Marginal Zinc Status Does Not Exacerbate Pancreatic Carcinogenesis Associated with Dietary Soybean Trypsin Inhibitor Concentrate in Rats

Purpose: Zinc status during gestation affects both maternal and fetal health. The study was designed to investigate maternal zinc status and relate it with dietary zinc and socioeconomic levels in first, second and third trimester pregnant women.
 Methods/Patients: Forty-five [15 for each trimester] pregnant women and thirty non-pregnant women that served as control were recruited for the study. Serum zinc concentrations were determined using atomic absorption spectrometry. From structured questionnaire, information was obtained on age, dietary zinc content, and socioeconomic status [education, occupation]. Zinc status was summarized as mean ± standard deviation. Data were analyzed using Student t- test, analysis of variance (ANOVA), and Chi-square test. P < 0.05 was considered significant.
 Results: Only first but not second and third trimester pregnant women featured significantly lower zinc levels compared with control. Non-significant difference in zinc levels were observed when the three trimesters were compared. Of the women in first trimester which featured significantly lower serum zinc level compared with control, all were of high educational status although only < 50% were of high occupational status yet over 70% belong to high dietary zinc sub-group.
 Conclusion: Data obtained from the study revealed that depleted serum zinc level was observed in the first trimester and educational status rather than socioeconomic status played a role in choice of zinc- rich containing food.

Assessing the prevalence and severity of zinc deficiency in populations is critical to determine the need for and appropriate targeting of zinc intervention programs and to assess their effectiveness for improving the health and well-being of high-risk populations. However, there is very little information on the zinc status of populations worldwide due to the lack of consensus on appropriate biochemical indicators of zinc status. The objective of this review was to evaluate the use of serum zinc concentration as an indicator of population zinc status. We have reviewed the response of serum zinc concentration to dietary zinc restriction and zinc supplementation. In addition, we completed pooled analyses of nine zinc intervention trials in young children to assess the relations between serum zinc concentration of individuals before treatment and their responses to zinc supplementation. Also, in updated combined analyses of previously published data, we investigated the relation between the mean initial serum zinc concentration of a study population and their mean growth responses to zinc supplementation in randomized intervention trials among children. The results from depletion/repletion studies indicate that serum zinc concentrations respond appreciably to severe dietary zinc restriction, although there is considerable interindividual variation in these responses. There is also clear evidence that both individual and population mean serum zinc concentrations increase consistently during zinc supplementation, regardless of the initial level of serum zinc concentration. By contrast, an individual's serum zinc concentration does not reliably predict that person's response to zinc supplementation. Serum zinc concentration can be considered a useful biomarker of a population's risk of zinc deficiency and response to zinc interventions, although it may not be a reliable indicator of individual zinc status.

The effect of varying dietary levels of zinc was evaluated in mice fed T-2 toxin. A semipurified diet was used to produce a low zinc (less than 2 parts per million (ppm], a zinc replete (100 ppm), and a high zinc (2500 ppm) diet. T-2 toxin was added to the three zinc diets at a concentration of 10 ppm. The mice were fed one of the six diets ad libitum for up to 28 days. Mice from each diet were submitted for necropsy after 14 and 28 days and after 14 days zinc absorption and retention was measured in mice from each of the low and replete zinc diets, with and without T-2 toxin. Animals receiving a low zinc diet with T-2 toxin had reduced weight gains. The high zinc diet did not depress growth and did not influence T-2 depression of growth. The diets produced significant hematological changes without evidence of a T-2 toxin - zinc interaction. While zinc absorption was greater in mice fed the low zinc diet than those fed the replete zinc diet, T-2 toxin decreased absorption of zinc in the low zinc group and increased absorption in the replete zinc group. T-2 toxin did not influence the biological half-life of retained zinc in either the low or replete zinc groups. The biological half-life of zinc was significantly increased in the mice fed the low zinc diet relative to the replete zinc diet.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

There is need for a reliable index of zinc status in humans. Considering the importance of zinc in membrane function, activities of erythrocyte membrane enzymes have been measured in animals of low and normal zinc status as possible indices. Immature rats and neonatal pigs were fed low and adequate zinc diets; the latter was fed both ad libitum and restricted so as to control for food intake effects. Low rates of gain and plasma zinc concentrations demonstrated that animals fed the low zinc diets were of low zinc status. Erythrocyte membranes were prepared and assayed for Na,K-ATPase, 5'-nucleotidase, and calcium-ATPase activities. Na,K-ATPase activity was not affected by zinc status, but 5'-nucleotidase was significantly lower in deficient animals of both species than in controls, whose food intake was restricted to maintain comparable weight (2.76 vs 3.94 nmol/hr/mg of protein in rats and 60.5 vs 119 in pigs). The basal calcium-ATPase activities were also decreased by low zinc status in both species. Addition of calmodulin in vitro stimulated activity two-fold to four-fold and resulted in the same maximal activities for all treatments. The results show that erythrocyte membrane 5'-nucleotidase activity is an index of zinc status in these species. It is suggested that the decreased membrane calcium-ATPase activity in zinc deficiency is caused by a defect in calmodulin metabolism.

Iron and zinc are found in similar foods and absorption of both may be affected by food compounds, thus biochemical iron and zinc status may be related. This cross-sectional study aimed to: (1) describe dietary intakes and biochemical status of iron and zinc; (2) investigate associations between dietary iron and zinc intakes; and (3) investigate associations between biochemical iron and zinc status in a sample of premenopausal women aged 18–50 years who were recruited in Melbourne and Sydney, Australia. Usual dietary intakes were assessed using a 154-item food frequency questionnaire (n = 379). Iron status was assessed using serum ferritin and hemoglobin, zinc status using serum zinc (standardized to 08:00 collection), and presence of infection/inflammation using C-reactive protein (n = 326). Associations were explored using multiple regression and logistic regression. Mean (SD) iron and zinc intakes were 10.5 (3.5) mg/day and 9.3 (3.8) mg/day, respectively. Median (interquartile range) serum ferritin was 22 (12–38) μg/L and mean serum zinc concentrations (SD) were 12.6 (1.7) μmol/L in fasting samples and 11.8 (2.0) μmol/L in nonfasting samples. For each 1 mg/day increase in dietary iron intake, zinc intake increased by 0.4 mg/day. Each 1 μmol/L increase in serum zinc corresponded to a 6% increase in serum ferritin, however women with low serum zinc concentration (AM fasting < 10.7 μmol/L; AM nonfasting < 10.1 μmol/L) were not at increased risk of depleted iron stores (serum ferritin <15 μg/L; p = 0.340). Positive associations were observed between dietary iron and zinc intakes, and between iron and zinc status, however interpreting serum ferritin concentrations was not a useful proxy for estimating the likelihood of low serum zinc concentrations and women with depleted iron stores were not at increased risk of impaired zinc status in this cohort.

Vegetarian diets across the lifecycle: impact on zinc intake and status.

We have previously reported a trapping of zinc in the placenta directly related to circulating cadmium that comes from cigarette smoke. The purpose of this study was to examine in detail the effect of smoking on (a) the relationship between maternal and fetal zinc status and (b) the relationship between zinc status and birth weight. One hundred and eighteen smokers and 172 nonsmokers without any medical complications during pregnancy were studied. Atomic absorption spectroscopy was used to assess zinc status in maternal and cord vein plasma and red blood cells. Plasma alkaline phosphatase was also determined as an index of zinc status. Thiocyanate was used as an index of smoking status. The data were analyzed using univariate correlations and repeated measures analysis of variance. Infants of smokers had a statistically significant decrease in plasma zinc (5%), alkaline phosphatase (13%), and in cord vein RBC zinc (12%). Furthermore, the results showed an altered relationship between maternal and fetal indices of zinc status and zinc status and birth weight due to maternal smoking. The infant of the nonsmoking mother appears to be able to maintain adequate zinc status due to depletion of maternal zinc. However, it appears that the infant of the smoking mother may be marginally zinc deficient. These findings support studies of zinc supplementation in the pregnancy complicated by smoking.

Low dietary zinc decreases erythrocyte carbonic anhydrase activities and impairs cardiorespiratory function in men during exercise2–3

Plasma zinc in adults with cystic fibrosis: Correlations with clinical outcomes

Introduction: Zinc is an essential nutrient that is related to many health issues, including cutaneous and hair health Aims: To study the prevalence of low and high zinc concentrations among university students and to evaluate the association between zinc status and various health issues including hair loss, skin health, immunity, diarrhea and weight status. Methods: Study outcomes which included age, BMI, gender, health variables such as diarrhea, hair loss, weight loss and others were collected using a structured questionnaire, whereas serum zinc concentration was measured using spectrophotometry. Results: 33% of the study participants had low zinc level, whereas 34.7% had zinc levels higher than normal. Both high and low zinc status were associated with significant hair loss (p&lt;0.0001). High and low zinc status were not significantly related to other study outcomes such as diarrhea, acne and weight loss. Healthy diet score was not significantly different between zinc status categories and was not significantly related to other study outcomes. Conclusion: Appropriate intake of zinc and zinc concentration may protect from hair loss and should be promoted.

Red Meat and a Fortified Manufactured Toddler Milk Drink Increase Dietary Zinc Intakes without Affecting Zinc Status of New Zealand Toddlers1–4

The present study focused on whether serum extracellular superoxide dimutase (EC-SOD) activity can be used as a functional indicator of marginal zinc deficiency in humans. Subjects in this study were 444 healthy adults over 30 yr of age living a normal rural life in Kyunggi province, Korea. The mean dietary zinc intake of subjects obtained from one 24-h recall was 6.41 +/- 4.35 mg and the average serum zinc concentration of the subjects was 11.06 +/- 2.44 micromol/L. Subjects were divided into three groups by serum zinc concentrations: adequate (serum zinc >10.7 micromol/L), low (serum zinc 9.0-10.7 micromol/L), and very low (serum zinc <9.0 micromol/L) groups. A total of 50 subjects were selected from the three groups for analysis of EC-SOD activities. The EC-SOD activity of subjects increased with increasing serum zinc concentrations, and the activities of the three groups were significantly different as indicated by the Kruskal-Wallis test (p = 0.0239). Also, serum EC-SOD activities were significantly correlated with serum zinc concentrations (r = 0.289, p = 0.04). Serum EC-SOD activities, however, were not significantly correlated to the dietary zinc intakes. In conclusion, these results show that EC-SOD activities are decreased in subjects with low serum zinc concentrations and suggest that EC-SOD activity may be a functional indicator of zinc nutritional status in humans.

Rainbow trout (Salmo gairdneri) were fed one of three different diets, based either on fish meal, soybean meal, or egg white, containing varying levels of zinc. Several fish tissues were analyzed for zinc content after 202 d to determine if any tissue was a sensitive indicator of zinc status. Caudal fin and whole-body zinc levels of the fish were found to reflect the dietary levels of zinc. We observed a strong statistical correlation between whole-body zinc levels and the zinc concentration of the caudal fin (r = 0.89; P < 0.01). At the same time, we observed a negative correlation between whole-body iron concentration and whole-body zinc levels (r = 0.87; P < 0.01). A strong negative correlation also was observed between dietary zinc and whole-body iron (r = 0.95; P < 0.001). Our data indicate that caudal fin zinc concentrations are a good indicator of zinc status.

The aim of the study was to determine the effect of weaning and the effect of increasing dietary zinc concentrations on the zinc and copper status of weaned piglets (study 1) and to study the effect of high concentrations of dietary zinc and/or copper on zinc and copper status of weaned piglets (study 2). Study 1 included 54 piglets (six litters of nine piglets). One piglet from every litter was killed 1 day before weaning. The remaining 48 piglets were allocated at weaning (28 days) to four dietary zinc treatments (100, 250, 1000 or 2500 ppm) and subsequently killed 1-2, 5-6 or 14-15 days after weaning. Study 2 included 48 piglets (six litters of eight piglets) allocated to four dietary treatments, consisting of low or high dietary zinc (100 or 2500 ppm) in combination with low or high dietary copper (20 or 175 ppm). All piglets in study 2 were killed 5-7 days after weaning. In both studies, the trace mineral status was assessed by zinc and copper concentrations and alkaline phosphatase (AP) activity in plasma and mucosal tissue. In study 2, lymphocyte metallothionein (MT) mRNA and intestinal mucosa MT mRNA concentrations were included as zinc status markers. The results showed that the zinc status, measured as zinc in plasma and mucosa, was not affected by weaning of the piglets. Plasma copper concentrations decreased during the first 2 weeks after weaning. High dietary copper concentrations did not affect the concentration of copper in plasma, but increased the concentration of copper in mucosa and the concentration of zinc in plasma. The dietary zinc treatments increased the zinc concentration in plasma as well as the zinc and MT mRNA concentration in mucosa. Lymphocyte MT mRNA concentrations did not reflect the differences in dietary zinc supplementation.