Enhanced zinc utilization during lactation may reduce maternal and infant zinc depletion.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
Janet C King
Publications and source records attributed to Janet C King.
Evaluating the impact of plant biofortification on human nutrition.
An evaluation of the efficacy of biofortified foods for improving human nutrition and health requires both laboratory- and community-based trials. A three-step process is proposed. First, tests of nutrient bioavailability should be conducted in the laboratory. Various genotypes of modified foods may be screened for bioavailability using in vitro cell-culture systems or experimental animals before testing in humans. Second, comprehensive feeding trials are conducted to test the efficacy of the biofortified food for improving the nutrition and health of target populations. These trials are generally done for several weeks or months, and they involve measuring a comprehensive set of endpoints. If efficacy is demonstrated in the feeding trial, the third step, a community-based trial, is planned. This final trial involves evaluating the nutritional, health, agricultural, societal, environmental and economic effects of the biofortified food in the community. A multidisciplinary team including consumers, policymakers, health leaders, as well as scientists is required for successful completion of the community trial.
Agriculture↗
Supplemental zinc lowers measures of iron status in young women with low iron reserves.
Zinc and iron compete during intestinal absorption, but postabsorptive interactions between these nutrients are less clear. Understanding these interactions is important to determine when supplementation with iron or zinc is proposed. The effect of zinc supplementation (22 mg Zn/d as zinc gluconate) or of iron supplementation (100 mg Fe/d as ferrous sulfate) for 6 wk on iron and zinc metabolism and absorption was evaluated in young women with low iron reserves. Young adult women (ages 20-28 y), nonanemic but with low iron stores (plasma ferritin< 20 microg/L), participated in the 70-d study. The women were divided in two groups (zinc-supplemented, n = 11; iron-supplemented, n = 12). The supplements were taken at bedtime. Iron and zinc biochemical indices and intestinal absorption were measured on d 1 and 56. Radioiron and stable isotopes of zinc were used to measure iron and zinc absorption from a test meal. In the iron-supplemented group, blood hemoglobin, plasma ferritin and the percentage of transferrin saturation increased (P < 0.01). Zinc indices did not change. In the zinc-supplemented group, plasma ferritin and the percentage of transferrin saturation decreased (P < 0.05), whereas the plasma transferrin receptor and erythrocyte zinc protoprophyrin levels increased (P < 0.05). Plasma and urinary zinc also increased (P < 0.01). Iron absorption (%) from the test meal increased (P < 0.01), whereas zinc absorption (%) decreased (P < 0.01) compared with baseline in the Zn-supplemented women. Our results indicate that the use of iron supplements in women with marginal iron status improves iron indices with no effect on zinc status. However, use of a modest zinc supplement improves zinc indices, but also appears to induce a cellular iron deficiency and, possibly, further reduce iron status.
Adult↗
Immune functions are maintained in healthy men with low zinc intake.
Although immunity is impaired during severe zinc deficiency, there is limited information about the effects of mild zinc depletion on immune response in humans. We evaluated the effects of a zinc-restricted diet (4.6 mg/d) on several indices of immunity in 8 healthy men. The subjects consumed zinc supplements with 9.1 mg/d during the 5-wk baseline (BL) and 5-wk repletion (RP) periods, and placebos during the 10-wk zinc-restriction (ZR) period. Leukocyte numbers and functions were studied at the end of each metabolic period. After ZR, there were reductions in the proliferation of peripheral blood mononuclear cells (PBMNC) stimulated with phytohemagglutinin (PHA, 1.2, 2.5, 5.0, 10.0 [corrected] and 20.0 mg/L; P < 0.01) and in the in vitro secretion of interleukin-2 receptor (IL-2R) (PHA, 2.5 mg/L; P = 0.058). These variables remained reduced (P < 0.05) even after 5 wk of zinc repletion. The amount of zinc consumed did not alter the numbers of circulating neutrophils, monocytes and lymphocytes, the in vitro PBMNC secretion of interferon-gamma and tumor necrosis factor-alpha or neutrophil superoxide production. The results suggest that changes in lymphocyte proliferation and IL-2R expression may be early markers of mild zinc deficiency.
Adult↗
Pregnancy and lactation affect markers of calcium and bone metabolism differently in adolescent and adult women with low calcium intakes.
Physiologic adaptation to the high calcium demand during pregnancy and lactation may be different in adolescents than in adults, particularly at low calcium intake. The aim of this cross-sectional study was to compare biochemical markers of calcium and bone metabolism between adolescent (14-19 y) and adult (21-35 y) women with calcium intake approximately 500 mg/d, in three different physiologic states, i.e., control (nonpregnant, nonlactating; NPNL), pregnant and lactating. Markers of calcium metabolism [serum Ca, P and intact parathyroid hormone (iPTH); urinary Ca and P] and of bone turnover [urinary deoxypyridinoline (D-Pyr) and plasma bone alkaline phosphatase (BAP)] were measured in NPNL (adolescents, n = 12 and adults, n = 25), pregnant (adolescents, n = 30 and adults, n = 36) and lactating (adolescents, n = 19 and adults, n = 26) women. In the NPNL women, iPTH, D-Pyr and BAP were higher (P < 0.001) and urinary Ca was lower (P < 0.001) in adolescents than in adults. Serum iPTH was higher (P < 0.001) and urinary Ca was lower (P < 0.01) in adolescents than in adults also in pregnancy and lactation. Compared with NPNL women, serum Ca decreased (P < 0.001) with pregnancy in adolescents but not in adults. The increase in D-Pyr with pregnancy and lactation was very pronounced in adults ( approximately 130%, P < 0.001) but less in adolescents (<25%, P < 0.01). BAP increased (P < 0.001) with pregnancy and lactation in adults ( approximately 60%) but decreased (P < 0.001) with pregnancy in adolescents ( approximately 13%). Pregnancy and lactation appear to affect bone turnover in adolescent and adult women with low calcium intake differently.
Adolescent↗
Double isotope tracer method for measuring fractional zinc absorption: theoretical analysis.
Several approaches for estimation of fractional zinc absorption (FZA) by calculating the ratio of oral to intravenous stable isotopic tracer concentrations (at an appropriate time) in urine or plasma after their simultaneous administration have been proposed in the last decade. These simple-to-implement approaches, often referred to as the double isotopic tracer ratio (DITR) method, are more attractive than the classical "deconvolution" method and the more commonly used single-tracer methods based on fecal monitoring and indicator dilution, after oral or intravenous tracer administration, respectively. However, the domain of validity of DITR for measuring FZA has recently been questioned. In this paper, we provide a theoretical justification of the validity of four different "approximate" formulations of the DITR technique by demonstrating mathematically that their accuracy is a consequence of the particular properties of zinc kinetics.
Absorption↗