Sourdough bread is naturally leavened using sourdough starter which is a living culture of wild yeast and lactic acid bacteria. This wild yeast and healthy bacteria makes sourdough bread easier to digest and less likely to spike blood sugar levels because of its lower glycemic index compared to standard white bread. Furthermore, sourdough bread is made with 3 simple ingredients: flour, water and salt. Normal white bread that you buy at the grocery store is made using commercial yeast and often has a very long ingredient list.