Biology:Zinc in biology

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Short description: Use of Zinc by Organisms
A twisted band, with one side painted blue and another gray. Its two ends are connected through some chemical species to a green atom (zinc).
Zinc fingers help read DNA sequences.

Zinc is an essential trace element for humans[1][2][3] and other animals,[4] for plants[5] and for microorganisms.[6] Zinc is required for the function of over 300 enzymes and 1000 transcription factors,[3] and is stored and transferred in metallothioneins.[7][8] It is the second most abundant trace metal in humans after iron and it is the only metal which appears in all enzyme classes.[5][3]

In proteins, zinc ions are often coordinated to the amino acid side chains of aspartic acid, glutamic acid, cysteine and histidine. The theoretical and computational description of this zinc binding in proteins (as well as that of other transition metals) is difficult.[9]

Roughly 2–4 grams of zinc[10] are distributed throughout the human body. Most zinc is in the brain, muscle, bones, kidney, and liver, with the highest concentrations in the prostate and parts of the eye.[11] Semen is particularly rich in zinc, a key factor in prostate gland function and reproductive organ growth.[12]

Zinc homeostasis of the body is mainly controlled by the intestine. Here, ZIP4 and especially TRPM7 were linked to intestinal zinc uptake essential for postnatal survival.[13][14]

In humans, the biological roles of zinc are ubiquitous.[15][2] It interacts with "a wide range of organic ligands",[15] and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression. It also regulates apoptosis. A review from 2015 indicated that about 10% of human proteins (~3000) bind zinc,[16] in addition to hundreds more that transport and traffic zinc; a similar in silico study in the plant Arabidopsis thaliana found 2367 zinc-related proteins.[5]

In the brain, zinc is stored in specific synaptic vesicles by glutamatergic neurons and can modulate neuronal excitability.[2][3][17] It plays a key role in synaptic plasticity and so in learning.[2][18] Zinc homeostasis also plays a critical role in the functional regulation of the central nervous system.[2][17][3] Dysregulation of zinc homeostasis in the central nervous system that results in excessive synaptic zinc concentrations is believed to induce neurotoxicity through mitochondrial oxidative stress (e.g., by disrupting certain enzymes involved in the electron transport chain, including complex I, complex III, and α-ketoglutarate dehydrogenase), the dysregulation of calcium homeostasis, glutamatergic neuronal excitotoxicity, and interference with intraneuronal signal transduction.[2][19] L- and D-histidine facilitate brain zinc uptake.[20] SLC30A3 is the primary zinc transporter involved in cerebral zinc homeostasis.[2]

Enzymes

Interconnected stripes, mostly of yellow and blue color with a few red segments.
Ribbon diagram of human carbonic anhydrase II, with zinc atom visible in the center
A twisted band, with one side painted blue and another gray. Its two ends are connected through some chemical species to a green atom (zinc).
Zinc fingers help read DNA sequences.

Zinc is an efficient Lewis acid, making it a useful catalytic agent in hydroxylation and other enzymatic reactions.[21] The metal also has a flexible coordination geometry, which allows proteins using it to rapidly shift conformations to perform biological reactions.[22] Two examples of zinc-containing enzymes are carbonic anhydrase and carboxypeptidase, which are vital to the processes of carbon dioxide (CO2) regulation and digestion of proteins, respectively.[23]

In vertebrate blood, carbonic anhydrase converts CO2 into bicarbonate and the same enzyme transforms the bicarbonate back into CO2 for exhalation through the lungs.[24] Without this enzyme, this conversion would occur about one million times slower[25] at the normal blood pH of 7 or would require a pH of 10 or more.[26] The non-related β-carbonic anhydrase is required in plants for leaf formation, the synthesis of indole acetic acid (auxin) and alcoholic fermentation.[27]

Carboxypeptidase cleaves peptide linkages during digestion of proteins. A coordinate covalent bond is formed between the terminal peptide and a C=O group attached to zinc, which gives the carbon a positive charge. This helps to create a hydrophobic pocket on the enzyme near the zinc, which attracts the non-polar part of the protein being digested.[23]

Signalling

Zinc has been recognized as a messenger, able to activate signalling pathways. Many of these pathways provide the driving force in aberrant cancer growth. They can be targeted through ZIP transporters.[28]

Other proteins

Zinc serves a purely structural role in zinc fingers, twists and clusters.[29] Zinc fingers form parts of some transcription factors, which are proteins that recognize DNA base sequences during the replication and transcription of DNA. Each of the nine or ten Zn2+ ions in a zinc finger helps maintain the finger's structure by coordinately binding to four amino acids in the transcription factor.[25]

In blood plasma, zinc is bound to and transported by albumin (60%, low-affinity) and transferrin (10%).[10] Because transferrin also transports iron, excessive iron reduces zinc absorption, and vice versa. A similar antagonism exists with copper.[30] The concentration of zinc in blood plasma stays relatively constant regardless of zinc intake.[21] Cells in the salivary gland, prostate, immune system, and intestine use zinc signaling to communicate with other cells.[31]

Zinc may be held in metallothionein reserves within microorganisms or in the intestines or liver of animals.[32] Metallothionein in intestinal cells is capable of adjusting absorption of zinc by 15–40%.[33] However, inadequate or excessive zinc intake can be harmful; excess zinc particularly impairs copper absorption because metallothionein absorbs both metals.[34]

The human dopamine transporter contains a high affinity extracellular zinc binding site which, upon zinc binding, inhibits dopamine reuptake and amplifies amphetamine-induced dopamine efflux in vitro.[35][36][37] The human serotonin transporter and norepinephrine transporter do not contain zinc binding sites.[37] Some EF-hand calcium binding proteins such as S100 or NCS-1 are also able to bind zinc ions.[38]

Nutrition

Dietary recommendations

The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for zinc in 2001. The current EARs for zinc for women and men ages 14 and up is 6.8 and 9.4 mg/day, respectively. The RDAs are 8 and 11 mg/day. RDAs are higher than EARs so as to identify amounts that will cover people with higher than average requirements. RDA for pregnancy is 11 mg/day. RDA for lactation is 12 mg/day. For infants up to 12 months the RDA is 3 mg/day. For children ages 1–13 years the RDA increases with age from 3 to 8 mg/day. As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of zinc the adult UL is 40 mg/day (lower for children). Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).[21]

The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For people ages 18 and older the PRI calculations are complex, as the EFSA has set higher and higher values as the phytate content of the diet increases. For women, PRIs increase from 7.5 to 12.7 mg/day as phytate intake increases from 300 to 1200 mg/day; for men the range is 9.4 to 16.3 mg/day. These PRIs are higher than the U.S. RDAs.[39] The EFSA reviewed the same safety question and set its UL at 25 mg/day, which is much lower than the U.S. value.[40]

For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value (%DV). For zinc labeling purposes 100% of the Daily Value was 15 mg, but on May 27, 2016, it was revised to 11 mg.[41][42] A table of the old and new adult daily values is provided at Reference Daily Intake.

Dietary intake

Several plates full of various cereals, fruits and vegetables on a table.
Foods and spices containing zinc

Animal products such as meat, fish, shellfish, fowl, eggs, and dairy contain zinc. The concentration of zinc in plants varies with the level in the soil. With adequate zinc in the soil, the food plants that contain the most zinc are wheat (germ and bran) and various seeds, including sesame, poppy, alfalfa, celery, and mustard.[43] Zinc is also found in beans, nuts, almonds, whole grains, pumpkin seeds, sunflower seeds, and blackcurrant.[44]

Other sources include fortified food and dietary supplements in various forms. A 1998 review concluded that zinc oxide, one of the most common supplements in the United States, and zinc carbonate are nearly insoluble and poorly absorbed in the body.[45] This review cited studies that found lower plasma zinc concentrations in the subjects who consumed zinc oxide and zinc carbonate than in those who took zinc acetate and sulfate salts.[45] For fortification, however, a 2003 review recommended cereals (containing zinc oxide) as a cheap, stable source that is as easily absorbed as the more expensive forms.[46] A 2005 study found that various compounds of zinc, including oxide and sulfate, did not show statistically significant differences in absorption when added as fortificants to maize tortillas.[47]

Deficiency

Main page: Medicine:Zinc deficiency

Nearly two billion people in the developing world are deficient in zinc. Groups at risk include children in developing countries and elderly with chronic illnesses.[48] In children, it causes an increase in infection and diarrhea and contributes to the death of about 800,000 children worldwide per year.[15] The World Health Organization advocates zinc supplementation for severe malnutrition and diarrhea.[49] Zinc supplements help prevent disease and reduce mortality, especially among children with low birth weight or stunted growth.[49] However, zinc supplements should not be administered alone, because many in the developing world have several deficiencies, and zinc interacts with other micronutrients.[50] While zinc deficiency is usually due to insufficient dietary intake, it can be associated with malabsorption, acrodermatitis enteropathica, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses.[48]

In the United States, a federal survey of food consumption determined that for women and men over the age of 19, average consumption was 9.7 and 14.2 mg/day, respectively. For women, 17% consumed less than the EAR, for men 11%. The percentages below EAR increased with age.[51] The most recent published update of the survey (NHANES 2013–2014) reported lower averages – 9.3 and 13.2 mg/day – again with intake decreasing with age.[52]

Symptoms of mild zinc deficiency are diverse.[21] Clinical outcomes include depressed growth, diarrhea, impotence and delayed sexual maturation, alopecia, eye and skin lesions, impaired appetite, altered cognition, impaired immune functions, defects in carbohydrate utilization, and reproductive teratogenesis.[21] Zinc deficiency depresses immunity,[53] but excessive zinc does also.[10]

Despite some concerns,[54] western vegetarians and vegans do not suffer any more from overt zinc deficiency than meat-eaters.[55] Major plant sources of zinc include cooked dried beans, sea vegetables, fortified cereals, soy foods, nuts, peas, and seeds.[54] However, phytates in many whole-grains and fibers may interfere with zinc absorption and marginal zinc intake has poorly understood effects. The zinc chelator phytate, found in seeds and cereal bran, can contribute to zinc malabsorption.[48] Some evidence suggests that more than the US RDA (8 mg/day for adult women; 11 mg/day for adult men) may be needed in those whose diet is high in phytates, such as some vegetarians.[54] The European Food Safety Authority (EFSA) guidelines attempt to compensate for this by recommending higher zinc intake when dietary phytate intake is greater.[39] These considerations must be balanced against the paucity of adequate zinc biomarkers, and the most widely used indicator, plasma zinc, has poor sensitivity and specificity.[56]

Soil availability and remediation

Zinc can be present in six different forms in soil namely; water soluble zinc, exchangeable zinc, organically bound zinc, carbonate bound zinc, aluminium and manganese oxide bound zinc and residual fractions of zinc.[57]

In toxic conditions, species of Calluna, Erica and Vaccinium can grow in zinc-metalliferous soils, because translocation of toxic ions is prevented by the action of ericoid mycorrhizal fungi.[58]

Agriculture

Zinc deficiency appears to be the most common micronutrient deficiency in crop plants; it is particularly common in high-pH soils.[59] Zinc-deficient soil is cultivated in the cropland of about half of Turkey and India, a third of China, and most of Western Australia. Substantial responses to zinc fertilization have been reported in these areas.[5] Plants that grow in soils that are zinc-deficient are more susceptible to disease. Zinc is added to the soil primarily through the weathering of rocks, but humans have added zinc through fossil fuel combustion, mine waste, phosphate fertilizers, pesticide (zinc phosphide), limestone, manure, sewage sludge, and particles from galvanized surfaces. Excess zinc is toxic to plants, although zinc toxicity is far less widespread.[5]

Biodegradable implants

Zinc (Zn), alongside Magnesium (Mg) and Iron (Fe), constitutes one of the three families of biodegradable metals.[60] Zinc, as an abundant trace element, ranks sixth among all the essential metallic elements crucial for sustaining life within the human body.[61] Zinc exhibits an intermediate biodegradation rate, falling between that of Fe (relatively slow) and Mg (relatively high) which positions it as a promising material for use in biodegradable implants.[62][63][64]

References

  1. ↑ "Zinc and Human Disease". Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences. 13. Springer. 2013. pp. 389–414. doi:10.1007/978-94-007-7500-8_12. ISBN 978-94-007-7499-5. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 "Zinc: indications in brain disorders". Fundamental & Clinical Pharmacology 29 (2): 131–149. April 2015. doi:10.1111/fcp.12110. PMID 25659970. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 "Dietary Zinc Acts as a Sleep Modulator". International Journal of Molecular Sciences 18 (11): 2334. November 2017. doi:10.3390/ijms18112334. PMID 29113075. "Zinc is the second most abundant trace metal in the human body, and is essential for many biological processes.  ... The trace metal zinc is an essential cofactor for more than 300 enzymes and 1000 transcription factors [16]. ... In the central nervous system, zinc is the second most abundant trace metal and is involved in many processes. In addition to its role in enzymatic activity, it also plays a major role in cell signaling and modulation of neuronal activity.". 
  4. ↑ "Zinc in human health: effect of zinc on immune cells". Molecular Medicine 14 (5–6): 353–357. 2008. doi:10.2119/2008-00033.Prasad. PMID 18385818. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 "Zinc in plants". The New Phytologist 173 (4): 677–702. 2007. doi:10.1111/j.1469-8137.2007.01996.x. PMID 17286818. 
  6. ↑ Zinc's role in microorganisms is particularly reviewed in: "Zinc and infection". Reviews of Infectious Diseases 5 (1): 137–147. 1983. doi:10.1093/clinids/5.1.137. PMID 6338570. 
  7. ↑ Cotton et al. 1999, pp. 625–629
  8. ↑ "The essential toxin: impact of zinc on human health". International Journal of Environmental Research and Public Health 7 (4): 1342–1365. April 2010. doi:10.3390/ijerph7041342. PMID 20617034. 
  9. ↑ "Molecular dynamics study of zinc binding to cysteines in a peptide mimic of the alcohol dehydrogenase structural zinc site". Physical Chemistry Chemical Physics 11 (6): 975–983. February 2009. doi:10.1039/b815482a. PMID 19177216. Bibcode: 2009PCCP...11..975B. https://zenodo.org/record/996012. Retrieved 2022-07-02. 
  10. ↑ 10.0 10.1 10.2 "Zinc and the immune system". The Proceedings of the Nutrition Society 59 (4): 541–552. November 2000. doi:10.1017/S0029665100000781. PMID 11115789. 
  11. ↑ Protein Nutrition and Mineral Absorption. Boca Raton, Florida: CRC Press. 1990. ISBN 978-0-8493-5227-0. https://books.google.com/books?id=qfKdaCoZS18C. Retrieved 2022-07-02. 
  12. ↑ Handbook of Nutrition and Food. Boca Raton, Florida: CRC Press. 2007. ISBN 978-0-8493-9218-4. https://books.google.com/books?id=PJpieIePsmUC. Retrieved 2022-07-02. 
  13. ↑ "TRPM7 is the central gatekeeper of intestinal mineral absorption essential for postnatal survival". Proceedings of the National Academy of Sciences of the United States of America 116 (10): 4706–4715. March 2019. doi:10.1073/pnas.1810633116. PMID 30770447. Bibcode: 2019PNAS..116.4706M. 
  14. ↑ "Genetic causes and gene–nutrient interactions in mammalian zinc deficiencies: acrodermatitis enteropathica and transient neonatal zinc deficiency as examples". Journal of Trace Elements in Medicine and Biology 29: 47–62. January 2015. doi:10.1016/j.jtemb.2014.10.003. PMID 25468189. 
  15. ↑ 15.0 15.1 15.2 "Zinc deficiency: a special challenge". The Journal of Nutrition 137 (4): 1101–1105. April 2007. doi:10.1093/jn/137.4.1101. PMID 17374687. 
  16. ↑ "The Role of Copper and Zinc Toxicity in Innate Immune Defense against Bacterial Pathogens". The Journal of Biological Chemistry 290 (31): 18954–18961. July 2015. doi:10.1074/jbc.R115.647099. PMID 26055706. "Zn is present in up to 10% of proteins in the human proteome and computational analysis predicted that ~30% of these ~3000 Zn-containing proteins are crucial cellular enzymes, such as hydrolases, ligases, transferases, oxidoreductases, and isomerases (42,43).". 
  17. ↑ 17.0 17.1 "Zinc: the brain's dark horse". Synapse 63 (11): 1029–1049. November 2009. doi:10.1002/syn.20683. PMID 19623531. 
  18. ↑ "Zinc and cortical plasticity". Brain Research Reviews 59 (2): 347–373. March 2009. doi:10.1016/j.brainresrev.2008.10.003. PMID 19026685. 
  19. ↑ "The role of zinc in the pathogenesis and treatment of central nervous system (CNS) diseases. Implications of zinc homeostasis for proper CNS function". Acta Poloniae Pharmaceutica 71 (3): 369–377. May 2014. PMID 25265815. http://www.ptfarm.pl/pub/File/Acta_Poloniae/2014/3/369.pdf. 
  20. ↑ "Blood-brain barrier flux of aluminum, manganese, iron and other metals suspected to contribute to metal-induced neurodegeneration". Journal of Alzheimer's Disease 10 (2–3): 223–253. November 2006. doi:10.3233/JAD-2006-102-309. PMID 17119290. 
  21. ↑ 21.0 21.1 21.2 21.3 21.4 Institute of Medicine (2001). "Zinc". Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press. pp. 442–501. doi:10.17226/10026. ISBN 978-0-309-07279-3. https://www.nap.edu/read/10026/chapter/14/. 
  22. ↑ Biochemical, Physiological & Molecular Aspects of Human Nutrition. W. B. Saunders Company. 2006. pp. 1043–1067. ISBN 978-0-7216-4452-3. 
  23. ↑ 23.0 23.1 Greenwood & Earnshaw 1997, pp. 1224–1225
  24. ↑ Isotope Effects in Chemistry and Biology. Boca Raton, Florida: CRC Press. 2006. p. 850. ISBN 978-0-8247-2449-8. https://books.google.com/books?id=7EiIqrRBBQgC. Retrieved 2022-07-02. 
  25. ↑ 25.0 25.1 Greenwood & Earnshaw 1997, p. 1225
  26. ↑ Cotton et al. 1999, p. 627
  27. ↑ "Effects of indole-3-acetic acid and zinc on the growth, osmotic potential and soluble carbon and nitrogen components of soybean plants growing under water deficit". Journal of Arid Environments 44 (4): 451–467. 2000. doi:10.1006/jare.1999.0610. Bibcode: 2000JArEn..44..451G. 
  28. ↑ "Targeting Zinc(II) Signalling to Prevent Cancer". Metal Ions in Life Sciences (de Gruyter GmbH) 18: 507–529. February 2018. doi:10.1515/9783110470734-023. ISBN 9783110470734. PMID 29394036. 
  29. ↑ Cotton et al. 1999, p. 628
  30. ↑ Understanding Nutrition (10th ed.). Thomson Learning. 2005. pp. 447–450. ISBN 978-1-4288-1893-4. 
  31. ↑ "The zinc sensing receptor, a link between zinc and cell signaling". Molecular Medicine 13 (7–8): 331–336. 2007. doi:10.2119/2006-00038.Hershfinkel. PMID 17728842. 
  32. ↑ Cotton et al. 1999, p. 629
  33. ↑ Vitamins and Minerals Demystified. McGraw-Hill Professional. 2007. p. 242. ISBN 978-0-07-148901-0. 
  34. ↑ "Zinc toxicity". The American Journal of Clinical Nutrition 51 (2): 225–227. February 1990. doi:10.1093/ajcn/51.2.225. PMID 2407097. 
  35. ↑ "SPECT and PET of the dopamine transporter in attention-deficit/hyperactivity disorder". Expert Review of Neurotherapeutics 8 (4): 611–625. April 2008. doi:10.1586/14737175.8.4.611. PMID 18416663. 
  36. ↑ "How addictive drugs disrupt presynaptic dopamine neurotransmission". Neuron 69 (4): 628–649. February 2011. doi:10.1016/j.neuron.2011.02.010. PMID 21338876. 
  37. ↑ 37.0 37.1 "The role of zinc ions in reverse transport mediated by monoamine transporters". The Journal of Biological Chemistry 277 (24): 21505–21513. June 2002. doi:10.1074/jbc.M112265200. PMID 11940571. "The human dopamine transporter (hDAT) contains an endogenous high affinity Zn2+ binding site with three coordinating residues on its extracellular face (His193, His375, and Glu396). ... Thus, when Zn2+ is co-released with glutamate, it may greatly augment the efflux of dopamine.". 
  38. ↑ "Functional Status of Neuronal Calcium Sensor-1 Is Modulated by Zinc Binding". Frontiers in Molecular Neuroscience 11: 459. 2018. doi:10.3389/fnmol.2018.00459. PMID 30618610. 
  39. ↑ 39.0 39.1 "Overview on Dietary Reference Values for the EU population as derived by the EFSA Panel on Dietetic Products, Nutrition and Allergies". 2017. https://www.efsa.europa.eu/sites/default/files/assets/DRV_Summary_tables_jan_17.pdf. 
  40. ↑ Tolerable Upper Intake Levels For Vitamins And Minerals, European Food Safety Authority, 2006, http://www.efsa.europa.eu/sites/default/files/efsa_rep/blobserver_assets/ndatolerableuil.pdf 
  41. ↑ "Federal Register May 27, 2016 Food Labeling: Revision of the Nutrition and Supplement Facts Labels. FR page 33982.". https://www.gpo.gov/fdsys/pkg/FR-2016-05-27/pdf/2016-11867.pdf. 
  42. ↑ "Daily Value Reference of the Dietary Supplement Label Database (DSLD)". https://www.dsld.nlm.nih.gov/dsld/dailyvalue.jsp. 
  43. ↑ Foods & Nutrition Encyclopedia (2nd ed.). Boca Raton, Florida: CRC Press. 1993. pp. 2368–2369. ISBN 978-0-8493-8980-1. https://books.google.com/books?id=XMA9gYIj-C4C. Retrieved 2022-07-02. 
  44. ↑ "Zinc content of selected foods per common measure". USDA National Nutrient Database for Standard Reference, Release 20. United States Department of Agriculture. http://www.nal.usda.gov/fnic/foodcomp/Data/SR20/nutrlist/sr20w309.pdf. 
  45. ↑ 45.0 45.1 "Zinc and micronutrient supplements for children". The American Journal of Clinical Nutrition 68 (2 Suppl): 495S–498S. August 1998. doi:10.1093/ajcn/68.2.495S. PMID 9701167. 
  46. ↑ "Zinc and copper: proposed fortification levels and recommended zinc compounds". The Journal of Nutrition 133 (9): 2985S–2989S. September 2003. doi:10.1093/jn/133.9.2985S. PMID 12949397. 
  47. ↑ "Zinc absorption from zinc oxide, zinc sulfate, zinc oxide + EDTA, or sodium-zinc EDTA does not differ when added as fortificants to maize tortillas". The Journal of Nutrition 135 (5): 1102–1105. May 2005. doi:10.1093/jn/135.5.1102. PMID 15867288. 
  48. ↑ 48.0 48.1 48.2 "Zinc deficiency". BMJ 326 (7386): 409–410. February 2003. doi:10.1136/bmj.326.7386.409. PMID 12595353. 
  49. ↑ 49.0 49.1 "The impact of zinc supplementation on childhood mortality and severe morbidity". World Health Organization. 2007. https://www.who.int/child_adolescent_health/documents/zinc_mortality/en/index.html. 
  50. ↑ "Zinc deficiency: what are the most appropriate interventions?". BMJ 330 (7487): 347–349. February 2005. doi:10.1136/bmj.330.7487.347. PMID 15705693. 
  51. ↑ "NHANES 2001–2002: Usual Nutrient Intakes from Food Compared to Dietary Reference Intakes". U.S. Department of Agriculture, Agricultural Research Service. 2005. Table A13: Zinc. https://www.ars.usda.gov/SP2UserFiles/Place/80400530/pdf/0102/usualintaketables2001-02.pdf. 
  52. ↑ What We Eat In America, NHANES 2013–2014 (Report). https://www.ars.usda.gov/ARSUserFiles/80400530/pdf/1314/Table_1_NIN_GEN_13.pdf. 
  53. ↑ "Zinc-altered immune function". The Journal of Nutrition 133 (5 Suppl 1): 1452S–1456S. May 2003. doi:10.1093/jn/133.5.1452S. PMID 12730441. 
  54. ↑ 54.0 54.1 54.2 American Dietetic Association; Dietitians of Canada (June 2003). "Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets". Journal of the American Dietetic Association 103 (6): 748–765. doi:10.1053/jada.2003.50142. PMID 12778049. https://www.vrg.org/nutrition/2003_ADA_position_paper.pdf. 
  55. ↑ "Zinc status of vegetarians". Journal of the American Dietetic Association 77 (6): 655–661. December 1980. doi:10.1016/S1094-7159(21)03587-X. PMID 7440860. 
  56. ↑ "Biomarkers of trace mineral intake and status". The Journal of Nutrition. 133 133 (3): 948S–955S. March 2003. doi:10.1093/jn/133.3.948S. PMID 12612181. 
  57. ↑ "krishikosh". https://krishikosh.egranth.ac.in/handle/1/5810196995. 
  58. ↑ "Metals, minerals and microbes: geomicrobiology and bioremediation". Microbiology 156 (Pt 3): 609–643. March 2010. doi:10.1099/mic.0.037143-0. PMID 20019082. http://mic.sgmjournals.org/content/156/3/609.full. 
  59. ↑ "Zinc in Soils and Crop Nutrition, International Fertilizer Industry Association, and International Zinc Association". 2008. http://www.fertilizer.org/HomePage/LIBRARY/Our-selection2/Fertilizer-use.html/Zinc-in-Soils-and-Crop-Nutrition.html. 
  60. ↑ "Updates on the research and development of absorbable metals for biomedical applications". Progress in Biomaterials 7 (2): 93–110. June 2018. doi:10.1007/s40204-018-0091-4. PMID 29790132. 
  61. ↑ "Additive manufacturing of biodegradable Zn-xMg alloys: Effect of Mg content on manufacturability, microstructure and mechanical properties". Materials Today Communications 32: 103805. August 2022. doi:10.1016/j.mtcomm.2022.103805. ISSN 2352-4928. 
  62. ↑ "Densification behavior of pure Zn metal parts produced by selective laser melting for manufacturing biodegradable implants". Journal of Materials Processing Technology 258: 128–137. 2018-08-01. doi:10.1016/j.jmatprotec.2018.03.007. ISSN 0924-0136. 
  63. ↑ "Laser additive manufacturing of Zn porous scaffolds: Shielding gas flow, surface quality and densification". Journal of Materials Science & Technology. Recent Advances in Additive Manufacturing of Metals and Alloys 35 (2): 368–376. 2019-02-01. doi:10.1016/j.jmst.2018.09.065. ISSN 1005-0302. https://www.sciencedirect.com/science/article/pii/S1005030218302524. 
  64. ↑ "Processability of pure Zn and pure Fe by SLM for biodegradable metallic implant manufacturing". Rapid Prototyping Journal 23 (3): 514–523. January 2017. doi:10.1108/RPJ-08-2015-0100. ISSN 1355-2546. 

Bibliography



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