Phytic acid interferes with the body’s ability to absorb calcium, zinc, iron, magnesium, and copper. Phytase
is a thermo-resistant flour enzyme that is at its most active as dough pH reduces. When dough is acidified
with a sourdough phase, the phytase virtually eliminates the effects of phytic acid, making the bound
nutrients available and improving the nutritional profile of the bread.
At the University of Guelph, Ontario lead a team of researchers who studied four types of breads to determine which had the most positive health effects when it comes to carbohydrate metabolism, blood sugar and insulin levels. The results were impressive.
They discovered that the long fermentation involved in baking with natural yeasts resulted in a loaf that was digested more slowly and caused less of a spike in blood sugar levels when it was eaten.
In an initial study, the research group chose four different breads to compare – white, whole wheat, whole wheat with barley and a white sourdough. Each member of a group of volunteers was given one of the breads for breakfast, then monitored to see how their blood sugar and insulin levels responded over the course of the next few hours. At the start of the research the team expected, as many of us would, that the whole wheat breads would show more health benefits than the white. In fact, the white bread and whole wheat breads showed very similar responses, an initial spike followed by declining levels. The white sourdough bread showed the least pronounced response, with both blood glucose and insulin increases significantly lower than those seen following a breakfast of non-sourdough bread. This is important because, from a health perspective, the aim is to keep blood sugar and insulin levels as close to normal as possible. The team also discovered that this response pattern was repeated when the volunteers were given lunch, not including bread, later in the day.
the sourdough fermentation process was altering the structure of the starch in the bread. These changes mean that the starch would be digested and assimilated into the body more slowly, resulting in less pronounced responses in terms of blood glucose and insulin.