Sourdough breads are considered low on the glycemic index and, unlike those made with yeast, they do not raise blood sugar levels. Sourdough breads break down easier in our stomachs because the beneficial microorganisms in the leaven start the process for us. Thus, people who are sensitive to gluten can happily eat sourdough breads . After all, research has shown that sourdough tends to eat gluten from whatever flour is used.