Total Zinc Absorption Research Articles

Modeling Zinc Absorption in the Adult Population of Colombia: Insights for Nutritional Evaluation and Intervention Strategies.

Zinc is a vital trace element, yet its deficiency is common in various populations. This study addresses the gap in understanding zinc intake and its relationship with key nutritional parameters in a Colombian population. We analyzed data from 12,987 individuals, focusing on the daily intake of zinc, phytate, protein, and calcium, and used the phytate/zinc molar ratio as an input parameter in the Miller et al. (2013) model. This model was employed to estimate the total absorbed zinc (TAZ) and the fractional absorption of zinc (FAZ). Our findings highlight a general trend towards insufficient intake compared to the standards of the Institute of Medicine (IOM) and Colombia, with a significant percentage of the population falling below the estimated average requirement (EAR) and recommended daily allowance (RDA) for zinc, underscoring the need for targeted nutritional strategies. Our study contributes to a broader understanding of zinc nutrition and public health implications in Colombia, providing a basis for future dietary guidelines and health interventions.

Biofortified Yellow-Fleshed Potatoes Provide More Absorbable Zinc than a Commonly Consumed Variety: A Randomized Trial Using Stable Isotopes in Women in the Peruvian Highlands

BackgroundZinc-biofortified potatoes have considerable potential to reduce zinc deficiency because of their low levels of phytate, an inhibitor of zinc absorption, and their high consumption, especially in the Andean region of Peru. ObjectivesThe purpose of this study was to measure fractional and total zinc absorption from a test meal of biofortified compared with regular potatoes. MethodsWe undertook a single-blinded randomized crossover study (using 67Zn and 70Zn stable isotopes) in which 37 women consumed 500-g biofortified or regular potatoes twice a day. Urine samples were collected to determine fractional and total zinc absorption. ResultsThe zinc content of the biofortified potato and regular potato was 0.48 (standard deviation [SD]: 0.02) and 0.32 (SD: 0.03) mg/100 g fresh weight, respectively. Mean fractional zinc absorption (FZA) from the biofortified potatoes was lower than from the regular potatoes, 20.8% (SD: 5.4%) and 25.5% (SD: 7.0%), respectively (P < 0.01). However, total zinc absorbed was significantly higher (0.49; SD: 0.13 and 0.40; SD: 0.11 mg/500 g, P < 0.01, respectively). ConclusionsThe results of this study demonstrate that biofortified potatoes provide more absorbable zinc than regular potatoes. Zinc-biofortified potatoes could contribute toward reducing zinc deficiency in populations where potatoes are a staple food.This trial was registered at clinicaltrials.gov as NCT05154500.

The Effect of Zinc Biofortified Wheat Produced via Foliar Application on Zinc Status: A Randomized, Controlled Trial in Indian Children

BackgroundAgronomic zinc biofortification of wheat by foliar application increases wheat zinc content and total zinc absorption in humans. ObjectivesTo assess the effect of agronomically biofortified whole wheat flour (BFW) on plasma zinc (PZC) compared with a postharvest fortified wheat (PHFW) and unfortified control wheat (CW) when integrated in a midday school meal scheme. MethodsWe conducted a 20-wk double-blind intervention trial in children (4–12 y, n = 273) individually randomly assigned to 3 groups to receive a daily school lunch consisting of 3 chapattis prepared with the 3 different wheat flour types. Measurements of anthropometry, blood biochemistry, and leukocyte DNA strand breaks were conducted. We applied sparse serial sampling to monitor PZC over time, and analysis was performed using linear mixed-effects models. ResultsMean zinc content in BFW, PHFW, and CW were 48.0, 45.1, and 21.2 ppm, respectively (P < 0.001). Mean (standard deviation) daily zinc intakes in the study intervention in BFW, PHFW, and CW groups were 4.4 (1.6), 5.9 (1.9) and 2.6 (0.6) mg Zn/d, respectively, with intake in groups PHFW and BFW differing from CW (P < 0.001) but no difference between BFW and PHFW. There were no time effect, group difference, or group × time interaction in PZC. Prevalence of zinc deficiency decreased in the BFW (from 14.1%–11.2%), PHFW (from 8.9%–2.3%), and CW (9.8%–8.8%) groups, but there was no time × treatment interaction in the prevalence of zinc deficiency (P = 0.191). Compliance with consuming the study school meals was associated with PZC (P = 0.006). DNA strand breaks were not significantly associated with PZC (n = 51; r = 0.004, P = 0.945). ConclusionsConsumption of either PHFW or BFW provided an additional ∼1.8 to 3.3 mg Zn/d, but it did not affect PZC or zinc deficiency, growth, or DNA strand breaks.This trial was registered on clinicaltrials.gov as NCT02241330 and ctri.nic.in as CTRI/2015/06/005913.

Zinc Absorption From Agronomically Biofortified Wheat Is Similar to Post-Harvest Fortified Wheat and Is a Substantial Source of Bioavailable Zinc in Humans

Limited data exist on human zinc absorption from wheat biofortified via foliar (FBW) or root (hydroponically fortified wheat, HBW) zinc application. Stable isotope labels added at point of consumption (extrinsic labeling) might not reflect absorption from native zinc obtained by intrinsic labeling. We measured fractional and total zinc absorption (FAZ, TAZ) in FBW and HBW wheat, compared with control wheat (CW) and fortified wheat (FW). The effect of labeling method was assessed in HBW (study 1), and the effect of milling extraction rate (EXR, 80% and 100%) in FBW (studies 2 and 3). Generally healthy adults (n=71, age: 18-45 y, body mass index: 18.5-25 kg/m2) were allocated to 1 of the studies, in which they served as their own controls. In study 1, men and women consumed wheat porridges colabeled intrinsically and extrinsically with 67Zn and 70Zn. In studies 2 and 3, women consumed wheat flatbreads (chapatis) labeled extrinsically. Zinc absorption was measured with the oral to intravenous tracer ratio method with a 4-wk wash-out period between meals. Data were analyzed with linear mixed models. In study 1 there were no differences in zinc absorption from extrinsic versus intrinsic labels in either FW or HBW. Similarly, FAZ and TAZ from FW and HBW did not differ. TAZ was 70-76% higher in FW and HBW compared with CW (P<0.01). In studies 2 and 3, TAZ from FW and FBW did not differ but was 20-48% higher compared with CW (P<0.001). Extraction rate had no effect on TAZ. Colabeling demonstrates that extrinsic zinc isotopic labels can be used to accurately quantify zinc absorption from wheat in humans. Biofortification through foliar zinc application, root zinc application, or fortification provides higher TAZ compared with unfortified wheat. In biofortified wheat, extraction rate (100-80%) has a limited impact on total zinc absorption. These studies were registered on clinicaltrials.gov (NCT01775319).

Effects of ZnSO4 and Zn-EDTA broadcast or banded to soil on Zn bioavailability in wheat (Triticum aestivum L.) and Zn fractions in soil

Human Zn deficiency is prevalent in developing countries, and staple grains are commonly bio-fortified to increase their Zn contents. We measured Zn content, distribution, and bioavailability in calcareous soil and in wheat plants (Triticum aestivum L.) in Shaanxi Province, China, when either an organic Zn-ethylenediaminetetraacetate (Zn-EDTA) or an inorganic zinc sulfate heptahydrate (ZnSO4·7H2O) Zn source was banded below the seedbed or broadcasted into soil. Compared with ZnSO4·7H2O, Zn-EDTA fertilization produced higher Zn concentration and uptake in wheat plants. However, Zn bioavailability in grain remained low, with [phytate]/[Zn] ratio >15 and the resulting estimated dietary total absorbed zinc (TAZ) < 3 mg Zn/d. ZnSO4 banded into soil had little short-term effect on grain Zn concentration but had a high residual effect and promoted the maintenance of a high concentration of the Zn fraction bound to loose organic matter (LOM-Zn) in rhizosphere soil. Both ZnSO4 and Zn-EDTA were more efficient if uniformly mixed through the soil than if banded to soil. Both ZnSO4 and Zn-EDTA had limited effects on Zn bioavailability in wheat plants due to the high rate of Zn fixation in this calcareous soil.

Upregulation of Zinc Absorption Matches Increases in Physiologic Requirements for Zinc in Women Consuming High- or Moderate-Phytate Diets during Late Pregnancy and Early Lactation

Background: Estimated physiologic requirements (PRs) for zinc increase in late pregnancy and early lactation, but the effect on dietary zinc requirements is uncertain.Objective: The aim of this study was to determine changes in daily fractional absorbed zinc and total absorbed zinc (TAZ) from ad libitum diets of differing phytate contents in relation to physiologic zinc requirements during pregnancy and lactation.Methods: This was a prospective observational study of zinc absorption at 8 (phase 1) and 34 (phase 2) wk of gestation and 2 (phase 3) and 6 (phase 4) mo of lactation. Participants were indigenous Guatemalan women of childbearing age whose major food staple was maize and who had been randomly assigned in a larger study to either of 2 ad libitum feeding groups: low-phytate maize (LP; 1.6 mg/g; n = 14) or control maize (C; 7.1 mg/g; n = 8). Total dietary zinc (milligrams per day, TDZ) and phytate (milligrams per day) were determined from duplicate diets and fractional absorption (FAZ) by dual isotope ratio technique (TAZ = TDZ × FAZ). All variables were examined longitudinally and by group and compared with PRs. TAZ values at later phases were compared with phase 1. Measured TAZ was compared with predicted TAZ for nonpregnant, nonlactating (NPNL) women.Results: TAZ was greater in the LP group than in the C group at all phases. All variables increased from phase 1 to phases 2 and 3 and declined at phase 4. TAZ increased by 1.25 mg/d (P = 0.045) in the C group and by 0.81 mg/d (P = 0.058) in the LP group at phase 2. At phase 3, the increases were 2.66 mg/d (P = 0.002) in the C group and 2.28 mg/d (P = 0.0004) in the LP group, compared with a 1.37-mg/d increase in PR. Measured TAZ was greater than predicted values in phases 2-4.Conclusions: Upregulation of zinc absorption in late pregnancy and early lactation matches increases in PRs of pregnant and lactating women, regardless of dietary phytate, which has implications for dietary zinc requirements of pregnant and lactating women.

A moderate increase in dietary zinc reduces DNA strand breaks in leukocytes and alters plasma proteins without changing plasma zinc concentrations1–3

Background: Food fortification has been recommended to improve a population’s micronutrient status. Biofortification techniques modestly elevate the zinc content of cereals, but few studies have reported a positive impact on functional indicators of zinc status.Objective: We determined the impact of a modest increase in dietary zinc that was similar to that provided by biofortification programs on whole-body and cellular indicators of zinc status.Design: Eighteen men participated in a 6-wk controlled consumption study of a low-zinc, rice-based diet. The diet contained 6 mg Zn/d for 2 wk and was followed by 10 mg Zn/d for 4 wk. To reduce zinc absorption, phytate was added to the diet during the initial period. Indicators of zinc homeostasis, including total absorbed zinc (TAZ), the exchangeable zinc pool (EZP), plasma and cellular zinc concentrations, zinc transporter gene expression, and other metabolic indicators (i.e., DNA damage, inflammation, and oxidative stress), were measured before and after each dietary-zinc period.Results: TAZ increased with increased dietary zinc, but plasma zinc concentrations and EZP size were unchanged. Erythrocyte and leukocyte zinc concentrations and zinc transporter expressions were not altered. However, leukocyte DNA strand breaks decreased with increased dietary zinc, and the level of proteins involved in DNA repair and antioxidant and immune functions were restored after the dietary-zinc increase.Conclusions: A moderate 4-mg/d increase in dietary zinc, similar to that which would be expected from zinc-biofortified crops, improves zinc absorption but does not alter plasma zinc. The repair of DNA strand breaks improves, as do serum protein concentrations that are associated with the DNA repair process. This trial was registered at clinicaltrials.gov as NCT02861352.

Whey‐Based Supplement Added to a Plant‐Based Diet Increases Total Zinc Absorption, but not Total Iron in Mexican Children.

The objective of the present study was to determine the effect of a whey‐based nutritional supplement (WPS) on zinc and iron absorption from a plant‐based diet (PBD) in Mexican children. Study 1 evaluated zinc absorption in a cross‐over design. Children (n=16) were randomly assigned to receive the PBD with and without WPS on days 1 and 2 and urine samples were collected on days 1 and 6 to 9 to measure zinc absorption. Study 2 evaluated iron absorption in a parallel study. Children were randomly assigned to one of two experimental groups. Group 1 consumed the PBD during 2 days (n=16) and group 2 consumed the PBD + WPS during 2 days (n=16). A reference dose of iron was consumed with 25 mg of ascorbic acid the first day. Blood samples were collected at baseline and 14 d after the last dose was given. Zinc and iron absorption were measured using 70Zn, 68Zn, 58Fe and 57Fe isotopes. Fractional absorption of zinc was similar in both the PBD and the PBD+WPS groups (0.09±0.03 vs 0.09±0.04 mg). Because total dietary zinc was significantly higher when receiving WPS, the total amount of zinc absorbed was higher compared to PBD alone (5.2±1.1 vs2.8±0.9 mg; p&lt;0.05). No differences were observed between groups in fractional absorption of iron, adjusted iron absorption or total absorbed iron between groups. With the simultaneous intake of WPS, fractional absorption of zinc and iron from a PBD is maintained and total absorption of zinc was increased. Partially supported by IAEA.

Total Zinc Absorption from a Diet Containing either Conventional Rice or Higher-Zinc Rice Does Not Differ among Bangladeshi Preschool Children

Information is needed on zinc absorption from grain cultivars having higher zinc content. Total absorbed zinc (TAZ) from mixed diets containing high-zinc rice (HZnR), conventional rice (CR), or CR plus zinc fortificant (CR+Zn) was measured. Forty-two nonmalnourished preschool-aged children were enrolled in 1 of 2 groups. Using a crossover design, children in group A (n = 22) received for 1 d each a mixed diet containing 150 g CR or HZnR. Children in group B (n = 20) received HZnR on 1 d and CR+Zn on the other day. Fractional zinc absorption (FZA) was measured during each dietary period by using a dual-isotope tracer ratio technique; TAZ was calculated as the product of zinc intake [total dietary zinc (TDZ)] and FZA. TDZ was 3.83, 4.83, and 6.03 mg/d when the children were fed the CR, HZnR, and CR+Zn–containing diets, respectively. Mean FZA from the CR diet was greater than from the HZnR diet (25.1 vs. 20.1%, P < 0.001), and the mean FZA from the CR+Zn diet (18.8%) was less than from both the CR diet (P < 0.001) and the HZnR diet (P = 0.014). The mean TAZ was 0.96 ± 0.16, 0.97 ± 0.18, and 1.13 ± 0.20 mg/d from the CR, HZnR and CR +Zn diets, respectively. TAZ was not different for the CR and HZnR diets (P = 0.99) but was significantly greater from the CR+Zn diet compared with the other 2 diets (P < 0.001). Rice cultivars with higher zinc and/or lower phytate content are needed to increase TAZ by young children consuming this amount of rice.

Comparison of complementary feeding strategies to meet zinc requirements of older breastfed infants

The low zinc intake from human milk at ∼6 mo of age predicts the dependence on complementary foods (CF) to meet the zinc requirements of older breastfed-only infants. The objective of this study was to compare major variables of zinc homeostasis and zinc status in 9-mo-old breastfed infants who were randomly assigned to different complementary food regimens. Forty-five exclusively breastfed 5-mo-old infants were randomly assigned to receive commercially available pureed meats, iron-and-zinc-fortified infant cereal (IZFC), or whole-grain, iron-only-fortified infant cereal (IFC) as the first and primary CF until completion of zinc metabolic studies between 9 and 10 mo of age. A zinc stable-isotope methodology was used to measure the fractional absorption of zinc (FAZ) in human milk and CF by dual-isotope ratios in urine. Calculated variables included the dietary intake from duplicate diets and 4-d test weighing, the total absorbed zinc (TAZ) from FAZ × diet zinc, and the exchangeable zinc pool size (EZP) from isotope enrichment in urine. Mean daily zinc intakes were significantly greater for the meat and IZFC groups than for the IFC group (P < 0.001); only intakes in meat and IZFC groups met estimated average requirements. Mean (±SEM) TAZ amounts were 0.80 ± 0.08, 0.71 ± 0.09, and 0.52 ± 0.05 mg/d for the meat, IZFC, and IFC groups, respectively (P = 0.027). Zinc from human milk contributed <25% of TAZ for all groups. The EZP correlated with both zinc intake (r = 0.43, P < 0.01) and TAZ (r = 0.54, P < 0.001). Zinc requirements for older breastfed-only infants are unlikely to be met without the regular consumption of either meats or zinc-fortified foods.

Plasma Zinc But Not the Exchangeable Zinc Pool Size Differs Between Young and Older Korean Women

This study was done to determine the effect of age on zinc metabolism and status among healthy Korean women. Measures of zinc metabolism and status were measured in eight young women (22–24 years) and seven elderly women (66–75 years) consuming a typical Korean diet. Oral and intravenous tracers highly enriched in 67Zn and 70Zn were administered simultaneously. Multiple plasma, 24-h urines, and fecal samples were collected after isotope administration. In the young women, additional plasma were collected to determine zinc kinetics using a seven-compartmental model. Exchangeable Zinc Pool (EZP) was estimated by Miller’s method. Plasma zinc concentrations were higher in older women than younger women (p < 0.05). EZP and urinary zinc tended to be higher in older women than younger women. Fractional and total zinc absorption and endogenous fecal zinc losses did not differ between young and older women. A comparison of the zinc kinetics of the Korean and American women showed no differences in plasma or EZP zinc parameters. However, absorbed zinc and zinc flux to slowly turning over tissues (Q7) were lower in Korean women than that of Americans (p < 0.01) suggesting the total body zinc content of Korean women is lower than that of American women.

A comparison of zinc metabolism and status among young and older Korean women

This study was done to determine the effect of age on zinc metabolism and status among healthy Korean women. Zinc measures were assessed in 8 young and 7 elderly women. Oral and intravenous tracers enriched in 67Zn and 70Zn, were administered. Multiple plasma and 24‐h urines were collected for 5 d with complete fecal samples for 9 d after isotope administration. In the young women, additional plasma samples were collected to determine zinc kinetics. The size of the Exchangeable Zinc Pool (EZP) was estimated by Miller's method. Plasma zinc was higher in older women than younger women (p&lt;0.05). EZP, EZP/kg, and urinary zinc tended to be higher in older women than younger women. Fractional and total zinc absorption and endogenous fecal zinc losses did not differ between young and older women. The zinc kinetics of the Korean and American women showed no differences in plasma or EZP parameters. However, total absorbed zinc and zinc flux to slowly turning over tissues (Q7) was significantly lower in Korean women than that of Americans (p &lt; 0.01). The zinc status of older Korean women, as measured by plasma zinc and EZP was higher than that of the younger women although there were no changes in zinc absorption or endogenous fecal excretion. The young Korean women absorbed less zinc and transferred less zinc to Q7 than American women suggesting the total body zinc content of the Korean women is lower than that of their American counterparts.

Impact of Zinc Fortification on Zinc Nutrition

Food fortification is increasingly recognized as an effective approach to improve a population's micronutrient status. The present report provides a critical review of the scientific evidence currently available on the impact of zinc fortification on zinc nutrition. The available studies clearly show that zinc fortification can increase dietary zinc intake and total daily zinc absorption. Most absorption studies also indicate that adding zinc to food does not adversely affect the absorption of other minerals, such as iron. Despite the positive effect of zinc fortification on total zinc absorption, only a few studies have found positive impacts of zinc fortification on serum zinc concentrations or functional indicators of zinc status. The reasons for these inconsistent results are uncertain but may relate to the choice of food vehicles, the age group and zinc status of the study populations, or particular aspects of the study design. Thus, additional research is needed to determine the impact of zinc fortification, with or without other micronutrients, in populations at risk for zinc deficiency. Because of the benefits of increasing intake in populations at high risk for zinc deficiency, the documented increase in total zinc absorption that occurs following zinc fortification, the absence of any adverse effects, and the relatively low cost of adding zinc, public health planners should consider including zinc in mass and targeted fortification programs in such populations. Because of the limited available information on program impact, it will be important to evaluate the outcomes of such programs.

Zinc Bioavailability from Zinc-Fortified Foods

Zinc fortification is considered a potentially useful strategy for the control of zinc deficiency, but the success of such intervention programs depends on the population's access to and consumption of zinc-fortified foods and adequate absorption of zinc from these foods. The latter issue has been assessed by a variety of studies that applied zinc isotopic tracers to assess zinc uptake from zinc-fortified foods. These studies show that the additional zinc provided by zinc fortification decreases fractional absorption of zinc, but increases total zinc absorption from these foods. Available studies show no significant difference in zinc absorption from foods fortified with either zinc oxide or zinc sulfate, which are the two cheapest chemical forms of zinc that are generally recognized as safe for human consumption. It appears that high-phytate meals depress zinc absorption from zinc-fortified foods, although total zinc absorption from such foods is still likely to be greater than if the foods were not fortified with zinc. With the possible exception of Na2EDTA, putative enhancers of zinc absorption do not seem to confer major benefits for zinc absorption from zinc-fortified foods. There is little information on the effect of fortification with other micronutrients on zinc absorption from co-fortified foods, and zinc fortification does not seem to suppress iron absorption from iron-fortified foods in most studies.

Effect of Dietary Phytate on Zinc Homeostasis in Young and Elderly Korean Women

Background: Previous studies suggest that consumption of predominantly plant-based diets with high phytate content contribute to zinc deficiency by inhibiting zinc absorption. Age of the individual may also affect the ability to maintain zinc homeostasis.Objective: This study was designed to determine the effect of dietary phytate on zinc homeostasis and to evaluate the effect of age on the capacity to maintain the zinc homeostasis with changes in dietary phytate in young and elderly Korean women.Design and Methods: Seven healthy young women (22–24 yr) and 10 healthy elderly women (66–75 yr) were studied consecutively for 3 months in 2 metabolic periods (MP) in two different metabolic units. During MP1 the women consumed a high phytate (HP) diet (P:Zn molar ratio = 23) for 9 days. After a 10 d wash-out period at home eating their usual diets, a lower phytate diet (LP) (P:Zn molar ratio = 10) was fed in MP2 for 9 d. Phytase was added to selected foods in the high phytate diet to reduce the phytate content of the meals in the LP period. The zinc content of both diets was about 6.5 mg/d. Stable isotopes of Zn (70Zn) were administered intravenously on d 5 of MP 1 and 2 for measuring endogenous fecal zinc excretion. Plasma samples were also collected on d 5 for measuring plasma zinc concentrations by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). 24 hr urine samples were collected for 5 d and complete fecal samples were collected for 9 d after isotope administration. Fractional zinc absorption (FZA) was calculated from mass balance corrected for endogenous fecal zinc (EFZ) excretion and EFZ was determined by using an isotopic dilution technique. Isotopic ratios for FZA and EFZ were measured by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Statistical analyses were done using ANOVA.Results: Both the young and elderly women were in negative zinc balance during the HP period. This was due to a significant decrease in FZA and total absorbed zinc (TAZ) with a HP diet (43 vs 22% in young women, 34 vs 20% in elderly women, p < 0.001). EFZ excretion did not differ in the young and elderly women during the LP and HP periods. Dietary phytate did not alter plasma zinc concentrations or and urinary zinc excretion in either group.Conclusions: Adjustments in zinc homeostasis with an increase in dietary phytate did not differ between young and elderly women in this study.

A mathematical model of zinc absorption in humans as a function of dietary zinc and phytate.

The quantities of zinc and phytate in the diet are the primary factors determining zinc absorption. A mathematical model of zinc absorption as a function of dietary zinc and phytate can be used to predict dietary zinc requirements and, potentially, enhance our understanding of zinc absorption. Our goal was to develop a model of practical and informative value based on fundamental knowledge of the zinc absorption process and then fit the model to selected published data to assess its validity and estimate parameter values. A model of moderate mathematical complexity relating total zinc absorption to total dietary zinc and total dietary phytate was derived and fit to 21 mean data from whole day absorption studies using nonlinear regression analysis. Model validity, goodness of fit, satisfaction of regression assumptions, and quality of the parameter estimates were evaluated using standard statistical criteria. The fit had an R(2) of 0.82. The residuals were found to exhibit a normal distribution, constant variance, and independence. The parameters of the model, A(MAX), K(R), and K(P), were estimated to have values of 0.13, 0.10, and 1.2 mmol/d, respectively. Several of these estimates had wide CI attributable in part to the small number and the scatter of the data. The model was judged to be valid and of immediate value for studying and predicting absorption. A version of the model incorporating a passive absorption mechanism was not supported by the available data.

Total zinc absorption in young women, but not fractional zinc absorption, differs between vegetarian and meat-based diets with equal phytic acid content

Zn bioavailability is often lower in vegetarian diets mainly due to low Zn and high phytic acid contents. The objective of the present study was to determine the fractional and total absorption of Zn from a vegetarian diet in comparison with meat diets with equal concentrations of phytic acid. A randomized cross-over design, comprising three whole-day diet periods of 5 d each, with a vegetarian diet or diets containing Polish-produced meat or Danish-produced meat, was conducted. Twelve healthy female subjects completed the study. All diets had a high content of phytic acid (1250 micromol/d) and in the meat diets the main meals contained 60 g pork meat. All main meals were extrinsically labelled with the radioactive isotope 65Zn and absorption of Zn was measured in a whole-body counter. The mean Zn content of the whole-day diet was: Polish meat diet 9.9 (SE 0.14) mg, Danish meat diet 9.4 (SE 0.19) mg and vegetarian diet 7.5 (SE 0.18) mg. No difference was observed in the fractional absorption of Zn (Polish meat diet: 27 (SE 1.2) %, Danish meat diet: 27 (SE 1.9) % and vegetarian diet: 23 (SE 2.6) %). A significantly lower amount of total Zn was absorbed from the vegetarian diet (mean Zn absorption of Polish meat diet: 2.7 (SE 0.12) mg/d (P<0.001), Danish meat diet: 2.6 (SE 0.17) mg/d (P=0.006) and vegetarian diet: 1.8 (SE 0.20) mg/d). In conclusion, the vegetarian diet compared with the meat-based diets resulted in lower amounts of absorbed Zn due to a higher content of Zn in the meat diets, but no difference was observed in the fractional absorption of Zn.

Zinc absorption from a micronutrient-fortified dried cow's milk used in the Chilean National Complementary Food Program

The objective was to compare the absorption of zinc from a micronutrient-fortified dried cow's milk, which is part of the Chilean National Complementary Food Program, with that from a standard nonfortified milk. Fortification included the addition of iron, zinc, copper, and ascorbic acid to provide total concentrations (in 100 g of powder) of 10, 5, 0.5, and 70 mg, respectively. Seven adults with normal plasma zinc concentrations (16.0 ± 0.9 μmol/L) were studied. Fractional absorption of zinc was determined from single test meals using a stable isotope–based methodology. Mean (± SD) fractional absorption of zinc of the test meal containing nonfortified milk was 0.29 ± 0.09 compared with 0.30 ± 0.09 of the test meal with the fortified milk ( P = not significant). Absolute zinc absorptions from the test meals were 0.43 ± 0.14 vs 0.57 ± 0.16 mg, respectively ( P = .02). Micronutrient fortification of dried cow's milk, including zinc, was associated with increased total zinc absorption.

Dietary Phytate Reduction Improves Zinc Absorption in Malawian Children Recovering from Tuberculosis but Not in Well Children

High dietary phytate content that compromises zinc nutriture is thought to be a major problem among children of the developing world. Zinc stable isotope techniques permit the quantitative assessment of the effect of phytate reduction on zinc homeostasis. We tested the hypothesis that zinc absorption would be increased in Malawian children fed a reduced-phytate corn-plus-soy diet compared with a standard high phytate diet. Twenty-three children hospitalized in Blantyre, Malawi, were enrolled. Children were selected from those recovering from tuberculosis and from well children (those with minor injuries, those awaiting elective surgery or healthy siblings). Children received a diet of corn-plus-soy porridge (either low phytate or high phytate) for a period of 3-7 d and then participated in a zinc stable isotope study. The study included the administration of oral and intravenous zinc stable isotopes and 7-d collections of urine and stool. The diet was maintained throughout the duration of specimen collection. Zinc isotopic enrichments in urine and stool were measured, and zinc fractional absorption, total zinc absorption, endogenous fecal zinc, net zinc retention and size of the exchangeable zinc pool were calculated. Among the 14 children recovering from tuberculosis, dietary phytate reduction resulted in higher fractional absorption (0.41 +/- 0.14 versus 0.24 +/- 0.09, mean +/- SD, P: < 0.05) and total zinc absorption (169 +/- 55 versus 100 +/- 46 microg/(kg. d), P: < 0.05). No effect of phytate reduction was seen in the well children (n = 9). Phytate reduction did not decrease the absolute endogenous fecal zinc, but it did decrease it relative to total absorbed zinc. These preliminary results indicate that phytate reduction may be beneficial in improving zinc nutriture in groups with increased zinc requirements who consume a cereal-based diet.

Zinc Utilization in Young Men Fed Adequate and Low Zinc Intakes

Zinc absorption and balances were measured in six young men who were confined while participating in a 75-d metabolic study. A diet of conventional food providing either 16.5 or 5.5 mg Zn/d was fed. Apparent absorption of zinc was calculated from the zinc balance data and from the absorption of a zinc stable isotope added to the diet. The apparent zinc absorption calculated from the isotope data was about 25% when 16.5 mg zinc was fed; it increased to about 53 and 49% after 13 and 42 d, respectively, when 5.5 mg zinc was fed. Total zinc absorption fell from 4.1 mg/d to 2.7–2.9 mg/d during the low zinc period, however. This zinc absorption was sufficient to maintain crude zinc balances in five of the six subjects. Neither serum nor urinary zinc levels changed significantly during the period of feeding low levels of zinc. It appears that zinc absorption readily responds to changes in dietary zinc and that an intake of 5.5 mg Zn/d for about 8 wk does not cause serum or urinary zinc level to fall.