Is Toast Less Nutritious Than Fresh Bread?
Q. Does toasting bread kill the yeast or nutrients? Is fresh bread more nutritious than toast?
A. The yeast are already dead--they would not have survived the temperatures needed to bake the dough into bread. And technically, you can’t "kill" vitamins and minerals because they were never "alive" to begin with. Nutrients can be degraded or destroyed by heat. But, again, this will already have occurred during the baking process.
However, there are 2 ways that toasting does affect the nutritional qualities of bread:
Toasting can have a small beneficial effect on the glycemic impact of the bread. In other words, toasted bread may cause a slightly lower elevation of blood sugar than fresh bread.
On the other hand, toasted bread is higher in acrylamide.
In the end, the nutritional differences between fresh and toasted bread are not significant enough to make a strong case for choosing one over the other.