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.

Methods of assessment of iodine status in humans: a systematic review

Worldwide, there are more than 10 million new cancer cases each year, and cancer is the cause of approximately 12% of all deaths. Given this, a large number of epidemiologic studies have been undertaken to identify potential risk factors for cancer, amongst which the association with trace elements has received considerable attention. Trace elements, such as selenium, zinc, arsenic, cadmium, and nickel, are found naturally in the environment, and human exposure derives from a variety of sources, including air, drinking water, and food. Trace elements are of particular interest given that the levels of exposure to them are potentially modifiable. In this review, we focus largely on the association between each of the trace elements noted above and risk of cancers of the lung, breast, colorectum, prostate, urinary bladder, and stomach. Overall, the evidence currently available appears to support an inverse association between selenium exposure and prostate cancer risk, and possibly also a reduction in risk with respect to lung cancer, although additional prospective studies are needed. There is also limited evidence for an inverse association between zinc and breast cancer, and again, prospective studies are needed to confirm this. Most studies have reported no association between selenium and risk of breast, colorectal, and stomach cancer, and between zinc and prostate cancer risk. There is compelling evidence in support of positive associations between arsenic and risk of both lung and bladder cancers, and between cadmium and lung cancer risk.

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Trace elements and cancer risk: a review of the epidemiologic evidence

Recently the United Nations has urged that priority should be given to developing programmless industrialized countries to prevent deficiencies of iodine, vitamin A, and Fe (United Nations, 1991). Nutritional Fe deficiency is associated with plant based diets which contain high levels of dietary fibre and phytate, components known to inhibit nonhaem Fe absorption, and low levels of flesh foods, rich sources of readily available haem iron (Monsen, 1988). Such plant based diets will also induce Zn deficiency. The consequences of Zn deficiency on human health in developing countries, however, have not yet been recognized. This is unfortunate because even mild Zn deficiency may contribute to pregnancy complications, low birth weight, impaired immune competence, maternal and infant mortality and morbidity, and growth failure in infancy and childhood (Swanson & King, 1987; Hambidge, 1989; National Academy of Sciences, 1991 ; United Nations, 1991). Hence Zn deficiency may have far reaching consequences on maternal, infant, and child health in many developing countries.

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Zinc nutrition in developing countries.

The role of zinc deficiency as an important cause of morbidity and impaired linear growth has prompted the need to identify indicators of population zinc status. Three indicators have been recommended - prevalence of zinc intakes below the estimated average requirement (EAR), percentage with low serum zinc concentrations, and percentage of children aged < 5 years who are stunted. This review outlines steps to estimate the prevalence of inadequate intakes, and confirm their validity based on the EARs set by International Zinc Nutrition Collaborative Group. Next, the appropriateness of serum zinc as a biochemical marker for population zinc status is confirmed by a summary of: (a) the response of serum zinc concentrations to zinc intakes; (b) usefulness of serum zinc concentrations to predict functional responses to zinc interventions; (c) relationship between initial serum zinc and change in serum zinc in response to interventions. Height- or length-for-age was chosen as the best functional outcome after considering the responses of growth, infectious diseases (diarrhoea, pneumonia), and developmental outcomes in zinc supplementation trials and correlation studies. The potential of other zinc biomarkers such as zinc concentrations in hair, cells, zinc-metalloenzymes, and zinc-binding proteins, such as metallothionein, is also discussed. Molecular techniques employing reverse transcriptase (RT)-polymerase chain reaction to measure mRNA in metallothionein and ZIP1 transporter hold promise, as do kinetic markers such as exchangeable zinc pools (EZP) and plasma zinc turnover rates. More research is needed to establish the validity, specificity, sensitivity, and feasibility of these new biomarkers, especially in community-settings.

/pdf/indicators-of-zinc-status-at-the-population-level-a-review-12m6unvni9.pdf

Indicators of zinc status at the population level: a review of the evidence.

/pdf/assessment-of-zinc-status-2ljrr88aev.pdf

R. P. H. Thompson

Papers

Assessment of zinc status.