Sourdough is naturally leavened bread, which means it doesn't use commercial yeast to rise. Instead, it uses a 'starter' – a fermented flour and water mixture that contains wild yeast and good bacteria – to rise. This also produces the tangy flavour and slightly chewy texture you'll find in sourdough. The starter we use is said to be over 500 years old. We know it’s old because it give our bread such a unique taste and texture! 
Millions of people are suffering from digestive malaise, and if you’re sensitive to foods containing gluten or have irritable bowel syndrome, sourdough bacteria’s ability to break down flour works in your favor. The wild yeast and bacteria in a sourdough starter break down some of the carbohydrates and proteins found in flour, says Kate Scarlata, a Boston-based dietitian and author of The Low-FODMAP Diet book. When bread is made with fast-rising yeast, the bacteria don’t have time to do any pre-digesting.