EIGHT WAYS ZINC AFFECTS THE HUMAN BODY
Zinc The Metal of Life
From the FMS Global News Desk of Jeanne Hambleton
Posted on July 19, 2014 Source Stone Hearth News – Newswise-Wiley OnLine Library
Newswise — CHICAGO—Researchers identified zinc as one of the most important essential trace metals in human nutrition and lifestyle in a new review article in Comprehensive Reviews in Food Science and Food Safety, published by the Institute of Food Technologists (IFT). Zinc is not only a vital element in various physiological processes; it is also a drug in the prevention of many diseases.
The adult body contains about two to three grams of zinc. It is found in organs, tissues, bones, fluids, and cells. Foods with high protein content, specifically animal protein, are major sources of zinc in the human diet. Zinc can also be used as fortification for other foods as well. Nearly half of the world’s population is at risk for inadequate zinc intake. The article reviewed numerous studies that showed a relationship between zinc and vital human physiological processes such as the following:
Brain: The blood zinc level is less in patients with Alzheimer’s and Parkinson’s disease (Brewer, and others 2010).In a rodent study, it was observed that zinc behaves like an antidepressant (Nowak and others, 2005).
Cardiovascular System: Zinc performs a noteworthy role in the regulation of arterial blood pressure. Males and females were reported to metabolize zinc differently when suffering from hypertension (Tubek, 2007).
Liver: Zinc deficiency in the liver occurs not only in those with liver cirrhosis, but also in less advanced alcoholic and nonalcoholic liver disease (Bode and others, 1998).
Pregnancy: A mild deficiency of zinc during a pregnancy can cause increased maternal morbidity, abnormal taste sensation, prolonged gestation, inefficient labor, atonic bleeding, and an increased risk to fetuses (Jameson, 1993).
Diabetes: Zinc is very important in the synthesis, storage, and secretion of insulin (Chausmer 1998). A low level of zinc has been shown to play a role in diabetics with associated disease conditions such as coronary artery disease and several related risk factors including hypertension, and elevated levels of triglycerides (Singh and others, 1998).
Endocrine System: Studies show a correlation between zinc deficiency in geriatric patients and reduced activity of the thymus gland and thymic hormones, decreased response to vaccinations, and reduced immunity (Haase and Rink, 2009).
Healing: Zinc deficiency has been linked with delayed wound healing, and has been found to be crucial to the healing of gastric ulcers especially at the early stage (Kennan and Morris, 1993; Andrews and Gallagher-Allred, 1999; Watanabe, 1995).
Pneumonia: Zinc may shorten the duration of severe pneumonia and time in the hospital (Brooks, 2004).
Zinc: The Metal of Life
Source Comprehensive Reviews in Food Science and Food Safety
Kuljeet Kaur1, Rajiv Gupta1, Shubhini A. Saraf2 andShailendra K. Saraf3,*
The importance of zinc was 1st reported for Aspergillus niger. It took over 75 y to realize that zinc is also an essential trace element for rats, and an additional 30 y went by before it was recognized that this was also true for humans. The adult body contains about 2 to 3 g of zinc. Zinc is found in organs, tissues, bones, fluids, and cells. It is essential for many physiological functions and plays a significant role in a number of enzyme actions in the living systems. Bioinformatics estimates report that 10% of the human proteome contains zinc-binding sites. Based on its role in such a plethora of cellular components, zinc has diverse biological functions from enzymatic catalysis to playing a crucial role in cellular neuronal systems. Thus, based on the various published studies and reports, it is pertinent to state that zinc is one of the most important essential trace metals in human nutrition and lifestyle. Its deficiency may severely affect the homeostasis of a biological system. This review compiles the role of zinc in prophylaxis/therapeutics and provides current information about its effect on living beings.
Zinc, the 23rd most abundant element in the earth’s crust, (Zinc: Human Health Fact Sheet 2005) having atomic number 30 and atomic weight 65.37, is vital in the living world. Pure zinc is a bluish-white, shiny metal, (Contaminants: Zinc 2002; Lew 2008) and is amphoteric in nature. Zinc, being colorless and diamagnetic, is invisible to most spectroscopic methods (Maret 2001). The normal concentration of zinc in human blood serum and urine (24 h) is 800 ± 200, 109 to 130, and <500 μg/dL, respectively (Goldfrank and Flomenbaum 2006). The mean serum zinc concentration is 1 mg/L. Red blood cells contain about 10 times higher concentration than that in the serum. Whole blood has about 5 times the serum concentration. It functions together as a structural component of numerous proteins and as a cofactor for many metalloenzymes (Noonan and others 2003). The relative concentration of free ions of zinc within the biological systems varies from ≤109 M in the cytoplasm of many cells to ≤103 M in some organelles (Fabris 1994). Most rocks and countless minerals contain zinc in varying amounts and it enters the air, water, and soil as a consequence of both natural processes and human activities. Zinc can be on the loose to the atmosphere during the production of steel and burning of coal or waste (Zinc: Human Health Fact Sheet 2005). There are approximately 55 mineralized forms of zinc. The most important zinc minerals in the world are sphalerite (ZnS), smithsonite (ZnCO3), and hemimorphite (Zn4Si2O7(OH)2H2O). Zinc appears in Group IIB of the periodic table and has 2 common oxidation states, Zn (0) and Zn (+2). Zinc forms a variety of compounds, such as zinc chloride, zinc oxide, and zinc sulfate. (ATSDR: Toxicological Profile for Zinc 2005) Powdered zinc being explosive can burst into flames if stored in a damp place. Because it is an element, zinc does not degrade nor can it be destroyed (Zinc: Human Health Fact Sheet 2005).
Zinc: Some Conventional Studies from Wiley’s OnLine Library.
Zinc, a versatile element, vital for all physiological processes, is a drug, which has been used as a therapeutic agent against various diseases, since long. Ayurveda mentions the use of zinc in its calcified form (Sodhana & Marana), as zinc ore or as zinc carbonate (Kharpara), as zinc metal (Yasada), as zinc oxide (Pushpanjana) or as an alloy-brass (Pittala). These forms have been mentioned in ancient texts dating back to the 14th century, where these were used to cure various diseases. Oral zinc supplementation has been used as an immunity-boosting agent in geriatric patients (Haase and others 2006). The percentage of Zinc can be analyzed in various body fluids such as saliva, plasma, blood as well as in human excreta. Its levels can also be monitored in hair, nails, and so on. A noteworthy link of zinc and copper concentration in sera collected from pediatric population with respect to their age, height, body mass index, and nutritional habits has been acknowledged (Arvanitidou 2007; Jing and others 2007). Zinc appurtenance exhibits affirmative effect on the occurrence of diarrhea and lessens infant infections (Walker and Black 2004). On the contrary, zinc concentration in patients having oesteoporosis, was not appreciably improved despite receiving calcium supplements (Morgan and others 2006). A zinc (II)-instant coffee complex, a brown amorphous compound, soluble in water was found to have the strongest chelating activity and antioxidative effect for linoleic acid (Homma and others 1997). Zinc therapy in gastrointestinal ailments, liver diseases, bacterial and microbial diseases, and even diabetes has proven beneficial effects.
Natural Foods That Contain High Level of Zinc
Foods having high protein content are also rich in zinc content, whereas those foods and diets containing mostly carbohydrate were found to be much lower in zinc content (Osis and others 1972). Foods derived from meat have a high percentage of zinc (0.40 to 6.77 mg per 100 g). The grain group has 0.30 to 2.54 mg per 100 g, dairy products have 0.36 to 0.49 mg per 100 g, vegetables have 0.12 to 0.60 mg per 100 g, and fruits have 0.02 to 0.26 mg per 100 g (Haeflein and Rasmussen 1977).
As evident from the above study, foods of animal origin are the major sources of zinc in the human diet. Oyster (Ostrea edulis Linnaeus) is rich in zinc and copper complexes (Coombs 1974). Lean red meat, beef liver, poultry red muscle meat, and turkey meat are all good sources of zinc. Zinc is also supplemented through skimmed milk powder, egg yolk, and Cheddar cheese (Murphy and others 1975).
Since in vegetarians, protein intake is mostly through pulses and not meat, they have a higher incidence of zinc deficiency (Hunt 2003). Intake of cereals, legumes, starchy roots like potatoes may result in a lesser bioavailability of zinc (Umeta and others 2005). The level of zinc absorption was found to be lesser in porridge as compared to bread, because of the greater phytate content in porridge (Romana and others 2003). Vitamin A is also absorbed and metabolized to a lesser extent in patients suffering from zinc deficiency (Rahman and others 2002).
Interaction of Zinc with Other Elements in the Diet
Zinc may change the relationship between lead (Pb) in soil and dust and corresponding levels of lead in blood (Noonan and others 2003). Copper supplementation boosts the conjugation of zinc with large molecules and depletes the ratio of zinc coupled with smaller molecules, thereby suggesting an antagonism between copper and zinc (Pang and Applegate 2007). Whenever there is an excess of zinc in the body, it may result in deficiency of copper since zinc is able to competitively inhibit gastro intestinal attachment of copper. The gene expression of upregulation of metallothionein may play an important role in this phenomenon.
Zinc in Excess
Excess zinc promotes obesity and related diseases in adolescents and makes diabetic patients more susceptible, as measured by an increase in glycosylated hemoglobin level in the blood (Singh and Taneja 2009) and is also related to occurrence of severe anemia (Fiske and others 1994. When the nutrients in the upper part of the GI tract are fermented to a lesser extent, extra energy is produced by the body, and this in turn results in better body growth, in the presence of sufficient quantity of zinc oxide in the diet. When the intake of zinc is high, enzymatic activity of pancreas increases and so does mucin production in the intestine. Zinc excess is not only linked with copper deficiency but also cytopenias that typically resolve with the elimination of surplus zinc sources (Fong 2007). Myeloneuropathy in some patients has been accredited to a “new zinc overload syndrome.” Hyperzincemia is the primary metabolic defect, whereas copper deficiency is a secondary phenomenon (Kumar and Ahlskog 2004). Numerous genes needed for host defense were among those recognized as zinc-responsive, together with cytokine receptors and genes associated with amplification of the Th1 immune response (Cousins 2003).
Effect of Zinc on Metabolic Pathways
Quantity of fat deposited was found to be directly proportional to zinc concentration in diet in the case of experiments on obese mice (Chen and others 1996). When insulin was supplemented with zinc, lipid synthesis increased by 74% in obese mice (Chen and others 1998).
The fatty acid metabolism in liver may be affected by zinc deficiency. In rats δ9 desaturase activity reduced when a lipid free diet was administered (Kudo 1990). The antagonistic action of zinc and cAMP on glycolysis together with the rapid and marked decrease in free zinc concentration induced by glucagon (cAMP) may indicate a role of zinc as an important link in the metabolic activity of carbohydrates (Brand and Kleineke 1996). An interrelationship between obesity, leptin, and Zn metabolism is indicated by reduced adipose Zn concentrations in high fat-fed mice and the negative correlation between serum leptin and adipose Zn concentrations (Tallman and Taylor 2003).
Effect of Zinc on Brain
Role of zinc in depression
Effect of zinc was studied in suitable rodent model. It was observed that zinc behaves like an antidepressant. Similar to antidepressants, zinc induces brain-derived neurotrophic factor gene expression and increases the level of synaptic pool of zinc in the hippocampus (Nowak and others 2005). To combat depression in female students, a diet rich in zinc has been recommended (Amani and others 2010). Zinc levels were analyzed in hair samples of thalassemic patients. Cases of depression were linked to the innate risk of zinc deficiency in such patients.
Zinc and Parkinson’s disease
The blood zinc level is less in patients with Alzheimer’s and patients with Parkinson’s disease (Brewer and others 2010). Zinc is present in many proteins, and is capable of passing on signals when released, at neural synapses.Choi and Koh 1998). An excess of aluminium and a deficiency of calcium, along with a deficiency of zinc in the central nervous system, may lead to Pakinson’s disease (Yasui and others 1993). Intranigral infusion of zinc caused degeneration of the nigrostriatal dopaminergic system in rat brain. When zinc and iron deposited together in the rat brain, they were found to be associated with an increased incidence of plaque formation (Lin 2001).
Zinc and Alzheimer’s disease
Alzheimer’s disease (AD) is complicated by pro-oxidant intraneuronal Fe2+ elevation as well as extracellular Zn2+ accumulation within amyloid plaque (Duce and others 2010). The body is not able to effectively metabolize zinc in AD, a condition where pathological catabolism of the amyloid protein precursor causes cerebral β-A4 amyloidosis (Bush and others 1993). The interactions of copper and zinc with neocortical β-amyloid have proved to be a novel therapy for the prevention and treatment of AD (Cherny and others 2001). Fluorescence experiments also reveal that both zinc and copper have similar affinities for amyloid β-peptide (Danielsson 2007) (Cuajungco and Faget 2003). Cu2+ or Zn2+binding to Aβ generated an allosterically ordered membrane-penetrating oligomer linked by superoxide dismutase-like bridging histidine residues (Curtain and others 2001). The domain where zinc binds on the amyloid β-peptide of extracellular deposits gives rise to free radicals because of aggregation. Such reactive oxygen species are the cause of many diseases. Minute quantities of zinc (II) are able to change the binding of β-A4 amyloid precursor protein to heparin side chains of proteoglycans (Multhaup and others 1994). The zinc–Aβ interaction is somewhat similar to that of platelet aggregation or blood coagulation, which takes place in the presence of zinc. This zinc–Aβ interaction is a reversible process. Coordination of Zn2+ to histidine-13 is critical to the zinc ion-induced aggregation of Aβ (Liu 1999). Synaptic zinc contributes predominantly to amyloid deposition in transgenic mice (Lee and others 2002). Total tissue zinc is markedly reduced in several brain regions of Alzheimer’s patients (Cuajungco and Lees 1997a, b). AD patients showed an increase in zinc in the hippocampal and amygdalar regions (Danscher and others 1997). The greater incidence of AD in females could be due to greater constitutive activity of the synaptic zinc transporter ZnT3, and attenuated binding of metal ions to the rodent homologue of Aβ, which might explain why these animals are spared Alzheimer’s pathology (Bush 2003). The nonstructural protein 3 (NS3) is stabilized by the presence of zinc and its folding pattern is also governed by it. Residues Cys-97, Cys-99, Cys-145, and His-149 form a trianglular pyramid of binding sites for zinc in NS3 proteinase. An 8-hydroxyquinoline derivative, Clioquinol, is able to exhibit a remarkable metal ion chelating effect with zinc (II) and copper (II). This results in free radical scavenging and in turn lesser plaques for patients of AD (Vaira and others 2004).
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For information on Zinc and the Cardiovascular, System,’ Zinc in cardiac injury, Role of zinc in blood pressure, Zinc and Liver, Zinc and the Endocrine System, Role of Zinc in Pregnancy various, Zinc and Diabetes, and much much more.