Universidad de Córdoba BIODISPONIBILIDAD MINERAL DE ...

Resultados
studied zinc absorption as zinc carbonate in the presence of several fibre
sources, and observed that some of these sources, such as corn husk fibre
improved zinc absorption in front of a fiber-free diet, when fiber intake in the diet
was low. However, when increased fiber intake in the diet, zinc absorption
diminished. This performance was justified, arguing that zinc ions released
from zinc carbonate by gastric acid remain bound to uronic acid residues of
fiber without precipitation as insoluble salts and the zinc bound to the fiber is
absorbed after passing into the small intestine. However, in the case of high
intakes of this kind of fiber, this effect cannot be explained and zinc absorption
is diminished, highlighting the dual effects of some kind of fiber on zinc
absorption. In other investigations, there is not agreement between studies in
vivo and in vitro. Debon and Tester (2001) studied in vitro binding of zinc and
other minerals by polyanionic polysaccharides classified as soluble fiber. The
polysaccharides with a high content of sulphate or carboxyl groups as pectin,
carrageenan and xanthan gum presented a great response for binding cations
because all these groups are deprotonated to the intestinal pH and can interact
electrostatically with mineral cations. At a pH of the small intestine of about 6.5-
7, a similar performance in vivo was expected; however, other experiments with
pectin and guar gum in human and animals models ( Muñoz and Harland, 1993;
Torre et al, 1991) have concluded that soluble dietary fiber does not have a
significant effect on mineral bioavailability. The differences between in vivo and
in vitro studies are due to the polysaccharides response to bind cations
measured in solutions where the ionic strength was low, far to the physiological
conditions in which ionic strength is high.
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