SELENIUM

DIETARY SOURCES, PROPERTIES
AND ROLE IN HUMAN HEALTH

been studied in chicks (Mutanen and Mykkänen 1984). It was seen that for 4%
of fat in the diet, the glutathione peroxidase activity rose as the percentage of
polyunsaturated fat in the diet increased (rapeseed oil, corn oil and sunflower
oil), which demonstrates that selenium is more bioavailable in diets containing
polyunsaturated fatty acids. However, the same study also showed that when
the percentage of fat was increased to 20%, that effect was not observed,
indicating that at this high level of fat intake the plasma glutathione peroxidase
activity may be maximally stimulated (Mutanen and Mykkänen 1984).
Finally, selenium has also been seen to have a strong negative interaction
with heavy metals like mercury and cadmium (Marval – León et al. 2014;
Burger et al. 2013; Calatayud et al. 2012; Pappas et al. 2011; Kaneko and
Ralston 2007). Apparently, selenium forms insoluble compounds with those
heavy metals thus diminishing their absorption in the intestinal lumen so that a
protective role against the toxicity of those elements can be attributed to it.
However, its bioavailability also declines. Taking into account that the chief
objective of this chapter is to review the main factors affecting selenium
bioavailability, next we have grouped the different studies made in this field
according to the principal groups of foods that are considered to be good
dietary sources of this element.