There are many gluten substitutes and binders you can use for gluten free baking but there really is only one for gluten free bread, psyllium husk. Till now either gums and numerous amounts of eggs are used to achieve what some would call a good gluten free bread. Gums are not only expensive but for those who are sensitive to gluten have been experiencing intolerance to the gums. Eggs too are expensive, especially if you're going to be using as many as what most recipes require. For those eating gluten free the reason can be allergies and those allergies can incorporate eggs.
Psyllium adds rise, flexibility and strength to gluten free baking. Thus the importance is more so for gluten free bread where the rise from yeast and structure in bread is greatly relied on the gluten contained in the flour. Psyllium mimics glutens job in bread baking. When mixed with water then the blend of gluten free flours, the dough becomes pliable like gluten bread dough. It can be kneaded. It has stretch. It has elasticity. No more bread dough that looks like cake batter!
Not only is psyllium great for gluten free bread it is also very good for us. The soluble fiber found in psyllium husks can help lower cholesterol. Psyllium can help relieve both constipation and diarrhea, and is used to treat irritable bowel syndrome, hemorrhoids, and other intestinal problems. Psyllium has also been used to help regulate blood sugar levels in people with diabetes.
When psyllium husk comes in contact with water, it swells and forms a gelatin like mass that helps transport waste through the intestinal tract. Several large population based studies also suggest that increased fiber intake may reduce risk of colon cancer, but other studies have been conflicting.
You may need to add a little more water to your recipe as psyllium coagulates with liquids more than other binders. For example a bread recipe that calls for 450gm of flour, use 20gm of psyllium and mix with the liquids, with the water amount being 400-450gm.
Shauna from gluten free girl has a great wee video demonstrating what is psyllium husk?