Even though it’s made from white flour, sourdough bread has a relatively mild effect on blood sugar compared to other white breads. Sourdough is an ancient bread with thousands of years of bread-making history behind it. It has a distinctive taste, the result of lactic acid produced by bacteria used to ferment the dough. A sourdough “starter” is made from a combination of yeast and bacteria growing in a paste of flour and water. Some is used for making a loaf, and the rest is saved to grow and use for future baking.
It’s the acid produced by the bacterial culture that makes a poor blood sugar choice into a better one. One small Swedish study involving 12 healthy people found that when the volunteers ate a breakfast that included bread with added lactic acid in an amount found in sourdough bread, the rise in their blood sugar was 27 percent less after 1 1/2 hours than it was when they ate the same breakfast but with a bread made with a combination of whole grain flour and processed white flour.
One study using sourdough bread made with specific strains of bacteria found that it could reduce gluten intolerance in people sensitive to wheat gluten. While that doesn’t mean that people diagnosed with gluten intolerance can eat sourdough bread with impunity, it does suggest that the bread is more easily digested than other breads made with wheat flour.
Glycemid Load: Low
You can either make your own sourdough bread using a sourdough starter or buy a loaf at the local bakery. Note that all rye breads made with whole grain rye are by nature sourdough. (For bread to rise, yeast reacts with the gluten in the wheat. Rye doesn’t contain enough gluten to rise with yeast, so sourdough starter is used to get the same effect.)
Some breads are called sour breads because they have sour flavoring agents added. While it’s possible they could have a beneficial effect on blood sugar (say, if the souring agent is vinegar), they haven’t been studied as sourdough bread has.
Sourdough bread has a distinctive tart taste, but you can use it whenever you might use regular bread. Try it for sandwiches and hamburgers, as a crunchy accompaniment to al dente spaghetti and sauce, or to go with soup.
Perfect Portion: 1 ounce (30 g)
A serving is about the size of one small slice, depending on the brand. Eat two slices, as you would in a sandwich, and the bread becomes a medium-GL food — still reasonable.