In yesterday's digest, Jenny writes,

"Dean Esmay indicated a week or so ago, that there are good reasons to
suggest that starch is a relatively recent addition to human diets.

It intrigues me then, why humans have such extraordinary ability to
secrete
aplha-amylase, the starch digesting enzyme, present in both saliva and
pancreatic secretions.  We have so much, that some biochemists call it
alph-amylase overkill.  Any suggestions?

Jennie"


The highest levels of alpha amylase occur in human pancreas followed by
the parotid glands.   The amylase isozyme levels in parotid glands are
of an order of magnitude less than those in pancreas (Sobiech KA et al.
Determination of amylase by measurement of enzmatic acitivity anb y
enzyme immunoassay and radioimmunoassay. Arch Immunol Therap Exp 1983;
31:845-8).   Because starch boluses do not remain in the mouth for more
than a few seconds, parotid derived alpha amylase has little influence
upon immediate starch digestion.  Additionally, if the starch is wheat
based, there are endogenous alpha amylase inhibitors in wheat (also in
legumes) which effectively inhibit salivary amylase (O'Donnell MD et al.
 Purification and properties of an alpha amylase inhibitor from wheat.
Biochimica et Biophysica Acta 1976;422:159-69.).   Further, wheat alpha
amylase inhibitors also influence pancreatic amylase secretion
(Buonocore V. et al.  Wheat protein inhibitors of alpha amylase.
Phytochemistry 1977 16:811-820) and  have been shown to result in
pancreatic hypertrophy in animal models (Macri A. et al.  Adaptation of
the domestic chicken, Gallus Domesticus, to continuous feeding of
albumin amylase inhibitors form wheat flour as gastro-resistant
microgranules. Poultry Science 1977; 56:434-441).   Legume starch
contains trypsin inhibitors which inactivate native pancreatic trypsin
so as to abnormally increase pancreatic cholecystokinin levels and also
cause pancreatic enlargement in animal models.  (Liener IE.
Implications of antinutritional components in soybean foods. Crit Rev
Food Sci Nutr 1994;34:31-67.).   The point here is that humans obviously
have adequate salivary and pancreatic amylase levels to digest moderate
amounts of certain kinds of starch, however, antinutrients in our main
starch sources (grains and beans) , when consumed in excessive
quantities may negatively impact endocrine function.

                                        Loren