| Traditionally, gluten is defined as a
cohesive, elastic protein that is left behind after starch is
washed away from a wheat flour dough. Only wheat is considered
to have true gluten. Gluten is actually made up of many
different proteins.
There are two main groups of
proteins in gluten, called the gliadins and the glutenins.
Upon digestion, the gluten proteins break down into smaller
units, called peptides (also, polypeptides or peptide chains)
that are made up of strings of amino acids--almost like beads
on a string. The parent proteins have polypeptide chains that
include hundreds of amino acids. One particular peptide has
been shown to be harmful to celiac patients when instilled
directly into the small intestine of several patients. This
peptide includes 19 amino acids strung together in a specific
sequence. Although the likelihood that this particular peptide
is harmful is strong, other peptides may be harmful, as well,
including some derived from the glutenin fraction.
It is certain that there are
polypeptide chains in rye and barley proteins that are similar
to the ones found in wheat. Oat proteins have similar, but
slightly different polypeptide chains and may or may not be
harmful to celiac patients. There is scientific evidence
supporting both possibilities.
When celiac patients talk about
"gluten-free" or a "gluten-free diet," they are actually
talking about food or a diet free of the harmful peptides from
wheat, rye, barley, and (possibly) oats. This means
eliminating virtually all foods made from these grains (e. g.,
food starch when it is prepared from wheat, and malt when it
comes from barley) regardless of whether these foods contain
gluten in the very strict sense. Thus, "gluten-free" has
become shorthand for "foods that don't harm celiacs."
In recent years, especially
among non-celiacs, the term gluten has been stretched to
include corn proteins (corn gluten) and there is a glutinous
rice, although in the latter case, glutinous refers to the
stickiness of the rice rather than to its containing gluten.
As far as we know, neither corn nor glutinous rice cause any
harm to celiacs. |
