28.5: Urine zinc (24c.5)
- Page ID
- 117295
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Daily excretion of zinc in the urine is typically 0.3–0.6mg. A systematic review and meta-analysis examining the response of urinary zinc excretion to changes in dietary intake was conducted by Lowe and co-workers (2009). They concluded that urinary zinc is a useful biomarker of increases in exposure to zinc supplements (i.e. > 15mg Zn/d) in adults with adequate zinc status at baseline. However, only when dietary zinc intakes are very low (< 1mg dietary Zn/d) is a decrease in urinary zinc excretion in adults apparent (Baer and King, 1984; Johnson et al., 1993; King et al., 2000). Comparable studies on infants and children have not been conducted.
Urinary zinc excretion is confounded by a variety of clinical conditions that induce hyperzincuria. These include sickle cell disease, alcoholism and liver disease, certain renal diseases and infections, injury, and burns. Starvation, strenuous physical exercise, diabetes, and trauma may also increase urinary zinc excretion (King et al., 2015). Hypertensive patients on long-term therapy with chlorothiazide also exhibit hyperzincuria(Prasad, 1983). Certain physiological conditions also influence urinary zinc excretion. Increases have been reported during pregnancy with concentrations returning to prepregnant levels after delivery (Fung et al., 1997). Whether changes occur during lactation is uncertain (King et al., 2015). Consequently, the overall health and diet of an individual must always be evaluated when using urinary zinc as a biomarker of zinc exposure.
The BOND Zinc Expert Panel classified urinary zinc as a “potential” biomarker that shows promise (King et al., 2015), based on its usefulness as a marker of compliance with zinc supplementation programs when at least 15mg Zn/d was given (Lowe et al., 2009). They emphasize, however, that the need to collect a 24‑hour urine sample and the lack of established cutoffs limit the usefulness of urinary zinc as a biomarker. Moreover, because urinary zinc only responds to very low dietary zinc intakes, its use as a biomarker of dietary zinc intake among free-living populations is limited.
24c.5.1 Measurement of urinary zinc excretion
The amounts of zinc excreted in the urine usually range from 300 to 600µg/d. A 24-h urine collection is preferred because diurnal variation in urinary zinc excretion may be significant. Measurements of urinary zinc are usually performed by flame AAS.