Chapter 1: Overview of Zinc Nutrition ............................................................................................................... S99 1.1 Biological functions of zinc ............................................................................................................................. S99 1.2 Tissue zinc distribution and reserves .............................................................................................................. S99 1.3 Zinc metabolism ........................................................................................................................................... S100 1.4 Importance of zinc for human health........................................................................................................... S101 1.5 Human zinc requirements............................................................................................................................. S105 1.5.1 Adult men ............................................................................................................................................. S106 1.5.2 Adult women......................................................................................................................................... S109 1.5.3 Children ................................................................................................................................................ S110 1.5.4 Pregnancy.............................................................................................................................................. S111 1.5.5 Lactation ............................................................................................................................................... S112 1.6 Dietary sources of zinc and suggested revisions of Recommended Daily Intakes .................................... S112 1.6.1 Dietary sources of zinc and factors affecting the proportion of zinc available for absorption ........ S112 1.6.2 Revised estimates of dietary requirements and recommended intakes for zinc ............................... S114 1.7 Zinc toxicity.................................................................................................................................................... S118 1.8 Causes of zinc deficiency and groups at high risk ....................................................................................... S121 1.9 Summary ........................................................................................................................................................ S123

International Zinc Nutrition Consultative Group (IZiNCG) technical document #1. Assessment of the risk of zinc deficiency in populations and options for its control.

Marginal zinc deficiency and suboptimal zinc status have been recognized in many groups of the population in both less developed and industrialized countries. Although the cause in some cases may be inadequate dietary intake of zinc, inhibitors of zinc absorption are most likely the most common causative factor. Phytate, which is present in staple foods like cereals, corn and rice, has a strong negative effect on zinc absorption from composite meals. Inositol hexaphosphates and pentaphosphates are the phytate forms that exert these negative effects, whereas the lower phosphates have no or little effect on zinc absorption. The removal or reduction of phytate by enzyme (phytase) treatment, precipitation methods, germination, fermentation or plant breeding/genetic engineering markedly improves zinc absorption. Iron can have a negative effect on zinc absorption, if given together in a supplement, whereas no effect is observed when the same amounts are present in a meal as fortificants. Cadmium, which is increasing in the environment, also inhibits zinc absorption. The amount of protein in a meal has a positive effect on zinc absorption, but individual proteins may act differently; e.g., casein has a modest inhibitory effect of zinc absorption compared with other protein sources. Amino acids, such as histidine and methionine, and other low-molecular-weight ions, such as EDTA and organic acids (e.g., citrate), are known to have a positive effect on zinc absorption and have been used for zinc supplements. Knowledge about dietary factors that inhibit zinc absorption and about ways to overcome or remove these factors is essential when designing strategies to improve the zinc nutrition of vulnerable groups.

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Dietary Factors Influencing Zinc Absorption

Zinc is required for multiple cellular tasks, and especially the immune system depends on a sufficient availability of this essential trace element. During the last decades, many studies attempted to affect the outcome of various diseases by zinc supplementation. These efforts either aimed at supporting immunity by zinc administration or at correcting a loss of zinc secondary to the disease to restore the zinc-dependent functions of the immune system. This review aims to summarize the respective findings and to discuss possible molecular mechanisms by which zinc could influence viral, bacterial, and parasitic infections, autoimmune diseases, and the response to vaccination. Zinc supplementation in diseases such as diarrhea, chronic hepatitis C, shigellosis, leprosy, tuberculosis, pneumonia, acute lower respiratory infection, and leishmaniasis seems beneficial. In contrast, the results for the common cold and malaria are still not conclusive, and zinc was ineffective in most vaccination and rheumatoid arthritis studies. For AIDS and type 1 diabetes, zinc supplementation may even be a risk factor for increased mortality or deterioration of the glucose metabolism, respectively. In these cases, zinc supplementation should be used with care and limited to clearly zinc-deficient individuals.

https://josorge.com/publications/Citations/IJL/008.pdf

Modulating the immune response by oral zinc supplementation: a single approach for multiple diseases.

Introduction. Scope of the Work. Guidelines for Research with Animals. Moral and Ethical Considerations. Principles and Training Programs. Design of Candidate Radiopharmaceuticals. Identification of Clinical Need. Choice of Radionuclide. Screening Studies. Drug Development. Concept of Biological Models. In vitro Models. Choice of Biological Models. Species Variations. Transgenic Mice. Dogs and Kangaroos. Poison Arrow Frog. Giraffe. Tomographic Physiological Chemistry. ARG. SPET. PET. SIMS. Keyword Guide to Selection of Biological Models. References. Glossary of Abbreviations.

Biological Models in Radiopharmaceutical Development

Zinc absorption in the small intestine is one of the main mechanisms regulating the systemic homeostasis of this essential trace element. This review summarizes the key aspects of human zinc homeostasis and distribution. In particular, current knowledge on human intestinal zinc absorption and the influence of diet-derived factors on bioaccessibility and bioavailability as well as intrinsic luminal and basolateral factors with an impact on zinc uptake are discussed. Their investigation is increasingly performed using in vitro cellular intestinal models, which are continually being refined and keep gaining importance for studying zinc uptake and transport via the human intestinal epithelium. The vast majority of these models is based on the human intestinal cell line Caco-2 in combination with other relevant components of the intestinal epithelium, such as mucin-secreting goblet cells and in vitro digestion models, and applying improved compositions of apical and basolateral media to mimic the in vivo situation as closely as possible. Particular emphasis is placed on summarizing previous applications as well as key results of these models, comparing their results to data obtained in humans, and discussing their advantages and limitations.

/pdf/a-guide-to-human-zinc-absorption-general-overview-and-recent-1e89ylf8gd.pdf

A Guide to Human Zinc Absorption: General Overview and Recent Advances of In Vitro Intestinal Models.

Bioavailability of zinc from zinc-histidine complexes. I. Comparison with zinc sulfate in healthy men

Bioavailability of zinc from zinc-histidine complexes. II. Studies on patients with liver cirrhosis and the influence of the time of application.

https://www.gastrojournal.org/article/0016-5085(91)90792-J/pdf

Portacaval Shunt As an Experimental Model of Impaired Hepatic Release of Vitamin A in Liver Disease

It has been established rather surely that patients with chronic liver disease, Crohn's disease, chronic pancreatis and celiac disease are deficient in zinc and vitamin A. A large number of clinical symptoms can be caused by these deficiencies, due to the fact that these compounds have numerous functions. Zinc deficiency in liver cirrhosis is probably caused by portosystemic shunting, whereas in Crohn's disease abnormalities of protein metabolism are suggested as etiologic factor. Vitamin A deficiency can be considered as a consequence of disturbed zinc metabolism. Some studies in appropriate patients receiving substitution therapy with zinc and/or vitamin A had positive results. However, the necessity of substitution in the diseases mentioned has not yet been conclusively demonstrated.

Zinc and vitamin A deficiency in gastrointestinal diseases

59 patients with chronic alcoholic liver disease and with negative history of ear infection, noise exposure, head injury, use of streptomycin and without hereditary deafness underwent a basic audiologic examination. In all age groups we found a depression of the pure tone threshold on from 2,000 Hz and compared to a control group and to the norm curves (Spoor 1966). Following the Carhart-test and the acoustic facial reflex there were always signs of cochlear lesions. Fifty per cent of the alcoholics in the Carhart tone decay test showed a depression of the threshold between 10 and 30 dB. The concentration of vitamin A, RBP, beta-Carotin and zinc in the blood measured at the same time were diminished. Considering recent electron microscopic findings on the pattern of the inner ear of young rats following vitamin A deficit we suppose that the vitamin A deficit in the alcoholics leads to poor hearing.

J Schölmerich

Papers

Bioavailability of zinc from zinc-histidine complexes. I. Comparison with zinc sulfate in healthy men

Bioavailability of zinc from zinc-histidine complexes. II. Studies on patients with liver cirrhosis and the influence of the time of application.

Portacaval Shunt As an Experimental Model of Impaired Hepatic Release of Vitamin A in Liver Disease

Zinc and vitamin A deficiency in gastrointestinal diseases

Vitamin A concentration in plasma and ability to hear in patients with chronic alcoholic liver diseases