Universidad de Córdoba BIODISPONIBILIDAD MINERAL DE ...

Biodisponibilidad mineral de menús escolares
rhythm, stress, infection, starvation, plasma protein levels…) which make
biochemical valuation of plasma zinc levels are not to be considered an
accurate reflection of zinc status of an individual. The alternative seems that it
is the determination of the metallothionein level, a zinc storage protein (Wood,
2000) whose levels diminished in young men fed a zinc-deficient diet for several
days and was rapidly increased after supplementation with 50 mg of zinc per
day (Grider et al., 1990). Although there is yet not enough data that identify to
metallothionein as a reliable indicator to detect marginal deficiencies of zinc,
and it would be necessary further investigations in the future, we can say that
subjects with low metallothionein concentrations may suffer a zinc deficiency
with a higher probability.
Zinc-mineral elements interactions
The mechanisms involved in these interactions between zinc and other
mineral nutrients are current investigation topics. In fact, the existence of a
divalent cation transporter with broad specificity has recently been described at
the brush border membrane level (Gunshin et al, 1997). This transporter is
probably a multidivalent metal channel that could justify numerous interactions
between zinc and other divalent metallic cations, due to competition for this
common transport. The effect of Ca +2 , Mg +2 , Fe +2 , Cu +2 and Mn +2 on zinc
absorption has been studied.
All of these metals were capable of inhibiting
Zn +2 uptake at various concentrations, and the results suggest that these metals
may compete with Zn +2
for transport across the brush border membrane.
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