Zinc is a mineral that has earned the status of an extremely deficient mineral. This is due to its features and is not only related to the absorption in the gastrointestinal tract but also with its easy disposal from the body under specific conditions.
Generally, we can divide the problems of zinc deficiency into two main categories - problems with absorption and problems associated with rapid loss of zinc in the body.
Low levels of zinc may negatively affect the fatigue strength and endurance during physical activity. Zinc supplementation demonstrates a delay in fatigue and improves endurance.
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What Is Zinc
Nutrients can be divided into two types. The first one called Type 1, is needed for specific metabolic processes. These are - iodine, iron, vitamin A, folic acid, copper. Others that belong to Type 2 play a role in many metabolic processes and also in general metabolism.
These ones include proteins, magnesium, and zinc. This article is dedicated to zinc. Zinc has definitely earned a place as an amazing micronutrient regarding many biological processes, clinical researches, and numerous major health problems.
Besides being a valuable element, zinc has earned the status of an extremely deficient mineral. This is due to its features and is not only related to the absorption in the gastrointestinal tract but also with its easy disposal from the body under specific conditions.
Zinc is also an essential mineral that plays an important role in the enzymatic reactions and hormonal balance of the body. Men are more affected by the deficiency and for those who sweat a lot, it is mandatory to take it as a dietary supplement because zinc is easy to get lost through sweat.
Vegans are another affected group of people that consume no animal foods and are deprived of the most valuable sources of zinc. Zinc deficiency leads to insulin resistance, weak immune system, decreased testosterone and increased odor.
Zinc is an important dietary mineral that can bolster the immune system and protect against the common cold and other infective diseases. Zinc supplementation, if begun at the first sign of symptoms, has been noted to reduce the length of sickness and may prevent symptoms from getting worse.
Causes of Zinc Deficiency
Generally, we can divide the problems of zinc deficiency into two main categories - problems with absorption and problems associated with rapid loss of zinc in the body.
In one of our previous articles about zinc, we explained the main issues related to the absorption of zinc in the gastrointestinal tract and the main obstacles for its absorption.
There should be an emphasis on zinc’s enormous dependence on other micro and macronutrients. For example, plants (rich in phytates and fibers) decrease the absorption of zinc. The minerals calcium, iron, and copper also cause the same effect.
On the other hand, animal proteins and the amino acids histidine and methionine can improve absorption. The only established "improver" of zinc absorption is red wine. Apart from the difficult absorption, zinc is often lost from the body as a result of various processes.
Negative factors may be some diseases on the intestinal tract, such as diarrhea, Crohn's disease, celiac disease, parasitic and protozoan infections. Other digestive problems that affect zinc absorption are pancreatic insufficiency, high acidity in the stomach and cystic fibrosis (mucoviscidosis).
Finally, conditions such as regular infections and fevers, inflammation, corticosteroid use, physical activity and sweating, kidney problems, regular use of alcohol and frequent ejaculation can also have a negative effect on the levels of zinc in the body.
Several Important Questions Related to the Ascertainment of Zinc Deficiency
In their recent studies, scientists haven’t definitely found out the most accurate indicator of zinc deficiency. The zinc absorption and the response of the body to the uptake of extra zinc, in the form of supplements, have been considered the answer for that for a very long period of time.
It should be noted that the sources of zinc deficiency are too various and that makes it difficult to look for a specific cause.
Due to the fact that zinc is contained in the body exclusively in the cells (95%) and zinc-dependent metabolic processes in the body get affected on a cellular level, more observations on changes in intracellular levels of zinc are needed.
That is why the zinc metabolism at the cellular level should be examined along with its overall homeostasis. Another important issue that concerns us is the comparison of the absorption of zinc in the form of supplements and the absorption of zinc, contained in food.
Several studies clearly demonstrate that zinc from supplements is much better absorbed than zinc in food. It should also be noted that its absorption rate falls reciprocally with the regular use of zinc and the increasing of its levels in the body.
A clinical study observed that zinc with water is absorbed far better than zinc from food. However, after 24 hours the absorption of zinc in the form of an additive falls dramatically due to the decrease of zinc transporters.
Various Forms of Zinc
Zinc gluconate is a composition of a zinc salt of gluconic acid. This is one of the most common and, at the same time, the most economical form of zinc. It's debatable how effective it is, though, given the current problems with the absorption of zinc gluconate.
Some studies indicate much lower absorption in comparison to other forms of zinc (zinc picolinate and citrate). Most scientific tests show positive results in the intake of zinc gluconate and the increase in the levels of zinc in the body.
It is interesting to note that zinc gluconate particularly has better absorption on an empty stomach than taken with a meal or after a meal. You can find zinc gluconate as solid tablets or coated sucking tablets more often. The second form is preferable, given better digestibility.
Zinc picolinate is also a popular and economical form of zinc. This is a compound of zinc with picolinic acid as zinc constitutes about 20% of the total compound. This chelate form has relatively good absorption and picolinic acid contributes to faster transport of zinc in the intestinal tract.
Comparative studies show better absorption of zinc picolinate compared to zinc citrate, zinc gluconate or zinc sulfate. It is believed that zinc picolinate has better absorption when taken with food. However, food from animal sources is much more recommended.
Vegetable sources are unadvisable. Intake of zinc picolinate from food is necessary because picolinic acid can cause stomach irritation in some people.
Most products in the market contain 50 mg per capsule/tablet, which means that the intake of zinc picolinate should be approached carefully in dosages due to the risk of overdosing.
Zinc aspartate is another chelated form of zinc and aspartic acid. Despite the lack of comparative comparisons with other forms of zinc, the zinc aspartate absorption is confirmed by its chemical properties. Some studies confirm its positive effect when administered orally.
Zinc aspartate does not dissolve in water but is soluble in hydrochloric acid, which makes it potentially absorbable in the intestinal tract. There are studies on a bigger scale that show the better properties of zinc aspartate when compared with other salts, such as zinc histidine, zinc orotate or zinc acetate.
Comparisons with the most popular forms on the market are missing (except for zinc glycinate). The effectiveness of zinc aspartate was confirmed in a study from 1986 with the participation of 179 pregnant women.
Zinc successfully demonstrated its prophylactic effect, drastically reducing problems of pregnancy, without noting any side effects. It is interesting to note that a zinc aspartate is a form of zinc in the patented complex formula ZMA (zinc, magnesium, and vitamin B6). However, it extremely difficult to find it as a standalone product.
Zinc monomethionine is a patented compound of zinc and methionine amino acid. Zinc constitutes about 20% of the total weight. Methionine is one of the well-absorbed amino acids in the human body which increases the possible potential of this form.
It is necessary to note that zinc monomethionine is patented by the name OptiZinc. That increases the chance for marketing and research, sponsored by the patent proprietor. There are several studies that demonstrate the effectiveness of zinc monomethionine.
One of them shows the comparison between zinc oxide and zinc monomethionine when taken by lambs, fed mainly on cereals.
Although the absorption of the two forms is identical, zinc monomethionine gets retained for a longer period of time in the body and its disposal through the urinary tract is drastically less.
Plasma zinc concentrations after 6 hours after the intake are equal. However, after 12 hours and 24 hours they are significantly altered in favor of zinc monomethionine. Other similar comparisons show better absorption of zinc monomethionine than zinc oxide and zinc sulfate.
Because of the structure of zinc monomethionine, it can be assumed that this form is well digestible when taken with food but we recommended avoiding large amounts of vegetable food.
Zinc glycinate is one of the last forms of zinc that appeared on the market. This is a compound of zinc and the glycine amino acid.
This form is typical with its high price and is patented by Albion Labs, a company known for its multiple proprietary forms of minerals, including a popular form of creatine - magnesium creatine chelate (MagnaPower).
Possible sponsorship of research and increased marketing for this form is a current topic. Despite being a new compound, there are several existing studies already, related to its properties.
According to comparative study, zinc glycinate indicates better absorption than zinc sulfate and also decreases the symptoms of zinc deficiency.
A second study on rats reveals that zinc glycinate has faster absorption than zinc lactate, zinc sulfate, and zinc gluconate, but its bioactivity is not as stronger as the one of zinc gluconate.
According to the third study on people taking zinc, zinc glycinate ranks on first place in bioactivity, followed by zinc picolinate, zinc oxide, and zinc gluconate.
In a fourth study, the researchers have used zinc glycinate and zinc aspartate in the treatment of gastric ulcer and both forms have demonstrated positive results, with only a slight advantage of zinc aspartate.
Given the recent emergence of zinc glycinate on the market, the substantial potential of this form must be underlined and this is shown by several studies. For the overall evaluation of the zinc glycinate, however, far more researches are needed.
There are some other forms of zinc on the market, namely: zinc oxide, zinc sulfate, zinc citrate, but they can be rarely found in standalone packages and are often part of complex formulas and vitamin-mineral complexes.
Often their properties are either controversial or neglected, but despite the lower potential, they should not be completely ignored. However, their importance is lower than already considered popular forms of zinc and therefore; will not be subject to a more detailed analysis.
Zinc Deficiency Consequences
One of the main problems, associated with zinc, is its deficiency and that includes ever-increasing groups of the population. Zinc is an essential mineral.
It is not needed for specific processes, but for maintaining of life as a whole, so its deficiency, especially in acute forms, affects the body in different ways due to its important role in dozens of metabolic reactions.
There are several known conditions that are a result of zinc deficiency in the body and we can divide the deficit as acute or moderate.
Conditions in Acute Zinc Deficiency
Acrodermatitis enteropathica is an inherited disorder (a result of a defective gene), related to a deficiency of zinc due to congenital causes. The result is blockage of its absorption through the intestinal tract.
The disease leads to severe conditions such as prolonged diarrhea, hair loss, immune system disorder, nervous system damage and worsened skin diseases. Due to the nature of the disease, the levels of zinc in the body drop dramatically.
It is also important to note that mortality in children in early childhood has been high before resorting to the use of zinc supplementation. Acute zinc deficiency rarely occurs due to reduced consumption of dietary zinc which makes it (except Acrodermatitis enteropathica) extremely rare.
Such deficit can cause the same health problems and other conditions such as decreased sexual function, difficulty night vision, difficulty in wound healing, decreased appetite, dulling the sense of smell, enhancing edema, dry skin, and extremely unusual behavior.
Despite limited cases of acute zinc deficiency, the average uptake of zinc is typical for the moderate diet of a modern urban person. Endangered individuals, that may suffer zinc deficiency, can be categorized into the following groups:
- Infants, children, pregnant and lactating women (especially minors);
- Patients undergoing complete intravenous nutrition;
- People suffering from malnutrition, lack of animal protein and anorexia;
- People suffering from severe/chronic diarrhea;
- People with intestinal tract diseases, such as Crohn's disease, ulcerative colitis, and celiac disease;
- People suffering from alcoholic kidney disease;
- Individuals with anemia;
- Elderly people over 65 years of age;
- Antioxidant activity and anti-inflammatory properties. Taking extra zinc influences infections, oxidative stress and reduces inflammatory cytokines. Zinc affects the A20 protein, which acts on the nuclear factor kappa-b, known to cause cell inflammation;
- Strengthening of the immune system due to its influence on protein kinase C in the lymphocytes membranes; zinc increases leukocytes and effects the activation of immunoregulatory genes;
- An important cofactor that stimulates the function of more than 100 enzymes;
- A positive effect in the acceleration of wound healing when taking high doses of 200 mg daily;
- Zinc has a protective function against the occurrence of respiratory allergies by reducing their severity;
- Numerous scientific studies indicate positive results in the reduction of days of illness from a common cold. Zinc also reduces the symptoms of the disease. There are other studies that reach opposite results;
- A study has demonstrated the potential value of zinc in the treatment of type 2 diabetes when combined with chromium picolinate. This may be due to its antioxidant properties, but more studies are required, especially with high doses;
- Zinc has been used successfully in cases of gastroenteritis due to the antimicrobial effect of zinc ions in the gastrointestinal tract;
- High doses of zinc are used for the treatment of Acrodermatitis enteropathica and genetic diseases, related to the disruption of zinc metabolism;
- A study has revealed the potential effect of zinc in the treatment of old patients with macular eye degeneration. More scientific documents for confirmation are needed;
- Zinc is used for the prevention and treatment of dermatitis and the maintenance of healthy skin. Better results can be seen in the initial deficit;
- Zinc is successfully used in acne treatment or regulation;
- Zinc affects serum testosterone. Its deficit can lead to a drop in the levels of this hormone. Recommended doses do not increase testosterone if it is within normal limits. A study in Turkey has shown that zinc increases testosterone levels when taken in high doses - 200 mg daily;
- Zinc affects aromatization and estrogen levels. The deficit can lead to increased estrogen and a decrease in the serum testosterone and luteinizing hormone;
- Increases libido and potency;
- It affects the prostate function. Zinc supplementation has positive effects on the prostate gland. The potential role of zinc in the prevention of prostate cancer. However, there are also controversial claims that say that higher levels of zinc may cause prostate cancer;
- Low levels of zinc may negatively affect the fatigue strength and endurance during physical activity. Zinc supplementation demonstrates a delay in fatigue and improves endurance.
Side effects of zinc occur very rarely when taking the recommended doses. There are basic complaints of stomach irritation or abdominal discomfort with the use of zinc picolinate or other forms in doses of 50 to 150 mg at one time.
Other cases of effects are related to the use of zinc gluconate and the blunting of the sense of smell, but this is indicated only in the form of a spray and not orally. It is advisable to pay attention to the combination of zinc with certain types of medications, such as antibiotics, as zinc can reduce or completely inhibit their effects.
On the other hand, simultaneous uptake of zinc with diuretics or agents, which can be coupled with metals (ethambutol, penicillamine), is unadvisable because these agents dispose of zinc out of the body. Exceptional care must be taken with the long-term risks of high doses of zinc.
Zinc is a mineral, distinguished by toxicity with high doses, so it is advisable to avoid doses higher than 200 mg per day. Doses that exceed the recommended ones should not be taken for long periods of time.
A different side effect, associated with long-term use of zinc, is the risk of copper deficiency. That is why the usage of more than 50 mg of zinc daily, without taking extra copper, is not recommended.
How Much Zinc to Take
It is enough to take 30 mg of zinc a day for prophylactic purposes. In deficiency cases, the dosage may be increased to 50-100 mg. Athletes and people that sweat heavily can take up to 100 mg. If the goal is inhibition of odor and increase of testosterone –the intake can be up to 150 mg daily.
Zinc is best absorbed when taken on an empty stomach or with animal foods. It was found that red wine improves absorption. You must avoid plant foods, especially those rich in fiber because they promote the excretion of zinc from the intestine.
Zinc picolinate is an acceptable form for maintaining the levels of zinc. Zinc monomethionine is a better absorbable form and is a good option for enhancing immunity and regulating the hormone balance. Zinc glycinate is the best choice for acute deficiency.