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Fractional Zn absorption (FZA) and total absorbed Zn (TAZ) in elderly are lower than values used to derive the adult Zn Estimated Average Requirement (EAR)
Author(s) -
Chung Carolyn Sue,
Montelius Lynn,
Nguyen Tuan Q,
Gildengorin Ginny,
Dare Doris,
King Janet
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.697.2
Subject(s) - urine , zoology , zinc , chemistry , urinary system , endocrinology , medicine , biology , organic chemistry
Zn intake and metabolism are altered in elderly individuals, yet dietary requirements have not been studied for this group. We measured FZA in response to mixed food diets containing approximately the Zn EAR and the EAR ± 40% consumed for 2 wks in 17 healthy elderly, 10 women and 7 men. All subjects consumed the 3 diets. 70 Zn and 67 Zn tracers were given orally and intravenously on d8 and 9 of each 2‐week diet period, respectively. Urine collected 3–5 d after infusion was analyzed by ICPMS for 67:66 Zn ratios and by ICP for total urinary and plasma Zn. FZA was determined using tracer/tracee ratios and averaged from d 3–5. TAZ equaled the total dietary zinc intake multiplied by FZA. FZA differed across all diet groups (p<0.0001, ANCOVA), regardless of age or sex. Conversely, TAZ did not vary by diet group, nor did plasma and urinary Zn. At EAR intakes, mean FZA adjusted for age was 29 ± 6.1 and 37 ± 2.9 % in men and women, respectively, and was 40 and 10% lower than absorption values used to determine EARs (48 and 41%). Mean TAZ was 2.99 ± 0.48 and 2.73 ± 0.19 mg/d in men and women, respectively, and was 21 and 17% lower than absorbed Zn values used for EARs (3.8 and 3.3 mg/d). The CV for FZA and TAZ in the elderly was 31% compared to the assumed 10% used to estimate the RDA. The lower measured FZA for these healthy elderly individuals suggests that the current Zn EAR underestimates the average requirement. Supported by USDA NRI 2004‐01842 and NIH MO1‐RR00083‐43.