Sourdough and grain processing impact blood glucose levels

Nutritional experts and recent studies suggest that the impact of bread on blood glucose levels depends more on processing and fermentation than simply whether it is labeled as white or whole grain.

Sourdough bread may provide a more gradual increase in blood glucose compared to varieties made with refined flour. This is attributed to the fermentation process, which produces lactic and acetic acids. These compounds can slow starch absorption in the digestive tract and alter starch structure, making it less accessible to digestive enzymes.

Furthermore, the physical structure of the grain plays a critical role. Research indicates that the size of cereal particles determines how quickly carbohydrates enter the bloodstream. Breads made with larger grain fractions tend to produce lower glucose spikes than those made with fine flour. Experts emphasize that the term ‘whole grain’ does not automatically guarantee a lower glycemic response if the grain has been finely milled, as high levels of processing can accelerate digestion.