Sourdough bread and regular bread along with many other types of breads are made using the same type of flour but the main difference is in the fermentation process that the sourdough bread goes through when made.
The fermentation process of the sourdough bread increases it's nutrition value and also makes the sourdough bread easier for people to digest than other bread.
When the sourdough bread goes through the fermentation process it prevents the effects of the phytic acid which is also what makes the sourdough bread easier to digest.
The fermentation process and the prevention of the effects of the phytic acid also allows the phytic acid molecules to bind with other minerals in the sourdough bread, such as calcium, magnesium, iron and zinc, which make these important nutrients unavailable to us.
So you get a lot of health benefits from all those nutrients when eating sourdough bread although regular bread is still healthy.
The sourdough bread is the healthiest bread of them all.