Zinc homeostasis in Malawian children consuming a high-phytate,maize-based diet

BACKGROUND: Zinc deficiency in children is an important public health concern in the developing world, and the consumption of predominantly cereal-based diets with a high phytate content may contribute to the risk. The gastrointestinal tract plays a central role in absorbing and conserving zinc, yet it has not been carefully studied in such children. OBJECTIVE: This study investigated zinc homeostasis in healthy, free-living Malawian children with habitually high-phytate diets to better understand the role of the gastrointestinal tract. DESIGN: We evaluated zinc homeostasis in 10 children aged 2-5 y who were consuming a maize-based diet (phytate:zinc molar ratio of 23:1). Zinc stable isotopes were administered orally and intravenously. The tracer and tracee were measured in urine and feces. RESULTS: Endogenous fecal zinc was high in comparison with results for this measure in previous studies. Typical correlations seen in subjects consuming a low-phytate diet between total absorbed zinc, the size of the exchangeable zinc pool, and endogenous fecal zinc were not observed. Fractional absorption of zinc was 0.24. CONCLUSIONS: Zinc homeostasis was perturbed, particularly by large, endogenous fecal zinc losses, in this vulnerable population. The effects of interventions to improve zinc status, including dietary phytate reduction, on zinc homeostasis merit further study.     

Metabolic adaptations to low zinc intakes in premenarcheal girls

BACKGROUND: Zinc deficiency is increasingly recognized as an important cause of mortality and morbidity. Children in developing countries are at especially high risk because of relatively low zinc intakes and poor bioavailability. OBJECTIVE: We assessed the effect of 2-wk adaptation to low zinc intake (4 mg/d) on fractional zinc absorption, endogenous fecal zinc excretion, and urinary zinc excretion. DESIGN: Sixteen healthy 9-14-y-old girls were studied twice in random order after 2-wk adaptation to diets providing either 12 mg/d (high) or 4 mg/d (low) zinc. Fractional zinc absorption and endogenous fecal zinc excretion were measured with use of established stable isotope techniques. RESULTS: Plasma zinc was not significantly lower during the low dietary intake period (1.06 +/- 0.18 mg/L) than during the high dietary intake period (1.14 +/- 0.23 mg/L, P = 0.30). Endogenous fecal zinc excretion was significantly lower during the low intake period (1.08 +/- 0.62 mg/d) than during the high intake period (1.82 +/- 0.95 mg/d, P < 0.026), but there was no significant change in fractional zinc absorption (30.6% +/- 12.4% compared with 26.6% +/- 9.0%, P = 0.32) or urinary zinc excretion (0.68 +/- 0.35 mg/d compared with 0.59 +/- 0.24 mg/d, P = 0.30). Approximate zinc balance was significantly lower during the low-intake period than during the high-intake period (P = 0.007) and significantly (P < 0.0001) less than zero. CONCLUSION: Short-term zinc restriction in premenarcheal girls leads to a significant decrease in endogenous fecal zinc excretion, which was inadequate to restore normal zinc balance.     

Zinc absorption in Guatemalan schoolchildren fed normal or low-phytate maize

BACKGROUND: Poor bioavailability of zinc from high-phytate diets is an important contributory factor to zinc deficiency in low-income populations. OBJECTIVE: The objective of this study was to determine the effect of low-phytate maize consumption on zinc absorption. DESIGN: The participants were apparently healthy children from the Central Highlands of Guatemala. Sixty children (20 per group) were randomly assigned to be fed only the low-phytate maize or 1 of 2 control maizes, the isohybrid wild-type maize or a local maize, for a 10-wk period. During the final week, the fractional absorption of zinc for all meals was measured during 1 d with the use of zinc stable isotopes and a dual isotope ratio technique based on urine enrichment data. RESULTS: Mean (+/-SD) phytate intakes for the low-phytate, wild-type, and local maize groups were 1536 +/- 563, 2056 +/- 517, and 2253 +/- 687 mg/d, respectively. Corresponding zinc intakes were 8.6 +/- 2.5, 8.1 +/- 2.0, and 9.7 +/- 2.6 mg/d, and the dietary phytate:zinc molar ratios were 18 +/- 5, 26 +/- 6, and 23 +/- 5. Corresponding fractional absorptions of zinc were 0.32 +/- 0.07, 0.28 +/- 0.07, and 0.29 +/- 0.06. The respective values for total absorbed zinc were 2.72 +/- 0.88, 2.30 +/- 0.96, and 2.78 +/- 1.04 mg/d. No significant differences in either the fractional absorption of zinc or total absorbed zinc were seen between the maize groups. CONCLUSION: Under the conditions of the present study, zinc absorption was not increased by the long-term use of low-phytate maize in children whose major dietary staple is maize.     

Intestinal excretion of endogenous zinc in Guatemalan school children

The intestine is the major route of excretion of endogenous zinc (Zn) and has a key role in maintaining Zn homeostasis. The principal objective of this paper is to provide an interpretative report of quantities of endogenous fecal Zn (EFZ) excreted by rural Guatemalan school children fed either normal or low phytate maize as their principal food staple. EFZ was measured by a Zn stable isotope technique. EFZ did not differ between control and low phytate maize groups. The overall EFZ (n = 53) was (mean +/- SD) 1.56 +/- 0.69 mg Zn/d or 0.07 +/- 0.03 mg Zn x kg body wt(-1) x d(-1). EFZ was not correlated with the quantity of Zn absorbed. The estimated EFZ at the level of absorption that matched the physiologic requirement (EFZ(PR)) did not differ from the above mean value. The EFZ(PR) of 0.07 +/- 0.03 mg Zn/kg body wt is twice the value currently used in the estimation of Dietary Reference Intakes. Supported by other recent childhood data, these results suggest that the current estimates of EFZ(PR) used in the calculation of Zn requirements for children are misleadingly low.     

A high oat-bran intake does not impair zinc absorption in humans when added to a low-fiber animal protein-based diet

Oat bran has a high phytate content and a low or inactivated phytase activity. A high intake of oat bran could therefore result in an impaired absorption of trace elements. The effect of a mean daily intake of 142 g of oat bran (102 g/10 MJ) on absorption of zinc was evaluated by the use of stable isotopes and fecal monitoring in 12 healthy subjects (6 males and 6 females). Each subject participated in two separate diet periods each of 21 d with identical low-fiber diets and with oat bran added in one of the periods. The oat bran was incorporated into bread and served at three daily main meals. The intake of zinc and phytate per 10 MJ was 138 micromol (9.0 mg) and 0.5 mmol, respectively, in the low-fiber period and 225 micromol (14.7 mg) and 4.0 mmol, respectively, in the oat bran period. Stable isotopes of zinc ((70)Zn) were added to the diets at d 7 of each period. The fractional absorptions (means +/- SD) of zinc from the low-fiber and oat bran diets were 0.48 +/- 0.11 and 0.40 +/- 0.15 (P = 0.07), respectively. The higher zinc content in the oat bran period resulted in a greater amount of zinc absorbed (64 +/- 19 micromol and 99 +/- 51 micromol, respectively, P = 0.009). Balance data suggest that the higher absorbed amount of zinc resulted in correspondingly higher intestinal endogenous excretion of zinc. In conclusion, the absorption of zinc was high and not affected by addition of oat bran.     

Magnesium absorption using stable isotope tracers in healthy children and children treated for leukemia

Intestinal magnesium (Mg) absorption was measured in six healthy children (control) and in four children treated for acute lymphoblastic leukemia with the single-isotope fecal recovery technique (SIFRT). The objective of this study was to determine Mg absorption in young children with acute lymphoblastic leukemia using stable isotope tracers. Fractional and absolute absorption levels determined by SIFRT were not significantly different between children with acute lymphoblastic leukemia (fractional absorption: 58.3 +/- 10.6% [mean +/- SEM], absolute absorption: 3.66 +/- 0.71 mg x kg(-1) x d(-1), [0.15 +/- 0.03 mmol x kg(-1) x d(-1)]) and control children (fractional absorption: 61.4 +/- 7.5%, absolute absorption: 5.69 +/- 0.85 mg x kg(-1) x d(-1), [0.23 +/- 0.03 mmol x kg(-1) x d(-1)]). Average Mg absorption in young children (aged 3--8 y) was 60.2 +/- 5.8%. This study describes the first application of the SIFRT to assess Mg absorption in young children and illustrates the feasibility of the SIFRT in this age group to obtain more accurate information on Mg absorption.     

Intrinsic and extrinsic stable isotopic zinc absorption by infants from formulas

The kinetics of fecal elimination and the extent of fractional absorption of intrinsic and extrinsic zinc from infant formula were studied in 11 human infants by using a direct, simultaneous dual-label method based on fecal monitoring of unabsorbed stable isotope labels. The relative positions of the two stable isotopic tags (67Zn, 70Zn) as extrinsic and intrinsic labels were reversed in two separate determinations of fractional absorption. Administration of doubly labeled formula for 24 h or less permitted elimination of unabsorbed labels before the end of a 72-h metabolic interval. The extent of enrichment and the kinetics of fecal elimination of unabsorbed extrinsic stable isotopic zinc tag were observed to agree closely with the corresponding values for the intrinsic tag. Fractional absorption of intrinsic and extrinsic tags was highly correlated and did not differ significantly. The ratio of fractional absorption of extrinsic tag to that of intrinsic tag was 1.05 +/- 0.19 (mean +/- SD). The results constitute strong support for validation of the use of enriched stable isotopes at low levels (less than or equal to 10%) of extrinsic addition to milk-based diets for studies of zinc absorption by humans.     

Milk consumption and zinc retention in postmenopausal women

We measured intestinal 65Zn absorption and whole-body retention in postmenopausal women following a meal extrinsically labeled with 65Zn. The meal was consumed with 200 mL of milk or with a calcium phosphate supplement. Fifteen elderly (mean age 69) subjects were studied during three 12-d experimental periods in which they were fed either a basal diet containing 16 mg Zn or the basal diet supplemented either with 400 mL of milk or with dibasic calcium phosphate supplements containing an equivalent amount of calcium (468 mg) and phosphorus (360 mg). Measurements of fractional zinc absorption were made in 9 of the 15 subjects by a dual-isotope technique using 65Zn and 51Cr (as nonabsorbable fecal markers). Fractional zinc absorption was 0.22 +/- 0.06 (mean +/- SEM) after the standard meal, 0.23 +/- 0.06 with added milk and 0.22 +/- 0.03% with the added calcium phosphate supplement. The corresponding values for 65Zn retention in 15 subjects 12 d after dosing were 0.10 +/- 0.01% for all treatments. No significant effect of milk or calcium phosphate supplementation was observed on either 65Zn absorption or retention. We conclude that increased milk consumption with meals has no detrimental consequences on zinc nutriture in elderly women.     

Major variables of zinc homeostasis in Chinese toddlers

BACKGROUND: Measurement of the major variables of zinc homeostasis is an essential prerequisite for estimating human zinc requirements, which currently require a factorial approach. The data required for this approach have not been available for toddlers, whose requirements have been estimated by extrapolation from other age groups. OBJECTIVE: The objective of the study was to measure key variables of zinc homeostasis in rural and small-town Chinese toddlers. DESIGN: Zinc stable-isotope tracers were administered intravenously and orally with all meals for 1 d to 43 toddlers. Subsequent metabolic collections in the homes included duplicate diets, quantitative fecal collections, and spot urine sampling. Fractional absorption of zinc (FAZ) was measured by a dual-isotope tracer ratio technique, and endogenous fecal zinc (EFZ) was measured by an isotope dilution technique. RESULTS: No group or sex differences were found. Therefore, results were combined for 43 toddlers aged 19-25 mo whose major food staple was white rice. Selected results (x+/- SD) were 1.86 +/- 0.55 mg total dietary Zn/d; 0.35 +/- 0.12 FAZ; 0.63 +/- 0.24 mg total absorbed Zn/d; 0.67 +/- 0.23 mg EFZ/d; and 65.0 +/- 8.3 microg plasma Zn/dL. The molar ratio of dietary phytate to zinc was 2.7:1. CONCLUSIONS: The mean intake and absorption of zinc in this population are low in comparison with estimated average dietary and physiologic requirements for zinc, and plasma zinc values are consistent with zinc deficiency. Intestinal losses of endogenous zinc exceed previous estimates for toddlers, and only modest evidence exists of conservation in response to low zinc intake and absorption.     

Zinc homeostasis during lactation in a population with a low zinc intake.

BACKGROUND: There is a major increase in endogenous zinc excretion, specifically via the mammary gland, in early human lactation. Whereas fractional absorption of dietary zinc has been reported to increase in early human lactation, it is not known to what extent adaptive mechanisms may maintain zinc homeostasis, especially when dietary zinc intake is relatively low. OBJECTIVE: The objective of this study was to quantitate major variables of zinc homeostasis during early lactation in subjects from a population whose habitual dietary zinc intake is low. DESIGN: We studied 18 free-living lactating women from a rural community of northeast China whose infants were exclusively breast-fed. The subjects were studied at approximately 2 mo of lactation with use of stable isotopes of zinc and metabolic collection techniques. Milk volume was measured with use of a deuterium enrichment method. RESULTS: The mean (+/-SD) secretion of zinc in milk was 2.01 +/- 0.97 mg/d, the intake of zinc was 7.64 +/- 1.61 mg/d, and the fractional absorption of zinc was 0.53 +/- 0.09, for a total daily zinc absorption of 4.00 +/- 0.71 mg/d. Endogenous zinc excretion in urine and feces was 0.30 +/- 0.10 and 1.66 +/- 0.97 mg/d, respectively. CONCLUSIONS: Zinc balance, including zinc secreted in breast milk, was maintained at approximately 2 mo of lactation in women whose habitual diet was low in zinc. Homeostasis was achieved by high fractional absorption of zinc and intestinal conservation of endogenous fecal zinc.     

Effect of beef and soy proteins on the absorption of non-heme iron and inorganic zinc in children

BACKGROUND: Iron and zinc deficiency remain substantial problems in small children in both developed and developing nations. Optimizing mineral absorption is an important strategy in minimizing this problem. OBJECTIVES: To assess the effects of beef and soy proteins on the bioavailability of non-heme iron and zinc in children. METHODS: We measured iron (n = 26) and zinc (n = 36) absorption in 4-8 y old children from meals differing only in protein source (beef or a low-phytate soy protein concentrate). Iron and zinc absorption were measured using multi-tracer stable isotope techniques. Iron absorption was calculated from the red blood cell iron incorporation measured after 14 days and zinc absorption from the ratio of the oral and intravenous excretion of the zinc tracers 48 hours after dosing. RESULTS: Iron absorption from the beef meal was significantly greater (geometric mean, 7.6%) than from the soy meal (3.5%, p = 0.0015). Zinc absorption from the beef meal was greater (mean +/- SD, 13.7 +/- 6.0%) than from the soy meal (10.1 +/- 4.1%, p = 0.047). CONCLUSION: These findings indicate that beef protein increases both non-heme iron and zinc absorption compared to soy protein. The effect of protein source on non-heme iron and inorganic zinc absorption should be one of the factors taken into account when designing diets for children. The inhibitory effect of the soy based meal on iron and zinc absorption could be overcome by fortifying the soy protein with these minerals during the production process.     

锌代谢池—判断人体锌营养状况的可靠指标

用稳定性同位素锌(~(68)Zn和~(70)Zn)对2例志愿者进行了历时15周不同锌营养水平的代谢实验。结果表明,锌代谢池能正确地反映人体的锌营养状况。空腹和餐后血浆锌浓度的差别比单独测定空腹血浆锌浓度更为可靠。每日尿锌和粪锌的排泄量则有一定的局限性。粪便中内源性锌排泄量的测定对确定人体每日锌的供给量标准,具有一定的参考价值。     

锌代谢池—判断人体锌营养状况的可靠指标

用稳定性同位素锌(~(68)Zn和~(70)Zn)对2例志愿者进行了历时15周不同锌营养水平的代谢实验。结果表明,锌代谢池能正确地反映人体的锌营养状况。空腹和餐后血浆锌浓度的差别比单独测定空腹血浆锌浓度更为可靠。每日尿锌和粪锌的排泄量则有一定的局限性。粪便中内源性锌排泄量的测定对确定人体每日锌的供给量标准,具有一定的参考价值。     

Zinc absorption in women: comparison of intrinsic and extrinsic stable-isotope labels

Fractional absorption of extrinsic and intrinsic zinc from milk-based formulated diets was measured in 10 young women by using a simultaneous triple-isotope method based on fecal monitoring of unabsorbed enriched stable-isotope labels. Zinc intake was held nearly constant (mean zinc intake = 1.48 mumol.kg body wt-1.d-1) throughout the 18-d controlled feeding phase of the study by addition of extrinsic 64Zn to all formula feedings, with substitution of the extrinsic 67Zn label for some of the 64Zn when formula intrinsically labeled with 70Zn was given. Fractional absorption values of intrinsic and extrinsic zinc labels, 0.267 +/- 0.092 (mean +/- SD) and 0.282 +/- 0.086, respectively, were highly correlated (r = 0.83, P less than 0.05) and did not differ significantly. The ratio of fractional absorption of the extrinsic to that of the intrinsic label, 1.08 +/- 0.20 (mean +/- SD), was not significantly different from unity. The results show that extrinsic labeling by use of enriched stable isotopes is a valid means of determining zinc absorption from milk-based diets in adult humans.     

六种锌含量指标对儿童锌营养状态评价的研究

本研究选取了１６例２－１４岁骨科矫形儿，用原子吸收光谱法例定了其白细胞，红细胞、血浆、骨骼肌、骨骼及发锌含量，并对各指标间相关性进行了分析。结果：１．白细胞锌与骨骼肌锌呈有意义正相关，可代表体内锌营养状态。２．血浆、红细胞锌与骨骼肌锌相关性差。３．发锌与各指标均未出现有意义相关，建议慎重使用。     

Zinc absorption from low-phytate hybrids of maize and their wild-type isohybrids

BACKGROUND: Identification of allelic variants in a single gene that determine the phytate content of maize kernels and the subsequent breeding of low-phytate maize have facilitated studies designed to determine quantitatively the effects of maize phytate on the bioavailability of minerals in maize. OBJECTIVE: The objective was to determine the relation between the fractional absorption of zinc (FAZ) and the phytate content and phytate:zinc molar ratios of maize tortillas prepared from hybrids with different phytate contents. DESIGN: Six healthy adults were fed, as the only food for 2 d, maize tortillas prepared from 1 of 2 low-phytate mutants: lpa1-1 (lpa1-1-LP) or Nutridense Low Phytate (ND-LP), which have phytate reductions of approximately 60% and approximately 80%, respectively, compared with their respective wild-type isohybrids. Four additional subjects were fed tortillas prepared from the corresponding wild-type isohybrids (lpa1-1-WT and ND-WT) according to the same study design. Meals were extrinsically labeled with zinc stable isotopes, and FAZ was determined with a dual-isotope-tracer ratio technique. Overall FAZ values were examined in relation to dietary phytate and phytate:zinc molar ratios by using a mixed nonlinear regression model. RESULTS: The mean (+/-SD) FAZ values from tortillas prepared from ND-LP, lpa1-1-LP, lpa1-1-WT, and ND-WT were 0.38 +/- 0.07, 0.28 +/- 0.04, 0.15 +/- 0.07, and 0.13 +/- 0.05, respectively. A negative relation (P < 0.001) was found between FAZ and both dietary phytate and the phytate:zinc molar ratio. The effect of dietary zinc (8-14 mg Zn/d) under these experimental conditions was not significant. CONCLUSIONS: FAZ from maize tortillas is positively related to the extent of phytate reduction achieved with low-phytate hybrids.     

Cadmium absorption in women fed processed edible sunflower kernels labeled with a stable isotope of cadmium, (113)Cd.

The apparent fractional absorption of cadmium (Cd) from sunflower kernels (SFK) was determined in women volunteers by using kernels labeled with a stable isotope of Cd ((113)Cd) by injecting it into the flowering head. Fourteen women who were between the ages of 30 and 70 years, who did not use tobacco products, who were in good health, and who had been consuming a self-selected diet low in Cd content participated in the study. The volunteers were fed a breakfast composed primarily of cereal, milk, and fruit juice. The breakfast also contained a portion of (113)Cd-labeled SFK processed into a buttery spread. Each volunteer collected individual stool samples for 21 days beginning immediately after they had consumed the labeled kernels. The total amounts of Cd and (113)Cd excreted in each stool were determined by isotope dilution inductively coupled plasma mass spectrometry. Mean fecal Cd excretion was 14.1+/-4.1 microg/day and mean (113)Cd absorption was 10.6+/-4.4%. In agreement with previous studies, no significant (P>0.3) correlation between Cd absorption and serum ferritin concentrations was found in women whose serum ferritin concentrations were >25 ng/mL. These data suggest that the availability of Cd from highly processed sunflower kernels to humans is similar to that reported for other types of food.     

Zinc supplementation reduces fractional zinc absorption in young and elderly korean women

BACKGROUND: Adjustments in zinc losses and absorption are thought to maintain zinc homeostasis with changes in intake, but the capacity to make these adjustments appears to be affected by aging. Zinc status of the individual may also influence adjustments in fractional zinc absorption. OBJECTIVE: The purpose of this study was to compare the effects of changes in zinc status due to zinc supplementation on fractional zinc absorption in young and elderly Korean women. DESIGN: Zinc status and absorption were measured initially in 15 young (20-24 yr) and 15 elderly women (64-75 yr) confined to a metabolic unit and consuming a typical Korean diet. Upon discharge from the unit the women were supplemented with 22 mg zinc/d for 28 days. On d 20, the women returned to the unit for measurement of zinc status and absorption. Fractional zinc absorption (FZA) was estimated from the same typical Korean breakfast at both time points using the dual isotopic tracer method. Zinc stable isotopic ratios were measured in urine samples collected for 3 days following isotope administration. RESULTS: Plasma and urinary zinc concentrations increased significantly with zinc supplementation in the young but not the elderly women. FZA decreased following zinc supplementation in the young women from 22 to 8% (p < 0.0001) and in the elderly women from 19 to 10% (p < 0.0001). The decline in young women was greater than that in elderly women (p < 0.05). CONCLUSIONS: Both young and elderly women reduced their efficiency of zinc absorption with zinc supplementation. But, plasma and urinary zinc concentrations did not increase in the elderly following zinc supplementation suggesting that age altered the use of the additional zinc.     

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 ((70)Zn) 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.     

Dephytinization of a complementary food based on wheat and soy increases zinc, but not copper, apparent absorption in adults

Complementary foods based on cereals may contain high amounts of phytic acid, which binds strongly to minerals and trace elements. The objective of the study was to evaluate the effect of dephytinization of a cereal-based complementary food on zinc and copper apparent absorption in adults. A dephytinized complementary food (<0.03 mg phytic acid/g) and one containing the native phytic acid concentration (4 mg/g) were labeled extrinsically with stable isotopes ((70)Zn and (65)Cu). Apparent zinc and copper absorption was based on fecal excretion of nonabsorbed labels in 9 adults, using a crossover design. Stable isotopes were quantified by thermal ionization MS. Apparent fractional zinc absorption was significantly higher (P = 0.005; Student's paired t test) from the dephytinized complementary food (34.6 +/- 8.0%; mean +/- SD) than from the complementary food with native phytic acid concentration (22.8 +/- 8.8%). Apparent fractional copper absorption did not differ (P = 0.167; 19.7 +/- 5.1% dephytinized vs. 23.7 +/- 8.1% native phytic acid). These results clearly demonstrate the beneficial effect of dephytinization of a complementary food on fractional absorption of zinc but not of copper in adults. The long-term nutritional benefits of dephytinization of complementary foods should be evaluated in young children.