Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001) / Chapter Skim
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12 Zinc
12 Zinc
Pages 442-501
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From page 442... ...
Factorial analysis was used to set the Estimated Average Requirement (EAR)
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From page 443... ...
Metallothionein expression is regulated by a mechanism that involves zinc's binding to the transcription factor, metal response element transcription factor (MTF1) , which activates gene transcription (Cousins, 1994; Dalton et al., 1997~.
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From page 444... ...
Induction of metallothionein by changes in clietary zinc intake has received considerable attention in experiments with both animals and humans (reviewoci in Chesters, 1997; Cousins, 1994~. Erythrocyte metallothionein concentrations clecreaseci rapidly in humans feci a phytate-containing cliet of very low zinc content (Gricler et al., 1990~.
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From page 445... ...
Homeostatic regulation of zinc metabolism is achieved principally through a balance of absorption and secretion of endogenous reserves involving adaptive mechanisms programmed by dietary zinc intake (King and Keen, 1999~. Zinc depletion in humans is accompanied by reduced endogenous zinc loss on the order of 1.3 to 4.6 mg/day, derived from both pancreatic and intestinal cell secretions.
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From page 446... ...
Clinical Effects of Inadequate Intake Individuals with malabsorption syndromes including sprue, Crohn's disease, and short bowel syndrome are at risk of zinc cleficiency due to malabsorption of zinc and increased urinary zinc losses (Pironi et al., 1987; Valberg et al., 1986~. In mild human zinc deficiency states, the detectable features and laboratory/functional abnormalities of mild zinc deficiency are diverse.
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From page 447... ...
SELECTION OF INDICATORS FOR ESTIMATING THE REQUIREMENT FOR ZINC Principal Indicator The selection of zinc absorption (more specifically, the minimal quantity of absorbed zinc necessary to match total daily excretion of endogenous zinc) as the principal indicator for adult Estimated Average Requirements (EAR)
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From page 448... ...
After it has been clefineci and acljusteci by the constant for other enclogenous losses, one can calculate the minimum quantity of absorbed zinc necessary to offset enclogenous zinc losses (Figure 12-1~. The clietary zinc intake corresponding to this average minimum quantity of absorbed zinc is the EAR.
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From page 449... ...
from means of ten data sets for healthy men ages 19 through 50 years. The bold dashed lines above and parallel to the regression line represent the total endogenous zinc losses for men and women in relation to zinc absorption.
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From page 450... ...
Third, baseline clietary ciata typically inclucleci in these studies are acloquate to use for group analyses. Size and Turnover Rates of Zinc Pools Strong positive correlations have been observed between dietary zinc content, especially the amount of absorbed zinc, and estimates of the size of the combined pools of zinc that exchange with zinc in
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From page 451... ...
Homeostatic mechanisms are effective in maintaining plasma zinc concentrations for many weeks of even severe clietary zinc restriction Johnson et al., 1993; Wacia et al., 1985~. A number of studies have reported no association between clietary zinc intake and plasma or serum zinc concentration (Artacho et al., 1997; Kant et al., 1989; Neggers et al., 1997; Thomas et al., 1988)
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From page 452... ...
In three of these studies, low zinc concentration in hair was used as a criterion for zinc supplementation in children and resulted in increased growth velocity. Low zinc concentrations in hair have been reported in Canaclian children with low meat consumption (Smit-Vanclerkooy and Gibson, 1987~.
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From page 453... ...
Moreover, this approach points the way for future exploration of molecular markers of zinc status including, for example, a whole family of zinc transporters that are now being iclentifieci (Failla, 1999; McMahon and Cousins, 1998~. Indexes of Immune Status Zinc is essential for the integrity of the immune system, and inaclequate zinc intake has many adverse effects (Shankar and Prasaci, 1998~.
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From page 454... ...
However, no studies have directly related hormone concentrations to decreases or increases in zinc intake. Circulating Hepatic Proteins Reductions in retinal binding protein, albumin, and pre-albumin concentrations have been reported with moderate clietary zinc restriction (Wacia and King, 1986~.
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From page 455... ...
The option for zinc to be absorbed by the paracellular route acicis to the lack of a unified form or path of zinc absorption from foocis. Furthermore, the methods used to assess zinc absorption have varied widely, including balance studies, intestinal perfusion, responses of plasma zinc to single meals or aqueous closes, and tracer studies with intrinsically or extrinsically stable or radioactive zinc isotopes (Sancistrom and Lonnercial, 1989~.
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From page 456... ...
, with low zinc intake decreasing folate absorption/status. More recent evidence floes not support any effect of low zinc intake on folate utilization and shows that folate supplementation floes not adversely affect zinc status (Kauwell et al., l995~.
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From page 457... ...
The markocily greater bioavailability of zinc from human milk than from cow's milk is an example of how protein digestibility, which is much lower in casein-rich cow's milk than in human milk, influences zinc absorption (Roth and Kirchgessner, 1985~. In general, zinc absorption from a cliet high in animal protein will be greater than from a diet rich in proteins of plant origin such as soy (King and Keen, 1999~.
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From page 458... ...
clevelopeci zinc requirements from low, meclium, and high bioavailabilitJv cliets on the basis of estimates of fractional absorption on single test meals with varying zinc and phytate content. The results of single test meals for measuring zinc absorption, however, may be different from the long-term response of zinc absorption, as has been shown to be the case for iron (see Chapter 9~.
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From page 459... ...
, calculated zinc intakes are 2.15 mg/day at 1 month, 1.56 mg/ciay at 2 months, 1.15 mg/ciay at 3 months, and 0.94 mg/ciay at 6 months (Table 12-1~. Measured zinc intake of infants feci human milk was 2.3 mg/ciay at 2 weeks and 1 mg/ciay at 3 months (Krebs et al., 1994~.
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From page 460... ...
460 DIETARY REFERENCE INTAKES TABLE 12-1 Zinc Concentration in Human Milk Maternal Intake Stage of Reference Study Group (mg/d) Lactatio, Picciano and Guthrie, 1976 50 women Not reported 6-12 wk Johnson and Evans, 1978 10 women Not reported 2 mo-2 Vuori et al., 1980 15 women, 24-35 y 13.7 + 2.7 mg/d 12.8 + 2.8 mg/d 6-8 wk 17-22 wl Fransson and Lonnerdal, 1982 23 women Not reported Various Moser and Reynolds, 1983 23 women, 30 y 9.4 1 mo 12.8 3 mo 9.6 6 mo Casey et al., 1985 11 women, 26-39 y Not reported 8 d 14 d 21 d 28 d Casey et al., 1989 22 women 10.9 7 d 1 mo 12 mo Sievers et al., 1992 10 women Not reported 17 d 35 d 56 d 85 d 117 d Anderson, 1993 6 women, 20-30 y Not reported Up to 5 Krebs et al., 1995 71 women, 30 y 13-25.7 0.5 mo 1 mo 2 mo 3 mo 4 mo 5 mo 6 mo 7 mo 8 mo 9 mo Aquilio et al., 1996 14 women, 21-29 y Not reported 2-6 d 12-16 d 21 d Biego et al., 1998 17 milk samples Not reported Mature r a Zinc intake based on reported data or concentration (mg/L)
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From page 461... ...
ZINC 461 Intake Stage of Milk Concentration Estimated Zinc Intake Lactation (mg/L) of Infants (mg/d)
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From page 462... ...
These factorial estimates are baseci on measurements of zinc intake of infants feci human milk, fractional absorption, and enclogenous losses (Krebs et al., 1996~. Integumental and urine losses are from published calculations (Krebs and Hambicige, 1986~.
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From page 463... ...
As a result, extrapolation from human milk intake cluring the O through 6 months postpartum period, which yields 2.4 mg/ciay, floes not reflect acloquate zinc intake cluring the second 6 months. ray ray Intake from Human Milk and Complementary Foods.
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From page 464... ...
The corresponding value for children ages 1 through 3 years is 744 ~g/day (Table 12-3~. Fractional Absorption of Dietary Zinc.
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From page 465... ...
Baseci on an average intake of 500 ~g/ciay from human milk and a fractional absorption of 0.5, the amount of zinc ingested from milk is approximately 250 ~g/ciay. Therefore the estimated absorbed zinc required from complementary foocis is 586 ~g/ciay (836 - 250~.
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From page 466... ...
These results indicate that 35.5 percent of 10 percent, or 3.6 percent of the overall population in this age group, haci growth-limiting zinc deficiency. The calculated mean clietary intake at baseline for the placebo-treateci children was 4.1 + 0.8 mg/ciay (stanciarci deviation tSD]
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From page 467... ...
No growth response was observed with zinc supplementation of healthy children of either gentler, unselected for growth, whose average calculated zinc intake was 6.3 mg/ciay (Hambicige et al., 1979a)
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From page 468... ...
, and a reference weight of 40 kg, the required amount of absorbed zinc is 2.1 mg/ciay (Table 12-~. Baseci on a fractional absorption of 0.3 observed in infants and young children (Davidsson et al., 1996; Fairweather-Tait et al., 1995)
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From page 469... ...
As determined by the summation of average zinc losses and the zinc requirement for growth (Kuczmarski et al., 2000; Widdowson and Dickerson, 1964) , the amount of absorbed zinc that is required for boys and girls is approximately 3.4 and 3.0 mg/ciay, respectively (Table 12-6~.
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From page 470... ...
Zinc EAR and RDA Summary, Ages I4 through IS Years EAR for Boys 14-18 years EAR for Girls 14-18 years 8.5 mg/day of zinc 7.3 mg/day of zinc The RDA for zinc is set by using a CV of 10 percent (see Chapter 1) because information is not available on the stanciarci deviation of the requirement.
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From page 471... ...
With this approach, the principal indicator selected is the minimal quantity of absorbed zinc that is acloquate to replace enclogenous zinc losses. The EAR is the average zinc intake that provides this quantity of absorbed zinc.
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From page 472... ...
Step 3: Determination of Minimal Zinc Absorption Required to Replace Total Endogenous Zinc Excretion. The sum of nonintestinal endogenous zinc losses (1.27 mg/ciay for men and 1.0 mg/ciay for women)
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From page 473... ...
Step 4: Determination of the Average Zinc Intake Required to Achieve Absorption of the Quantity of Zinc Necessary to Match Total Endogenous Losses. The EAR is cletermineci from the asymptotic regression of absorbed zinc on zinc intake (Figure 12-2)
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From page 474... ...
In contrast, clietary zinc was positively correlated with serum albumin in a group of 82 elderly Canadians whose zinc intakes averaged ~ mg/ciay for women and 6.5 mg/ciay for men (Payette and Gray-Donalci, 1991 ~ . Several stuciies in which improvements in laboratory inclexes of zinc status with zinc supplementation were reported clici not, unfortunately, include information on habitual zinc intake (Boukaiba et al., 1993; Cakman et al., 1997; Duchateau et al., 1981; Fortes et al., 1998~.
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From page 475... ...
. Zinc EAR and RDA Summary, Ages ~9 Years and older EAR for Men 19-30 years 31-50 years 51-70 years > 70 years EAR for Women 19-30 years 31-50 years 51-70 years > 70 years 9.4 mg/day of zinc 9.4 mg/day of zinc 9.4 mg/day of zinc 9.4 mg/day of zinc 6.8 mg/day of zinc 6.8 mg/day of zinc 6.8 mg/day of zinc 6.8 mg/day of zinc The RDA for zinc is set by using a CV of 10 percent (see Chapter 1)
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From page 476... ...
Dietary supplementation recluceci the decline in plasma/serum zinc concentration across pregnancy in a large cohort of Peruvian women whose clietary zinc intake was estimated to be 7 mg/day (Caulfield et al., 1999a) , but not in North American women whose dietary zinc intake averaged 11 mg/day (Hambidge et al., 1983~.
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From page 477... ...
A report that zinc intakes of less than 7.5 mg/ciay cluring the third trimester are associated with lower zinc concentrations in human milk is consistent with the EAR (Ortega et al., 1997~. Zinc EAR and RDA Summary, Pregnancy EAR for Pregnancy 14-18 years 19-30 years 31-50 years 10.0 mg/day of zinc 9.5 mg/day of zinc 9.5 mg/day of zinc The RDA for zinc is set by using a CV of 10 percent (see Chapter 1)
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From page 478... ...
Reported values for fractional absorption of zinc for adult women outside the reproductive cycle averages 27 percent (Fung et al., 1997; Hunt JR et al., 1992, 1998; Sian et al., 1996; Turnlunci et al., 1991~. If this value were applied to the calculation of increased dietary zinc required during lactation (1.35 .
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From page 479... ...
and lower than intake from nonvegetarian cliets (Faber et al., 1986; Freeland-Graves et al., 1980a; Harland and Peterson, 1978; Hunt et al., 1998; Janelle and Barr, 1995~. In most older adult and elderly populations, vegetarians have lower zinc intakes than non
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From page 480... ...
A11coho11 Long-term alcohol consumption is associated with impaired zinc absorption and increased urinary zinc excretion. Low zinc status is observed in approximately 30 to 50 percent of alcoholics.
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From page 481... ...
The meclian total (food plus supplements) zinc intakes by adults taking supplements were similar to those of adults who clici not take zinc supplements (Appenclix Table C-26.
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From page 482... ...
Reduced copper status has been associated with increased zinc intake (Boukaiba et al., 1993; Burke et al., 1981; Festa et al., 1985; Fischer et al., 1984; Prasaci et al., 1978; Samman and Roberts, 1988; Yacirick et al., 1989) (Table 12-7)
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From page 483... ...
There is one case report of three premature deliveries and one stillborn infant after excess zinc intake during pregnancy (Kumar, 1976~. Because details on other contributing factors were not provided, interpretation of these results is limited.
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From page 484... ...
Status Study Subjects Zinc Intake (mg/d) Duratior Prasad et al., 1978 1 black man, 150-200 2 y 26 y w/sickle cell anemia Greger et al., 1978 14 girls, 12-14 y 7.4 (food)
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From page 485... ...
(1993) is a crossover study designed to determine the effects of lowdose zinc supplementation on food intake, nutritional status, immune and lipid indexes.
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From page 486... ...
Multiplying the NOAEL for infants O through 6 months of age by the estimated average intake of human milk of 0.78 L/ciay (Allen et al., 1991; Butte et al., 1984; Heinig et al., 1993) results in a NOAEL of 4.5 mg/day.
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From page 487... ...
Zinc UT Summary, Ages O through IS Years UL for Infants 0-6 months 7-12 months UL for Children 1-3 years 4-8 years 9-13 years UL for Adolescents 14-18 years Pregnancy and Lactation Because the UL is baseci on recluceci copper status and because there are inacloquate ciata to justify a different UL for pregnant and lactating women, the UL for pregnant and lactating women is the same as that for nonpregnant and nonlactating women. 4 mg/day of zinc 5 mg/day of zinc 7 mg/day of zinc 12 mg/day of zinc 23 mg/day of zinc 34 mg/day of zinc Zinc UT Summary, Pregnancy and Lactation UL for Pregnancy 14-18 years 19-50 years UL for Lactation 14-18 years 19-50 years 34 mg/day of zinc 40 mg/day of zinc 34 mg/day of zinc 40 mg/day of zinc
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From page 488... ...
The ninety-fifth percentile intake of zinc coming from food and supplements for adult men and nonpregnant women was approximately 25 to 32 mg/day (Appendix Table C-26. For pregnant and lactating women, the zinc intake from food and supplements was approximately 40 and 47 mg/ciay, respectively, at the ninety-fifth percentile.
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From page 489... ...
· Quantitative ciata on human zinc homeostasis uncler a wicle range of clieta~y conditions and at all ages using recent advances in zinc stable isotope methodology; quantification of what happens to zinc homeostasis as zinc intakes and absorption are increased and clecreaseci beyond the range typically seen until recently; these metabolic studies neeci to be long-term. REFERENCES Abrams SA, Wen l, Stuff ~E.
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From page 490... ...
1994. Marginal zinc deficiency in older adults: Responsiveness of zinc status indicators.
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From page 491... ...
1983. Effect of dietary zinc and protein levels on the utilization of zinc and copper by adult females.
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From page 492... ...
2000. Changes in dietary zinc and copper affect zinc-status indicators of postmenopausal women, notably extracellular superoxide dismutase and amyloid precursor proteins.
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From page 493... ...
1979b. Plasma zinc concentrations of breast-fed infants.
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From page 494... ...
1977. Zinc excretion in young women on low zinc intakes and oral contraceptive agents.
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From page 495... ...
1985. The effects of a dietary zinc supplement during lactation on longitudinal changes in maternal zinc status and milk zinc concentrations.
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From page 496... ...
1994. Size of the zinc pools that exchange rapidly with plasma zinc in humans: Alternative techniques for measuring and relation to dietary zinc intake.
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From page 497... ...
1997. Plasma and erythrocyte zinc concentrations and their relationship to dietary zinc intake and zinc supplementation during pregnancy in low-income African-American women.
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From page 498... ...
1996. Zinc absorption and intestinal losses of endogenous zinc in young Chinese women with marginal zinc intakes.
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From page 499... ...
1992. Erythrocyte metallothionein response to dietary zinc in humans.
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From page 500... ...
1985. Zinc utilization in young men fed adequate and low zinc intakes.
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From page 501... ...
1978. Zinc balance studies in normal infants.
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