ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

C.4.1 Introduction
CHAPTERC-4
DISCUSSION
This section ofthe study was conducted to investigate the effects ofbeta-sitosterol on the
digestive and absorptive enzymes of Sprague-Dawley rats. Results obtained for the
nutritional evaluation are discussed in this chapter.
C.4.2 Experimental test
The rats were in good health throughout the study: no mortality was observed in any of
the groups tested with beta-sitosterol. This is in agreement with studies conducted on
phytosterols. Similar studies have consistently demonstrated a lack oftoxicity in animals
and humans fed beta-sitosterol., except for individuals with an extremely rare genetic
condition, sitostero1aemia (Malini and Vanithakumari, 1990; Hicks and Morean, 2001).
Plasma phytosterol levels are generally very low in mammalian tissues. Poor absorption
from the intestine and quicker excretion from the liver, compared to that of cholesterol,
are responsible for these low levels (Ling and Jones, 1995). Intestinal absorption of total
dietary beta-sitosterol consumed is negligible in mammals. Animal studies have
demonstrated that this absorption should possibly be as little as five percent (Borgstrom,
1968; Gould, 1955). In rats, the absorption of beta-sitosterol is about four percent
(Sanders et al., 2000). A reason for the low absorption ofplant sterols might be that plant
sterols are poorly esterified, possibly due to the low affinity ofACAT (acyl-coenzyme A
cholesterol acyltransferase) for these components (Bhattacharyya, 1981; Ntauios et al.,
1998). Within the enterocyte, free cholesterol is is esterified by ACAT, incorporated into
chylomicrons, which are subsequently excreted into the circulation and converted into a
chylomicron-remnant by the action oflipoprotein lipase (Kwiterovich, 2000). Absorption
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