 mg of zinc per day could reduce infection rates in older adults by almost 66% (24).

Zinc can accelerate wound healing

Zinc is used in hospitals to treat burns, certain ulcers and other skin injuries (25).

Because zinc plays a critical role in collagen synthesis, immune function and the inflammatory response, it is essential for wound healing. In fact, the skin contains relatively high amounts of zinc - about 5% of the total amount of zinc in the body (26).

While zinc deficiency can slow wound healing, zinc supplementation can accelerate wound healing.

A 12-week study of 60 patients suffering from diabetic foot ulcers found that those treated with 200 mg of zinc per day showed significant reductions in ulcer size compared to the placebo group (27).

Zinc can slow down macular degeneration

Macular degeneration is a common eye disease and one of the leading causes of vision loss worldwide (28).

Zinc supplements are commonly used to slow the progression of age-related macular degeneration and prevent vision loss and blindness.

A study of 72 patients suffering from macular degeneration showed that taking 50 mg of zinc sulfate per day for 3 months slowed the progression of the disease (29).

In addition, a large-scale study involving 4,200 participants showed that daily intake of an antioxidant supplement - vitamin E, vitamin C and beta-carotene - in combination with 80 mg of zinc can reduce vision loss and lower the risk of macular degeneration progression (30).

A review of 10 studies reported that zinc supplementation was effective in reducing the risk of progression to advanced macular degeneration (31).

However, other studies in the review suggested that zinc supplementation alone may not be enough to significantly improve vision, so it should be combined with other treatments to maximize results.

Deficiency symptoms

The concentration of zinc can be determined in the blood. When using serum, zinc levels should be between 0.7-1.3 mg/l in adults and 0.75-1.0 mg/l in children. If zinc is measured in whole blood, values of 4.0-7.5 mg/l are considered normal.

Zinc deficiency can lead to the following symptoms:

• Lack of drive, depression, concentration problems, learning difficulties
• Increased susceptibility to infections and reduced resistance to environmental toxins
• Growth disorders and impaired sexual development
• Impairment of sensory perception, such as night blindness, taste and smell disorders
• Damage to the oral mucosa, delayed wound healing and increased incidence of fungal skin infections
• thinning hair and even hair loss, as well as brittle and white-spotted nails
• the often observed in strength athletes

In the past, acute zinc poisoning has occasionally occurred due to the consumption of acidic foods or drinks that have been stored in galvanized containers for long periods of time. Acute zinc poisoning can also be caused by inhaling zinc vapor or zinc dust when working in foundries or using smoke bombs.

The symptoms of acute poisoning are symptoms in the gastrointestinal tract, such as nausea, vomiting, diarrhea, abdominal pain and a metallic taste. Furthermore, accelerated breathing, circulatory weakness and even coma may occur. If zinc dust or zinc vapors have been inhaled, this can also lead to the so-called casting or metal fever, which is also known for the inhalation of other metals.

In the case of chronic poisoning, which can be caused by a prolonged intake of zinc, other symptoms come to the fore. Due to the interactions between copper and zinc during absorption, a chronic overdose of zinc results in a copper deficiency. Copper deficiency in turn can cause hypochromic anemia, a form of anemia in which the erythrocytes contain too little hemoglobin.

Symptoms of zinc toxicity include (32):

• Nausea and vomiting
• loss of appetite
• diarrhea
• Stomach cramps
• Headaches
• Reduced immune function
• Reduced levels of the "good" HDL cholesterol

The treatment of zinc poisoning can consist of the administration of D-penicillamine, which binds zinc in the body.

Safety and side effects

When used properly, zinc supplements can be a safe and effective way to increase daily zinc intake and improve various aspects of health. However, in some cases, these supplements can also cause unwanted side effects including nausea, vomiting, diarrhea and stomach pain (33, 34).

Exceeding a daily intake of 40 mg of elemental zinc can cause flu-like symptoms such as fever, cough, headache and fatigue (35). In addition, too much zinc can also impair the body's ability to absorb copper, which over time can lead to a potential deficiency of this key trace element (36). Zinc has also been shown to interfere with the absorption of certain antibiotics, reducing their effectiveness when taken at the same time (37). To reduce the risk of undesirable side effects, the recommended dosage of zinc should be adhered to and an upper intake of 40 mg of elemental zinc per day should not be exceeded unless otherwise prescribed by a doctor.

If undesirable side effects occur after taking zinc supplements, it is advisable to reduce the amount taken and consult a doctor if the symptoms persist.

Interactions

The simultaneous intake of supplements containing iron or copper reduces the absorption of zinc into the body. Zinc in turn impairs the absorption of copper, which is supplied with food.

Contraindications

Zinc supplements must not be taken in the case of severe kidney damage or acute kidney failure.

Requirements

The daily requirement of zinc for adults and adolescents is 7-10 mg. Pregnant women are recommended to take approx. 10 mg daily and breastfeeding mothers approx. 11 mg.

A study presented in 2005 at a conference of the American Society for Nutritional Sciences in San Diego indicates that children who receive sufficient zinc daily (20 milligrams) experience a significant improvement in mental performance. Zinc improved visual memory, performance in a word-finding test and the ability to concentrate. It is particularly important to ensure a regular intake of zinc with food, as the trace element apparently cannot be stored in the body. A drastic reduction in zinc intake therefore leads relatively quickly to a zinc deficiency.

Zinc is absorbed into the blood from the middle section of the small intestine (jejunum). In addition to the passive transport of zinc through the intestinal mucosa, active transport also appears to take place with the help of certain proteins. In the blood, zinc is bound to proteins, primarily to albumin and alpha-macroglobulin. The absorption of zinc, i.e. its absorption from the intestine, is promoted by a large number of organic compounds, such as citrate, cysteine and glutamate. A high phytic acid content, on the other hand, reduces absorption. Phytic acid is a plant-based storage form for phosphorus and inositol and is able to bind zinc in a complex manner. The absorption-reducing effect of phytic acid is further enhanced by a high calcium content in the diet. Zinc-calcium-phytate complexes are formed, which are particularly difficult to dissolve. As plant-based foods contain high concentrations of phytate, a purely vegetarian diet can lead to a zinc deficiency. With a normal diet, zinc intake is usually sufficient.

Approximately 90% of zinc is excreted in the stool.

Increased requirement

Some circumstances can lead to an increased need for zinc or a zinc deficiency:

• when taking certain medicines,
• in people with an unbalanced diet, e.g. vegans (vegetarians who also do not eat eggs or dairy products) and people who are fed parenterally with zinc-free nutrient solutions over a longer period of time
• due to a reduced absorption of zinc after operations or in the case of intestinal diseases
• as a result of various illnesses, such as acquired immune deficiency (AIDS), acne, allergies, diabetes, neurodermatitis, cancer, liver and kidney diseases, acute or chronic infections, etc.
• during pregnancy and breastfeeding
• during growth
• for competitive athletes and bodybuilders.

Demand in sport

The results of a study by Brilla and Conte showed a significantly higher increase in strength in football players and an increase in testosterone levels of up to 30% when they were given 30mg of zinc daily as a dietary supplement. At the same time, the level of IGF-1, which also has an anabolic effect, remained constant when zinc was taken, whereas it fell by more than 20% in the placebo group. My recommendation is to take a dose of 30-50mg a day, with meals.

Zinc as an aromatase inhibitor

Zinc, like letrozole, blocks the enzyme responsible for converting testosterone into oestrogen. Good results are achieved with 75-150mg of pure zinc per day. However, it should be noted that zinc is stored in the body and removes copper from it. Therefore, the application should not exceed the cure and weaning period. It should also be mentioned that zinc in lower doses tends to promote the development of oestrogen. Compared to other aromatase inhibitors, zinc is virtually cheap and preferable for a mild cure.

Different types of zinc supplements

If you look at the zinc supplements available on the market, you will find different forms of zinc. These different forms can affect health in different ways.

Here are some of the most common forms of zinc:

• Zinc Gluconate: This is one of the most common zinc dosage forms, often found in cold medications such as lozenges and nasal sprays.
• Zinc acetate: Like zinc gluconate, zinc acetate is often added to cold medications to reduce cold symptoms and speed healing (38).
• Zinc sulfate: In addition to helping prevent zinc deficiency, zinc sulfate has been shown to relieve acne (39).
• Zinc Picolinate: Some research suggests that zinc picolinate may be better absorbed by the body than other forms of zinc including zinc gluconate and zinc citrate (40).
• Zinc orotate: This form of zinc is bound to orotic acid and is one of the most widely used zinc supplements on the market.
• Zinc citrate: A study found that this form of zinc is absorbed just as well as zinc gluconate, but has a less bitter and unpleasant taste (41).
• Zinc bisglycinate: This form of zinc has a 40% higher bioavailability than zinc gluconate and zinc citrate and is one of the best forms of zinc available. Zinc is available in the form of capsules, tablets and lozenges. Nasal sprays containing zinc are best avoided as they have been associated with a loss of sense of smell (42, 43).

References:

1. https://www.ncbi.nlm.nih.gov/pubmed/28515951
2. https://www.ncbi.nlm.nih.gov/pubmed/15451058/
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3492709/
4. https://www.ncbi.nlm.nih.gov/pubmed/1734450
5. https://www.ncbi.nlm.nih.gov/pubmed/26365743
6. https://www.ncbi.nlm.nih.gov/pubmed/22515411
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4360427/
8. https://www.ncbi.nlm.nih.gov/pubmed/27587022
9. https://www.ncbi.nlm.nih.gov/pubmed/29193602
10. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120804
11. https://www.ncbi.nlm.nih.gov/pubmed/11586012
12. https://www.ncbi.nlm.nih.gov/pubmed/29193602
13. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5408160/
14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4523910/
15. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3796663/
16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4738046/
17. https://www.ncbi.nlm.nih.gov/books/NBK6288/
18. https://www.ncbi.nlm.nih.gov/books/NBK493173/
19. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2869512/
20. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2702361/
21. https://www.ncbi.nlm.nih.gov/pubmed/18341424
22. https://www.ncbi.nlm.nih.gov/pubmed/20041998
23. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4321209/
24. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3649098/
25. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4413488/
26. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793244/
27. https://www.ncbi.nlm.nih.gov/pubmed/28395131
28. https://www.ncbi.nlm.nih.gov/pubmed/20887239
29. https://www.ncbi.nlm.nih.gov/pubmed/25393287
30. https://www.ncbi.nlm.nih.gov/pubmed/23644932
31. https://www.ncbi.nlm.nih.gov/pubmed/23652490
32. https://www.ncbi.nlm.nih.gov/pubmed/17914213
33. https://www.tandfonline.com/doi/abs/10.1081/CLT-100102426
34. https://www.ncbi.nlm.nih.gov/pubmed/22566526
35. https://www.ncbi.nlm.nih.gov/pubmed/9891606
36. https://www.ncbi.nlm.nih.gov/pubmed/26085547
37. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
38. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5410113/
39. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC412080
40. https://www.ncbi.nlm.nih.gov/pubmed/3630857
41. https://www.ncbi.nlm.nih.gov/pubmed/24259556
42. https://www.ncbi.nlm.nih.gov/pubmed/15283486
43. https://www.ncbi.nlm.nih.gov/pubmed/16467707

Further sources:

• Micheletti A, Rossi R, Rufini S. Zinc status in athletes: relation to diet and exercise. Sports Med 2001;31(8):577-82
• McDonald R, Keen CL. Iron, zinc and magnesium nutrition and athletic performance. Sports Med 1988 Mar;5(3):171-84
• Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone levels of healthy adults. Nutrition 1996 May;12(5):344-8
• Om AS, Chung KW. J Nutr. Dietary zinc deficiency alters 5 alpha-reduction and aromatization of testosterone and androgen and estrogen receptors in rat liver. 1996 Apr;126(4):842-
• Ibs KH, Rink L. Zinc-altered immune function. J Nutr. 2003 May;133(5):1452S-6S
• Lonnerdal B. Dietary factors influencing zinc absorption. J Nutr 2000 May;130(5S Suppl):1378S-83S
• Ott ES, Shay NF. Zinc deficiency reduces leptin gene expression and leptin secretion in rat adipocytes. Exp Biol Med (Maywood). 2001 Oct;226(9):841-6
• Navarro M, Wood RJ. Plasma changes in micronutrients following a multivitamin and mineral supplement in healthy adults. J Am Coll Nutr 2003 Apr;22(2):124-32
• Beutler KT, Pankewycz O, Brautigan DL. Equivalent uptake of organic and inorganic zinc by monkey kidney fibroblasts, human intestinal epithelial cells, or perfused mouse intestine. Biol Trace Elem Res 1998 Jan;61(1):19-31
• Barrie SA, Wright JV, Pizzorno JE, Kutter E, Barron PC. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents Actions. 1987 Jun;21(1-2):223-8
• Abdallah SM, Samman S. The effect of increasing dietary zinc on the activity of superoxide dismutase and zinc concentration in erythrocytes of healthy female subjects. Eur J Clin Nutr 1993 May;47(5):327-32