Gluten

Attack

Gluten
By Margaret Hill ou wouldn’t know it if you looked at her now, but a year ago, amy was a mess. she had skin rashes and stomach cramps that would mysteriously come and go. every time she had a flare-up, amy suffered in silence, thinking that the skin rashes and stomach cramps were temporary. when they continued, she decided to tell her parents. medical tests revealed that amy hasceliac disease, a condition caused by an abnormal sensitivity to gluten in the diet. Unfortunately, gluten is found in many foods. with the help of a nutritionist, amy and her mother have been working on removing gluten from her diet. it has not been easy because gluten is found in wheat, rye, barley, and oats. amy misses some of her favorite foods, but she feels better and has fewer skinreactions than before. amy is relieved that by eating gluten-free foods, she can avoid much of the distress she felt last year. what is gluten and why did amy’s body react so negatively to it?

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Keeping it together
gluten is a substance found in the grains of wheat and related plants, including barley and rye. it is present in a part of the grain called the endosperm (fig. 1). cerealgrains are one of the main ingredients in flour, which is often used in household baking because gluten gives elasticity to dough and helps it to rise. without gluten, a loaf

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Figure 1. The structure of a grain of wheat

Chemmatters, FEBRUARY 2012 9

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of baked bread would be flat and dense—not light and fluffy. How does gluten work? let’s look at what happens when bread dough bakes in the oven. bread dough is made by mixing flour, water, sugar (sucrose), and yeast—tiny single-celled organisms that feed on sugar in a process called fermentation. but these ingredients are mixed in acertain order, and the resulting dough must be kneaded. Kneading consists of pressing and folding dough to give it a smoother consistency. during this process, the gluten in the flour becomes elastic and helps the bread to rise and set. The dough rises as a result of yeast fermentation, which consists of several sequential chemical reactions that can be summarized as follows:

Glutensensitivity
why does amy’s body react negatively to gluten? The immune system of people with celiac disease mistakenly identifies parts of gliadin and glutenin as foreign and destroys them. The immune system usually looks for “foreign” epitopes—parts of proteins that do not belong to our bodies. once such epitopes are found, specialized cells from the immune system, called lymphocytes, destroy the foreignproteins. epitopes (fig. 4) usually contain between eight and 11 amino acids. normally during digestion, the digestive enzymes within the small intestine break up proteins into single amino acids and small chains of amino acids. This is necessary because the intestine can only absorb single amino acids or, at most, chains of three to four amino acids. single amino acids and small chains of aminoacids do not cause problems for the intestine nor would they be expected to cause problems with the immune system because lymphocytes are looking for longer chains. it appears, however, that gliadin is not com-

Kneading is a technique of folding the dough and  pushing it down over and over. It helps to stretch  out gluten in the flour, which allows the dough to  rise and set.

H N H C R

O CAmino acid repeat unit

C6H12O6 ➔ 2 CH3CH2OH + 2 CO2
glucose ethanol carbon dioxide

The carbon dioxide causes the dough to increase in volume and rise, but this increase in volume occurs only because gluten supports the dough surrounding the pockets of carbon dioxide. The ethanol evaporates when bread is baked in the oven.

NH2 H C R COOH

Single amino acid

anTHony fernandez,...