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Background: Low zinc intakes and reduced blood zinc concentrations have been reported to be associated with osteoporosis in women. Objective: The objective was to examine the independent association between dietary zinc and plasma zinc and the association of each with bone mineral density (BMD) and 4-y bone loss in community-dwelling older men. Design: Of the original Rancho Bernardo Study subjects, 396 men (age: 45-92 y) completed BMD measurements at baseline in 1988-1992 and 4 y later. Osteoporosis was defined as a BMD ⩾ 2.5 SDs below the mean for young women (a T-score⩽-2.5). At baseline, dietary intake data were collected by using a standard food-frequency questionnaire, and plasma zinc concentrations were measured by using inductively coupled plasma spectroscopy. Results: The mean dietary zinc intake was 11.2 mg, and the mean plasma zinc concentration was 12.7 ⩾mol/L. Plasma zinc was correlated with total zinc intake (diet plus supplements). Dietary zinc intake and plasma zinc concentrations were lower in men with osteoporosis at the hip and spine than in men without osteoporosis at those locations. BMDs for the hip, spine, and distal wrist were significantly lower in men in the lowest plasma zinc quartile (<11.3 ⩾mol/L) than in men with higher plasma zinc concentrations. The association between plasma zinc and BMD was cross-sectional, longitudinal, and independent of age or body mass index. However, plasma zinc did not predict bone loss during the 4-y interval. Conclusion: Dietary zinc intake and plasma zinc each have a positive association with BMD in men. [ABSTRACT FROM AUTHOR]

Background: Plasma and serum zinc concentrations are the most widely used markers of zinc status in individual persons and populations. Objective: The objective was to identify factors that influence plasma zinc concentrations during acute childhood diarrhea. Design: This was a cross-sectional study of 1757 cases of acute diarrhea in 6-35-mo-old Nepalese children. The association between plasma zinc concentration and several clinical, anthropometric, socioeconomic, and biochemical variables was estimated in simple and multiple linear regression analyses. Results: We observed a reduction in the mean plasma zinc concentration of 0.59 (95% CI: 0.44, 0.74)μmol/L per degree (°C) increase in axillary temperature. Having dysentery and an elevated plasma C-reactive protein concentration was also independently associated with lower plasma zinc. Children with clinical features of dehydration had higher plasma zinc concentrations than did those who were not dehydrated. Furthermore, a decrease in plasma albumin of 1 g/L was associated with a decrease in plasma zinc of 0.25 (95% CI: 0.21, 0.29) μmol/L. The plasma albumin concentration confounded the associations between some clinical variables and plasma zinc, but the association between axillary temperature and dehydration on one hand and plasma zinc on the other was not substantially influenced by the albumin concentration. Moreover, the plasma zinc concentration increased with an increase in observed hemolysis. Conclusions: Dehydration, clinical and biochemical indicators of inflammation and hemolysis, and, when possible, plasma albumin concentrations should be taken into account when the plasma zinc concentration is used to estimate zinc status during episodes of diarrhea in childhood [ABSTRACT FROM AUTHOR]

Background: Zinc homeostasis and normal plasma zinc concentrations are maintained over a wide range of intakes. Objective: The objective was to identify the homeostatic response to severe zinc depletion by using compartmental analysis. Design: Stable zinc isotope tracers were administered intravenously to 5 men at baseline (12.2 mg dietary Zn/d) and after 5 wk of acute zinc depletion (0.23 mg/d). Compartmental modeling of zinc metabolism was performed by using tracer and mass data in plasma, urine, and feces collected over 6-14 d. Results: The plasma zinc concentration fell 65% on average after 5 wk of zinc depletion. The model predicted that fractional zinc absorption increased from 26% to essentially 100%. The rate constants for zinc excretion in the urine and gastrointestinal tract decreased 96% and 74%, respectively. The rate constants describing the distribution kinetics of plasma zinc did not change significantly. When zinc depletion was simulated by using an average mass model of zinc metabolism at baseline, the only change that accounted for the observed fall in plasma zinc concentration was a 60% reduction in the rate constant for zinc release from the most slowly turning over zinc pool. The large changes in zinc intake, excretion, and absorption--even when considered together--only explained modest reductions in plasma zinc mass. Conclusion: The kinetic analysis with a compartmental model suggests that the profound decrease in plasma zinc concentrations after 5 wk of severe zinc depletion was mainly due to a decrease in the rate of zinc release from the most slowly turning over body zinc pool. [ABSTRACT FROM AUTHOR]

Zinc nutriture and immune function were studied in 100 subjects, age 60-89 yr. Mean (±SD) zinc concentrations found were 84.8 ± 15.5 µ1 .04 ± 0.24 ; µg (0.016 ± 0.004 µmol)/109 cells for mononuclear cells, 3.9 1 ± 1 .77 µg (0.060 ± 0.027 µmol)/109 cells for platelets, and 222 ± 101 µg (3.39 ± 1.54 µmol)/g for hair. Zinc ingestion was below the RDA in more than 90% of study subjects. The incidence of anergy to a panel of seven skin test antigens was 41%; responses to these antigens were significantly associated with the plasma zinc concentration. Subjects with depressed lymphocyte responses to mitogens had significantly lower platelet and significantly higher mononuclear cell zinc concentrations than those with normal responses. [ABSTRACT FROM AUTHOR]

Seven men consumed a low-zinc (3.3 mg/day) diet for 8 wk, followed by zinc-repletion (+15 mg/day) for 12 days. Zinc tolerance tests (50 mg) were administered initially and following depletion and repletion periods. Plasma zinc after 2 h in the zinc tolerance test was marginally higher after both the depletion (p < 0.06) and repletion (p < 0.001) periods as compared to the initial test. No changes were seen in parotid zinc tolerance tests or fasting levels of zinc in plasma or parotid saliva. In a subsequent study, zinc tolerance tests were given to normal subjects before and after 12 days of zinc supplementation (15 mg/day). Again, zinc levels in plasma were increased following zinc supplementation at the 2nd h post-zinc dose, but levels in saliva did not change. The elevation of plasma zinc curves with both zinc deficiency and supplementation suggests that this test is not a reliable indicator of zinc status. [ABSTRACT FROM AUTHOR]

The association between low initial plasma zinc concentration and risk of morbidity over the subsequent 3 mo was examined in a cohort of 116 children aged 12–59 mo recovering from acute diarrhea. Children with low initial plasma zinc (≤ 8.4 μmol/L) had more episodes of diarrhea [risk ratio (RR): 1.47; 95% CI: 1.03, 2.49) and severe diarrhea, defined as passage of ≥5 liquid stools in a 24-h period, (RR: 1.70; 95% CI: 1.06, 2.72) than did children with normal plasma zinc (> 8.4 μmol/L). The mean prevalence rate of diarrhea associated with fever was 4 times higher in the zinc-deficient group (P = 0.01). Overall, the difference in the number of episodes of acute lower respiratory tract infections (ALRIs) between the two groups was not statistically significant (RR: 1.76; 95% CI: 0.88–3.53) but the mean prevalence rate of ALRIs was 3.5 times higher in children with low plasma zinc (P = 0.05). The increased risk of diarrhea and ALRIs episodes in zinc-deficient children was larger in boys than in girls. These results show that children with low plasma zinc concentrations are at risk for increased diarrheal and respiratory morbidity. [ABSTRACT FROM AUTHOR]

The development of intervention programs to control zinc deficiency is hampered by the lack of sensitive, specific, low-cost indicators of zinc status. The mean plasma zinc concentration of groups of individuals has been suggested as a possible indicator of a population’s zinc status because the plasma zinc concentration seems to predict whether growth will increase in response to zinc supplementation. However, experimental studies in both animal models and adult human volunteers as well as clinical studies of infected and noninfected adults indicate that systemic infections that produce an acute phase response also cause the plasma zinc concentration to fall. Therefore, concerns have been raised about the usefulness of plasma zinc concentration as an indicator of zinc status in populations with high prevalences of infections. By contrast with the aforementioned studies in adults, cross-sectional, community-based surveys of children with and without common infections have not found any association between the presence of infection and plasma zinc concentration, possibly because the severity of those infections observed in children in field settings was less than that of the infections studied in adults. Thus, it appears that the mean plasma zinc concentration may be a useful indicator of population zinc status for children in low-income countries despite the high prevalence of common childhood infections encountered in these settings. [ABSTRACT FROM AUTHOR]

One hundred thirty children (65-95 mo old) from a low-socioeconomic neighborhood of Guatemala City participated in a randomized, double-blind, controlled trial of zinc supplementation. One group received 10 mg Zn/d (n = 65) and the other group received a placebo (n = 65); 90 ± 9.2 doses were given over 120-150 d. Stools were examined for prevalence and intensity of helminths and prevalence of protozoa at the beginning and end of the study. The initial prevalence was 42% for helminths and 18% for protozoa, with no differences between groups. Mebendazole was administered to all children, and protozoal infections were treated specifically at the beginning of the study. The reinfection rates were 17% (11 of 65) for helminths and 12.3% (8 of65) for protozoa in the zinc group and 15% (10 of 65) and 10.7% (7 of 65), respectively, in the placebo group (P > 0.05). Analysis by specific parasites revealed no treatment effect. We conclude that neither plasma or hair zinc status nor oral zinc supplementation had an effect on parasite status in children. [ABSTRACT FROM AUTHOR]

This study was undertaken to investigate the effect of pregnancy and glucose loading on zinc metabolism. In a completely random design with repeated measures, 18 nonpregnant women, 16 early-pregnant women (13-17 wk), and 16 late-pregnant women (28-34 wk) had blood collected at 0, 30, 60, 120, and 180 mm after ingesting 100 g glucose to evaluate changes in variables of Zn nutriture. Fasting plasma Zn concentrations decreased significantly as pregnancy progressed. Late-pregnant women had significantly higher erythrocyte Zn levels and greater 24-h urinary Zn and glucose excretions. Erythrocyte Zn responses to glucose loading were unaffected by gestational age. Plasma Zn after a glucose load in nonpregnant women exhibited a curvilinear response whereas pregnant women showed no change. This lack of response by pregnant women may be related to their lower plasma Zn concentrations. Plasma Zn in pregnant women may not be as readily available to assist in glucose utilization. [ABSTRACT FROM AUTHOR]