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#1
09.07.2012, 23:43
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Äåôèöèò öèíêà: ïóáëèêàöèè è ìàòåðèàëû ïî òåìå
Zinc deficiency can present in many ways and should be considered in people with at-risk conditions. Aside from the severe rash of acrodermatitis enteropathica seen in profound zinc deficiency, the manifestations of zinc deficiency are protean and non-specific. The diagnosis can be especially elusive because symptoms may overlap with the many conditions that predispose to zinc deficiency. For this reason, a high index of suspicion is critical.
Clinical evaluation Acquired zinc deficiency may result from poor nutritional intake, ingestion of foods or drugs that reduce zinc absorption, chronic illness, or any combination of these. Symptoms are quite diverse and clinical suspicion for this must be high in at-risk people. Acquired zinc deficiency can be seen in many patient groups. These include patients with malabsorption syndrome, chronic GI and liver disease, diabetes, renal disease, sickle cell disease, anorexia nervosa, and HIV infection; chronic treatment with certain medication (hydrochlorothiazide, penicillamine, ethambutol, certain antibiotics); and patients >65 years. Zinc deficiency may contribute to many of the problems associated with ageing, including susceptibility to infection and osteoporosis. Pica (clay eating) is common in children in some communities. Clay efficiently binds zinc, leading to dramatically decreased bioavailability. Other risk factors include alcoholism, vegetarianism or veganism, and living in a developing region: Alcoholics tend to be deficient in zinc, along with a variety of other nutrients Low meat intake or high phytate/oxalate intake can contribute to zinc deficiency. Phytates and oxalates are found in many grain and vegetable products including soy, bran, whole grains, spinach, berries, chocolate, and tea. This is compounded by the tendency of diets low in meat to be high in the fibrous plant products that bind zinc, further limiting absorption. Zinc is a key micronutrient important in growth and development, immune function, taste, smell, wound healing, protein synthesis, and maintenance of skin and hair. Some clinical features affected by zinc deficiency include: Growth and development: growth retardation, hypogonadism, osteopenia (increased risk of bone fracture), weight loss Neurological: intention tremor, depression, impaired concentration, nystagmus, dysarthria, night blindness, hypogeusia, anosmia, dementia Dermatological: alopecia, dermatitis, paronychia, stomatitis Gastrointestinal: anorexia, abdominal pain, diarrhoea, glossitis Miscellaneous: fatigue, delayed wound healing, fever, pica, increased infections, blepharitis, impaired glucose tolerance, infertility/adverse pregnancy outcomes. Symptoms may overlap with the many conditions that predispose to zinc deficiency. Because there is such a non-specific presentation of zinc deficiency, it may be clinically difficult to differentiate it from from hypothyroidism and depression; other nutrient deficiencies that may co-exist with cases of zinc deficiency, including iron, vitamin D, vitamin A, vitamin B12, and folate, may also be difficult to differentiate. These deficiencies should be considered and tested for appropriately. Acrodermatitis enteropathica is a manifestation of severe zinc deficiency typically caused by an autosomal-recessive disease, through impaired absorption. This disorder typically presents in infancy with crusting, vesicular dermatitis, View imageView image diarrhoea, growth retardation, and infections. However, acrodermatitis enteropathica may also rarely occur in adults with severe nutritional deficiency. Laboratory tests If zinc deficiency is suspected, serum or plasma zinc testing should be done. Serum and plasma zinc levels are most commonly used and are the only tests available in routine clinical practice. Data support the use of either <9.2 micromols/L (60 micrograms/dL) or <10.7 micromols/L (70 micrograms/dL) as abnormal in non-pregnant adults. Owing to the relatively low sensitivity of serum zinc levels in marginal deficiency, oral supplementation should be considered if symptoms are typical, even if test results are normal. Other nutrient deficiencies often co-exist with zinc deficiency. Deficiencies in iron, vitamin D, vitamin B12, and folate should be tested for. Deficiencies of other fat-soluble vitamins are relatively rare and hard to measure and thus, are not commonly tested. In cases where zinc deficiency is due to dietary factors, no further evaluation is generally necessary. Evaluation for occult GI disease such as c0eliac disease or Crohn's disease is warranted if zinc deficiency is found in an individual without known risk factors. Cell zinc content and analysis of zinc levels in hair are two emerging tests. Cell zinc content: because 95% of zinc is intracellular, zinc levels in a variety of cell populations (red blood cells, platelets, white blood cells) have been evaluated in research settings. Although cellular zinc levels fluctuate less than serum, they are technically more difficult than serum- or plasma-based tests, and superiority has not been clearly demonstrated. Analysis of zinc levels in hair: the utility of hair zinc analysis is unclear, and has been used primarily in research settings. ([Ññûëêè äîñòóïíû òîëüêî çàðåãèñòðèðîâàííûì ïîëüçîâàòåëÿì ]) |
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#2
09.07.2012, 23:51
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Zinc Diagnostic Tests
1. Zinc Taste Test (Oral Zinc Test)
Because we know that taste and smell are dependant on there being enough zinc in the body we are able to get an idea of the zinc status by giving the patient a standard test solution of zinc sulphate for tasting and comparing the response to defined standards. This is a very quick, 10 second test that can be done at home or in the doctors rooms. Obviously assessment of altered taste perception by zinc 'taste tests' is very subjective and cannot be considered scientifically accurate. A test solution of zinc sulphate in purified water, at a concentration of 1gm/liter is prepared. The solution can be kept for up to 6 months in a refrigerator, after which it should be discarded. The solution should be removed from the fridge and left at room temperature for about two hours prior to the test. You must not eat, drink, or smoke for at least one hour before the test. How the test is done. About 1-2 teaspoons of the solution is sipped and help in the mouth for exactly ten seconds after which you can spit it out. The defined standards are: 1. No specific taste sensation: tastes like plain water. This indicates a major deficiency of zinc 2. No immediate taste is noticed but, within the ten seconds of the test, a 'dry' or 'metallic' taste is experienced. Some people describe it as ‘like baking soda’. This indicates a moderate deficiency. 3. An immediate slight but not necessarily unpleasant taste is noted, which builds up over the ten second period. This indicates a deficiency of minor degree. 4. An immediate, strong and unpleasant taste is experienced. The patient generally wants to rinse his mouth out. This indicates that no zinc deficiency exists. If the latter response (4) occurs prior to any form of supplementation then it is obvious that one is getting sufficient zinc from ones diet. If the patient had a prior test response that showed a deficiency and has taken supplemental zinc and is now showing no deficiency then one must conclude that their previous diet was lacking in zinc. If there is no hope of a change to a more zinc intense diet then it will be necessary to take a regular maintenance dose of zinc daily. Note - It is possible that if the patient has a quantity of amalgam fillings in the mouth (which contain a fair amount of mercury) the zinc test may be less precise. The zinc liquid plus mercury could cause a nasty, metallic taste in the mouth in spite of the zinc deficiency in the body. 2. Serum Zinc This is the simplest way of assessing zinc status but the factors that can cause inaccuracies are high. They include diurnal variations, fluctuations after meals, increased levels after fasting, stress, pregnancy, certain malignancies, renal failure, low albumin concentrations etc. Analysis of the 250µL (minimum) blood sample is done by atomic absorption spectroscopy, The reference range is 10.7 - 22.9µmol/L (70-150 µg/dl). A concentration below 7 µmol/L (46µg/dl) is indicative of a decided deficiency. 3. Plasma Zinc This is the main lab test done to establish zinc deficiency. Although it is very good at picking up major deficiencies it is quite insensitive to marginal deficiency because a change in plasma zinc does not occur until zinc intake is extremely low. So a patient with `normal' results may still be deficient. Plasma levels of zinc can be influenced by hypo or hyperproteinemia, acute infections, stress, time of sampling (how long after a meal), pregnancy, liver disease, malignancies and pernicious anaemia. Zinc supplements will affect the results of plasma tests so one needs to avoid taking these for at least 24 hours prior to the test. The optimal range of plasma zinc is 13.8 - 22.9µmol/L ( 90-150µg/dl). Clinical signs of zinc deficiency may occur when plasma zinc concentrations drop below 9.9µmol/L (65 µg/dl). Values less than 5µmol/L (33 µg/dl) are particularly associated with loss of the senses of taste and smell, abdominal pain, diarrhoea, skin rash, and loss of appetite. 4. Zinc Tolerance Test This test measures the changes in plasma zinc after zinc is orally administered. A normal response is a doubling of plasma zinc peaking at three hours, but this varies from person to person. Fasting from 10pm the previous evening is necessary before this test is done. 5. Hair Zinc This is a test often used in research studies where it’s results are of more use than in general practise because of the ability of the researchers to keep a tight control over external factors. These factors include the presence of zinc in some hair products like shampoos and perming lotions. A sample of hair, about 0.5g (1 heaped tablespoon full) cut close to the scalp from the back of head or nape of neck is required. A normal range is around 150 - 240µg/gram. Levels of less than 70µg/gram would be indicative of zinc deficiency. One cannot use this test if the subject is severely malnourished as malnutrition causes a decrease in the rate of hair growth. 6. Urinary Zinc Excretion Again this is an unreliable test because though low amounts may indicate zinc deficiency the results are influenced by other factors. Zinc chelates to other substances, like proteins, and if an excess of those are being excreted zinc will be as well. In catabolic states large amounts of zinc which are released from tissues may be excreted in the urine. Normal range is 3.3 to 21.4 µmol/24 h 7. New Tests Serum alkaline phosphatase enzyme reactivation. As this enzyme contains zinc a low activity is indicative of a zinc deficiency. Leukocyte zinc content correlates well with muscle zinc content and so may offer an improved indication of zinc status. However this test requires a large sample of blood, which needs particularly careful handling soon after collection. [Ññûëêè äîñòóïíû òîëüêî çàðåãèñòðèðîâàííûì ïîëüçîâàòåëÿì ] |
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#3
10.07.2012, 23:28
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Zinc deficiency and clinical practice-validity of zinc preparations.
Yanagisawa H. Yakugaku Zasshi. 2008 Mar;128(3):333-9. [Ññûëêè äîñòóïíû òîëüêî çàðåãèñòðèðîâàííûì ïîëüçîâàòåëÿì ] |
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#4
29.11.2012, 01:21
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Äåôèöèò âèòàìèíà À è öèíêà ìîæåò óñóãóáëÿòü è áåç òîãî íàðóøåííûé èììóííûé ñòàòóñ ó ïàöèåíòîâ ñ èììóíîäåôèöèòîì:
Äåôèöèò âèòàìèíà À è öèíêà ìîæåò óñóãóáëÿòü è áåç òîãî íàðóøåííûé èììóííûé ñòàòóñ ó ïàöèåíòîâ ñ èììóíîäåôèöèòîì: J Investig Allergol Clin Immunol. 2012;22(6):427-31. Assessment of nutritional status: vitamin A and zinc in patients with common variable immunodeficiency. We included 17 patients (mean age, 28.54 years) and 17 controls. Mean (SD) retinol levels were lower in patients: 1.99 (0.67) micromol/L vs 2.72 (0.96) micromol/L... Median serum zinc levels were 50.0 microg/dL (50-100 microg/dL) in the patients and 100.0 microg/dL (50-150 microg/dL) in the controls. Mean levels of erythrocyte zinc were lower among patients: 37.32 (10.51) ugZn/gHb vs 44.91 (7.67) ugZn/gHb in the controls. Median CRP levels were significantly higher among patients: 4.99 (0.15-34.51) mg/L vs 0.55 (0.17-6.06) mg/L. [Ññûëêè äîñòóïíû òîëüêî çàðåãèñòðèðîâàííûì ïîëüçîâàòåëÿì ] |
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#5
18.06.2013, 23:53
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Ïðèëîæåíèå ê æóðíàëó Ann Nutr Metab 2013;62(suppl 1) ïîñâÿùåíî îáìåíó öèíêà:
Update on Zinc Biology Solomons N.W. Update on Zinc Deficiency and Excess in Clinical Pediatric Practice Krebs N.F. Zinc Supplementation in Public Health Penny M.E. Systematic Review of Zinc Fortification Trials Das J.K. · Kumar R. · Salam R.A. · Bhutta Z.A. [Ññûëêè äîñòóïíû òîëüêî çàðåãèñòðèðîâàííûì ïîëüçîâàòåëÿì ] FREE ONLINE ACCESS |
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#6
01.10.2014, 22:14
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Adv Nutr. 2013 Mar 1;4(2):176-90.
Discovery of human zinc deficiency: its impact on human health and disease. [Ññûëêè äîñòóïíû òîëüêî çàðåãèñòðèðîâàííûì ïîëüçîâàòåëÿì ] |
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#7
24.04.2015, 22:23
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Ñðàâíèòåëüíîå íàçíà÷åíèå ïðåïàðàòîâ öèíêà ïîêàçàëî, ÷òî ïðèåì öèíêà ãëèöèíàòà ïîâûøàåò åãî êîíöåíòðàöèþ â êðîâè, òîãäà êàê èçìåíåíèÿ íà ôîíå ëàêòàòà öèíêà íå îòëè÷àëèñü îò ïëàöåáî:
Biol Trace Elem Res. 2015 Apr 17. Moderately High Dose Zinc Gluconate or Zinc Glycinate: Effects on Plasma Zinc and Erythrocyte Superoxide Dismutase Activities in Young Adult Women. DiSilvestro RA, Koch E, Rakes L. Some zinc (Zn) research studies have used either Zn gluconate or Zn glycinate, but the two forms have not been compared much. Therefore, a moderately high dose of the two forms (60 mg Zn/day) were compared in a 6-week intervention in young adult women. Plasma Zn, the traditional assessment of Zn status, was increased in all subjects given Zn glycinate (N = 10), while no significant change was seen overall for Zn gluconate or placebo (N = 10 each). Erythrocyte superoxide dismutase activity, a marker for Zn-induced copper deficiency, was unchanged in all three groups. Thus, for the conditions of this study, Zn glycinate effectively changed Zn status better than Zn gluconate, but neither impacted copper status. |
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#8
11.05.2015, 19:41
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Determination of Zinc Status in Humans:
Which Indicator Should We Use? [Ññûëêè äîñòóïíû òîëüêî çàðåãèñòðèðîâàííûì ïîëüçîâàòåëÿì ] |
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#10
16.02.2018, 20:01
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Zinc and Skin Disorders
Several human disorders accompanied with skin manifestations are caused by mutations or dysregulation in Zn transporters; acrodermatitis enteropathica (Zrt-, Irt-like protein (ZIP)4 in the intestinal epithelium and possibly epidermal basal keratinocytes), the spondylocheiro dysplastic form of Ehlers-Danlos syndrome (ZIP13 in the dermal fibroblasts), transient neonatal Zn deficiency (Zn transporter (ZnT)2 in the secretory vesicles of mammary glands), and epidermodysplasia verruciformis (ZnT1 in the epidermal keratinocytes). Additionally, acquired Zn deficiency is deeply involved in the development of some diseases related to nutritional deficiencies (acquired acrodermatitis enteropathica, necrolytic migratory erythema, pellagra, and biotin deficiency), alopecia, and delayed wound healing.
--- Nutrients. 2018 Feb 11;10(2). Zinc and Skin Disorders. Ogawa Y, et al. |
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