Determination of Zinc Status in Humans: Which Indicator Should We Use?

Prevalence of iron and zinc deficiencies among preschool children ages 3 to 5 y in Vhembe district, Limpopo province, South Africa

Development of a Plasma Zinc Concentration Cutoff to Identify Individuals with Severe Zinc Deficiency Based on Results from Adults Undergoing Experimental Severe Dietary Zinc Restriction and Individuals with Acrodermatitis Enteropathica

ABSTRACTBackgroundZinc biofortification of rice could sustainably improve zinc status in countries where zinc deficiency is common and rice is a staple, but its efficacy has not been tested. Fatty acid desaturases (FADS) are putative new zinc status biomarkers.ObjectivesOur objective was to test the efficacy of zinc-biofortified rice (BFR) in preschool-aged children with zinc deficiency. Our hypothesis was that consumption of BFR would increase plasma zinc concentration (PZC).MethodsWe conducted a 9-mo, double-masked intervention trial in 12–36-mo-old rural Bangladeshi children, most of whom were zinc-deficient (PZC <70 µg/dL) and stunted (n = 520). The children were randomly assigned to receive either control rice (CR) or BFR provided in cooked portions to their households daily, with compliance monitoring. The primary outcome was PZC. Secondary outcomes were zinc deficiency, linear growth, infection-related morbidity, FADS activity indices, intestinal fatty acid binding protein (I-FABP) and fecal calprotectin. We applied sparse serial sampling for midpoint measures and analyzed data by intention-to-treat using mixed-effects models.ResultsAt baseline, median (IQR) PZC was 60.4 (56.3–64.3) µg/dL, 78.1% of children were zinc deficient, and 59.7% were stunted. Mean ± SD daily zinc intakes from the CR and BFR during the trial were 1.20 ± 0.34 and 2.22 ± 0.47 mg/d, respectively (P < 0.001). There were no significant time-by-treatment effects on PZC, zinc deficiency prevalence, FADS activity, I-FABP, or fecal calprotectin (all P > 0.05). There was a time–treatment interaction for height-for-age z-scores (P < 0.001) favoring the BFR group. The morbidity longitudinal prevalence ratio was 1.08 (95% CI: 1.05, 1.12) comparing the BFR and CR groups, due to more upper respiratory tract illness in the BFR group.ConclusionsConsumption of BFR for 9 mo providing ∼1 mg of additional zinc daily to Bangladeshi children did not significantly affect PZC, prevalence of zinc deficiency, or FADS activity.The trial was registered at clinicaltrials.gov as NCT03079583.

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.

Breast milk provides adequate nutrients during the first 6 months of life. However, there are some reports of zinc deficiency in breastfed infants. This study was conducted to determine the prevalence of zinc deficiency in infants aged 4-6 months and the associated factors. Healthy infants aged 4-6 months and their mothers were enrolled. They were classified by feeding types as breastfed (BF), formula-fed (FF), and mixed groups (MF). Data collection included demographic data, perinatal data, given diets, and anthropometric measurement. Blood from infants and lactating mothers, and breast milk samples were collected to assess plasma and breast milk zinc concentrations. From 158 infants, the prevalence of zinc deficiency (plasma level below 10.7 mol/L) was 7.6%, and according to feeding groups 14.9%, 5.3%, and 2.9% in the BF, the FF, and the MF groups, respectively. Breastfed infants with zinc deficiency had significantly lower maternal zinc concentrations compared with those without zinc deficiency. There was a higher proportion of maternal zinc deficiency in zinc-deficient infants than those without zinc deficiency (66.7% vs 16.2%, p=0.02). There was a positive correlation between zinc concentrations in breast milk and plasma zinc concentrations of infants (r=0.62, p=0.01) and plasma zinc concentrations of lactating mothers (r=0.56, p=0.016). Using the regression analysis, infant zinc status was associated with maternal plasma zinc concentrations among breastfed infants. The results of this study suggest that breastfed infants aged 4-6 months may have a risk of zinc deficiency and that risk is associated with maternal zinc status and breast milk zinc concentrations.

The role of zinc and vitamin A in persistent diarrhea among infants and young children.

To describe the prevalence of serum iron and zinc deficiencies and low serum concentrations (LSC) of copper and magnesium in Mexican adults. Blood samples from subjects (≥20 years, both genders) participating in the 2006 National Health and Nutrition Survey were used to measure the serum concentrations of s-ferritin, soluble- transferrin-receptor (s-TfR), zinc, copper, and magnesium. The prevalence of s-ferritin≤12 ug/L was 18.1 and 3.6% while s-TfR>6 mg/L was 9.5 and 4.4%, for females and males, respectively. The prevalence of zinc deficiency was 33.8% females and 42.6% males; LSC of copper were 16.8 and 18.2%, and 36.3 and 31.0% for magnesium, for females and males, respectively. The prevalence of deficiencies in iron (in females), and zinc are still high in the adult population. LSC of copper and magnesium are published for the first time and show significant prevalence of deficiencies. Corrective actions are necessary in order to diminish these nutritional deficits in the Mexican population.

Duration of Exclusive Breast-Feeding and Infant Iron and Zinc Status in Rural Bangladesh ,

Efficacy of highly bioavailable zinc from fortified water: a randomized controlled trial in rural Beninese children

To describe the epidemiology of iron, zinc and iodide deficiencies in a probabilistic sample of Mexican women and children and explore its association with some dietary and socio-demographic variables. We carried out in 1999 an epidemiological description of iron (percent transferrin saturation, PTS, < 16%), serum zinc (< 65 ug/dl) and iodide (< 50 ug/l urine) deficiencies in a probabilistic sample of 1,363 Mexican children under 12 years and of 731 women of child-bearing age. Serum iron, Total Iron Binding Capacity (TIBC) and zinc were measured by atomic absorption spectrometry, and urinary iodide by a colorimetric method. Logistic regression models explored determinants for such micromineral deficiencies. Iron deficiency was higher (67%) in infants < 2 years of age. Prevalence declined (34-39%) at school age. The prevalence for iron deficiency in women was 40%. Zinc deficiency was higher in infants < 2 years of age (34%) than in school-age children (19-24%). Prevalence in women was 30%, with no rural/urban difference. In women the likelihood of iron deficiency decreased as SEL improved (p = 0.04) and increased with the intake of cereals (p = 0.01). The likelihood of low serum zinc levels was greater in women and children of low socioeconomic level (SEL) (p < 0.02 and p = 0.001) iodide deficiency was negligible in both children and women. The data shows high prevalence of iron deficiency-specially in infants 12 to 24 months of age. It is suggested that in older children and women 12 to 49 years of age that iron bioavailability is low. The prevalence of zinc deficiency was also very high. The English version of this paper is available too at: http://www.insp.mx/salud/index.html.

This paper summarizes recent research on the importance of zinc for human health, and reviews available methods of evaluating zinc status in individuals and populations. The lack of generally accepted biomarkers of zinc status has impeded estimation of the global prevalence of zinc deficiency. Although measurement of zinc consumption and/or plasma zinc concentration can be used to assess population zinc status, few countries have collected adequate data to permit estimation of the prevalence of zinc deficiency. An alternative method, described herein, is to estimate the zinc content of national food supplies, using FAO food balance sheets; the assumed bioavailability of that zinc based on phytate:zinc molar ratios; and the relation between absorbable zinc and theoretical requirements according to country-specific demographics. The results of these analyses indicate that nearly half of the world's population is at risk for inadequate zinc intake, suggesting that public health programs are urgently needed to control zinc deficiency.

Zinc

Background: It is known that patients on hemodialysis (HD) are prone to developing zinc deficiency due to removal of zinc by HD, inadequate dietary intake, and reduced gastrointestinal zinc absorption. However, the prevalence of zinc deficiency in patients on peritoneal dialysis (PD) has not been well established. Methods: Serum zinc levels were compared between 47 patients on PD and 47 patients on HD matched for age, sex, and duration of dialysis. A serum zinc level < 60 μg/dL was defined as clinical zinc deficiency and a level of 60–80 μg/dL as subclinical zinc deficiency. The prevalence of zinc deficiency and associated clinical factors were determined in both groups. Results: Clinical zinc deficiency was found in 59.6% of the PD group and 70.2% of the HD group (p = 0.391). Subclinical zinc deficiency was found in 40.4% of the PD group and 29.8% of the HD group. Age, body mass index, and serum albumin level were identified as independent predictors of zinc deficiency in the PD group by multivariate analysis. Conclusions: A higher prevalence of clinical and subclinical zinc deficiency was found in patients on PD. The rates were comparable between patients on PD and those on HD after adjustment for confounding factors.

Background: Iron Deficiency Anemia (IDA) is the most common anemia in all age groups. The coexistence of iron deficiency anemia and zinc (Zn) deficiency is quite common, for most of the etiologic factors are common. The purpose of this study is to determine the prevalence of zinc deficiency in children with iron deficiency and/or iron deficiency anemia. Method: One hundred and sixty child patients within 6month-5 year age range diagnosed with iron deficiency and/or iron deficiency anemia and 91 children with no iron deficiency and/or iron deficiency anemia diagnosis were included in the study. The relationships between serum zinc levels and other biochemical and hematological parameters were examined. Results: It was observed that the study and control groups had similar demographic characteristics, and there was no statistically significant difference between two groups in terms of average age (months), distribution of age groups, and gender groups. Statistically significant differences were observed between hemoglobin (Hb), haematocrit (Hct), mean corpuscular volume (MCV), red cell distributionwidth (RDW), iron (Fe), total iron binding capacity (TIBC), transferrin saturation (TS) and Ferritin values of the study group and control group, and the cases in the study group were determined to be highly anemic. Statistically significant difference was determined between groups in terms of zinc levels, and zinc levels in the study group were determined to be lower than those in the control group. Zinc deficiency (10%) in children diagnosed with iron deficiency and/or iron deficiency anemia was found more common compared to the control group (2.2%). A positive correlation between serum zinc levels and Hb, Hct, MCV, Fe, TS and Ferritin, and a negative correlation between serum zinc levels and RDW and total TIBC were detected in the study group. Conclusion: According to these results, it was concluded that children with iron deficiency could simultaneously have zinc deficiency, the iron-zinc combination might be more effective for the treatment of iron deficiency than treatment with only iron, and early age supplementation programs might be useful for the highrisk groups such as childhood until zinc deficiency tests gave routine results.

Zinc, as an essential trace element for health, plays various biological roles in human body functions. Serum zinc reference values are essential for assessing zinc-associated abnormalities and the prevalence of zinc deficiency. This study aims at determining age- and sex-specific reference values for serum zinc concentrations in adult Iranian subjects. Serum zinc concentration was measured by flame atomic absorption spectrometry in 4,698 adult subjects, aged 20-94 years, randomly selected from the population of the Tehran, Lipid, and Glucose Study. After application of exclusion criteria, reference values for serum zinc were determined in 2,632 apparently healthy subjects according to guidelines of the International Federation of Clinical Chemistry (nonparametric method). Dietary zinc was assessed in 2,906 individuals, of which 1,685 were healthy subjects, using a validated semiquantitative food frequency questionnaire. Reference values for serum zinc concentrations ranged between 9.6 and 31.6, 8.9 and 29.9, and 9.3 and 30.8 μmol/L in men, women, and the total population, respectively. Prevalence of serum zinc deficiency was 3.0 and 2.4 % in men and women, respectively (p = 0.267); in men, but not in women, the prevalence increased significantly with age (p for trend <0.001). Of the total participants, 10.3 % (6.5 men and 3.8 % women, p < 0.01) had lower zinc intake compared to dietary reference intakes. The zinc density of the population was 6.3 mg/1,000 kcal. In conclusion, this study presents reference values for serum zinc concentration in adult Iranian subjects for both sexes and different age groups. Prevalence of serum zinc deficiency and dietary zinc inadequacy seems to be lower in Iranians, compared to some other populations.